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  • 1
    Electronic Resource
    Electronic Resource
    The Menschutkin reaction of benzyl p-toluenesulfonates with N,N-dimethylanilines. Evidence for the duality of SN1 and SN2 mechanisms (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 254-260 
    Details
    ISSN: 0894-3230
    Keywords: Menschutkin reaction ; duality of SN1, SN2 mechanisms ; benzyl tosylates ; Yukawa-Tsuno equation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate data for the Menschutkin reaction between strongly activated Z-substituted benzyl p-toluenesulfonates and Y-substituted N,N-dimethylanilines in acetonitrile at 35 °C fit the equation, kobs  =  k1 + k2 [DMA], which is consistent with concurrent first- and second-order processes. The k1 and k2 values for each substrate were separated based on the above equation. The SN1 rate constant, k1, is unaffected by the nature of the nucleophile, whereas the SN2 rate constant, k2, increased with the electron-donating substituent of the N,N-dimethylaniline. The substituent effect on the k1 values is linearly correlated by the Yukawa-Tsuno equation with ρ  =  -5.2 and r  =  1.3. The unimolecular reaction can be regarded as a classical SN1 mechanism. In contrast, that on the k2 values shows an upward curvature when analyzed by the Brown σ+ treatment. These results are ascribed to the simultaneous and independent occurrence of SN1 and SN2 mechanisms in the present Menschutkin reaction. © 1998 John Wiley & Sons, Ltd.
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  • 2
    Electronic Resource
    Electronic Resource
    Editorial (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 231-231 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
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  • 3
    Electronic Resource
    Electronic Resource
    Solvent effects on infrared spectroscopic and calorimetric characteristics of aliphatic ketones in binary solvent mixtures (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 283-289 
    Details
    ISSN: 0894-3230
    Keywords: calorimetry ; IR spectra ; ketones ; solvation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solution enthalpies of n-hexane, acetone, butan-2-one and octan-2-one in a series of tetrachloromethane-acetonitrile mixtures and the carbonyl stretching absorption frequencies in the IR spectra of these ketones were determined. It was found that over the whole range of concentrations (varying from neat tetrachloromethane up to neat acetonitrile) the solvation enthalpy of these compounds can be obtained additively from the contributions of the alkyl and carbonyl fragments. The solvent effect on the solvation enthalpy of the carbonyl group was found to be satisfactorily correlated with the corresponding IR frequency shifts of the C=O group. It was also found that the sensitivities of the carbonyl IR frequencies to the solvent composition are different for various ketones. From both IR and calorimetric data, the preferential solvation parameters were evaluated. The differences between the IR spectroscopic and calorimetric data are discussed. © 1998 John Wiley & Sons, Ltd.
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  • 4
    Electronic Resource
    Electronic Resource
    Solvent effects on C=O stretching frequencies of some 1-substituted 2-pyrrolidinones (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 261-272 
    Details
    ISSN: 0894-3230
    Keywords: 1-substituted 2-pyrrolidinones ; C=O stretching frequencies ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In an effort to model solute-solvent interactions, the C=O stretching frequencies of five 1-substituted 2-pyrrolidinones and four other carbonyl-containing compounds were measured for 30 common solvents. These were then correlated with four empirical parameter sets and one theoretical (computational) parameter set. While an empirical parameter set gave the best correlation equations, the theoretical parameter equations are physically and statistically significant. Solvent volume, polarizability and hydrogen bond donor acidity (capacity) terms are significant in the correlation equations. © 1998 John Wiley & Sons, Ltd.
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular orbital calculations on the P - S bond cleavage step in the hydroperoxidolysis of nerve agent VX (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 232-240 
    Details
    ISSN: 0894-3230
    Keywords: P - S bond cleavage ; hydroperoxidolysis ; nerve agent VX ; molecular orbital calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The P - S bond cleavage process in the hydroperoxidolysis of a model system for the nerve agent VX was studied using ab initio and semiempirical molecular orbital methods. Aqueous solvation effects were included through single-point calculations using the semiempirical SM5.2PD/A continuum solvation model and geometries optimized at the HF/MIDI! level of theory. The predominant pathway for P - S bond cleavage involves pseudorotation of a low-energy trigonal bipyramidal intermediate followed by apical ligand ejection. In aqueous solution, the free energy barriers for these processes are found to be 14.3 and 4.6 kcal mol-1, respectively, with electronic energies calculated at the MP2/cc-pVDZ//HF/MIDI! level of theory. By comparison with another continuum model of solvation (PCM), it is concluded that the SM5.2PD/A model performs well even for hypervalent phosphorus species, in spite of not having included any such molecules in the model's parameterization set. © 1998 John Wiley & Sons, Ltd.
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  • 6
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of N-methyl-N-phenyl-tert-butylsulfenamide and morpholinyl-tert-butylsulfenamide (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 407-410 
    Details
    ISSN: 0894-3230
    Keywords: gas-phase thermolysis ; N-methyl-N-phenyl-tert-butylsulfenamide ; morpholinyl-tert-butylsulfenamide ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390 °C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s-1, Ea, kJ mol-1): MPSA, log A  =  12.41 ± 0.02, Ea  =  158.8 ± 0.2; MOSA, log A  =  12.91 ± 0.22, Ea  =  159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as co-products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.
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  • 7
    Electronic Resource
    Electronic Resource
    NMR and semi-empirical study of the tautomerism of­2,2′-bisbenzimidazolyl (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 411-418 
    Details
    ISSN: 0894-3230
    Keywords: 2,2′-bisbenzimidazolyl ; tautomerism ; NMR ; semi-empirical calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A dynamic NMR study of the tautomerism of 2,2′-bisbenzimidazolyl in DMSO-d6 and a mechanistic interpretation of the process, based on a stepwise, single-proton transfer and formation of a zwitterionic intermediate, are presented. This interpretation is substantiated by semi-empirical calculations of the postulated intermediate and transition state, that yield results which are compared with previous studies on related aliphatic systems. © 1998 John Wiley & Sons, Ltd.
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of sulfenyl, sulfinyl and sulfonyl groups on acidities and homolytic bond dissociation energies of adjacent C - H and N - H bonds (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 397-406 
    Details
    ISSN: 0894-3230
    Keywords: bond dissociation energy ; acidity ; phenylsulfenylamides ; phenylsulfenylanilides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acidities and bond dissociation energies (BDEs) of the N-H bond in two phenylsulfenylamides, PhSNHBz and PhSNH-t-Bu, and four phenylsulfenylanilides, 4-GC6H4NHSPh, where G  =  MeO, H, Br and CN, were measured in order to compare the effects of substituents on acidities and BDEs of N - H bonds with those of C - H bonds. The effects of PhS groups on acidities and BDEs in a series of C - H acids were found to be comparable to those on acidities and BDEs of PhS in a similar series of N - H acids. Comparisons were also made of the effects of changing the oxidation state of sulfur in the series PhS, PhSO and PhSO2 on the acidities and BDEs of adjacent N - H and C - H bonds in weak acids. Hammett-type plots of pKHA values for phenyl benzyl sulfones (4-GC6H4CH2SO2Ph) and phenylsulfenylanilides (4-GC6H4NHSPh) were linear vs σp- values. A linear plot was obtained and explained for a plot of BDE of the N - H bonds in remotely substituted phenylsulfonylanilides with σ+ values. Plots of BDEs vs Eox(A-) were also linear for 4-substituted phenylsulfenylanilides (4-GC6H4NHSPh), phenylsulfonylanilides (4-GC6H4NHSO2Ph) and phenyl benzyl sulfones (4-GC6H4CH2SO2Ph). © 1998 John Wiley & Sons, Ltd.
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  • 9
    Electronic Resource
    Electronic Resource
    17O NMR studies on α-diamides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 387-391 
    Details
    ISSN: 0894-3230
    Keywords: α-diamides ; 17O NMR ; conformation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 17O NMR spectra of several α-diamides were obtained at natural isotopic abundance in acetonitrile solution in order to study the conformations of these compounds in solution. The 17O NMR shifts vary with the intercarbonyl dihedral angle α in a sense opposite to that observed for α-diketones. © 1998 John Wiley & Sons, Ltd.
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical study of the tautomerism of 8-azaadenine (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 392-396 
    Details
    ISSN: 0894-3230
    Keywords: 8-azaadenine ; tautomerism ; theoretical study ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The prototropic tautomerism of 8-azaadenine (azaade) was studied theoretically by means of ab initio methods, in both the gas phase and aqueous solution. A number of tautomeric forms were not included in the calculations after applying a stepwise elimination procedure based on both AM1 and HF/6-31G* energy values. The tautomers 9H-azaade, 8H-azaade and 7H-azaade survived to this elimination and their optimized geometries and energies were calculated at the MP2/6-31*//HF/6-31G* level. To include the solvent effects, two self-consistent reaction field method were used: (1) Onsager's SCRF with multipolar expansion up to the hexadecapolar term and (2) the isodensity polarizable continuum method (IPCM). Both methods produce similar results, although the latter represents better the situation in aqueous solution. The stability order in solution, 8H- 〉 9H- 〉 7H-azaade, differs slightly from that found in the gas phase, implying that in general the electrostatic effects in solution are important, but the intrinsic stability of these species in the gas phase overcomes the solvent effect. © 1998 John Wiley & Sons, Ltd.
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  • 11
    Electronic Resource
    Electronic Resource
    Editorial (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 377-377 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
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  • 12
    Electronic Resource
    Electronic Resource
    Electrochemical study of the π* probe dye 5-nitro-5′-dimethylamino-2,2′-bisthiophene (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 419-425 
    Details
    ISSN: 0894-3230
    Keywords: 5-nitro-5′-dimethylamino-2,2′-bisthiophene ; π* probe dye ; cyclic voltammetry ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cyclic voltamograms of the solvatochromic dye 5-nitro-5′-dimethylamino-2,2′-bisthiophene (1), introduced recently as a sensitive π* probe, were recorded in different solvents. An EPR spectrum of the anionic radical of 1 in DMSO was obtained and compared with other spectra of analogous substituted bisthiophene radicals. It was found that the presence of a donor- acceptor pair of substituents in 1-⋅ reduces significantly the rotational barrier of the radical compared with the unsubstituted bithienyl radical anion 2-⋅. This is the result of an electronic repulsion between the donor ring fragment and the added electron in the coplanar radical, which does not exist in 2-⋅. © 1998 John Wiley & Sons, Ltd.
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  • 13
    Electronic Resource
    Electronic Resource
    Host-guest interactions of calix[4]resorcinarenes with benzene derivatives in conditions of reversed-phase high-performance liquid chromatography. Determination of stability constants (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 426-437 
    Details
    ISSN: 0894-3230
    Keywords: calix[4]resorcinarenes ; organophosphorus compounds ; solvatophobic interactions ; host-guest complexation ; high-performance liquid chromatography ; x-ray analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reversed-phase high-performance liquid chromatography [LiChrosorb RP-18,UV detection at 254 nm and acetonitrile-water (86:14,v/v) as mobile phase] was applied to studies of the host-guest complexation of tetraalkylcalix[4]resorcinareneoctols and their upper rim phosphoryl, sulfonyl and dialkylaminomethyl derivatives with some aromatic guests in the mobile phase. It was shown that the formation of the inclusion complexes results in changes in the retention of aromatic guests and improves their separation. Stability constants of the complexes were calculated from the dependences of the l/k′ values of the aromatic guest on the concentration of the calix[4]resorcinarene in the mobile phase. The molecular structure of 4,6,16,18-tetrahydroxy-10,12,22,24-tetrakis(dipropoxyphosphoryloxy)-2,8,14,20-tetramethylcalix[4]resorcinarene (12) was determined. Crystal data for 12 are P21/n, a  =  16.708(9) Å, b  =  18.683(6) Å, c  =  20.243(5) Å, β  =  95.75(3)°, V  =  6287(4) Å3 and Z  =  4. Compound 12 exists in a boat conformation, in which two opposite unsubstituted resorcinol rings of the macrocyclic skeleton lie in the plane formed by four methine bridges and two diphosphorylated rings are perpendicular to the plane. © 1998 John Wiley & Sons, Ltd.
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  • 14
    Electronic Resource
    Electronic Resource
    Ab initio and molecular mechanics (MM3) calculations on alkyl- and arylboronic acids (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 378-386 
    Details
    ISSN: 0894-3230
    Keywords: alkylboronic acids ; arylboronic acids ; ab initio ; MM3 ; molecular mechanics ; force field parameters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The boronic acid functional group has been incorporated into various biologically important compounds. In order to study this class of compounds better with molecular mechanics, five alkyl- and arylboronic acids were calculated using ab initio methods (Spartan) at the RHF/6-31G* level. MM3 force field parameters were developed based on the theoretically calculated geometries, vibrational spectra, and torsional profiles. © 1998 John Wiley & Sons, Ltd.
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  • 15
    Electronic Resource
    Electronic Resource
    Base-catalysed hydrolysis of γ-lactones: reactivity-structure correlations for 3-(substituted phenoxy- and thiophenoxymethylene)-(Z )-1(3H )-isobenzofuranones (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 467-474 
    Details
    ISSN: 0894-3230
    Keywords: γ-lactones ; base-catalysed hydrolysis ; reactivity-structure correlations ; isobenzofuranones ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxy- or thiophenoxymethylene)-(Z)-1(3H)-isobenzfuranones (3-phenoxy- or thiophenoxymethylenephthalides) in 70% (v/v) aqueous dioxane at 30.0 °C, in addition to the carbonyl stretching frequencies in chloroform and tetrachloromethane following deconvolution and band separation, when required. The Hammett reaction constants for the alkaline hydrolysis of the 3-/4-substituted phenoxy and thiophenoxy series are ca 0.75 and 1.10, respectively. These results are related to electrostatic field and resonance effects. Successful correlations between the carbonyl stretching frequencies and substituent constants and the rates of alkaline hydrolysis were found. Computational studies using the semi-empirical AM1 method correctly model both the details of the mechanistic pathway and the substituent effects. © 1998 John Wiley & Sons, Ltd.
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  • 16
    Electronic Resource
    Electronic Resource
    A new approach to the theoretical estimation of inductive constants (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 437-447 
    Details
    ISSN: 0894-3230
    Keywords: inductive constants ; theoretical estimation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new model of the inductive effect is proposed, allowing highly accurate theoretical calculations of inductive constants for a diversity of substituents, using a simple and readily available system of mathematics. According to this approach, the inductive effect of a substituent is considered in terms of the additive influence of its constituent atoms. A constant inherent capacity for inductive interaction with a reactive center (with a four-coordinate carbon atom chosen for such a center), represented by an atomic constant σA, is ascribed to each atom. Values of σA for a wide variety of atoms are determined, and their physical meaning is revealed to elucidate to a certain extent the physical nature of the inductive effect. In addition, the proposed model permits the convenient use in calculations of group constants σG characterizing the inductive power of groups. Values of σG are determined for molecular fragments that are most widely dealt with in organic chemistry, and the use of σA or σG constants and of their superposition is shown to have, in most cases, little or no effect on the accuracy and reproducibility of the results obtained. It is also shown that, in terms of the developed approach, the inductive effect of a substituent is closely associated with its conformation. Theoretical inductive constants were calculated for 427 organic, aromatic, organometallic and charged substituents, and they showed perfect correlation with the corresponding experimental values. © 1998 John Wiley & Sons, Ltd.
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  • 17
    Electronic Resource
    Electronic Resource
    Oxidation of mandelic acid by alkaline potassium permanganate. A kinetic study (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 448-454 
    Details
    ISSN: 0894-3230
    Keywords: mandelic acid ; alkaline permanganate ; oxidation ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the oxidation of mandelic acid (MA) by permanganate in aqueous alkaline medium at a constant ionic strength of 1.0 mol dm-3 were studied spectrophotometrically. The reaction shows first-order kinetics in [permanganate ion] and fractional order dependences in [MA] and [alkali]. Addition of products, manganate and aldehyde have no significant effect on the reaction rate. An increase in ionic strength and a decrease in dielectric constant of the medium increase the rate. The oxidation process in alkaline medium under the conditions employed in the present investigation proceeds first by formation of an alkali permanganate complex, which combines with mandelic acid to form another complex. The latter decomposes slowly followed by a fast reaction between the free radical of mandelic acid and another molecule of permanganate to give products. The reaction constants involved in the mechanism were derived. There is good agreement between the observed and calculated rate constants under different experimental conditions. The reaction was studied at different temperatures and activation parameters were computed with respect to the slow step of the proposed mechanism. © 1998 John Wiley & Sons, Ltd.
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  • 18
    Electronic Resource
    Electronic Resource
    Selective arylation of exocyclic N-position of 2-pyrimidylnitrenium ion photolytically generated from tetrazolo-[1,5-a]pyrimidine in the presence of trifluoroacetic acid (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 478-484 
    Details
    ISSN: 0894-3230
    Keywords: Selective arylation ; exocyclic N-position ; 2-pyrimidylnitrenium ion ; tetrazolo[1,5a]pyrimidine ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photo-reactions of tetrazolo[1,5-a]pyrimidine (1) with benzene (2a) and substituted benzenes (2b-f) in the presence of trifluoroacetic acid (TFA) gave 2-(2-, 3- and 4-substituted anilino)pyrimidines (3-5) together with 2-aminopyridine (6) and biphenyl (7) or diarylmethanes (8b, 8c and 8e). From the effect of heavy-atom solvent on the reactions, it is reasonable to assume that 3-5 are formed via a singlet species, but 6-8 via a triplet species. The intermediacy of 2-pyrimidylnitrenium ion is consistent with the evidence derived by the above effect, by a Hammett plot with ρ = -2.9 and by effects of solvent nucleophilicity and counter-anions. The selective exocyclic N-arylation giving 3-5 is discussed. © 1998 John Wiley & Sons, Ltd.
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  • 19
    Electronic Resource
    Electronic Resource
    Synthesis, structural, conformational and pharmacological study of esters derived from 3-methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol as potential analgesics (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 125-132 
    Details
    ISSN: 0894-3230
    Keywords: 3-methyl-2, 4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol esters ; analgesics ; synthesis ; structure ; conformation ; pharmacological assays ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of esters derived from 3-methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol (1) was synthesized and studied by 1H and 13C NMR spectroscopy, and the crystal structure of 3-methyl-2,4-diphenyl-9α-(3,5-dimethylbenzoyloxy)-3-azabicyclo[3.3.1]nonane (2) was determined by x-ray diffraction. The compounds studied display in CDCl3 a preferred flattened chair-chair conformation. This bicycle conformation is similar to that found for 2 in the crystal state. Pharmacological assays on mice were performed to evaluate drug-induced behavioral alteration, peripheral or central acute toxicity and analgesic activity. © 1998 John Wiley & Sons, Ltd.
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  • 20
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    Stereospecific nucleophilic trapping of encounter complexes between photoexcited 1-cyanonaphthalene and norbornadiene (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 101-108 
    Details
    ISSN: 0894-3230
    Keywords: encounter complexes ; 1-cyanonaphthalene ; norbornadiene ; stereospecific ; nucleophilic trapping ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photo-induced electron donor-acceptor reactions between 1-cyanonaphthalene (CNN) and norbornadiene (N) generate products of several structure types. Methanol adducts (1-3) formed in polar solvents are rationalized via the radical cation, N+·, and stereospecific (exo-) nucleophilic attack by methanol. In less polar solvents, CNN and N form [2 + 2]-cycloadducts, exclusively on the exo-face of N. In non-polar solvents containing methanol, CNN, N and methanol combine to form 1:1:1 adducts, containing the sensitizer on the endo- and the methoxy groups on the exo-face. The formation of these products is rationalized via the trapping of encounter complexes of different geometries. Any rearrangement of the norbornenyl system can be eliminated, since neither tricyclyl nor 7-methoxynorbornenyl structures are formed. Apparently, the alcohol captures an endo-encounter complex of CNN and N by attack from the exo-face, similar to the attack of methanol on N+·. © 1998 John Wiley & Sons, Ltd.
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    Gain or loss of aromaticity in Diels-Alder transition states and adducts: a theoretical investigationThis paper was presented at the Satellite Meeting on Structural and Mechanistic Organic Chemistry: A Tribute to Norman L. Allinger, held in Athens, GA, USA, June 3-7, 1997. (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 133-140 
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    ISSN: 0894-3230
    Keywords: aromaticity ; Diels-Alder transition states ; Diels-Alder adducts ; reaction mechanism ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semiempirical, ab initio and DFT investigations on the mechanism of the Diels-Alder reactions of a set of masked dienes (ring-fused dienes), viz. o-quinodimethane, anthracene and α-vinylnaphthalene, with ethylene, and reactions of α-vinylnaphthalene with maleic anhydride and p-benzoquinone were performed with a view to understanding the role of masking factors on the activation and reaction energies. The reactions were found to occur in a concerted fashion through synchronous transition states (TSs) in the first two reactions and through asynchronous TS in the other case. Of the compounds studied, o-quinodimethane is the most reactive diene both in a kinetic and a thermodynamic sense. α-Vinylnaphthalene reacts faster with maleic anhydride than p-benzoquinone, as expected, and two possible stereoselective TSs, one endo and the other exo, have been located for the reactions of α-vinylnaphthalene with the above dienophiles. Calculations show that the relative gain or loss of aromatic stabilization of the benzonoid ring in the transition state and in the product seems to play a major role in the kinetic and thermodynamic control of these reactions. © 1998 John Wiley & Sons, Ltd.
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    Infrared spectra and conformation of methyl-substituted benzoic acidsPresented in part at the VIth International Conference on Correlation Analysis in Chemistry, Prague, 5-9 September 1994. (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 141-148 
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    ISSN: 0894-3230
    Keywords: methylbenzoic acids ; infrared spectra ; conformation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of all isomers of polymethyl-substituted benzoic acids were recorded in the carbonyl and hydroxyl regions in tetrachloromethane at various concentrations and interpreted in terms of conformation. According to a plot of ν(C=O) of the monomeric form vs Hammett substituent constants σ, these compounds may be classified into two classes. Derivatives with none or only one methyl group in the ortho position are concluded to exist in an equilibrium of two planar conformations, unless the equilibrium is degenerate. Derivatives with two ortho-situated methyl groups are concluded to take up one non-planar conformation. These findings are supported by the shape of the hydroxyl and carbonyl bands, which are unsymmetrical in the former class, although they could not be reliably separated into bands pertinent to the individual conformers. This conclusion is at variance with the common interpretation which has invariably ascribed to these and similar ortho derivatives non-planar conformations with a variable torsional angle. © 1998 John Wiley & Sons, Ltd.
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    Ab initio calculations on P - C bond cleavage in phosphoranyl radicals: implications for the biodegradation of organophosphonate derivatives (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 149-154 
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    ISSN: 0894-3230
    Keywords: P - C bond cleavage ; phosphoranyl radicals ; organophosphonate biodegradation ; ab initio calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Barrier heights for P - C bond homolysis in P-hydroxy-P-methyl-P,P-dioxophosphoranyl and P,P,P-trihydroxy-P-methylphosphoranyl were calculated using well correlated levels of electronic structure theory. The best estimate for the difference in barriers between the two indicates that homolysis is more facile for P,P,P-trihydroxy-P-methylphosphoranyl by roughly 9 kcal mol-1. This result suggests that bacterial pathways leading to P - C bond cleavage in organophosphonate derivatives will preferentially proceed via initial one-electron reduction of substrates rather than oxidation. © 1998 John Wiley & Sons, Ltd.
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    Mechanism of cycloaddition to indolizines (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 201-208 
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    ISSN: 0894-3230
    Keywords: indolizines ; cycloaddition ; reaction mechanism ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The peculiarities of [8+2] cycloaddition reactions of indolizines with dienophiles are reviewed. Quantum chemical SINDO1, AM1 and ab initio calculations of transition states were performed for [8+2] cycloaddition reactions of indolizine and 6-nitroindolizine with a series of alkenes with donor and acceptor groups. The calculations predict a dipolar cycloaddition mechanism (electrophilic addition and ring closure) for reactions of indolizine and 6-nitroindolizine with nitroethylene. For the reaction of 6-nitroindolizine with N,N-dimethylaminoethylene, the predicted mechanism corresponds to a previously unknown ‘inverse’ dipolar cycloaddition (nucleophilic addition and ring closure). © 1998 John Wiley & Sons, Ltd.
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    Theoretical studies on the gas-phase nucleophilic substitution reactions of benzyl chlorides with phenoxides and thiophenoxides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 115-124 
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    ISSN: 0894-3230
    Keywords: cross-interaction constants ; gas-phase nucleophilic substitution reactions ; PM3 MO ; benzyl chlorides ; phenoxides ; thiophenoxides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gas-phase nucleophilic substitution reactions of Y-benzyl chlorides with X-phenoxide and X-thiophenoxide nucleophiles were investigated theoretically using the PM3 semi-empirical MO method. The Leffler-Grunwald rate-equilibrium and Brønsted correlations predict that the degree of bond formation in the transition state (TS) is approximately 45 and 40% on the reaction coordinate for the phenoxides and thiophenoxides, respectively. For a weaker nucleophile, a later TS is obtained with an increased bond making and breaking. The variation of the TS structure with substituents in the nucleophile is thermodynamically controlled and is well correlated by rate-equilibrium relationships. In contrast, the TS variation (a tighter TS) with substituent (for a stronger acceptor Y) in the substrate is dependent only on variations of the intrinsic barrier and so cannot be correlated by such thermodynamically based rate-equilibrium relationships. The gas phase ρX and ρY values are much greater in magnitude than those in solution. A similar gas-phase theoretical cross-interaction constant, ρXY (ca -0.60), is obtained for both phenoxides and thiophenoxides, which is in good agreement with the experimental value (-0.62) for the thiophenoxide reactions in MeOH at 20.0 °C. The oxy and sulfur anion bases lead to a similar TS structure, but a lower reactivity for the former is due to a greater endothermicity of the reaction. A relatively wide range variation of the reaction energies, ΔG°, can be ascribed to the loss of resonance stabilization of anion nucleophiles upon product formation. © 1998 John Wiley & Sons, Ltd.
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    Osmium(VIII)/ruthenium(III) catalysis of periodate oxidation of acetaldehyde in aqueous alkaline medium (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 171-176 
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    ISSN: 0894-3230
    Keywords: acetaldehyde ; oxidation ; periodate ; osmium (VIII) catalysis ; ruthenium (III) catalysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Os(VIII) and Ru(III) catalysis of the periodate oxidation of acetaldehyde in aqueous alkaline medium was investigated. The catalytic efficiency is Ru(III)〈Os(VIII). The product of oxidation in both cases is acetate and IO3-. The stoichiometry is the same in both catalyzed reactions, i.e. [IO4-]:[CH3CHO] = 1:1. Probable mechanisms are proposed and discussed. The reaction constants involved in the mechanisms are derived. © 1998 John Wiley & Sons, Ltd.
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    Solvolysis of benzylic chlorides with extended charge delocalization. α-tert-butyl(2-naphthyl)methyl, 9-fluorenyl and monosubstituted benzhydryl chlorides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 223-229 
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    ISSN: 0894-3230
    Keywords: Solvolysis ; Grunwald-Winstein-type analysis ; Hammett-type analysis ; YxBnCl scale ; 1-aryl-1-phenylmethyl cations ; Mulliken population analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate constants of solvolysis of α-tert-butyl(2-naphthyl)methyl chloride (1), 9-fluorenyl chloride (2) and a series of monosubstituted benzhydryl chlorides (3) in a wide range of solvents were measured. Grunwald-Winstein-type correlation analysis of log k for 2 and 3 against YBnCl, with or without nucleophilicity N, yielded less satisfactory linear correlations than that against log k(1). A new scale of solvent ionizing power, YxBnCl, for the correlation of solvolytic reactivities of benzylic chlorides with extended charge delocalization based on log k(1) was developed. Application to the mechanistic study suggested the solvolysis of 2 and 4-nitrobenzhydryl chloride were non-limiting. Hammett plots against σ+ constants exhibited more negative ρ values in less nucleophilic solvents. In a benzhydryl chloride containing a strong deactivating substituent, such as 4-nitro, the positive charge delocalizes mainly over the unsubstituted ring in the cationic transition state. The uneven charge distribution was also confirmed by Mulliken population analysis at the level of the RHF/6-31G*//RHF/3-21G(*) basis set for cations. Comparison of the results of correlation analysis using the equation log(k/k0) = mY vs the equation log(k/k0) = mY+hI, and using the equation log(k/k0) = mY+lN vs the equation log(k/k0) = mY+lN+hI indicated the use of YBnCl or YxBnCl could give a better understanding of solvolytic mechanisms than the combinatorial use of YCl and I. © 1998 John Wiley & Sons, Ltd.
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    Empirical treatment of solvent-solute interactions: medium effects on the electronic absorption spectrum of β-carotene (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 193-200 
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    ISSN: 0894-3230
    Keywords: Solvent-solute interactions ; β-carotene ; electronic absorption spectrum ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvent effects on the wavenumber of the maximum of the longest wavelength electronic absorption band of all-trans-β-carotene were determined in 34 solvents. Together with results from previous studies, a data set for 51 solvents, mostly non-hydrogen bond donors, was constructed. This information was analyzed in terms of reaction field models and also showed its value for correlation purposes when used either alone or in combination with standard empirical solvent polarity-polarizability scales. © 1998 John Wiley & Sons, Ltd.
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    Theoretical study on pyrolysis and sensitivity of energetic compounds. Part 4. Nitro derivatives of phenols (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 177-184 
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    ISSN: 0894-3230
    Keywords: nitro derivatives of phenols ; pyrolysis initiation reactions ; impact sensitivity ; UHF-SCF-AM1 MO method ; activation energy. ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The UHF-SCF-AM1 MO method was applied to the study of two kinds of pyrolysis reactions of six nitro derivatives of phenols (homolysis reaction by rupture of the C - NO2 bond into radicals and isomerization reaction involving phenolic hydrogen transferring to oxygen on the NO2 group). The molecular geometries of reactants, transition states and products were fully optimized. The potential energy curves and activation energies were first obtained. The results show that this category of compounds is more easily initiated via isomerization reactions than by homolysis reactions. The parallel relationship among the Wiberg bond order of the pyrolysis-initiation H - O bond in the molecule of a reactant, the activation energy of the isomerization reaction breaking the H - O bond and impact sensitivity of the reactant gives ‘the principle of the smallest bond order’ (PSBO) powerful support. The sensitizing effect of a phenol group was elucidated based on calculation results. The different influences of OH and NO2 groups on the heat of formation of a molecule are discussed. © 1998 John Wiley & Sons, Ltd.
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    Unexpected rate enhancement in the intramolecular carboxylic acid-catalyzed cleavage of o-carboxybenzohydroxamic acid (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 216-222 
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    ISSN: 0894-3230
    Keywords: o-carboxybenzohydroxamic acid ; phthalic anhydride ; phthalic acid ; hydrolysis ; intramolecular acid catalysis ; kinetics ; activation parameters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Phthalic anhydride was detected spectrophotometrically in the hydrolysis of o-carboxybenzohydroxamic acid (OCBA) in CH3CN-H2O solvent containing 0.03 mol dm-3 HCl. Pseudo-first-order rate constants (k1) for hydrolysis of OCBA are almost independent of the change in CH3CN content from 10 to 80% (v/v) in mixed aqueous solvents. The rate constants k1 are more than 10-fold larger than the corresponding rate constants for hydrolysis of phthalamic acid. These observations are explained in terms of a mechanism slightly different from the mechanism for hydrolysis of phthalamic acid. The activation parameters, ΔH* and ΔS*, are not affected appreciably by an increase in CH3CN content from 10 to 80% in mixed aqueous solvents. © 1998 John Wiley & Sons, Ltd.
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    Solute-solvent and solvent-solvent interactions in binary solvent mixtures. Part 7. Comparison of the enhancement of the water structure in alcohol-water mixtures measured by solvatochromic indicators (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 185-192 
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    ISSN: 0894-3230
    Keywords: solute-solvent interactions ; solvent-solvent interactions ; binary solvents ; alcohol-water mixtures ; water structure ; solvatochromic indicators ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A preferential solvation model that takes into account the enhancement of the structure of water when small amounts of alcohol are added was applied to solvatochromic data for binary mixtures of water with 2-methylpropan-2-ol, propan-2-ol, ethanol and methanol. Application of the model allows the calculation of the effect of the enhancement of the water structure on solvatochromic solvent properties. It is demonstrated that the enhancement of water structure increases the solvent dipolarity/polarizability and hydrogen-bond donor acidity and decreases the solvent hydrogen-bond acceptor basicity. The effect decreases in the order 2-methylpropan-2-ol-water, propan-2-ol-water, ethanol-water and methanol-water. © 1998 John Wiley & Sons, Ltd.
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    Structural dependence of heterolytic bond dissociation energy of carbon-carbon σ bonds in hydrocarbons (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 157-170 
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    ISSN: 0894-3230
    Keywords: heterolytic bond dissociation energy ; carbon-carbon σ bonds ; hydrocarbons ; structural dependence ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The coordination of a resonance-stabilized hydrocarbon cation and anion yielded a series of unprecedented hydrocarbons, which are susceptible to thermal heterolytic cleavage of carbon-carbon σ bonds in polar media, generating the original ions under reversible conditions. When the component ions were sufficiently stabilized, some ion pairs were even isolated as solids, thus providing the first examples of hydrocarbon salts. The direct observation of the heterolysis by means of spectroscopy permitted reliable thermodynamic treatments of the observed degree of ionic dissociation. Correlation of the free energy of heterolysis with solvent dielectric constants and parameters of ion stabilities such as pKHA, pKR+ and redox potentials revealed the importance of the thermodynamic stabilities of ions, the degree of solvation and steric congestion in the starting molecule as major controlling factors in the heterolysis. © 1998 John Wiley & Sons, Ltd.
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    Correlation of the rates of solvolysis of the N,N-diphenylcarbamoylpyridinium ion (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 273-276 
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    ISSN: 0894-3230
    Keywords: N,N-diphenylcarbamoylpyridinium ion ; solvolysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvolyses of the N,N-diphenylcarbamoylpyridinium ion are subject to specific and/or general base catalysis, which can be eliminated by addition of perchloric acid or increased, especially in fluoroalcohol-containing solvents, by addition of pyridine. The uncatalyzed solvolyses in aqueous methanol and aqueous ethanol involve a weakly nucleophilically assisted (l  =  0.22) heterolysis and the solvolyses in the pure alcohols are anomalously slow. © 1998 John Wiley & Sons, Ltd.
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    Effects of ionic and non-ionic micelles on rate of hydroxide ion-catalyzed hydrolysis of securinine (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 209-215 
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    ISSN: 0894-3230
    Keywords: securinine ; cationic micelles ; anionic micelle ; non-ionic micelle ; alkaline hydrolysis ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of micelles of cetyltrimethylammonium bromide (CTABr), tetradecyltrimethylammonium bromide (TTABr), sodium dodecyl sulfate (SDS) and polyoxyethylene 10 lauryl ether (C12E10) on the rates of alkaline hydrolysis of securinine were studied at a constant [-OH] (0.05 M). An increase in the total concentrations of CTABr, TTABr, SDS and C12E10 from 0.0 to 0.2 M causes a decrease in the observed pseudo-first-order rate constants (kobs) by factors of ca 2.5, 3, 7 and 4, respectively. The observed data are explained in terms of pseudophase and pseudophase ion-exchange (PIE) models of micelle. The binding constants, KS, of securinine with SDS, C12E10, CTABr and TTABr micelles are 32.4, 14.8, 22.1, and 9.1 M-1, respectively. The magnitudes of the second-order rate constants, kM, for the reactions in the micellar pseudophase are negligible compared with the corresponding rate constant, kW, for the reaction occurring in the aqueous pseudophase for CTABr, TTABr, SDS and C12E10. © 1998 John Wiley & Sons, Ltd.
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    Colloidal CdS-induced photocatalytic reaction of 2-methylindole - mechanistic analysis of oxidation of indoles (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 277-282 
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    ISSN: 0894-3230
    Keywords: colloidal CdS-induced photochemical reactions ; photocatalytic reactions ; photooxidation ; 2-methylindole ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2-Methylindole (2-MI) is adsorbed on the surface of colloidal CdS particles with an adsorption intensity of 0.6 × 103 dm3 mol-1. A new emission band at 530 nm is produced by forming an exciplex between excited CdS and 2-MI and the red emission due to CdS is simultaneously quenched. The emission maxima of green bands for different indoles increase in the order indole 〈 tryptophan 〈 2-MI 〈 3-MI and are observed at 508, 520, 530 and 540 nm, respectively. The shift in emission maxima is related to the oxidation potential of these substrates. The irradiation of an aerated reaction mixture containing CdS and 2-MI with visible light induces the oxidation of adsorbed 2-MI by photogenerated holes to produce 2-methyl-3-indolinone and 2-acetamidobenzaldehyde. The latter product is formed due to oxidative C - C bond cleavage of the pyrrole ring. The reactivity of trapped holes towards the adsorbed 2-MI is evidenced by a decrease in the lifetime of the red emission of CdS in the presence of 2-MI. In this reaction the possibility of the participation of singlet oxygen is ruled out. A general mechanism of CdS-induced oxidation of indoles is discussed. © 1998 John Wiley & Sons, Ltd.
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    Conformational analysis of a 12-membered crown dithioether in the solid state and in solution (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 241-253 
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    ISSN: 0894-3230
    Keywords: crown dithioether ; conformational analysis ; multicomponent equilibrium ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid-state molecular structure and the conformational behaviour in solution of the 12-membered crown dithioether 8-methyl-1,4-dioxa-7,10-dithiacyclododecane-5,12-dione were studied by x-ray crystallography, 1H and 13C NMR spectroscopy and molecular mechanics. The conformational rigidity of some constituent structural fragments allowed a detailed analysis of the structure and distribution of the conformers. A protocol for studies of multiconformational equilibrium was developed by means of the combined use of structure calculations and dynamic NMR measurements. © 1998 John Wiley & Sons, Ltd.
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    Metal-catalyzed carbenoid reactions with iodonium and sulfonium ylides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 321-333 
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    ISSN: 0894-3230
    Keywords: metal-catalyzed carbenoid reactions ; iodonium ylides ; sulfonium ylides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transition metal-catalyzed decomposition of phenyliodonium and diphenylsulfonium ylides was investigated with regard to application in asymmetric carbenoid reactions. Phenyliodonium ylides react in the presence of Rh(II) catalysts with the same selectivity in inter- and intramolecular cyclopropanations as the corresponding diazo compounds, and intramolecular CH insertions proceed with identical enantioselectivities. With diphenylsulfonium ethoxycarbonylmethylide the Cu(I)-catalyzed cyclopropanation of olefins affords trans/cis ratios and asymmetric inductions identical with those of diazo compounds, but with Rh(II) catalysts some small, although significant, selectivity variations occur, which are ascribed to coordination of diphenyl sulfide to one of the coordination sites of the catalyst. © 1998 John Wiley & Sons, Ltd.
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    Principles of physical organic chemistry for molecular architecture and functions (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 299-304 
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    ISSN: 0894-3230
    Keywords: molecular architecture ; molecule-based magnets ; biopolymers ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Application of the principles of physical organic chemistry to the construction of molecule-based magnets is discussed. Not only the magnetic structures of conventional magnets but also secondary and tertiary structures of biopolymers are instrumental in the molecular design. © 1998 John Wiley & Sons, Ltd.
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    Studies of reactive intermediates using matrix and gas-phase techniques (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 350-355 
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    ISSN: 0894-3230
    Keywords: 1,3-dipoles ; cumulenes ; infrared spectroscopy ; mass spectrometry ; flash vacuum thermolysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the direct investigation of reactive intermediates it is particularly valuable to use a combination of several spectroscopic techniques. This commentary highlights recent examples, using primarily flash vacuum thermolysis for the generation of the intermediates, and matrix IR spectroscopy in conjunction with gas-phase mass spectrometric methods for their identification. The examples include nitrile imines, nitrile ylides, nitrile sulfides and selenides, dinitrogen sulfide and several novel cumulenes (X=C=C=Y, RN=C=C=C=X). © 1998 John Wiley & Sons, Ltd.
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    Non-cross-linked and cross-linked poly(alkylmethyldiallylammonium halides): synthesis and aggregation behavior (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 305-320 
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    ISSN: 0894-3230
    Keywords: poly(alkylmethyldiallylammonium halides) ; aggregation behavior ; polyelectrolytes ; polysoaps ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrophobically modified polyelectrolytes (polysoaps) are a unique class of water-soluble polymers containing distinct hydrophobic and hydrophilic regions. Above a certain concentration, polysoaps form intramolecular and intermolecular aggregates in aqueous solution. They have attracted much attention not only for their ability to mimic some functions demonstrated by biopolymers but also for their important industrial applications. This review highlights some interesting features of novel non-cross-linked and cross-linked poly(alkylmethyldiallylammonium halides) that have been described in recent years. © 1998 John Wiley & Sons, Ltd.
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    Is the brain ready for physical organic chemistry? (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 334-340 
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    ISSN: 0894-3230
    Keywords: brain chemistry ; membrane proteins ; molecular neurobiology ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Efforts to developed detailed insights into the structure and function of the molecules of memory, thought and sensory perception - physical organic chemistry on the brain - are described. By combining more conventional chemical tools with a number of techniques adapted from modern biology, it is now possible to perform systematic structure-function studies on the integral membrane proteins that play a central role in molecular neurobiology. There are substantial challenges associated with such studies, but we believe the potential payoff is considerable. © 1998 John Wiley & Sons, Ltd.
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    Vicarious nucleophilic substitution of hydrogen. Mechanism and orientation (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 341-349 
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    ISSN: 0894-3230
    Keywords: vicarious nucleophilic substitution ; hydrogen ; mechanism ; orientation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrogens located at activated positions in electrophilic arenes, e.g. ortho and para hydrogens in nitrobenzenes, can be replaced with a nucleophile moiety provided there is at least one nucleofuge X connected to the nucleophilic centre. As the group really leaving in this hydrogen substitution process is not the hydride anion but X, the reaction has been named vicarious nucleophilic substitution of hydrogen (VNS). The concepts on the mechanism of the reaction and their experimental background are presented. Reactivity and orientation - the fundamental questions concerning synthetical applications of VNS - are discussed in light of the supposed mechanistic picture.
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    Preface (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 291-291 
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    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
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    Unusual reactivity of highly strained cyclophanesDedicated to Prof. Dr Maitland Jones, Jr, on the occasion of his 60th birthday (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 362-376 
    Details
    ISSN: 0894-3230
    Keywords: highly strained cyclophanes ; reactivity ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An essential feature of the concept of aromaticity has been the stability and lack of reactivity of aromatics relative to that of other unsaturated compounds. Contrary to this general experience, high and unusual reactivity is encountered when simple, monocyclic benzene rings are bent by short bridges into a boat-shaped conformation, as is the case in small [n] paracyclophanes (n ≤ 8) and [n]metacyclophanes (n ≤ 7). This is illustrated, mostly with examples taken from the authors' own work, for thermal and photochemical behavior and reactions with electrophiles, nucleophiles and dienophiles. © 1998 John Wiley & Sons, Ltd.
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    Heterogeneous catalysis of organic reactions (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 356-361 
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    ISSN: 0894-3230
    Keywords: heterogeneous catalysis ; organic reactions ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A decade's worth of work is reviewed: building on the demonstrated prowess of heterogeneous catalysis in industrial organic chemistry, the author's laboratory devised efficient catalysts for a number of organic reactions, based on aluminosilicates such as clays and zeolites. This review also spells out, at a time when creative research is overshadowed by imitative research, some of the methodological musts that also happen to characterize physical organic chemistry: the devising of experiments so that accurate numerical data can be obtained; the importance of remote, interdisciplinary connections; the need for estrangement from stereotypic preconceptions that may obscure the true explanations for the phenomena; and the over-riding need for concerning oneself only, or at least predominantly, with the important facts that nature tells, if one cares to listen. © 1998 John Wiley & Sons, Ltd.
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    Flash photolytic generation and investigation of short-lived reaction intermediates: a case study (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 292-298 
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    ISSN: 0894-3230
    Keywords: flash-photolysis ; short-lived reaction intermediates ; mandelic acid ; keto-enol tautomers ; enzyme-catalyzed racemization ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The advantage of adding more structure-diagnostic information to the simple detection of flash photolytically generated transient species by changes in UV-visible light absorbance is illustrated by a case study involving the mandelic acid keto-enol system. An early report based on preliminary evidence proposed that flash photolysis of phenyldiazoacetic acid produces the enol of mandelic acid by hydration of phenylhydroxyketene, itself generated by a photo-Wolff reaction of the diazo acid. Further examination, however, shows that this is only a minor route, and that the major pathway is a new enol-forming reaction involving what appears to be hydration of a carboxycarbene formed by dediazotization of the diazo compound. Hydration of phenylhydroxyketene is nevertheless the reaction by which mandelic acid enol is generated when esters of benzoylformic acid are the flash photolysis substrates. These mechanisms, and also identification of the enol as a tranisent species, are supported by detailed arguments involving acid-base catalysis, solvent isotope effects, and the use of oxygen-18 as a tracer. The work produces a keto-enol equilibrium constant for the mandelic acid system, pKE  =  16.19, and also acidity constants of the enol ionizing as an oxygen acid, pKEa  =  6.39, and the keto isomer ionizing as a carbon acid, pKKa  =  22.57. The bearing of these results on the enzyme-catalyzed racemization of mandelic acid is discussed. © 1998 John Wiley & Sons, Ltd.
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    Novel one-pot polymer syntheses based on dithiols obtained from a five-membered cyclic dithiocarbonate and diamines (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1909-1915 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel one-pot syntheses of sulfur-containing polymers from a five-membered cyclic dithiocarbonate (5-phenoxymethyl-1,3-oxathiolane-2-thione (1)) and diamines were examined. Polydisulfides with M̄n 5400 ∼ 15800 were obtained in the oxidation polymerization of dithiols 2, which were obtained in situ by the reactions of 1 and diamines. When 1,12-dodecanediamine was employed, a polydisulfide with relatively high M̄n was obtained, while in the case of m-xylylenediamine, the polymerization was accompanied by intermolecular cyclization to give a polydisulfide with low M̄n. Polythiourethanes with M̄n 6500 ∼ 17200 were obtained in the polyaddition of 2 with 4,4′-methylenebis(phenyl isocyanate). The yields and M̄n values increase with increasing methylene chain length of 2. Polythioethers with M̄n 2600 ∼ 19900 were obtained by the polycondensations of 2 with α,α′-dibromo-p-xylene. The glass transition temperature (Tg) of the polymer decreases with increasing methylene chain length in the main chain.
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    Synthesis of novel oligomeric peroxides via condensation of dihydroperoxides with aromatic diols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1927-1933 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel oligoperoxides α-hydro-ω-hydroperoxyoligo(dioxydimethylmethylene-1,4-phenylene-dimethylmethylene) (BPB) (Tm = 143°C, Td = 176°C), α-hydro-ω-hydroxyoligo(dioxydimethylmethylene-1,4-phenylenedimethylmethylenedioxydimethylmethyleneethy lenedimethylmethylene) (EPB) (Tm = 100°C, Td = 175°C) and α-hydro-ω-hydroperoxyoligo(dimethylmethylene-2,6-naphthylenedimethylmethylene (NPN) (Tm = 137°C, Td = 177°C)), the products of condensation of tertiary diols with tertiary dihydroperoxides, were obtained. The structure of the oligoperoxides was confirmed by spectroscopic methods (IR, NMR). Their thermal properties were studied by differential scanning calorimetry (DSC), and the mechanism of the thermal decomposition of the oligomeric peroxides was proposed basing on the GC-MS analysis of the degradation products.
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    Liquid crystalline thermosets from triaromatic azomethine group containing diepoxides and 4,4′-methylenedianiline (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1935-1938 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Five triaromatic azomethine-linked diepoxides have been cured by reaction with 4,4′-methyl-enedianiline (MDA) in a molar ratio epoxide/amine of 1:1 and 2:1. The influence of the structure of monomers, of the molar ratio epoxide/amine, and of the curing conditions on the formation of liquid crystalline networks was studied. Initially a decrease of the clearing temperature was caused by mixing with the nonmesogenic diamine. The clearing point of the mixture increased with conversion, and thermosets with a liquid crystal order of the monomers were obtained from the 2:1 combinations. Curing occurs in two stages as revealed by DSC: first epoxy/amine reaction occurs, and at higher temperature homopolymerisation of residual oxirane takes place. This is due to non-homogeneous melting of the diepoxides in dynamic curing.
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    Vinylic polymerization of bicyclo[2.2.1]hept-2-ene by Co(II)-catalysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1951-1956 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The vinylic polymerization of bicyclo[2.2.1]hept-2-ene (norbornene) with Co(II) compounds, such as Co(II) stearate, substituted bis(1,3-diketo)cobalt(II), Co(dppe)Cl2, and the metallocene [η5-(C5Me5)Co-η2-Cl]2, in chlorobenzene activated with methylaluminoxane (MAO) is reported. MAO* synthesized by the hydrolysis of trimethylaluminium in chlorobenzene instead of toluene increases the catalytical activity strongly, and a turn over of 2.7 tons of poly(2,3-bicyclo[2.2.1]hept-2-ene) per mol cobalt per hour was achieved. The polymers obtained are amorphous (WAXS). They show weight-average molecular weights up to M̄w = 1.5 · 106 and are soluble in chlorobenzene, 1,2-dichlorobenzene, cyclohexane, and decahydronaphthalene.
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    Influence of batch reaction conditions on norbornene/ethylene copolymers made using C2v- and Cs-symmetric metallocene/MAO catalysts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1939-1942 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The norbornene/ethylene copolymerization was studied using C2v- and Cs-symmetric metallocene catalysts in the presence of methylaluminoxane as a cocatalyst. The batch reactions were carried out at four different temperatures copolymerizing a constant amount of ethylene with the appropriate amount of norbornene. The activity decreases for the Cp2ZrCl2 catalyst and increases to a constant level for the [Ph2C(Flu)(Cp)]ZrCl2 catalyst when the norbornene/ethylene ratio in the reaction increased. The highest activities and the highest norbornene contents in the copolymers were achieved using the [Ph2C(Flu)(Cp)]ZrCl2. The microstructure of the copolymer determined with 13C NMR was observed to depend on catalyst, temperature and monomer ratio. Cp2ZrCl2 produces more norbornene blocks as a function of norbornene content in the copolymer and longer norbornene sequences than [Ph2C(Flu)(Cp)]ZrCl2. The correlation between the increasing norbornene content in the copolymer and the increasing glass transition temperature is more obvious for [Ph2C(Flu)(Cp)]ZrCl2.
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    New azo-dye containing side group copolymethacrylates (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1943-1949 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new type of side group copolymethacrylates was synthesized, characterized and tested with respect to its behavior on irradiation with an Ar+-laser beam. The side groups consist of methylene spacer units with different length and of three-ring mesogens with an ester group between the first and the second aromatic ring and on the other hand of two-ring mesogens with an azo-structure between the aromatic rings, respectively. The azochromophoric structure contains different substituents in the terminal aromatic ring. The homopolymers of the azo-dye containing monomers do not display liquid crystalline (lc) mesophases, but the three-ring mesogens induce lc-phases in opposition to the equimolaric copolymers with two-ring ester group mesogens. The lc phases are important for the stability of the recorded change of birefringence (photorecording process) which is influenced by irradiation of the polymers.
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    Miscibility of functionalized polyolefins with polyamide-6 as detected by solid-state NMR (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1957-1963 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solid-state NMR was used to investigate the miscibility of LLDPE/polyamide-6 blends. Two different blends B1 and B2, obtained with LLDPE only and with LLDPE functionalized with diethyl succinate, respectively, as well as their individual components, were characterized by means of 13C selective techniques. Measurement of 1H spin-lattice relaxation times in both laboratory and rotating frames allowed the miscibility at a molecular level to be investigated for both blends: in B1 the domains of the different components are on average larger than 100-200 Å, whereas in B2, where two different fractions could be separated on the basis of their solubility in heptane, the average linear dimensions of the insoluble fraction are between 20 and 200 Å.
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    Tetrahexylsexithiophene: crystal structure and molecular mechanics calculations (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1973-1979 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis, crystal structure and detatiled molecular mechanics calculations, including crystal packing interactions, of tetrahexylsubstituted sexithienylene are presented. Unexpectedly the molecule, which arranges in the P-1 space group, displays no herringbone arrangement, thienylenic rings are far from coplanarity and the alkylic side chains present different conformations. Molecular mechanics fully accounts for these findings. From crystal packing computations it is derived that different arrangements are unable to lower the packing energy, due to the closeness of two alkyl chains on the same side of the thienylenic backbone, which prevents interspersion of non-parallel molecules.
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    Copolymerization of ethene with 1-hexene or 1-hexadecene over ethylene, dimethylsilylene and 1,4-butanediylsilylene bridged bis(indenyl) and bis(tetrahydroindenyl)zirconium dichlorides (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1965-1972 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ethene was copolymerized with 1-hexene and 1-hexadecene over five different homogeneous methylaluminoxane (MAO) activated racemic ansa-metallocene catalysts in order to study both the influence of the ligand (indenyl and tetrahydroindenyl) and the influence of the interannular bridge (ethylene, dimethylsilylene and 1,4-butanediylsilylene) on the copolymerization behaviour. Hydrogenation of the indenyl ligands was found to decrease comonomer content and molar mass of the copolymers. A similar tendency was observed for the ethylene bridge compared to the silylene bridges. The reasons for this behaviour are discussed and related to structural differences of the catalyst precursors. In addition a segregation fractionation technique was applied to study the chemical composition distribution (CCD) of the produced copolymers. Batchwise feed of comonomer resulted in a broad CCD. More homogeneous copolymers could be produced using partly continuous feed of comonomer.
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    4-[Diphenyl(trimethylsilyl)methyl]benzophenone as initiator in the photopolymerization of methyl methacrylate and styrenePartly presented at the 4th Greek Polymer Chemical Congress, Patras, November 1997, Greece. (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1981-1987 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of methyl methacrylate (MMA) and styrene (St) has been studied using 4-[diphenyl(trimethylsilyl)methyl]benzophenone 1 as photoinitiator. The polymerization follows a free radical mechanism; the polymerization rate increases linearly with the monomer concentration and was found to be proportional to the 0.33 and 1.40 power of the photoinitiator and the monomer (MMA) concentration, respectively. The overall activation energy in the case of MMA photopolymerization was calculated to be 25.0 kJ/mol. From 1H NMR studies it is concluded that the obtained polymers contain two different trimethylsilyl moieties, one at the head and the other at the tail of the polymer chain, showing primary termination reactions even at low initiator concentrations. The p-benzoyltrityl radical 1· is incorporated into the polymer chain to a very small extent, acting as a scavenger. This is also concluded by laser flash photolysis (LFP) and ESR spectroscopy measurements. A “living” character of the polymerization was observed only at very low initiator concentrations. The triplet state (31*) of the initiator was quenched by styrene, reducing its efficiency. The rate constant kq of the quenching process of 31* was measured by LFP (kq = 3.1 · 109 M-1 · S-1). The triplet state and the photodissociation efficiency of the initiator is unaffected by MMA at various concentrations.
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    Reactivity ratios and sequence determination of acrylonitrile/hexyl methacrylate copolymers by one and two dimensional NMR spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2005-2015 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acrylonitrile/hexyl methacrylate copolymers of different monomer composition were prepared by photopolymerization using uranyl ions as photosensitizer. The copolymer composition data were used to calculate the comonomer reactivity ratios according to the Kelen Tüdős (KT) and the error-in-variables model (EVM) method. The reactivity ratios obtained from the EVM method are rA = 0.14 ± 0.03 and rH = 1.32 ± 0.17. The microstructure was obtained in terms of distribution of A and H centred triad sequences from 13C{1H} NMR spectra of the copolymers. The copolymerization mechanism was determined by using Cheng's methodology. It was found that the Markov second order model gave a good fit to the experimental data. The complex and overlapping proton and carbon signals of A/H copolymers were assigned to various compositional and configurational sequences with the help of inverse HETCOR experiments.
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    The effect of temperature on the polymerization of propene with dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. Modeling of kinetics (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1989-2004 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Propene polymerizations were performed using the two ansa-zirconocene catalyst systems dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. The polymerization rate was observed by continuously monitoring the monomer consumption. Reaction rate profiles were obtained in the temperature range from 40°C to 130°C at pressures between 1 and 2.5 bar and catalyst concentrations from 4.6 · 10-6 M to 4.2 · 10-5 M. Isotacticity, as measured by NMR, melting point and molecular weight decreases markedly at higher temperatures. Small amounts of 1,3-inserted monomer (〈1 mol-%) was observed at polymerization temperatures above 80°C. No 2,1-inserted monomer was detected. A kinetic model was developed that describes the polymerization rate for Me2Si(Ind)2ZrCl2 as the catalyst over the entire observed temperature range, and the polymerization rate for Me2Si(2-Me-Ind)2ZrCl2 in a limited temperature range. The model includes an activation reaction, latent sites that may revert to active sites and a permanent deactivation that is second order with respect to the active sites. The activation energy for the propagation reaction was found to be 37 kJ/mol for Me2Si(Ind)2ZrCl2 and 32 kJ/mol for Me2Si(2-Me-Ind)2ZrCl2/MAO. Several kinetic models are compared and discussed.
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    Preparation of poly(lactic acid)-grafted amylose through the trimethylsilyl protection method and its biodegradation (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2017-2022 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Biodegradable poly(lactic acid)-grafted amylose was synthesized using a trimethylsilyl (TMS) protection method. Tetrahydrofuran soluble, mostly trimethylsilyl protected amylose was prepared and reacted with potassium tert-butoxide to give the corresponding alkoxide. Poly(lactic acid)-grafted amyloses were obtained by ring-opening anionic polymerization of lactide using the polymeric alkoxides as initiators and subsequent removal of the TMS groups. The obtained graft copolymers show biodegradability and a microphase-separated morphology.
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    On the multiple melting behavior of polymorphic syndiotactic polystyrene and its behavior in a miscible state (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2041-2049 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Differential scanning calorimetry (DSC) and X-ray diffraction analysis were performed to study the multiple melting behavior and crystal forms of neat syndiotactic polystyrene (s-PS) in comparison with its miscible blends with amorphous atactic polystyrene (a-PS) or poly(2,6-dimethyl-p-phenylene oxide) (PPO). For neat s-PS annealed at 242 to 250°C, three melting peaks of changing intensity were observed (labeled I, II, and III from low to high temperature), while if annealed at high temperatures (254°C or higher) only two melting peaks were left. The missing peak was determined to be Peak-III for s-PS annealed at high temperatures. For the s-PS/a-PS or s-PS/PPO blends, two melting peaks were observed, and the missing peak is Peak-II. The missing Peak-II in the blend systems is attributed to the β-modification. Apparently, the condition of s-PS being compatible with a-PS or PPO is unfavorable for generating the β-modification upon melt crystallization. This study also showed that Peak-I is associated with the β-modification. Peak-III may be associated with the less stable β′ form, which can be transformed to the β form upon annealing at high temperatures. For the s-PS/a-PS or s-PS/PPO blends upon annealing at higher temperatures, Peak-III quickly decreases, leaving only a single melting peak (Peak-I) for the blends. The phenomenon of the decrease of Peak-III crystals in the blend is similar to that for neat s-PS annealed at high temperatures.
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    Rheological behavior of cured acrylate-terminated unsaturated copolyesters (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2029-2039 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The viscoelastic properties of cured acrylate-terminated copolyesters were studied by means of dynamic mechanical analysis. The influence of terminal double bonds, as well as of the cis-trans configuration and distribution along the main chain, on the transition temperatures and rheological properties of the cured polyesters are presented. The presence of double bonds at both chain ends allows the formation of a regular network by crosslinking copolymerization with styrene. The present investigation was carried out on three series of acrylate-terminated copolyesters: poly[(tetramethylene maleate)-co-(tetramethylene phthalate)] (BMPA), poly[(tetramethylene fumarate)-co-(tetramethylene phthalate)] (BFPA) and poly[(tetramethylene phthalate)-co-(tetramethylene succinate)] (BPSA). The results of the mechanical spectrometric analysis are presented as master curves by applying the time-temperature superposition principle. The WLF parameters of the cured unsaturated polyesters were determined above the glass transition temperatures. The glass transition temperatures shift to higher temperatures with increasing degree of crosslinking. The equilibrium shear storage modulus plateau changes as a consequence of the different configuration of the double bonds and the degree of crosslinking. The degree of crosslinking, nc, determined from the equilibrium shear modulus G′e, was higher than those determined from equilibrium swelling measurements, which is apparently connected with the contribution of physical entanglements.
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    Preparation of poly(methyl methacrylate) microspheres modified with amino acid moieties (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2023-2028 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(methyl methacrylate) microspheres [poly(SerMA-co-MMA), poly(AlaMAm-co-MMA), poly(AlaEMA-co-MMA), and poly(AlaMAm/AlaEMA-co-MMA)] modified with O-methacryloyl-L-serine (SerMA), N-methacryloyl-L-alanine (AlaMAm) and L-alanine 2-methacryloyloxyethyl ester (AlaEMA) were prepared by the emulsifier-free emulsion copolymerization of methyl methacrylate (MMA) with SerMA, AlaMAm and AlaEMA, respectively, initiated with 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (ABIP). The series of polymer microspheres showed unimodal distribution of the particle size (290-800 nm) in water. From X-ray photoelectron spectroscopy it was concluded that the amino acid moieties are located on the surface of the particles in all cases. Poly(SerMA-co-MMA) showed the most effective suppression of adsorption of proteins such as albumin (Alb), γ-globulin (Glo) and fibrinogen (Fib) among the examined poly(methylmethacrylate) microspheres.
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    Thermotropic liquid crystalline poly(vinyl ether)s with pendant cellobiose residues: Synthesis and mesophase structure (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2071-2077 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This study concerns the synthesis of poly(vinyl ether)s (VEs) carrying pendant cellobiose heptadecanoate (CHD) residues and their mesomorphic properties examined by DSC, polarization microscopy and X-ray diffraction. The poly(VE)s were synthesized through cationic polymerization of a CHD-substituted VE, i.e., 10-(vinyloxy)decyl-2,2′,3,3′,4′,6,6′-hepta-O-decanoyl-β-D-cellobioside. From X-ray diffraction analyses, the mesophase of the poly(VE) proved to be closely similar to that of the star-shaped triplet derivative. The mesophase is characterized by the following features; (i) it consists of discotic columns built up by a regular stacking of the pendant CHD residues, (ii) each polymer main chain is presumed to have an extended conformation due to the periodic stacking of the pendant CHD moieties into a columnar structure, and (iii) each polymer molecule independently forms three discotic columns, which surround the main chain, without any intercalation of the CHD pendants originating from different polymer molecules.
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    Effects of mixed surfactants on the styrene miniemulsion polymerization in the presence of an alkyl methacrylate (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2051-2061 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the mixed surfactants sodium dodecyl sulfate (SDS) and nonylphenol polyethoxylate with an average of 40 ethylene oxide units per molecule (NP-40) on the styrene (ST) miniemulsion polymerization in the presence of dodecyl methacrylate (DMA) and stearyl methacrylate (SMA) was investigated. Both Ostwald ripening and creaming could not be neglected for the miniemulsions stabilized by SDS/NP-40 in combination with DMA upon aging at 35°C, whereas no appreciable Ostwald ripening and creaming were detected for the SMA containing miniemulsions. For both the DMA and SMA containing polymerizations at 80°C, the rate of polymerization (Rp) decreases with increasing NP-40 concentration ([NP-40]). Incorporation of a small quantity of the extremely water-insoluble blue dye into the reaction system was applied to probe the particle nucleation loci. For the DMA containing polymerizations with [NP-40] = 0, 1.25, and 2.50 mM and the SMA polymerization with [NP-40] = 0 mM, homogeneous or micellar nucleation can not be ignored. On the other hand, the more hydrophobic SMA in combination with SDS/NP-40 effectively retards the particle nucleation occurring in the aqueous or micellar phase.
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    Crystallization kinetics and melting behavior of poly(butylene adipate), poly(butylene isophthalate) and their copolymers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2063-2070 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melting behavior and the isothermal crystallization kinetics of poly(butylene adipate), poly(butylene isophthalate) and their random copolymers were investigated by means of differential scanning calorimetry. Multiple endotherms, commonly observed on the melting polyesters, were found to be influenced by crystallization temperature and composition. By applying the Hoffman-Weeks method to the isothermally crystallized samples, the equilibrium melting temperatures of the homopolymers were obtained. From calorimetric results on samples with different degree of crystallinity, the equilibrium melting enthalpy of poly(butylene isophthalate) was calculated and the presence of a crystal-amorphous interphase in copolymers was evidenced. Isothermal melt crystallization kinetics was analyzed according to the Avrami equation. As expected, the introduction of a comonomer was found to decrease the overall crystallization rate of the polymers. Values of Avrami exponent close to three were obtained for all the samples, independently of composition and crystallization temperature, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. In the case of poly(butylene isophthalate), the dependence of the rate of crystallization on Tc shows a maximum at an undercooling of approximately 60°C.
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    Preparation, properties and biodegradation of stereoregular copolymers of (R,S)-3-butyrolactone and 4-butyrolactone (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2079-2085 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers obtained from the copolymerization of (R,S)-3-butyrolactone ((R,S)-3-BL) and 4-butyrolactone (4-BL) catalyzed by isobutylaluminoxane were compared in structure and properties to copolymers having the same types of repeating units produced by Alcaligenes eutrophus when grown with an appropriate substrate or substrate or substrate mixtures. Copolymers with 4-BL contents up to 33 mol-% were prepared and characterized by 1H NMR, 13C NMR, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The copolymers had a sequence distribution of 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB) units which were non-random in that very few, if any, sequences of more than two successive 4-HB units were present. The 3-HB units are believed to be separated into isotactic (R) and (S) blocks, but thermal analysis by DSC showed that both the glass transition temperatures and melting temperatures decreased in a regular manner with increasing contents of 4-HB units. Number average molecular weights of the copolymers (Mn) ranged from 7000 to 15000. Biodegradation tests with a bacterial hydrolase showed that the biodegradation rates increased with increasing contents of 4-HB units, as is the case for the equivalent bacterial copolymers.
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    Preparation of side-chain liquid-crystalline polymers via pyridylphenol hydrogen bonding (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2101-2105 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of side-chain liquid-crystalline polymers via pyridyl-phenol hydrogen bonding complexation was prepared by using non-liquid-crystalline precursors, such as poly[(4-vinylpyridine)-co-(butyl acrylate)] and 4-(4′-nitrophenylazo)phenol, 4-(4′-methoxyphenylazo)phenol or 4-(phenylazo)phenol. The association by hydrogen bonding was confirmed by means of FTIR. While the hydrogen bonds are weakened, and some dissociation occurs at the isotropization temperature, complete dissociation needs much higher temperature. The hydrogen bonds re-form as the complex is cooled to room temperature. The nematic liquid crystallinity of the polymer complexes was shown by means of wide-angle X-ray diffraction (WXRD) and polarized optical microscopy (POM). The different substitution groups of azophenol give isotropization temperatures of the polymer complexes in the following sequence: —NO2 〉 —H 〉 —OCH3.
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    Tailored rigid-flexible block copolymers, 4Part 3: cf. ref.3. Synthesis and properties of diblocks of poly(p-benzamide) and poly(m-benzamide) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2087-2094 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers were prepared by the condensation of rigid benzoyl-terminated poly(p-benzamide) and flexible anilino-terminated poly(m-benzamide) prepolymers. The use of two monomers of the AB type and of end-capped prepolymers resulted in the formation of diblock molecules uncontaminated by triblock or multiblock sequences. Moreover, selective extraction techniques in N,N-dimethylacetamide (DMAc) with varying amounts of LiCl resulted in the complete elimination of unreacted prepolymers, as evidenced from material balance and 1H NMR data. The above extraction technique also allowed a fractionation of the copolymers in terms of their rigid/flexible compositional distribution ratio. The molecular weight-intrinsic viscosity dependence of poly(m-benzamide) determined in a nonaggregating solvent using light scattering yielded a persistence length of 8 Å, suggesting a relatively large chain flexibility. A tailored copolymer with a fraction β of flexible residues = 0.70 was fractionated, determining the solubility, the viscosity, and the critical composition for mesophase formation in DMAc/LiCl and in 96% H2SO4 solutions. The results, in line with those previously reported for a related system, reveal that the addition of the flexible segment has a little effect on the critical concentration of poly(p-benzamide), whereas the biphasic gap is strongly reduced. Moreover, the solubility of the copolymer is substantially increased over that of the rigid homopolymer. The net result is an unexpected widening of the range of stability of the pure mesophase, with significant implications from both a fundamental and an applied standpoint.
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    Synthesis and characterization of a new polymer containing an electron accepting perfluoro group (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2107-2112 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly{oxy-4,4′-octafluorobiphenylyleneoxy-alt-[1,4-phenylenevinylene(3-trimethylsilyl-1,4-phenylene)vinylene-1,4-phenylene]} (PFSi) was synthesized and characterized to investigate its thermal, optical, electrical and xerographic properties. An LED (light emitting device) using PFSi as the light emitting layer exhibits maximum emission for blue light, but a high turn-on voltage. The origin of the low device performance was examined by investigating the photoconducting behavior. PFSi shows a high photoconductivity in the presence of electron acceptors such as 5-nitroanthranilonitrile (5NAN), and the photoconductivity of PFSi is improved by introducing charge transport materials such as triphenylamine (TPA).
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    Synthesis and phase behavior of side-chain liquid crystalline polymers with pendant quinoline rings bearing either a polar or a non-polar end group (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2095-2099 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Four methacrylate monomers, 2a-2d, containing a quinoline ring with a NO2 or a OCH3 group at the end of the mesogen were synthesized and polymerized. The copolymers with six methylene units as spacer, 3b-3d, showed a smectic phase induced by electron donor-acceptor interactions of the side groups. The homopolymer with eleven methylene units as spacer and methoxy end group, 3f, showed a smectic phase induced by the large length of the spacer. The copolymers with eleven methylene units, 3g-3i, showed a smectic phase induced by both the electron donor-acceptor interactions of the side groups and the large length of the spacer.
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    Molecular character of sharkskin phenomenon in metallocene linear low density polyethylenes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2113-2118 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of molecular weight on sharkskin dynamics is systematically studied using three metallocene-catalyzed linear low density polyethylenes (mLLDPE) of different molecular weights. A new experimental method is developed to enable in-situ characterization of the time scale τ on which sharkskin forms on the extrudate. This laser scattering technique directly measures the periodic variation of the refracted light of the rough sharkskin-like extrudate surface. It is found that τ increases with molecular weight as strongly as the overall molecular chain relaxation time, τ*, determined from oscillatory shear measurements. The observed molecular weight dependence provides additional support for the recently proposed interfacial stress growth/relaxation mechanism for sharkskin formation.
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    Synthesis and properties of poly(dimethyldiphenylsilylenemethylene) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2119-2127 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The novel polycarbosilane poly(dimethyldiphenylsilylenemethylene) (PDMDPSM) (2) was prepared by H2PtCl6-catalyzed ring-opening polymerization (ROP) of 1,1-dimethyl-3,3-diphenyl-1,3-disilacyclobutane (1). Polymerization in bulk at elevated temperature afforded high molecular weight PDMDPSM (Mw = 577000) with monomodal molecular weight distribution and regularly alternating SiR2/CH2 backbone structure. NMR spectroscopy revealed that a minor fraction of the monomer units is incorporated irregularly during polymerization in bulk, leading to structural units of the type —SiPh2—CH2—SiPh2— and —SiMe2—CH2—SiMe2—. The amount of regularly alternating dimethyl- and diphenylsilylenemethylene units increases when the polymerization is performed in solution at lower temperatures. PDMDPSM shows a glass transition temperature (Tg) at 50°C, which lies between the TgS of poly(methylphenylsilylenemethylene) (PMPSM) and poly(diphenylsilylenemethylene) (PDPSM), demonstrating the stiffening effect of the SiPh2 groups. Thermogravimetric analysis (TGA) evidenced nearly identical thermal stability of PDMDPSM and PMPSM.
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    Supramolecular structures of poly(p-phenylenes) with oxyethylene side chains and their mixtures with lithium salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2129-2140 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of poly(p-phenylenes) with linear and branched oxyethylene side chains was synthesized. Microphase separation in the solid state causes polymers with linear side chains to form supramolecular structures, which consist of main chain layers separated by an amorphous side chain matrix. If mixed with lithium salts such as lithium triflate (LiOTf) or lithium bis(trifluoromethanesulfone)imide (LiNTf), the polymers form solid solutions. The experimental data suggest that the layered structures undergo a one-dimensional swelling in the direction perpendicular to the main chain layers when blended with LiOTf and that this salt is only incorporated into the side chain matrix. The observed melting point depression in polymer-LiNTf mixtures is explained by the assumption that the salt species are incorporated both into the side chain and the main chain microphase.
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    Dielectric relaxation and relationships of local molecular mobility in linear and comb-like thermotropic polymers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2147-2152 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric behavior of several thermotropic linear and comb-like polymers with flexible spacers and mesogenic fragments with different structure has been studied in a frequency range from 60 Hz to 1 MHz in the bulk state (below the glass transition temperature). Two regions of dipole relaxation caused by local mobility were detected. It was shown that the relaxation parameters of the first process virtually do not change with increasing spacer length and have similar values in polymers with different structure. In the case of the second process, in increase in spacer length considerably increases the mobility of kinetic elements.
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    Sequential reordering in condensation polymers, 5Parts 1-4: refs.4-7. Preparation and characterization of copolymers via transesterification of a polycaprolactonepoly(2,2-dimethyltrimethylene carbonate) blend (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2153-2164 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A blend of polycaprolactone (PCL) and poly(2,2-dimethyltrimethylene carbonate) (PDTC) containing catalytic amounts of dibutyltin dimethoxide was prepared from solution. The blend was then subjected to melt-mixing at 200°C and samples were taken after different times. According to thermal analysis data, with the increase of reaction time a gradual loss of the crystallizability of the blend components is observed, and after 70 min at 200°C the system becomes completely amorphous. 13C NMR data suggest that the loss of crystallizability of the blend is accompanied by an abrupt decrease in PCL and PDTC sequence lengths reaching after 70 min at 200°C an average length of about two repeating units each. These effects are explained by transesterification reactions between the lactone and carbonate units.
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    Crystallization kinetics and morphology of poly(ferrocenyldimethylsilane) (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2141-2145 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of poly(ferrocenyldimethylsilanes) were prepared via anionic ring-opening polymerization. The isothermal crystallization kinetics were investigated by means of differential scanning calorimetry and analyzed in terms of the Avrami equation. The value of the Avrami exponent is approximately 3 for the majority of samples and crystallization temperatures. This suggests a three-dimensional spherulitic growth and an instantaneous nucleation mechanism. The morphology of melt-crystallized samples was studied by atomic force microscopy. Hedrites (immature spherulites) were formed at low undercoolings whereas at high levels of undercooling mature, well developed spherulites were observed with small hedritic features in their center. The melting enthalpy for a 100% crystalline polymer was estimated to be 36 J/g from differential scanning calorimetry and X-ray diffraction data obtained by using specimens with different degrees of crystallinity.
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    Reactive polymers incorporating silyl enol ether groups, 3Part 2: cf. ref.1. Incorporation of α,β-bis(siloxy)vinylene units into the backbone of vinyl polymers by free-radical (co)polymerization of 2,3-bis(trialkylsiloxy)butadienes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2173-2178 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2,3-Bis(trimethylsiloxy)butadiene (1) and 2,3-bis(tert-butyldimethylsiloxy)butadiene (2) have been homopolymerized and copolymerized with styrene (St) and methyl methacrylate (MMA) under freeradical conditions. Comparison of initial rates and molecular weights with polymerizations conducted under identical experimental conditions on monosubstituted analogs, 2-trimethysiloxybutadiene (3) and 2-(tert-butyldimethylsiloxy)butadiene (4), demonstrated that the second substituent does not decrease the polymerizability significantly despite the additional steric hindrance introduced in the monomer. Extensive 1H and 13C NMR characterization of the polymers demonstrated that the main incorporation mode is of the 1,4-type, allowing more than 95% of the butadienyl subunit to be incorporated in the main chain as an α,β-bis(trialkylsiloxy)vinylene functional group. Monomer reactivity ratios r1 and r2 at 60°C were determined from copolymer composition curves obtained at low conversions and are compared with values obtained for other 1,2-butadienyl systems.
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    Radical polyaddition-isomerization of bifunctional vinylcyclopropanes with dithiols (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2165-2172 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Synthesis and radical polyaddition-isomerization of novel bifunctional vinylcyclopropane derivatives, 1,4-xylylene bis(2-isopropenyl-2-methylcyclopropanecarboxylate) (1a), ethylene bis(2-isopropenyl-2-methylcyclopropanecarboxylamide) (1b), and bis(2-isopropenyl-2-methylcyclopropanemethyl) terephthalate (1c) with dithiols were carried out. Polymers with molecular weights and polydispersities of 1100-11000 and 1.18-7.35, respectively, were obtained. The radical polyadditions of 1a with dithiols afford polymers containing a homopolymer of 1a, while those of 1b and 1c with dithiols afford polymers with a content of dithiol units of exactly 50 mol-%.
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    Ge- and sn-containing poly(p-xylylene): synthesis, structure and thermal behavior (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2179-2184 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Block copolymers of unsubstituted poly(p-xylylene)(PPX) and Ge- or Sn-organic bridged PPX (GePPX and SnPPX) were prepared by pyrolysis of specially synthesized organometallic p-cyclophane precursors followed by deposition and polymerization of the thus produced p-xylylene monomers. The copolymer structure and thermal behavior were investigated depending on deposition temperature (10 and -196°C). The copolymer PPX-GePPX obtained from solid monomers deposited at -196°C (2a) consists of long quasi-independent PPX and GePPX blocks and has paracrystalline structure. Thermal treatment of 2a near 160°C yields crystalline regions of PPX along with paracrystalline aggregates of GePPX. Pyrolysis of this system near 300°C in an inert atmosphere results in the formation of Ge crystals in PPX matrix. In contrast, the copolymer PPX-GePPX produced by simultaneous deposition and polymerization at 10°C (2a′) contains shorter blocks of PPX and GePPX than the copolymer deposited at -196°C. Copolymer 2a′ turns to the amorphous state during thermal treatment, and its pyrolysis does not lead to Ge-crystal formation; hence the supramolecular structure of the polymer plays an important role in inorganic phase formation. The copolymer PPX-SnPPX (2b) is formed only at a deposition temperature of -196°C; deposition at 10°C yields oligomeric resins. The structure of 2b is nearly the same as that of 2a; pyrolysis of 2b in air results in SnO2-crystal formation in a PPX matrix.
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    PVC modification with pyridine groups. Synthesis, characterization and transformation to ionomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2199-2204 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification of PVC with 4-mercaptopyridine is described. The content of pyridine groups in the products is measured by NMR and IR spectroscopy. The degree of modification depends on the reaction conditions, and values of up to 70% are achieved without degradation or other appreciable side reactions. The tertiary amino groups in the polymer can be alkylated with iodides of varying chain length to form quantitatively quaternary pyridinium salt groups, leading to PVC ionomers and polyelectrolytes.
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    Free radical polymerization of a sugar residue-carrying styryl monomer with a lipophilic alkoxyamine initiator: synthesis of a well-defined novel glycolipid (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2193-2197 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Controlled free radical polymerization of N-p-vinylbenzyl-2,3,5,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-D-gluconamide (Ac-VLA) was achieved by the nitroxide-mediated free radical polymerization with a lipophilic alkoxyamine “initiator” with a dioctadecyl group in 1,2-dichloroethane at 90°C. The polymerization proceeds in a “living” fashion, providing Ac-VLA polymers with low polydispersity. The hydrolysis of the polymers results in well-defined glycopolymer-carrying amphiphiles, viz., artificial “glycolipids”.
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    Synthesis of a diphenylethylene derivative carrying aromatic tertiary amine groups and its use in chain end functionalization of alkyllithium-initiated polymerizations (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2185-2191 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1,1-Bis[(4-dimethylamino)phenyl]ethylene was successfully synthesized through the ‘Wittigtype’ reaction of 4,4′-bis(dimethylamino)benzophenone with the ‘Tebbe’ reagent. The methylenation yields were over 80 wt.-% on the basis of the initial amount of benzophenone derivative used. Terminally functionalized polymers having aromatic tertiary amine groups at one end or at both ends were prepared by the crossover reactions of n-butyllithium (n-BuLi), poly(styryl)lithium (PSLi), and poly(isoprenyl)lithium (PILi) with the diphenylethylene analogue. The functionalization yields were over 87 mol.-% based on the results of 1H NMR spectroscopic analysis. The number-average molecular weights of the polymers based on the ratio [gram of monomer]/[mole of initiator] are in good accordance with those observed from size exclusion chromatographic and 1H NMR spectroscopic analysis (3,0 × 103 ∼ 7,5 × 103 g/mol).
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    Restriction of mobility in model liquid crystalline ionomers (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2205-2210 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Model liquid crystalline ionomers have been analyzed by SAXS both in bulk and in toluene solution. These compounds are referred to as liquid crystalline halatosemitelechelic polystyrenes (LC HSTP's) and consist of low molecular weight polystyrene chains end-capped at one end by a sulfonate group associated to a mesogenic counterion. The results are in agreement with a microphase separation between the polymer chain and the mesogenic counterion. The main characteristic feature of the SAXS profile for the bulk material is the so-called ionic peak, whose position obeys a general law which is in favor of a rod-like organization of the multiplets and which shows that the polymer chains are stretched in the very close vicinity of the mesogenic core, in agreement with the Eisenberg, Hird and Moore model for ionomers. The thickness of this region of restricted mobility has been estimated to 1 nm, which is the order of magnitude of the persistence length of polystyrene. This very local restriction in mobility persists in toluene solution, in contrast to what is observed for the ω-Li-sulfonato-polystyrene precursors. The results also agree with an isotropic distribution of the multiplets in toluene.
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    Polymerization and asymmetric oligomerization of allylsilanes using chiral ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium and -hafnium complexes (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2211-2215 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Stereospecific polymerization and asymmetric oligomerization of allylsilanes were investigated by using C2- and Cs- symmetric zirconocene catalysts. Isotactic and syndiotactic poly(allylsilane)s were produced with rac-ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride (1) and diphenylmethylene(η5-cyclopentadienyl)(η5-fluorenyl)zirconium dichloride (6), respectively. Bulky allylsilanes afforded optically active oligomers in the reactions using optically active ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium and -hafnium complexes.
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    Microhardness under strain, 4. Reversible microhardness in polyblock thermoplastic elastomers with poly(butylene terephthalate) as hard segments (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2217-2220 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The microhardness (H) technique was recently applied to poly(butylene terephthalate) (PBT) and its multiblock copolymers for examination of the stress-induced polymorphic transition. Following these investigations the present study attempts to observe the reversible variation of microhardness under strain. For this purpose bristles of drawn and annealed (at 160°C in vacuum) poly(ether ester) (PEE) were characterized with respect to their microhardness at various stages of tensile deformation. H was measured under and after loading (σ) in deformation steps of 5% each. In accordance with previous results on PBT and PEE, H values at σ ≠ 0 show a sharp drop (by 40%) in a relatively narrow deformation interval (ε = 10-15%), owing to the stress-induced α ⇔ β polymorphic transition. The hardness measurements at σ = 0 show a continuous decrease of H with a remaining strain. H values at σ = 0, corresponding to plastic deformation up to 5%, are much higher than the corresponding ones taken under stress at an overall deformation between 10 and 25%. The higher H values are explained by the regeneration of the starting α modification. Results reveal that in materials characterized by high and reversible deformability it is possible to observe a reversible microhardness behaviour, provided the strain-induced structural changes are reversible.
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    Living ring-opening isomerization polymerization of 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole with sulfonate initiators (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2237-2246 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The cationic ring-opening isomerization polymerization of a bicyclic pseudourea, 2,3,5,6-tetra-hydroimidazo[2,1-b][1,3]oxazole (1), was examined. The polymerization of 1 with methyl trifluoromethane-sulfonate or p-toluenesulfonate proceeds even at -40°C and gives poly(1,3-oxazolidin-2-one-1,3-diylethylene) (2) in high yield. Postpolymerization experiments revealed that the present polymerization proceeds in a “living” fashion. The mechanism of the polymerization was determined from in situ 1H NMR measurements as well as kinetic analysis, which proved that the polymerization proceeds via ionic propagating species, although the apparent propagating species in the polymerization with methyl p-toluenesulfonate is covalent.
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    Radiation-induced radical formation and crosslinking in aqueous solutions of N-isopropylacrylamide (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2229-2235 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To investigate chain-initiating and crosslinking mechanisms, radical formation in dilute aqueous solutions of N-isopropylacrylamide (NIPAAm) and poly-NIPAAM was studied using electron pulse radiolysis with optical detection at room temperature. Several transients of NIPAAm generated by reactions with electrons, hydroxyl radicals and hydrogen atoms were observed. Electron attachment to the carboxyl group (ke = 9.0 x 109 dm3 · mol-1 · s-1) forms the radical anion, which undergoes fast and reversible protonation (pKa = 7.8) at the carboxyl oxygen. At pH 〉 pKa, slow and irreversible protonation of the electron adduct at the vinyl group leads to the α-carboxyalkyl radical CH3(.CH)CONHCH(CH3)2, which is also formed by addition of H atoms to NIPAAm (kH = 7.3 × 109 dm3 · mol-1 · s-1). Addition of OH radicals (kOH = 5.4 × 109 dm3 · mol-1 · s-1) forms CH2(OH)(.CH)CONHCH(CH3)2. Hydrogen abstraction was not observed in the case of NIPAAm monomer, but it was found for the reaction of OH radicals with thermally polymerized NIPAAm. Semi-empirical quantum chemical calculations support the assignment of the observed spectra to the radicals. A reaction mechanism for the formation of crosslinks is discussed.
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    Homopolymerization and copolymerization of styrene and norbornene with Ni-based/MAO catalysts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2221-2227 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The homopolymerization of styrene (Sty) and norbornene (NBE) was investigated in the presence of the nickel stearate (NiSt)/methylaluminoxane (MAO) catalytic system in toluene and in chlorobenzene at 20°C. The fully saturated structure of polynorbornene indicates that the two monomers polymerize by an ethylenic type addition reaction. The synthesis of true copolymers shows that one type of active species is operating for the tow monomers. Determination of reactivity ratios (rNBE = 20.8 and rSty = 0.02) indicates a much higher reactivity of NBE, which is interpreted by a coordination mechanism. The styrene-norbornene copolymers exhibit glass transition temperatures (Tg) which range from 100°C to 320°C and follow Kovacs' law. The absence of crystallinity and the homogeneous repartition of monomer units along the chains yield highly transparent materials of high thermal stability.
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    Methacrylate networks containing chiral calamitic liquid crystalline side groups (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2247-2254 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A one-step copolymerization of ferroelectric methacrylate monomers leading to networks is presented. Oriented networks are obtained and electro-optical investigations are described. Smectic C* and another smectic phase are found in slightly crosslinked networks. For higher crosslinking densities, only the high temperature smectic C* phase was found. Electro-optical measurements were performed on the networks, and significant changes in the ferroelectrical properties were found. For crosslinking densities higher than 0.5 mol-%, switching times increased dramatically and the spontaneous polarization decreased. Networks with crosslinking densities of 2 mol-% did not exhibit ferroelectric properties.
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    Reactive groups on polymer coated electrodes, 8. Novel conducting polymer interfaces produced by electrochemical copolymerization of functionalized thiophene activated esters with 3-methylthiophene (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2255-2266 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: With the synthesis of two new functionalized thiophene activated esters and their electrocopolymerization with 3-methylthiophene, two types of redox active polymers have been prepared. FTIR studies of the resultant polymers reveal that both types of activated ester groups withstand the applied electrooxidative conditions and are correctly integrated into the corresponding polymers. The electrocopolymerization experiments show that the composition of the obtained polymers strongly depends on the ratio of the components in the reaction medium. With the increase of the ratios of pentafluorophenyl thiophene-3-acetate-3-methylthiophene or succinimido thiophene-3-acetate/3-methylthiophene, a higher concentration of functionalized thiophene units is incorporated into the polymer chains. The measurement of the conductivity on these polymeric films gave a value in the range of 10-3 to 10-2 S · cm-1, which is comparable to that of the unsubstituted polythiophene and consistent with the conjugation grade suggested by electrochemical and UV-vis spectroscopic data. As expected, the pendant reactive ester groups on the electrode surfaces react rapidly with different amino compounds without loss of the electroactivity of the polymers. Therefore, these novel polymeric materials can be used as electrode interfaces for further functionalizations, especially for the immobilization of amines, peptides, and enzymes.
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    A novel modification of poly(L-lysine) leading to a soluble cationic polymer with reduced toxicity and with potential as a transfection agent (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2565-2575 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chemical modification of poly(L-lysine) by hydrogen transfer addition of N,N-dimethylacrylamide to the primary amino groups results in new water soluble derivatives with reduced cell toxicity which maintain basic properties. Kinetic studies on the addition reaction were performed using model compounds, and a reliable kinetic model was obtained which proved to be valuable also in the case of poly(L-lysine). A peculiar feature of the addition reaction of poly(L-lysine) on N,N-dimethylacrylamide is that, starting from partially protonated poly(L-lysine), the reaction stops after that all the unprotonated units originally present have reacted. Toxicological studies on modified poly(L-lysine) in comparsion with parent poly(L-lysine) showed that the modifying reaction leads to a reduction in toxicity.
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    Synthesis, characterization and hydrolysis of poly[styrene-co-(6-methylene-1,4-oxathiepane-7-one)] and poly[styrene-co-(6-methylene-5-methyl-1,4-oxathiepane-7-one)] (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2577-2582 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Vinylic-type polymers bearing ester groups inside the polymer backbone have been synthesized by free radical copolymerization of styrene (St) and 6-methylene-1,4-oxathiepane-7-one (MOTPO) or 6-methylene-5-methyl-1,4-oxathiepane-7-one (MMOTPO). The addition-fragmentation ring-opening polymerization of both MOTPO and MMOTPO leads to the formation of ester linkages located inside the vinylic polymer backbone. A strong decrease of the molar mass of the copolymer has been observed when the copolymers were dissolved in a mixture of THF and water in the presence of sodium hydroxide. This decrease can be attributed to the hydrolysis of the ester linkages, as followed by size exclusion chromatography (SEC). The molar mass of the degraded polymer samples was correlated with the number of ester linkages in the backbone, showing that only a fraction of these ester groups have been hydrolyzed.
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    Unique morphologies found in freeze-dried poly(ethylene oxide) prepared from dilute solutions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2597-2600 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Freeze-dried particles of poly(ethylene oxide) (PEO) were prepared from sublimation of a 1 × 10-2 wt.-% solution of PEO in benzene in an ice-salt bath. After isothermal crystallization at 318.2 ± 0.1 K for 2 h, an unusual planar zigzag form of PEO was found. A variety of unique spherulite-like morphologies were also observed, and their formation is discussed on the basis of the interaction between solvent molecules and segment of the polymer chains.
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    Effect of filler on kinetics and energy of activation of phase separation in poly(methyl methacrylate)/poly(vinyl acetate) blend (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2609-2612 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of a filler on the rate and energy of activation of phase separation was studied for binary poly(methyl methacrylate)/poly(vinyl acetate) blends (system with LCST) using light scattering. It was found that the rate of phase separation of the filled blends at close quench depth ΔT = T-Ts is much lower as compared with the unfilled one at close quench depth. The activation energy for the filled blends is lower than that of unfilled blends. The drop of the rate of phase separation and of the activation energy in filled systems is explained by the formation of a border layer at the interface with solid where molecular packing is less dense and molecular mobility is restricted in comparison with unfilled polymer. Equal rates of phase separation or the equilibrium state may be achieved at higher quench depth for the filled blend.
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    Reduction of the cationic growing center of polyisobutylene by activated magnesium. Block copolymerization of isobutylene with tert-butyl methacrylate (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2619-2623 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transformation of the tert-chlorine end group of poly(isobutylene) into a terminal Grignard group was studied with the motivation of producing a PIB macroanion. The reduction of the terminal tert-chlorine group was completed within 30 min at room temperature by using activated magnesium (Mg*) prepared by the reaction of MgCl2 with lithium naphthalenide. The efficiency of the transformation was 28%, which was determined by end-group analysis of the polymer obtained after quenching the reduction with methyl 2-phenylacetate in the presence of CeCl3. The terminal carbanion prepared by this method initiated the polymerization of tert-butyl methacrylate (TBMA) to give a block copolymer consisting of an anionically and a cationically polymerizable monomer.
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    The characterization of the interfacial reaction in polyamide 1010/poly(propylene)-graft-(glycidyl methacrylate) blends (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2631-2634 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Binary blends of polyamide 1010/poly(propylene) and polyamide 1010 (PA1010)/poly(propylene)-graft-(glycidyl methacrylate) (PP-g-GMA) were prepared. The epoxy groups in PP-g-GMA react with the amino end-groups in PA1010, thus a PA1010-graft-PP copolymer is formed and acts as a compatibilizer between PA1010 and PP-g-GMA. The reaction was confirmed by electron spectroscopy for chemical analysis (ESCA) and attenuated total reflection (ATR)-FTIR spectroscopic analysis, and also evaluated by the stability of the suspension obtained by dissolving the blends in formic acid and by the morphologies of the blends.
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    Structure-property relationships of core-shell type waterborne polyacrylate-polyurethane microemulsions (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2635-2640 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Different cross-linking types of core-shell types waterborne polyacrylate-polyurethane (PAC-PU) microemulsions, in which polyurethane acts as the shell of the latex particles and a copolymer of acrylate monomers as the core, were synthesized. In the anionic polyurethane film. there is a certain degree of softhard phase mixing and different extents of short-range order of the hard segments. The introduction of a polyacrylate core increases the soft-hard phase separation in the polyurethane and breaks the short-range order of the hard segments in polyurethane to some extent. The hard segments in the shell and the core cause a widened tan δ peak. This peak shifts to higher frequencies as the core-shell ratio increases and also when a Type A or Type B cross-linking structures exist. The cross-linking structure, especially Type B, improves the soft-hard separation and the phase mixing of the core and the hard segments in the shell and at the same time breaks the short-range order in the hard segments. The cross-linking structure does not affect the thermogravimetric properties of the PAC-PU films.
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    An approach to hyperbranched polymers with a degree of branching of 100%Dedicated to the memory of Prof. Dr. Reimund Stadler (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2655-2664 
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    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: General guidelines for the design of monomers for the synthesis of hyperbranched polymers without linear units are presented. The synthesis of one monomer fulfilling these requirements and the first results of the polymerization of this monomer are described. 4-(3-Maleimidopropoxy)-4′-methoxybenzaldehyde azine was used as a monomer of the AB2-type in a “criss-cross” cycloaddition with the maleimide group as A-function and the azine as two B-groups. Melt condensation of this monomer gave a polymer (Mn = 5700) which showed 1H and 13C NMR spectra corresponding well to the expected completely branched structure.
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    Swelling behavior of polyelectrolyte gels in the presence of salts (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2665-2670 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling behavior of weakly crosslinked polyelectrolyte gels based on sodium methacrylate (PMA) and diallyldimethylammonium chloride (DADMAC) in aqueous medium was studied in the presence of different types of salts (NaCl, arginine hydrochloride, cetylpyridinium chloride (CPC), sodium dodecyl sulfate (SDS), and sodium dodecylbenzenesulfonate (SDBS)). It is shown that, starting from some characteristic concentration of a salt, a further increase of the salt concentration results in the shrinking of the gels. This characteristic concentration is defined by the gel parameters (polymer concentration in the gel that is a function of the monomer concentration at the conditions of hydrogel synthesis) and does not depend on the kind of salt used, except for the system polyelectrolyte gel/oppositely charged surfactant (PMA-CPC and DADMAC-SDS or SDBS). It is shown that the initial rate of gel shrinking for all studied systems, including the system gel/oppositely charged surfactant, is determined by the salt concentration and the gel parameters. For the systems PMA-CPC and DADMAC-SDS the gel collapse is a two-step process.
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    Ni(acac)2-DAD/MAO: A new catalytic system for ethylene polymerization (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2677-2681 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The halide-free combination of Ni(acac)2 and DAD(diazadiene, ArN=CH—CH=NAr, where Ar = 2,6-C6H3(i-Pr)2) is active for ethylene polymerization in the presence of methylaluminoxane (MAO). The performance of this new catalytic system was evaluated with respect to activity and polymer structure. The degree of branching of the obtained polyethylenes is substantially influenced by the polymerization conditions. The activation mechanism was investigated by 1H NMR. MAO is proposed to participate in the ligand exchange process.
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