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  • Physics  (9)
  • Calculations, ab initio  (3)
  • Wiley-Blackwell  (12)
  • Blackwell Publishing Ltd
  • 1
    Electronic Resource
    Electronic Resource
    Compositional and molecular weight analysis of polyether macromonomers by chromatographic techniques (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3795-3804 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper critically examines the scope and limitations of state-of-the-art chromatographic techniques (GPC, GC, HPLC) for separating and analyzing the composition, molecular weight, and molecular weight distribution of acrylate and styrene based polyether macromonomers. Of the three chromatrographic techniques investigated, HPLC is found to be the most useful technique for macromonomer analysis, being applicable over a wide molecular weight range and having favorable selectivities towards the many macromonomer components. Macromonomer purity, n-mer distribution, and molecular weight can be derived from a single chromatographic run. In addition, conformational information can be obtained.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170221217
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  • 2
    Electronic Resource
    Electronic Resource
    The Structures of [X2Y—N—YX2]+ Cations (X = F, Cl; Y = S, Se). A Comparison of X-ray and ab Initio Studies[1] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 35-40 
    Details
    ISSN: 0009-2940
    Keywords: Selenium-nitrogen compounds ; Sulfur-nitrogen compounds ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of cationic species of the series [X2Y—N—YX2]+ (X = F, Cl; Y = S, Se) have been computed ab initio using all electron treatments for first-row elements and sulfur and quasi-relativistic pseudopotentials for Se and Cl. Splitvalence basis sets with polarization and diffuse functions were employed. The MP2 results for the (non-isostructural!) cations [Cl2Se—N—SeCl2]+ (1: Cs) and [F2S—N—SF2]+ (2: C2v) are in excellent agreement with the experimental (X-ray) observations. Both structures represent local minima. A deeper minimum for either of the cations is represented by another C2v isomer which for crystal lattice energy reasons is stable in the isolated state only. The geometries of the hitherto unknown species [Cl2S—N—SCl2]+ (3) and [F2Se—N—SeF2]+ (4) have been assessed by ab initio HF calculations. In analogy to 2, cations 3 and 4 are predicted to prefer C2v symmetry. Therefore, 1 exhibits unusual structural features. According to strictly localized natural bond orbital analysis (NBO), the central nitrogen atoms in 1 and 2 possess two lone pairs of electrons (LP: one sp hybrid and one p orbital). The relatively short Se—N and S—N bond distances in 1 (1.741-1.760 Å) and 2 (1.551 Å) can best be attributed to LP(N)→s̰*(Y—X) negative hyperconjugation (1: Y = Se, X = Cl; 2: Y = S, X = F).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280106
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  • 3
    Electronic Resource
    Electronic Resource
    Zerfall von Nitrosylazid, N4O: Existieren auch cyclische Stickstoff-Oxide? (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 201-203 
    Details
    ISSN: 0009-2940
    Keywords: Nitrogen oxides ; Calculations, ab initio ; Tetranitrogen monoxide ; Dinitrogen monoxide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decomposition of Nitrosyl Azide, N4O: Are Cyclic Nitrogen Oxides Existent?The unimolecular decomposition of nitrosyl azide (tetranitrogen monoxide), N4O, was studied at the electron-correlated, spin-restricted RMP2 level with the 6-31G(d,p) and 6-31+G* basis sets. Frequency calculations were performed at 6-31+G* on the optimized structures. It is demonstrated that the experimentally established trans-trans-N4O (Cs) may either interconvert into cis-cis-N4O which upon decomposition forms cyclic N4O (C2v) as an intermediate species to finally give N2O (C∞v) and N2, or trans-trans-N4O may directly dissociate into cyclic N2O (C2v) and N2. All structures determined were rationalized by energy hypersurface calculations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280220
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  • 4
    Electronic Resource
    Electronic Resource
    A light-scattering photometer for use at elevated pressures (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1885-1896 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new light scattering photometer has been designed in order to perform light-scattering measurements at various temperatures and under pressures of 1-1000 atm. Since the scattering angle is constant (90°C), the dimensions of the dissolved molecules are determined by measuring the intensity at different wavelengths. The method of measurement, the calibration of the instrument, and the treatment of data are described. By a series of test measurements on polystyrene in trans-decalin solutions it is shown that one obtains reliable results and finds considerable effects of pressure on the radius of gyration and the fundamental thermodynamic properties of the system.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160081104
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  • 5
    Electronic Resource
    Electronic Resource
    Phase-distribution chromatography (PDC) of polystyrene (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 833-839 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A chromatographic technique is described where the stationary phase is a layer of a very high molecular polystyrene fraction (M = 107) on glass beads (ballotines). The mobile phase is cyclohexane passing the column at a constant temperature below the theta-temperature. A polystyrene sample of sufficiently low molecular weight (M ≤ 106) injected as a small plug at the top of the column is fractionated because the distribution between the mobile and the stationary phase depends on the molecular weight. Since the large molecules preferentially remain in the stationary phase, the smaller molecules leave the column first. The fractionation effect is inverse to that found in GPC experiments. The separation efficiency is rather good and can be described by a simple thermodynamic theory.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080602
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  • 6
    Electronic Resource
    Electronic Resource
    Ab Initio Molecular Orbital Calculations on Allylic 1,3-Strain of Electron-Donor- and Electron-Acceptor-Substituted Alkenes (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1575-1579 
    Details
    ISSN: 0947-3440
    Keywords: Allylic 1,3-strain ; Calculations, ab initio ; sp2-Geminal effect ; Ene reaction ; Allylsilanes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations on the conformations of several electron-rich and electron-poor alkenes 2, 8-15 were performed up to the MP2/6-31G*/RHF/6-31G* level. It was proven that allylic 1,3-strain can be traced back to steric interactions between the allylic center and the (Z) substituent of the double bond. The electron density of the double bond seems to have no effect on the difference in energy between the global and the local minimum. The local minimum (180° conformation) of (Z)-methyl-substituted alkenes 2, 14 and 15 carrying a methyl, carboxyl and methoxy group, respectively, at the double bond in (E) position, lies 3.37-3.52 kcal/mol above the 0° conformation (global minimum); thus, the (E) substituent has no significant influence on this energy difference and therefore on the equilibrium distribution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961012
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  • 7
    Electronic Resource
    Electronic Resource
    Precipitation chromatography. III. Optimization of the experimental conditions and determination of the polydispersity of fractions (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 239-254 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the solvent-nonsolvent gradient and the temperature gradient on the efficiency of the precipitation chromatography is investigated with radically and anionically prepared polystyrene samples. Only a combination of both gradients gives optimal effectiveness of the column. The separating power of the column was determined by using mixtures of well defined samples. From the elution curves of the mixtures the nonuniformity Ufr of fractions can be estimated. For fractions of anionically prepared polystyrenes Ufr is on the average 0.001; this value is of the same order of magnitude as the statistical error. These results show that with this chromatographic method it is possible to determine the narrow molecular weight distributions of anionically prepared polystyrenes (or other polymers) with an accuracy sufficient for kinetic studies.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120202
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  • 8
    Electronic Resource
    Electronic Resource
    Anionic polymerization initiators containing protected functional groups and functionally terminated diene polymersPresented in part at the Division of Polymer Chemistry, American Chemical Society, August 26-31, 1973, Chicago, Illinois. (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 153-166 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organolithium reagents substituted with hydroxyl-carrying mixed acetals (i.e., tetra-hydropyranyl and α-ethoxyethyl ethers) have been prepared in high yields and used to polymerize 1,3-butadiene to various acetal-terminated polybutadiene polymers. A method is described for converting acetal-containing polymers into hydroxyl-containing polymers. The polybutadienes have been characterized with regard to endgroup types, quantitative functionalities, molecular weights, molecular weight distributions, and microstructures. Dihydroxyl terminated polymers are prepared anionically in the absence of gel. Such materials are more suitable from the standpoint of f(OH) and M̄w/M̄n for chain extension studies than are prepolymers prepared by radical methods.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.170120114
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  • 9
    Electronic Resource
    Electronic Resource
    Graft polymers with macromonomers. II. Copolymerization kinetics of methacrylate-terminated polystyrene and predicted graft copolymer structures (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 1633-1652 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymerization studies of methacrylate-terminated polystyrene macromonomers (M1) with several comonomers (M2) verified the modified kinetic scheme and permitted prediction of graft polymer compositions and structures. Instantaneous and cumulative copolymer compositions, average graft distributions, and grafts per molecule are predicted from FORTRAN IV or BASIC programs. The r2 relative reactivity ratios determined from styrene copolymerization (0.61) or from low conversion acrylic monomer in aqueous suspension (∼0.4) had good agreement with literature values (about 0.6 and 0.4, respectively). Decreased macromonomer reactivity determined at high acrylic monomer conversions was attributed to phase separation phenomena. The Macromers also exhibited lower reactivity than predicted when copolymerized with acrylic monomers in DMSO/benzene solutions (r2 ∼ 0.8).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170220711
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal decomposition of poly(tert-butyl N-vinylcarbamate) (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 1451-1460 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrolysis of poly(tert-butyl N-vinylcarbamate) at 185-200°C in bulk yields a rigid foam containing cyclic urea units, primary amine units, and a small amount of urea crosslinks. The yield of primary amine units (ca. 13%) and the yields of carbon dioxide (ca. 57%), isobutylene (ca. 57%), and tert-butanol formed in this reaction indicate that it involves pairwise decomposition of adjacent carbamate units to form cyclic urea units, tert-butanol, carbon dioxide, and isobutylene. The vinyl amine units are formed from carbamate units that become flanked by urea units. The amounts of amine units and residual carbamate units were determined as a function of degree of pyrolysis by an ion-exchange technique and agreed with values expected for a random cyclization process. The pyrolyzed polymers are useful as ion-exchange resins and as rigid foams having good thermal stability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.170120709
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