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  • Articles  (8,168)
  • Chemistry  (8,168)
  • GEOPHYSICS
  • General Chemistry
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  • LUNAR AND PLANETARY EXPLORATION
  • 1980-1984  (8,168)
  • Physics  (8,168)
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  • Articles  (8,168)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-07-20
    Description: The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Argade, P V -- Ching, Y C -- Rousseau, D L -- New York, N.Y. -- Science. 1984 Jul 20;225(4659):329-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6330890" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Monoxide/metabolism ; Cattle ; Chemical Phenomena ; Chemistry ; Electron Transport Complex IV/*metabolism ; Myoglobin/metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Spectrum Analysis, Raman
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-01-20
    Description: Peptide synthesis can be used for elucidating the roles of secondary structures in the specificity of hormones, antigens, and toxins. Intermediate sized peptides with these activities assume amphiphilic secondary structures in the presence of membranes. When models are designed to optimize the amphiphilicity of the secondary structure, stronger interactions can be observed with the synthetic peptides than with the naturally occurring analogs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, E T -- Kezdy, F J -- HL-18577/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1984 Jan 20;223(4633):249-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6322295" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Apolipoprotein A-I ; Apolipoproteins ; Binding Sites ; Calcitonin ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone ; Endorphins ; Glucagon ; Growth Hormone-Releasing Hormone ; *Hormones/pharmacology ; Lipoproteins, HDL ; Melitten ; Models, Structural ; *Peptides/chemical synthesis/metabolism/pharmacology ; Protein Conformation ; Structure-Activity Relationship ; beta-Endorphin
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-10-19
    Description: Fourier transform mass spectrometry will play an important role in the future because of its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. These features have already found application in gas chromatography-mass spectrometry, multiphoton ionization, laser desorption, and secondary ion mass spectrometry. However, its most notable feature is the ability to store ions. This characteristic, when combined with the others, will allow expeditious study of the interaction of gas-phase ions with both photons (photodissociation) and neutral molecules, and the convenient application of this fundamental information for chemical analysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gross, M L -- Rempel, D L -- 2-8423576/PHS HHS/ -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):261-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6385250" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Fourier Analysis ; Ions ; Lasers ; *Mass Spectrometry/instrumentation/methods
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  • 4
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-08-31
    Description: High-resolution carbon-13 nuclear magnetic resonance (NMR) spectra of enzyme-inhibitor and enzyme-substrate complexes provide detailed structural and stereochemical information on the mechanism of enzyme action. The proteases trypsin and papain are shown to form tetrahedrally coordinated complexes and acyl derivatives with a variety of compounds artificially enriched at the site or sites of interest. These results are compared with the structural information derived from x-ray diffraction. Detailed NMR studies have provided a clearer picture of the ionization state of the residues participating in enzyme-catalyzed processes than other more classical techniques. The dynamics of enzymic catalysis can be observed at sub-zero temperatures by a combination of cryoenzymology and carbon-13 NMR spectroscopy. With these powerful techniques, transient, covalently bound intermediates in enzyme-catalyzed reactions can be detected and their structures rigorously assigned.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, N E -- Malthouse, J P -- Scott, A I -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):883-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6433481" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon Isotopes ; Carboxypeptidases/metabolism ; Carboxypeptidases A ; Catalysis ; Chemical Phenomena ; Chemistry ; Coenzymes/*metabolism ; Endopeptidases/metabolism ; Enzymes/*metabolism ; Freezing ; Fructose-Bisphosphate Aldolase/metabolism ; Magnetic Resonance Spectroscopy ; Papain/metabolism ; Pepsin A/metabolism ; Peptide Hydrolases/*metabolism ; Protease Inhibitors ; Pterins/metabolism ; Pyridoxal Phosphate/metabolism ; Serine Endopeptidases
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  • 5
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maugh, T H 2nd -- New York, N.Y. -- Science. 1984 Mar 9;223(4640):1051-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6695193" target="_blank"〉PubMed〈/a〉
    Keywords: *Air Pollutants ; *Atmosphere ; Carbon Tetrachloride ; Chemical Phenomena ; Chemistry ; *Chlorofluorocarbons, Methane ; Free Radicals ; Nitrogen Dioxide ; Nitrous Oxide ; Oxygen ; *Ozone ; Photochemistry ; Risk ; Singlet Oxygen ; Trichloroethanes ; Ultraviolet Rays
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  • 6
    Publication Date: 1984-10-19
    Description: Pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis enables qualitative and quantitative analysis of nonvolatile organic materials containing molecular assemblies of a complexity and size far beyond the capabilities of direct mass spectrometry. The state of the art in pyrolysis mass spectrometry techniques is illustrated through specific applications, including structural determination and quality control of synthetic polymers, quantitative analysis of polymer mixtures, classification and structural characterization of fossil organic matter, and nonsupervised numerical extraction of component patterns from complex biological samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meuzelaar, H L -- Windig, W -- Harper, A M -- Huff, S M -- McClennen, W H -- Richards, J M -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):268-74.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6484572" target="_blank"〉PubMed〈/a〉
    Keywords: Biochemical Phenomena ; Biochemistry ; Chemical Phenomena ; Chemistry ; Coal ; Enterobacteriaceae/analysis/isolation & purification ; Hot Temperature ; Mass Spectrometry/*methods ; Polymers
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  • 7
    Publication Date: 1984-08-31
    Description: The splicing of messenger RNA precursors in vitro proceeds through an intermediate that has the 5' end of the intervening sequence joined to a site near the 3' splice site. This lariat structure, which has been characterized for an adenovirus 2 major late transcript, has a branch point, with 2'-5' and 3'-5' phosphodiester bonds emanating from a single adenosine residue. The excised intervening sequence retains the branch site and terminates in a guanosine residue with a 3' hydroxyl group. The phosphate group at the splice junction between the two exons originates from the 3' splice site at the precursor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Padgett, R A -- Konarska, M M -- Grabowski, P J -- Hardy, S F -- Sharp, P A -- P01-CA14051/CA/NCI NIH HHS/ -- P01-CA26717/CA/NCI NIH HHS/ -- R01-GM32467/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):898-903.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6206566" target="_blank"〉PubMed〈/a〉
    Keywords: Adenoviruses, Human/metabolism ; Base Sequence ; Chemical Phenomena ; Chemistry ; Nucleic Acid Conformation ; Nucleic Acid Precursors/analysis/*metabolism ; Oligoribonucleotides/metabolism ; Phosphates/metabolism ; RNA/analysis/*metabolism ; RNA Precursors ; *RNA Splicing ; RNA, Messenger/analysis/*metabolism ; RNA, Viral/analysis/*metabolism
    Print ISSN: 0036-8075
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  • 8
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-05-11
    Description: The mechanism of lipid peroxidation and the manner in which antioxidants function is reviewed. beta-Carotene is a purported anticancer agent, which is believed by some to have antioxidant action of a radical-trapping type. However, definitive experimental support for such action has been lacking. New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants. Specifically, it exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air. Such low oxygen partial pressures are found in most tissues under physiological conditions. At higher oxygen pressures, beta-carotene loses its antioxidant activity and shows an autocatalytic, prooxidant effect, particularly at relatively high concentrations. Similar oxygen-pressure-dependent behavior may be shown by other compounds containing many conjugated double bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burton, G W -- Ingold, K U -- New York, N.Y. -- Science. 1984 May 11;224(4649):569-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6710156" target="_blank"〉PubMed〈/a〉
    Keywords: Antioxidants/*metabolism ; Carotenoids/*metabolism ; Chemical Phenomena ; Chemistry ; Free Radicals ; Humans ; Linoleic Acids/metabolism ; *Lipid Metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Partial Pressure ; Peroxides/metabolism ; Tetrahydronaphthalenes/metabolism ; beta Carotene
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  • 9
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-16
    Description: Yeast phenylalanine transfer RNA was subjected to a 12-picosecond molecular dynamics simulation. The principal features of the x-ray crystallographic analysis are reproduced, and the amplitudes of atomic displacements appear to be determined by the degree of exposure of the atoms. An analysis of the hydrogen bonds shows a correlation between the average length of a bond and the fluctuation in that length and reveals a rocking motion of bases in Watson-Crick guanine X cytosine base pairs. The in-plane motions of the bases are generally of larger amplitude than the out-of-plane motions, and there are correlations in the motions of adjacent bases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey, S C -- Prabhakaran, M -- Mao, B -- McCammon, J A -- New York, N.Y. -- Science. 1984 Mar 16;223(4641):1189-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6560785" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Computers ; Cytosine ; Guanine ; Hydrogen Bonding ; Nucleic Acid Conformation ; *RNA, Fungal ; *RNA, Transfer, Amino Acyl ; Yeasts/analysis
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  • 10
    Publication Date: 1984-11-16
    Description: Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hurley, L H -- Reynolds, V L -- Swenson, D H -- Petzold, G L -- Scahill, T A -- New York, N.Y. -- Science. 1984 Nov 16;226(4676):843-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6494915" target="_blank"〉PubMed〈/a〉
    Keywords: Antibiotics, Antineoplastic/*metabolism ; *Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/*metabolism ; *Indoles ; Leucomycins/*metabolism ; Molecular Conformation ; X-Ray Diffraction
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  • 11
    Publication Date: 1984-06-15
    Description: A new class of synthetic antifungal agents, the allylamines , has been developed by modification of naftifine , a topical antimycotic. SF 86-327, the most effective of these compounds so far, is highly active in vitro against a wide range of fungi and exceeds clinical standards in the oral and topical treatment of guinea pig dermatophytoses. SF 86-327 is a powerful specific inhibitor of fungal squalene epoxidase, a key enzyme in sterol biosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petranyi, G -- Ryder, N S -- Stutz, A -- New York, N.Y. -- Science. 1984 Jun 15;224(4654):1239-41.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6547247" target="_blank"〉PubMed〈/a〉
    Keywords: Allylamine/analogs & derivatives/*chemical synthesis/pharmacology ; Amines/*chemical synthesis ; Animals ; Antifungal Agents/*chemical synthesis/pharmacology ; Chemical Phenomena ; Chemistry ; Dermatomycoses/drug therapy ; Fungi/*drug effects/enzymology ; Guinea Pigs ; Naphthalenes/chemical synthesis/pharmacology ; Oxygenases/*antagonists & inhibitors ; Squalene Monooxygenase
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  • 12
    Publication Date: 1984-11-02
    Description: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perry, L J -- Wetzel, R -- New York, N.Y. -- Science. 1984 Nov 2;226(4674):555-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6387910" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; DNA, Recombinant/metabolism ; Escherichia coli/enzymology ; *Genetic Engineering ; Kinetics ; Muramidase/*genetics/metabolism ; Protein Denaturation
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  • 13
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-06-08
    Description: The effect of a partial pressure of nitrogen of 50 atmospheres (5065 kilopascals ) on the hydrogen evolution reaction of nitrogenase has been investigated. Evolution of hydrogen was not blocked completely by 50 atmospheres of nitrogen in any of four experiments; rather, 27.3 +/- 2.4 percent of the total electron flux through nitrogenase was directed toward production of hydrogen. The ratio of hydrogen evolved to nitrogen fixed was close to 1:1, which implies that hydrogen evolution is obligatory in the fixation of molecular nitrogen by nitrogenase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, F B -- Burris, R H -- AI-00848/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1984 Jun 8;224(4653):1095-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6585956" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen ; *Nitrogen ; Nitrogen Fixation ; *Nitrogenase ; Partial Pressure
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  • 14
    Publication Date: 1984-05-25
    Description: Polypeptide analogs of the known members of the corticotropin-releasing factor (CRF) family were synthesized and tested in vitro and in vivo for enhanced potency or competitive antagonism. Predictive methods and physicochemical measurements had suggested an internal secondary alpha-helical conformation spanning about 25 residues for at least three members of the CRF family. Maximization of alpha-helix-forming potential by amino acid substitutions from the native known sequences (rat/human and ovine CRF, sauvagine, and carp and sucker urotensin 1) led to the synthesis of an analog that was found to be more than twice as potent as either of the parent peptides in vitro. In contrast, certain amino-terminally shortened fragments, such as alpha-helical CRF or ovine CRF residues 8 to 41, 9 to 41, and 10 to 41, were found to be competitive inhibitors in vitro. Selected antagonists were examined and also found to be active in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rivier, J -- Rivier, C -- Vale, W -- AA03504/AA/NIAAA NIH HHS/ -- AM20917/AM/NIADDK NIH HHS/ -- AM26741/AM/NIADDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1984 May 25;224(4651):889-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6326264" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/secretion ; Animals ; Binding, Competitive ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone/*antagonists & inhibitors ; Rats
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  • 15
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 6 (1984), S. 239-243 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The abrupt decrease of electric resistance of thin polymer dielectric films and metal-polymer compositions has been observed in the course of their uniaxial compression. At pressures exceeding the critical one the conductivity of some metal-polymer compositions has been found to be as high as that for such metals as titanium. The dependences of specimen resistance on thickness, temperature and uniaxial pressure strongly support a new mechanism fo polymer dielectric conductivity based on the pressure induced injection of current carriers from a metal to the dielectric conduction band.
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  • 16
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 429-439 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The initiation of acrylamide polymerisation in aqueous media with a redox system of the type Fe3+/organic complex of Fe(III)/Na2S2O2 was studied. Several carboxylated amines containing the iminodiacetate group as a basic structural unit were used as complex forming reagents. A direct relation between complex stability and initiation efficiency was found. The polymerisation kinetics were studied with the most effective intiating system. Several kinetic parameters were determined and an essential relationship between polymerisation behaviour, polymer characteristices and component ratio of the initiation and polymerisation system was found. An attempt was made to explain these results.
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  • 17
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 459-465 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new HPLC method for cyclo-oligoamides 6 and 66 separation is proposed. Using an RP 8 column and an H2O/CF3CH2OH mixtures, all cyclic amides up to the decamer were separated and quantitative results were obtained using an internal standard.
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  • 18
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1063-1068 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic viscoelasticity measurements at 90°C suggest an oxidation process for pristine polyacetylenes (PA's). For cis-rich PA, the oxidation can be divided into three regions: surface oxidation, bulk oxidation, and crosslinking. Crosslinking also occurs at the end of the surface oxidation period but does not occur in the bulk reaction period. For trans-rich PA, oxygen doping was complete after the first 15 min and occurred to a smaller extent than that of the cis-rich PA. The rate of reaction of trans PA chains with oxygen is slow in comparision to that of crosslinking by radical combination or addition reactions with the PA chains. In the case of trans PA the concentration of radical chains formed by reaction with oxygen retains a steady value after the initial period up to the end of oxidation.
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  • 19
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1095-1104 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ethylene/propylene/5-ethylidene-2-norbornene terpolymers (1) are very sensitive to photooxidation. In the early stages, hydroperoxidation occurs specifically at the carbon atom in α-position to the ethylidene group. Isolated and hydrogen-bonded hydroperoxides can be detected by IR spectrophotometry at 3550 and 3380 cm-1, respectively. In post-thermolysis experiments at temperatures above 60°C the associated hydroperoxides were found to be less stable than the isolated hydroperoxides. Saturation of the ethylidene groups is concomitant with the decomposition of associated hydroperoxides, which are transformed thermally and photochemically into alcohols and cyclic saturated ketones. The lack of vinyl groups shows that hydroperoxidation proceeds only at the norbornene cycle.
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  • 20
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1133-1138 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relationships between the valence state of titanium in MgCl2-supported titanium catalysts and polymerization performances for ethylene and propylene were studied. When the titanium species of the supported titanium catalyst 1 was preliminarily reduced by treating it with AlEt3, the resulting catalyst system 2 had lost the activity for propylene polymerization completely. The catalyst activity for ethylene polymerization was found to be reduced to 20% of that of the original catalyst 1. In the AlEt3-pretreated catalyst 2 no Ti4+ is found and 80% of the total titanium is present as Ti2+. The catalyst system 2 plus AlEt3, however, does exhibit activity towards ethylene-propylene copolymerization, propylene insertion being possible if the end of the growing polymer chain is an ethylene unit. The titanium in the AlEt3-reduced catalyst 2 could be oxidized again by treatment with various agents. The oxidized catalysts 3, in conjunction with freshly added AlEt3 as cocatalyst, are active for propylene polymerization and show increased activity for ethylene polymerization in relation to the extent of oxidation.
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  • 21
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1177-1186 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolymerization parameters of N,N-dimethyl-2-aminoethyl methacrylate (DAMA) with methacrylic acid (MAA) were determined at 50°C in benzene, dimethylformamide, and pyridine solutions. The Alfrey-Price constants e and Q of the two monomers were determined by copolymerization of DAMA and MAA with styrene in the same solvents. Using these constants, the copolymerization diagrams of the pair DAMA-MAA were calculated and compared with the experimentally determined ones. The mutual interaction between the comonomers is discussed.
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  • 22
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    Die Makromolekulare Chemie 185 (1984), S. 1233-1234 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 23
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    Die Makromolekulare Chemie 185 (1984), S. 1265-1275 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We analysed by raster electron microscopy Luttinger-polyacetylene as a powder and as a film, both in pristine and (SbF6--electrochemically) doped form. The samples had been intensively washed with MeOH/HCl. One sample had, according to the results of transmission electron microscopy, fiber morphology. All samples show globules as primary structure arranged in clusters (in powder), mono-layers, or chains (in film) (which previously led to “fibril theory”). The primary spherical particles have diameters from 0,02-0,05 μm. The “fibril” sample has very small spherical primary particles, which may develop using low catalyst amounts. Our results support that the conductivity characteristics is governed by phenomena antiparallel to the chain direction (change-transfer-complexes).
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  • 24
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Heterotactic poly(methyl methacrylate) (PMMA) is studied by light scattering and viscometry in the mixture acetonitrile + CCl4. Both liquids are poor solvents of PMMA, but their mixture is a very good solvent of this polymer. The total sorption potential of the coil is calculated from second virial coefficient and intrinsic viscosity results. Unperturbed dimensions, Mark-Houwink exponent, Schulz-Blaschke constant, and coil expansion factor are also determined. The enhanced total solvent sorption is larger in this mixture than in any other cosolvent system of PMMA thus far studied. This is due to the strong repulsive interactions between acetonitrile and CCl4. Such interactions also determine the inversion in preferential sorption that occurs close to equimolar composition. Acetonitrile can interact favourably with the ester group of PMMA and unfavourably with its methylene backbone. The role of such opposing interactions and of liquid order in acetonitrile are taken into account to discuss the results.
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  • 25
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    Die Makromolekulare Chemie 185 (1984), S. 839-846 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The addition of benzoic acid to the oxirane ring of epoxidized polymers of dienes is limited by side reactions which are promoted by increase of time, temperature, or epoxide concentration. Only high [Acid]/[Epoxide] ratios afford good yields of modification of the epoxidized polymers.
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  • 26
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enantioselective hydrolysis of dipeptide-type amino acid esters (Z-(L)-Ala-(L or D)-Ala-PNP (5a), Z-(L)-Ala-(L or D)-Leu-PNP (5b), and Z-(L)-Ala-(L or D)-Phe-PNP (5c)) by di- or tri-peptide nucleophiles (Z-(L)-Leu-(L)-His (2a), Z-(L)-Phe-(L)-His (2b), and Z-(L)-Leu-(L)-His (3)) in the bilayer vesicular aggregates of didodecyldimethylammonium bromide (6) resulted in the enantiomer rate ratio of LL/LD = 1, 1 to 18, the value of which was considerably higher than that (L/D = 1,0 to 4,6) in the hydrolysis of Z-(L or D)-Ala-PNP (4a), Z-(L or D)-Leu-PNP (4b), and Z-(L or D)-Phe-PNP (4c) by the identical vesicular system and that (L/D = 0,7 to 3,1) in the hydrolysis of the dipeptide substrates 5a - c by Z-(L)-His (1) and 6. The high enantioselectivity (LL/LD = 18) in the hydrolysis of 5c by the system of 2a and 6 was enhanced to be LL/LD = 36 by lowering the temperature from 25 to 10°C.
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  • 27
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    Die Makromolekulare Chemie 185 (1984), S. 957-967 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Six unfractionated samples of polyacrylamide were hydrolysed to varying extents. The partially hydrolysed polyacrylamides were investigated by viscosity, osmatic pressure and light scattering techniques in 0,12 M NaCl. The molecular weights of the hydrolysed polyacrylamides confirmed the absence of main chain degradation during hydrolysis. Intrinsic viscosities and dimensions increased with increasing extent of hydrolysis. On correlating the intrinisic viscosities with the extent of hydrolysis, a linear relationship between intrinsic viscosities and the square root of the extent of hydrolysis was obtained.
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  • 28
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    Die Makromolekulare Chemie 185 (1984), S. 983-989 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dimensions of partially hydrolysed polyacrylamides with varying molecular weights and extents of hydrolysis determined by light scattering were used to verify the relative applicability of the various macroion expansion theories. Expansions attributable solely to the presence of electrostatic charges were evaluated with references to the dimensions of the polyacrylamides used for hydrolysis. Total expansions and expansions due to long-range interactions were evaluated with reference to the estimated unperturbed dimensions of the strating polyacrylamides and the hydrolysed polyacrylamide samples, respectively. The expansion coefficients obtained from light scattering measurements were higher than those evaluated from intrinsic viscosities. The differences were maximum (30 - 100%) for the total expansion coefficients. Considering the variation of the Flory viscosity constant Φ with molecular weight and charge density, these differences were ascribed to the uncertainty in the applicability of the light scattering method for the determination of the dimensions of polyelectrolytes. However, the variation of the expansion coefficients with the extent of hydrolysis and molecular weight were similar to those of the expansion coefficients obtained from viscosity measurements. The total expansion coefficient was qualitatively in confirmity with the theory of Chien and Ishihara with reference to its dependence on charge density.
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  • 29
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The particle size distribution is one of the most important characteristics of aqueous polymer dispersions (diameter range 20 〈 D 〈 2000 nm). In addtion, the knowledge of the average particle density ρPM, the density distribution, and the particle refractive index nPM gives information about the chemical composition of dispersions. We report of an ultracentrifuge method which allows to determine all these values simultaneously in one single run. For that purpose the dispersion is measured simultaneously in 3 media of different density, i.e., in H2O, H2O/D2O (1:1, by wt.), and D2O. We use a preparative ultracentrifuge with an analystical rotor with trubidity optics, but instead of an 1-cell-rotor an 8-cells-rotor and a multiplexer are used. In order to measure very small and very large particles simultaneously in one single run we do not work at the usual constant number of rotor revolutions, but at a rate of revolutions increasing from 0 to 40000 min-1. The ultracentrifuge is connected with a computer on-line. The calculations are based on Stokes' law and Mie's light scattering theory for homogeneous isotropic spherical particles.
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  • 30
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    Die Makromolekulare Chemie 185 (1984), S. 1827-1833 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Soluble catalysts of V(acac)3 and AIR2X (R = C2H5, n-C3H7, i-C4H9; X = Cl, Br) initiate a living polymerization of propene at -78°C to afford monodisperse polymers of syndiotactic structure. The stereochemistry of the living polymerization was investigated by examining the structures of monomdisperse polypropylenes and of propylene-ethylene block copolymers by means of 13C NMR spectroscopy. It was found that syndiotactic- and regio-specificities of the soluble vanadium-based catalysts are not influenced by the sequence length of the living polymer chain.
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  • 31
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    Die Makromolekulare Chemie 185 (1984), S. 1145-1154 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The possibilities of coupling size exclusion chromatography with light scattering (GPC-DDL) are studied. The continuous light scattering detector is a modified (laser He-Ne excitation) classical light scattering apparatus Fica 42000, equipped with a flow cell of low capacity (120μl). With this cell, a detection of the scattered light is obtained only at an angle of 90°. The light scattering detector is coupled with a GPC apparatus (packed with 10 μm gel particles). The precision, reproducibility and limitation to obtain molecular weight distribution curves of “standard” linear polystyrenes are studied.
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  • 32
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    Die Makromolekulare Chemie 185 (1984), S. 1187-1197 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Similarly to the three-block copolymer poly(styrene-b-butadiene-b-styrene), a radial block copolymer with four brances consisting of inner polybutadiene and outer polystyrene blocks forms, in a mixed solvent tetrahydrofuran/ethanol, spherical micelles with a polybutadiene core and polystyrene shell. The equilibrium between these micelles and the molecularly dissolved copolymer was studied as a function of the solvent composition by means of light scattering, sedimentation velocity, and GPC. The sedimentation diagrams were interpreted taking into account the Gilbert theory of mobile equilibrium in systems of associating macromolecules.
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  • 33
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    Die Makromolekulare Chemie 185 (1984), S. 1371-1381 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Simultaneous action of high pressure and shear deformation on various organic compounds is studied using an apparatus of Bridgeman anvil type. This apparatus allows to work in a temperature range from -196°C to 200°C at different shear forces. It is established that under these conditions the investigated materials are in the plastic flow state. Chemical transformations of more than 300 organic compounds of different chemical classes are observed. Reactions such as polymerization, polycondensation, polyaddition etc. are realized under plastic flow. In addition, copolymerization reactions with the formation of random copolymers occur for some substances. Kinetic peculiarities of the polymerization process under plastic flow are investigated on the example of acrylamide.
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  • 34
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    Die Makromolekulare Chemie 185 (1984), S. 1409-1417 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Complexation between tetrabutylammonium bromide, or oligomeric tetramethyl-2,6-ionene bromide (1), and high molecular weight poly(ethylene oxide) (PEO) was studied viscometrically, using the following media as solvents: water; 0,1 M aq. KCl; 2 M aq. KCl and 0,1 M aq. HCl. It was found that tetrabutylammonium bromide as well as the ionene 1 convert the initially linear ηred vs. cPOE relationships into bent and hunchbacked curves, thus suggesting the formation of water soluble complexes. In aqueous KCl and HCl solutions these complexes behave as typical polyelectrolytes. Contrary to cations of alkali metals, however, protons do not influence the linear ηred vs. cPOE relation, so that it is possible to determine intrinsic viscosities by use of 0,1 M aq. HCl as solvent. These viscosities are rising if the complexation between POE and ammonium salt is accomplished by the polyfunctional ionene. The increase of [η] depends on the unit mole ratio (u.m.r.) of the ionene to POE. With increasing unit mole ratio from 0 to 7 [η] increases from 9 up to 21 dl · g-1. In water the complexation between one unit mole of POE and two unit moles of ionene 1 causes an increase of the reduced viscosity ηred from 11,2 up to 80,2 dl · g-1.
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  • 35
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of tributylin hydride on different vanadium-based homogeneous catalytic systems for the ethylene/propylene/diene (EPD) terpolymerization was studied. Productivity improvements were always observed. Studied on the composition of the polymerization residues as well as on the interaction between single components of the catalytic system were also carried out. The results are interpreted on the basis of the enhanced oxidation of the vanadium(II) species by radical intermediates resulting from the reaction between tin hydrides and the chlorinated organic activator.
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  • 36
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly[(2-alkoxy (or 2,5-dialkoxy)-1,4-phenylenevinylene-1,4-phenylene)vinylene]s containing alkyl groups of different lengths (8a, b or 9a - c), were prepared by Wittig-reaction of terephthalaldehyde with “bis(Wittig-salt)s”. To establish the structure of the polymers, alkoxy(and dialkoxy)di-α-styrylbenzenes 10a, b and 11a - c were prepared as model compounds under similar conditions. Electrical conductivities, σ288K, of the polymers and their charge transfer (donor-acceptor) complexes with iodine were studied. The doped polymers show increased room temperature conductivities by several orders of magnitude.
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  • 37
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Some new divinylidene compounds, 1,3-bis[4-(β-styryl)phenyl]propane (2b), 1,6-bis[4-(β-styryl)phenyl]hexane (2d), 2,6-bis(β-styryl)pyridine (1b), and 1,5-bis(β-styryl)naphthalene (1c), were prepared. Their reaction with electron transfer agents was investigated and compared with that of homologous divinylidene compounds. The cyclic oligomers formed after protonation were separated and characterized spectroscopically. In general, no preferential formation of isomers is observed. The cyclic dimer, however, is the main product of the electron transfer reaction of 1b and 1c.
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  • 38
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    Die Makromolekulare Chemie 185 (1984), S. 1937-1941 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal stability and degradation kinetics of methyl cellulose, polyacrylamide and methyl cellulose grafted with different amounts of polyacrylamide were investigated by thermogravimetry. Polyacrylamide was found to be more stable than methyl cellulose. The thermal stabilities of the graft copolymeres lie in between these two extremes. The order of reaction, n, and energy of activation, E, of the thermal degradation were determined for all polymer samples. It was found that E for the degradation of polyacrylamide (41,4 kcal/mol = 173,2 kJ/mol) is higher than that of methyl cellulose (31,3 kcal/mol = 131,0 kJ/mol) and that E for the graft copolymers lies in between those of the two homopolymers. The over-all reaction order of the degradation reactions was found to be unity for all polymer samples investigated.
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  • 39
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    Die Makromolekulare Chemie 185 (1984), S. 1979-1989 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends of poly(ethylene oxide) with a poly(ether sulfone) were prepared by casting from a common solvent and were found to be miscible and show a single, composition dependent, glass transition temperature. Mixtures in both cyclohexanone and N,N-dimethylformamide phase, separated on heating and thus conditions need to be carefully chosen to obtain homogeneous blends. At higher PEO contents, PEO crystallised from the blends at lower temperatures. The melting point depression, as determined by trubidity measurements, was used to calculate an interaction parameter which was negative, as expected for miscible polymers. The blends also phase separated on heating, and the cloud point curve could be measured by turbidity measurements and confirmed by both visible and electron microscopy. The cloud point curve was very skew with a minimum at around 10 wt.-% PES content. This was not a strong function of the molecular weight and the skew nature was thus presumably due to differences in the state parameters of the pure components. The blends showed a very high mobility with sharp and reproducible could points which might make them ideal for future miscibility studies.
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  • 40
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reactions of insertion of components serving as bridges between a pharmacologically active constituent and a water-soluble telomeric chain, were carried out. Model compounds containing hydroxyl, amine or carboxylic functions were studied. In each case a bifunctional compound could be found, which is capable of reacting with the model. The resulting products could be fixed on a telomer. The results with the model compounds were applied to the fixation of the carboxylic drug indometacin.
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  • 41
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly[γ-benzyl L-glutamate (BLG)-co-N5-(3-hydroxypropyl)-L-glutamine (HLG)] (3) and polyBLG/poly(ethylene glycol) (PBLG/PEG) block copolymers (6) were synthesized, and the adhesion behavior of rat lymphnode lymphocytes on these polymers was examined by the column method. An increase in the HLG content of polymer 3 caused a slight decrease in lymphocyte adhesivity. Lymphocyte subpopulation B cells were found to be more adhesive to polymers 3 than T cells, by a factor of 1,4 - 1,6. On the other hand, an increase in the PEG content of PBLG/PEG block copolymer caused a remarkable decrease inlymphocyte adhesivity and an increase in selectivity in the adhesivity between B cells and T cells up to a factor of 2,3.
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  • 42
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    Die Makromolekulare Chemie 185 (1984), S. 1843-1854 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mass polymerised poly(vinyl chloride) (PVC), subjected to annealing treatment between 85-140°C under air, nitrogen, vacuum, and hydrogen chloride environment, was found to undergo very slight decomposition in which long polyenes (with more than ten conjugated carbon-carbon double bonds) were produced. Despite the presence of these polyenes the thermal stability of the resin at 190°C remained unaltered. Resin stability was also unaffected by the atmosphere in which the resin was annealed. By contrast, urea clathrate PVC, known to be highly crystalline, decomposed 300% faster than mass PVC and generated very long polyene sequences (n ≥ 42) at 190°C. The results are discussed in terms of two possible morphological populations of polymer.
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  • 43
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    Die Makromolekulare Chemie 185 (1984), S. 1905-1913 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several mono- and diesters of four selected 2,2′-methylenediphenols with acrylic, methacrylic, and crotonic acid were synthesized for the first time. Special emphasis was paid to the preparation of diesters with two different acyl groups which could be obtained via the corresponding monoesters. The radical polymerization of these esters with AIBN (mainly in benzene) gave insoluble (crosslinked) products from dimethacrylates and soluble (linear) polymers from mixed diesters with methacrylic and crotonic acid, while the dicrotonates are not reactive.
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  • 44
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    Die Makromolekulare Chemie 185 (1984), S. 1921-1935 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal structure of three tetranuclear phenolic compounds - 6,6′-bis (2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylenediphenol (1), 6-(2-hydroxy-3,5-dimethylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylendiphenol (2), and 6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylene-diphenol (3) -, was determined by single crystal X-ray analysis. Intramolecular hydrogen bonds between all hydroxyl groups of adjacent phenolic units are found for all molecules. They are directed to the opposite end of the molecule by the ortho-methyl or ortho-tert-butyl group in compounds 2 and 3, while no special orientation is found in 1. The conformation of the phenolic units is trans/trans (anti/anti) in 1 and cis/trans (syn/anti) in 2 and 3. Consequently, in the crystal lattice, 2 and 3 form cyclic dimers via intermolecular head-to-tail hydrogen bonds, while the molecules of 1 are arranged to chains of indefinite length by head-to-head and tail-to-tail hydrogen bonds.
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  • 45
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    Die Makromolekulare Chemie 185 (1984), S. 2269-2281 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Examinations by GPC, HPLC and NMR of several commercial prepolymers containing epoxy groups show that they are based on bisphenol A (DGEBA) and brominated bisphenol A (DGEBtBr). In some cases, brominated monepoxides are also added to the mixture to diminish its viscosity. Consequently, the three-dimensional networks resulting from the polycondensation of brominated resins with diamines can be greatly affected by the presence of these monoepoxides that modify the epoxy/amine ratios.
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  • 46
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Methyl methacrylate (MMA) was radically polymerized in the presence of highly syndiotactic deuterated or undeuterated poly(methyl methacrylate)s. In contrast to observations found in the literature no increase in isotacticity was observed. The stereoregularity of the polymers formed in the presence of an undeuterated PMMA as matrix was found by 1H NMR spectroscopy to be about the same as that in polymers prepared without any matrix, except the polymers formed in the early stage of polymerization which show a little lower syndiotacticity. Determinations of triad tacticities of polymers formed in the presence of deuterated PMMA, gave values of syndiotacticity a little higher than in the case of undeuterated matrixes. The polymer formed in the graft copolymerization of MMA onto pre-irradiated syndiotactic PMMA was fractionated by GPC. The high molecular weight fraction showed a lower syndiotacticity than that of lower molecular weight.
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  • 47
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    Die Makromolekulare Chemie 185 (1984), S. 2337-2346 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The anionic polymerization of exo-3,4,5-trithiatetracyclo[5.5.1.O2,6.O8,12]tridec-10-ene (1) in bulk and/or in aromatic solvents (benzene, toluene) was studied. The polymerization was initiated with sodium benzenethiolate (sodium cation complexed with dibenzo-18-crown-6). Polymers with high-molecular weights were obtained (Mn ≈ 105, osmometrically). The polymerization was found to be living and reversible; the equilibrium monomer concentration increases with the temperature. The ceilling temperature was estimated as 167°C. The thermodynamic data of the polymerization in toluene was determined and compared with those of the polymerization of exo-3,4,5-trithiatricyclo[5.2.O2,6]decane. The standard enthalpy ΔH0ss = -(6,6 ± 0,6)kJ · mol 1 and entropy ΔS0ss = -(29,3 ± 2,1)J · mol 1 · K 1 of the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentration, determined dilatometrically.
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  • 48
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    Die Makromolekulare Chemie 185 (1984), S. 2347-2359 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New macrocyclic oligoesters 3a - d, containing furan rings, were synthesized by condenzation of 5-hydroxymethyl-2-furancarboxylic acid (1) using 2-chloro-1-methylpyridinium iodide (2) as condensing agent. Water-insoluble products were separated by GPC and characterized by IR, NMR, MS, and elemental analysis. The product distribution was found to depend remarkably on the reaction conditions. When the mole ratio of 2 to 1 was 1,65 in pyridine was solvent, the cyclic trimer 3a and the tetramer 3b were obtained, both in more than 30% yield. In addition higher cyclic oligoesters (3c - d), linear oligoesters (5b - e), and the polyester (6) were formed. When a large amount of tributylamine was used as a scavenger of hydrogen halides in toluene as solvent, the polyester was the main product. Condensation in hexane in place of toluene, yielded the linear oligoesters as main products. A mechanism is proposed for the formation of the cyclic oligoesters.
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  • 49
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    Die Makromolekulare Chemie 185 (1984), S. 2451-2457 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relative reactivities of ethylene, 1-butene and 3-methyl-1-butene in the insertion reaction into the metal-methyl bond of the active site of the catalytic system δ-TiCl3/Al(13CH3)3/Zn(13CH3)2 are determined by 13C NMR end groups analysis. The relative reactivities of propene, 3-methyl-1-pentene and 3-ethyl-1-pentene are also calculated from previous data. Some correlations between relative reactivities and reaction mechanism are proposed.
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  • 50
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    Die Makromolekulare Chemie 6 (1984), S. 3-27 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A review is given in the field of liquid crystalline polymers having mesogenic groups in side branches and in the main chain. Conditions for liquid crystalline state formation are discussed in relation with chemical structure of monomeric units, molecular mess and type of mesogenic groups. Pathways to synthesize nematic, smectic, and cholesteric mesophases in polymers are discussed, peculiarities of structure and properties of polymeric mesophases and models of chain packing in them are analyzed. Electrooptical properties of such systems, when an electric and magnetic field is applied, are discussed-Frederick's effect, electrohydrodynclmic instability, “guest-host” effect, cooperative structural transi- tion induced by electric field, and some others. The possible directions of application of polymeric liquid crystals are considered.
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  • 51
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    Die Makromolekulare Chemie 6 (1984), S. 55-75 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyarylate-polyarylenesulfone oxide block copolymers were used as an example to consider several general problems of synthesizing polycondensation copolymers of the polyblock type and the dependence of their properties on the weight ratio of different blocks and their degree of polymerization. It was found that in glassy block copolymers, on the basis of homopolymers similar in structure, and in the whole complex of physico-chemical properties, microphase separation occurs when the degree of polymerization of one of the blocks becomes corresponding to that of the statistical segment, and when the content of this block reaches a proper value.
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  • 52
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    Die Makromolekulare Chemie 6 (1984), S. 141-161 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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  • 53
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    Die Makromolekulare Chemie 6 (1984), S. 211-226 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By partial sulfonation, desulfonation and ion exchange polytsyrene sulfonic acid resins were synthesized having the same capacity (1.3 milliequivalents/g). By the variation of the preparation methods, however, the distribution of the acid groups within the resins could be changed in a defined way so that different concentration profiles were obtained. It is shown that the properties and reaction behavior of the polymeric resins are determined to a large extent by the local concentration of the functional groups.
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  • 54
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    Die Makromolekulare Chemie 6 (1984), S. 29-29 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
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  • 55
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    Die Makromolekulare Chemie 6 (1984), S. 41-46 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The orientational order in liquid crystalline side chain polymers was analysed by means of electric birefringence and small angle X-ray scattering studies. Strong pre-transitional effects were observed in the isotropic phase in the neighbourhood of the nematic phase transition.
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  • 56
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    Die Makromolekulare Chemie 6 (1984), S. 93-106 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A structon model of supercrystals for describing the dynamic properties and multiple phese transitions of superlattices, formed in systems of block copolymers with segregated domains, is applied and experimentally substantiated.
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  • 57
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    Die Makromolekulare Chemie 185 (1984), S. 9-18 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Silicone macromers 5, having a methacryloyl group at one end, and controiled molecular weights, were prepared by anionic polymerization of hexamethylcyclotrisiloxane (2) and subsequent termination with chlorosilane compounds containing a polymerizable vinyl groups. Graft polymers with siloxane grafts were prepared by copolymerization of these macromers with methyl methacrylate (MMA) or styrene. The surface active properties of MMA-based graft polymers were investigated by studying the extent of surface modification of films of graft polymer-poly(methyl methacrylate) blends.
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  • 58
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    Notes: The structure of a number of polymers of the polyphenylene type, prepared by polycyclocondensation of aromatic diketones and their acetals was investigated by 13C NMR spectroscopy. The spectra provide a means to determine the content of 1,3,5-trisubstituted benzene rings and defective β-methylchalcone fragments, as well as the endgroups.
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  • 59
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    Notes: The anionic polymerization of β-propiolactone (βPL) in DMF initiated with CH3COO-K+ or CH3O-K+ has been found to proceed via the carboxylate ion as growing species. This is valid for all polymerization steps in the former system, starting from the first monomer addition, whereas in the latter CH3O-K+ was found to produce in the initiation reaction both alcoholate and carboxylate anions in almost equal properties. The alcoholate reproduces approximately half of itself in each subsequent step; thus, after a few addition steps all of the active species have become carboxylate ones. The anionic polymerization of ε-caprolactone (εCL), on the other hand, can only be induced by alcoholates and the growing species are alcoholate anions. Carboxylate anions, even with crowed cations, are inactive as initiators of εCL. These conclusions are based on NMR studies of the end-groups originating from the initiator and on UV-VIs studies of the reaction products of the active species with 2,4,6-trinitroanisole. The difference between the polymerizations of βPL and εCL are explained in terms of ring strain and conformation.
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  • 60
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    Notes: Provided a polymer is soluble, i. e., molecularly dispersed in another polymer irrespective of the molecular weight of the components, the solution is exothermic. By increasing the temperature two effects, both unfavourable to mixing become larger: (i) the excess entropy of mixing caused by contact interaction and (ii) the total effect from the difference of the free volumes of the pure components. So, an upper miscibility gap occurs. The thermodynamic properties of the mixture cannot be derived from the properties of the pure components. They can be described by the corresponding states theory of Prigogine, Flory, and Patterson with suitable values for the contact energy and contact entropy parameters X12 and Q12. The temperature of separation can be predicted from measurements on the mixture at low temperatures.
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  • 61
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    Notes: Tetrahydrofuran (THF) was polymerized by protic and non-protic cationic initiators in presence of acetic anhydride (Ac2O) in methylene dichloride. Due to a low transfer coefficient (CAc2o = 0,058) the molecular weight increases during the early part of the reaction. The consumption of Ac2O continues even when the THF concentration approaches zero, which results in a lowering of the number-average degree of polymerization Pn. Degradation of poly(THF) continues until the Ac2O is exhausted. The equilibrium concentration of THF can reach almost zero at small Pn. The equilibrium constants K2, K3, K4, etc., up to K23 for the successive monomer additions are obtained from gel permeation chromatography. With the exception of K2 the equilibrium constants Kn are independent of n.
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  • 62
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    Die Makromolekulare Chemie 8 (1984), S. 89-100 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: It is evidenced that charge-transfer interaction of electron-donor and acceptor groups incorporated in polymer chains improves substantially the rheological properties, mainly by extending the rubber plateau to higher temperatures and lower frequencies, respectively. The effect is attributed to thermoreversible network formation and can be used to increase the stability of incompatible polymer blends at least from the viscoelastic point of view.
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  • 63
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    Die Makromolekulare Chemie 8 (1984), S. 101-108 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Sizes and shapes of the component phases of immiscible polymer blends are strongly influenced by the viscoelastic properties of each component. For mixtures of different poly(ethylene terephthalate)s and polyamide-6 it can be established that the morphology under shear is the result of the viscosity ratio, which determines the size of the droplet-phase, and of the difference in the component elasticities affecting the shape of the dispersed phase.
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  • 64
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    Die Makromolekulare Chemie 185 (1984), S. 37-49 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate constants of the reaction of 1-azabicyclo[4.2.0]octane (1) with different alkyl esters or halides were measured using 1H NMR and UV spectroscopy as well as conductometric methods. The reactivities of the alkylating agents were found to decrease with increasing nucleophilicity of the derived anions (CF3SO⊖3 〉 I⊖ 〉 Br⊖ 〉 picryl⊖ 〉 Cl⊖). Reactivities of all ethyl derivatives, except ethyl chloride, are higher than the reactivity of the 1-alkyl-1-azoniabicyclo[4.2.0]octane cation (2), which means that for these compounds the rate constant of initiation is higher than that of propagation. The reactions proceed much slower in methanol than in nitrobenzene due to the strong donor-acceptor interactions between methanol and 1. Attempts to observe covalent active centers directly by NMR spectroscopy in the polymerization mixture or to detect them kinetically, were unsuccessfull. The reactivity of ethyl triflate, modelling the hypothetical active center, was found to be 2.104 times higher than the reactivity of ions 2. This is ascribed to the high strength of the bond in the cation 2, not sufficiently compensated by the strain of the four-membered ring.
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  • 65
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    Die Makromolekulare Chemie 185 (1984), S. 51-66 
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The cationic ring-opening polymerization of 1-azabicyclo[4.2.0]octane (1) was studied with initiators providing small and large anions, namely F⊖, Br⊖, I⊖, picryl(Pic⊖), CF3SO3⊖. In nitrobenzene as solvent the macroions and macroion-pairs, independently of the anion size, propagate with the same rate constant kp+ = kp± = 7,0 · 10-3 mol-1 · l · S-1 at 35°C ( Δ HP≠ = 55 ± 5kj· mol-1, Δ SP≠ = 105 ± 11 j · mol-1 · K-1). This result strongly indicates that it is not the large size of anoins which is exclusively responsible for the equality kP+ = kP±. The structure of the onium ions, their strong solvation, and the resulting weak interactions with anions are primarily responsible for the observed equalities. In methanol as solvent polymerization proceeds 30 times slowlier than in nitrobenzene and ion-pairs are more reactive by 40% than ions, in agreement with Enikolopyan's findings.
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  • 66
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    Die Makromolekulare Chemie 185 (1984), S. 157-165 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Alkaline hydrolyses of anionic phenyl esters such as 4-acetoxy-3-nitrobenzoic acid and 4-butyryloxy-3-nitrobenzoic acid were examined in the presence of cationic and polymeric liposomes, liposomes of low molecular weight compounds, and micelles. All the additives accelerate the reaction due to the hydrophobic interaction between substrates and additives and the electrostatic interaction both between substrates and additives and between OH- and additives. In the Arrhenius plots of the reactions catalyzed by the liposomes, discontinuous regions were observed due to the phase transition of liposomes from the gel state to the liquid crystal state. Activation parameters ΔH≠, ΔS≠ and ΔV≠ for these reaction systems were evaluated. Both ΔS≠ and ΔV≠ values increase upon the addition of cationic liposomes and micelles. These results were attributed to the desolvation of the activated complex by the strong electrostatic affinity to the cationic colloidal additives.
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  • 67
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    Notes: A systematic investigation of transparent systems (“polymeric microemulsions”), obtained with amphiphilic block copolymers in the presence of water, toluene, and alcohol, was carried out. Their domain of existence in the pseudo-ternary phase diagram is limited compared to that observed for microemulsions with classical surfactants and located in the vicinity of the miscibility curve of the ternary solvents mixture. From dialysis equilibrium and viscosity measurements, it has been established that, whatever the respective lengths of the sequences are, these stable systems consist of a dispersed “phase”  -  containing the compolymer molecules  -  surrounded by an continuous “phase”. Both “phases” are composed of a mixture of the three considered solvents, the continuous phase being constituted by a ternary solvent mixture located on the mutual solubility curve. As a consequence, all water or oil is not trapped within the dispersed particles as in the case of classical micromulsions, but there is a preferential obsorption of the solvents by each type of blocks of the copolymer.
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  • 68
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    Die Makromolekulare Chemie 185 (1984), S. 249-253 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The ring opening polymerization of oxetane and 3,3-dimethyloxetane was carried out in dichloromethane at 25°C with triethyloxonium hexafluoroantimonate as catalyst. After polymerization, the flow times were measured for active and terminated solutions in high vacuum. In the case of oxetane, the data support the presence of branched structures in the active solutions formed by an intermolecular chain transfer reaction to the polymer chains, to give non-strained oxonium-ions. This intermolecular side reaction was not detected in the case of 3,3-dimethyloxetane, if the presence of intramolecular chain transfer to a small extent is not excluded.
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    Die Makromolekulare Chemie 185 (1984), S. 297-316 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The epoxy resins (TGMDA) obtained from 4,4′-methylenedianilic (2) and 1-chloro-2,3-epoxypropane (epichlorohydrin) were found to consist of oligomers with large distribution of molecular weights and functionalities. The structure of the main components separated by preparative gel permeation chromatography and by high pressure liquid chromatography (HPLC) was studied by 1H NMR. The best separation was obtained by HPLC on a preparected TGMDA with tert-butyl isocyanate at 60°C. For the impurities, as found with DGEBA prepolymers, we identified primary and secondary alcohol groups on chain ends but also secondary amino groups inside the oligomer chains.
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  • 70
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    Notes: Reduction and hydrolysis of the ladder oligomers 1, 2, 3, 4, and 5 prepared from the acrylates of oligo (hydroxyphenylene-methylene)s was found to lead to a homologous series of oligo (allylalcohol)s (6a, 7a, 8a, 9a and10a) with good yields. These alcohols were characterized by analytical and spectroscopic methods. The reaction sequences, starting with the esterification of the oligo[(hydroxyphenylene) methylene]s 11a - 11e with acryloyl chloride followed by the formation of the ladder oligomers and ending with their reduction and hydrolysis into the oligo(allyl alcohol)s and the starting compounds 11a - 11e, represent a simple matrix reaction. A mixture of multiple acrylates was also subjected to the same reaction sequences, resulting in a multiple matrix reaction. A mixture of matrix compounds 11b - 11e with a known mole ratio was esterified with acryloyl chloride, then transformed into a mixture of ladder oligomers and subsequently reduced and hydrolyzed to afford a mixture of oligo(allyl alcohol)s with the same mole ratio of the starting matrices as shown by gas chromatographic analysis. This represents a paradigm for a replica oligomerisation.
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    Die Makromolekulare Chemie 185 (1984), S. 697-707 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Furan-based diisocyanates and diamines were prepared unambiguously as potential monomers for polyurethane and polyamide production, starting from methyl furoate and furfurylamine, respectively. The syntheses were optimized and the product identity was confirmed by elemental analysis, IR and NMR spectroscopy, and also by preparation of derivatives which were similarly characterized.
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  • 72
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    Die Makromolekulare Chemie 185 (1984), S. 757-764 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interactions of counterions with segmented kappa- and iota-carrageenan sulfated polysaccharides were investigated by means of microcalorimetric and potentiometric measurements in dilute aqueous solution. The condensation of counterions onto the charged polymer chains leads, in general, to conformational transitions of the disorder-to-order type. A difference in the ability of different pairs of ionic species (monovalent/divalent counterions) to induce conformational transitions of carrageenate salts is demonstrated.
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    Die Makromolekulare Chemie 185 (1984), S. 787-795 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectroscopy was used to investigate the molecular orientation and the conformational change upon drawing for various ethylene/1-butene copolymers in a wide range of crystallinity (0 ≤ Xc ≤ 85% ). The degree of crystalline orientation at constant draw ratio decreases with increasing crystallinity. The orientation function for the amorphous CH2 sequence in the trans conformation, f(am), was calculated assuming additivity for the orientation functions of the trans bands. f(am) increases with drawing in a characteristical way for the different materials and reaches a value higher than that of the amorphous gauche bands. Furthermore, it was found that f(am) is strongly dependent on crystallinity. The relative concentration of the amorphous CH2 sequences in the trans conformation increases at the expense of that of the gauche sequences. The transformation from gauche to trans in the amorphous phase occurs simultaneously with the orientation of the amorphous CH2 sequences.
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    Die Makromolekulare Chemie 185 (1984), S. 829-837 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A qualitative analysis of NMR relaxation data is reported, using motional models based on the consideration of conformational states arising from the architectural specificity of the different building units of a polysaccharide. The choice of a pertinent referential axis, such as either a local helical axis or a local inertial axis is discussed.
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  • 75
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    Notes: Various poly(trialkyl-3-(and 4-)vinylbenzylammonium chloride)s were prepared and their antibacterial activities were assessed by the conventional spread plate method and the viable counting method. They are in general more active against Gram-positive bacteria such as Bacillus subtilis and Staphylococcus aureus than against Gram-negative bacteria such as Escherichia coli, Aerobacter aerogenes and Pseudomonas aeruginosa. Compounds with the longest alkyl chain studied (dodecyl) were found to exhibit particularly high activity, and this was ascribed to the contribution of the increased hydrophobicity of the compounds to the activity. The most significant finding was that the polymers was discussed and interpreted in terms of their greater contribution to each elementary process in the cidal action: their favored adsorption onto the bacterial cell surface and the cytoplasmic membrane with subsequent disruption of its integrity.
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  • 76
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    Notes: The molecular structures of (RS)-1,2-diphenylethyl methacrylate (DPEMA) and (RS)-α-tert-butylbenzyl methacrylate (t-BBMA) were determined by means of X-ray diffraction. Crystals of (RS)-DPEMA are monoclinic, space group C2/c, a = 33,341(3), b = 5,916(1), c = 15,911(2) Å, β = 106,42(1)°, and Z = 8. Crystals of (RS)-t-BBMA are also monoclinic, space group P21/c, a = 6,028(1), b = 31,009(3), c = 15,207(1) Å, β = 96,780(8)°, and Z = 8. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure: DPEMA, R = 0,113 for 1 100 observed reflections and t-BBMA, R = 0,081 for 2206 non-zero reflections, respectively. The molecule of DPEMA has an antiperiplanar conformation as to the C=C and C=O double bonds about the C(1)—C(2) bond, a synperiplanar conformation as to the C=O and C—O bond about the C(1)—O(1) bond, and an anticlinal conformation about the O(1)—C(5) bond. One of the two t-BBMA molecules in an asymmetric unit has an antiperiplanar conformation as to the C=C and C=O double bonds about the C(1)—C(2) bond, whereas the other antiperiplanar molecule may contain some synperiplanar conformation. Both molecules have a synperiplanar conformation as to the C=O and C—O bonds about the C(1)—O(1) bond and an anticlinal conformation about the O(1)—C(5).
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    Die Makromolekulare Chemie 185 (1984), S. 991-1001 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal degradation of polystyrene (PS) was carried out in the absence of oxygen between 292 and 336°C. The formed volatile products were analysed qualitatively and quantitatively by means of gas charomatography. It was found that the composition of the volatile fraction is a function of conversion and independent of temperature for most of the products. A radical chain mechanism is proposed to explain these experimental results.
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  • 78
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    Die Makromolekulare Chemie 185 (1984), S. 749-755 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The blue colored complex between poly(vinyl alcohol) (PVA) and iodine was prepared at 5°C by mixing an aqueous solution of PVA with an aqueous ethanolic solution of iodine containing boric acid. The absorption spectrum of the system shows bands at 226 nm (A), 290 nm (B), 355 nm (C), and 650 nm (D). Their relative absorbances change largely depending on temperature. When the system is gradually warmed, the chromophoric band D decays and the intensity of band A increases. By lowering the temperature again to 5°C the concentration of chromophore increases. It was found that the decay and the re-formation of the chromophore are reversible in the temperature range 5 to 15°C. Above 15°C, contrarily, hysteresis effects are encountered for the re-formation. Thus, when the chromophore is re-formed at 5°C, the spectra shows an isosbestic point at 420 nm, between bands C and D. The dependence on temperature of bands B and C is quite independent from each other, which strongly indicates that the latter band should be assigned to another iodide species than the I-3 ion (band B) and the I- ion (band A). Based on these experimental data a new mechanism is proposed involving the complex ion I-3 · I2 which is supposed to be a precursor of the chromophoric pentaiodide ion I5-.
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  • 79
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 7-oxo-5-phenyl-5λ-5-phospha-1,4,6-trioxaspiro[4.4]nonane (3a) (C11H13O4P, monoclinic, P21/n, a = 14,751(2), b = 5,577(1), c = 14,490(3) Å, β = 106,91(2)°, V = 1140,5 Å3, Dx(Z = 4) = 1,398 g · cm-3, MW = 240,20, mp = 80°C) forms hygroscopic white needle-like crystals. The structure was solved by direct methods and the final R value is 0,068. The geometry around the phosphorus is trigonal bipyramidal with two five-membered rings in the apical-equatorial planes. The three P-O bond lengths are 1,615(5) (equatorial), 1,670(4) and, 1,808(4) Å (apical).
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  • 80
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    Die Makromolekulare Chemie 185 (1984), S. 877-890 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(allylbenzene)s were synthetised by Ziegler-Natta catalysts: {VCl3 + Al[CH2CH(CH3)2]3} and {TiCl4 + Al[CH2CH(CH3)2]3}. Two different polymers were obtained. Examination of their microstructures by IR and 1H13C NMR spectroscopy suggests that one of the polymerization mechanisms proceeds via isomerization of allylbenzene.
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  • 81
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermodynamics of the binary system oligo(ethylene glycol) (OEG) - oligo(propylene glycol) (OPG) is investigated by lightscattering. The Flory-Huggins interaction parameter χ12 for this system is determined by the decrease of the OEG melting point in a mixture with OPG. At 310,8 K the system is compatible in the concentration range between 0 and 30 vol.-% of OPG in the mixture. The analysis of the temperature dependence of χ12 according to the novel Flory theory leads to the assumption that mixing in this system occurs at a lower critical mixing temperature.
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  • 82
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    Die Makromolekulare Chemie 185 (1984), S. 969-982 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Partially hydrolysed polyacrylamide samples were used as model polyelectrolytes and the variations of the intrinsic viscosities with the extent of hydrolysis and molecular weight were used to determine the relative applicability of the various macroion expansion theories. Expanison coefficients solely attributable to the presence of electrostatic charges were calculated with reference to the intrinisic viscosities of the parent polyacrylamides, assuming that the polyacrylamide corresponds to the discharged state of the macroion from hydrolysed polyacrylamides. Similarly, total expansions and expansions attributable to long-range interactions were evaluated using the estimated intrinsic viscosities at the theta temperature of the parent polyacrylamide and the hydrolysed sample, respectively. The electrostatic expansion coefficients are independent of molecular weight and the long-range expansion coefficients are almost independent of the extent of hydrolysis at high charge densities. In the absence of closed expressions predicting the variation of the expansion coefficients with the concentration of ionizable groups, equivalent expressions based on different theories were deduced assuming that i2/Cs is proportional to the concentration of ionizable groups where i is the extent of ionization of the polyelectrolyte and Cs is the concentration of the added salt. The variation of the electrostatic expansion coefficient with the charge density could not be represented according to any of the theories on macroion expansion. However, attributing the total expansion to the presence of electrostatic charges alone, the Fixman and Chien-Ishihara theories allow a good representation of the data. At very low charge densities, the expansions due to long-range interference effects also can be accounted for by the Fixman and Chien-Ishihara theories.
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  • 83
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    Die Makromolekulare Chemie 185 (1984), S. 1041-1061 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The morphology, the crystallization and thermal behaviour of isotactic polypropylene (IPP) in its blends with two different samples of low density polyethylene (LDPE) was investigated at temperatures high enough to prevent any solidification of LDPE. It is found that pre-existing liquid LDPE domains are incorporated in intra-spherulitic regions during the isothermal crystallization of iPP. The radial growth rate of spherulites is almost unaffected by the LDPE content. The overall rate of crystallization of iPP, on the contrary, is strongly depressed by the addtion of LDPE. A depression of the equilibrium melting temperature of iPP, due to kinetic and morphological effects, is also observed. The depression of the overal kinetic rate constant is accounted for by the negative effect (decrease in the number of nuclei) that the addition of LDPE has on the primary nucleation process of iPP.
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  • 84
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    Die Makromolekulare Chemie 185 (1984), S. 1079-1093 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Oligoureas with diisocyanato end groups (6a - f) were transformed into the respective parabanic acid derivatives (7a - f) with the aid of oxalyl chloride (2). In the reaction of 2 with certain diurea model compounds (12) in 1,2-dichloroethane at room temperature besides the corresponding parabanic acids, diurea dihydrochlorides were formed. Their solutions in 1,2-dichloroethane exhibit electrical conductivity. IR spectra confirm their structure. The reaction of the α,ω-diisocyanatopoly(parabanic acid)s with diols (8a - e) led to copolymers and block copolymers, poly(urethane-parabenic acid)s. The experimental conditions and the influence of the structure of the polymers on certain properties of the final products were investigated.
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  • 85
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    Die Makromolekulare Chemie 185 (1984), S. 1139-1144 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of thermal polymerization of methyl methacrylate (MMA) initiated by manganese(III) in sulfuric acid is studied in the temperature range between 40 and 607deg;C. The rate of monomer consumption is found to be dependent on [MMA]2, [H+]-1 but independent of [Mn3+]. The rate of manganic ion consumption is directly proportional to [MMA], [Mn3+] and inversely proportional to [H+]. The chain length is directly proportional to [MMA] and inversely proportional to [Mn3+] and [H+]. A plausible reaction mechanism with initiation by Mn3+ OH- species and termination by the interaction of Mn3+ with the polymer radical is proposed.
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  • 86
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Linear poly(1,4-piperazinediyl-1-oxotrimethylene) (1), in which amido and tertiary amino groups regularly alternate along the macromolecular chain, the isomeric poly[1-(1-piperazinyl-carbonyl)ethylene] (8) for polyvinylic structure and its N-methylated derivative, poly{1-[(4-methyl-1-piperazinyl)carbonyl]ethylene} (3), were prepared and characterized. Their protonation behaviour was investigated in aqueous solution by potentiometric and calorimetric techniques. In all cases the basicity constants were found to decrease linearly with α (the degree of protonation), whereas the enthalpy changes show a different behaviour toward protonation. The thermodynamic values indicate the important role of hydrophobic interactions.
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  • 87
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The telomerization of vinylidene chloride with CHCl3, CCl3Br, Cl3C—CO2CH3, Cl3C—CF3, Cl3C—CF2—CFClX (X = Cl, Br), and CCl3CF2CCl3 was carried out by redox catalysis. The first adducts of each reaction were isolated and identified. The hydrolysis of these telomers containing a CCl3 group at the chain-end by means of oleum led to a series of halogenated acids, some of them being olefinic ones.
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  • 88
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The general validity of the “Exponents' Rule”, i.e. the interdependencies of the exponents from exponential property versus molar mass M relationships, is based on the general definition for the average of a molar mass dependent property. From this, the numerical value of the product KsD · Ks · KD-1 of the pre-exponential constants of the sedimentation constant (s) versus molar mass relationship, Ks, the diffusion coefficient (D) versus molar mass relationship, KD, and the constant of Svedberg's equation \documentclass{article}\pagestyle{empty}\begin{document}$ K_{sD} = {{RT} \mathord{\left/ {\vphantom {{RT} {(1 - \tilde \nu _2 \cdot 2\rho _1 )}}} \right. \kern-\nulldelimiterspace} {(1 - \tilde \nu _2 \cdot 2\rho _1 )}} $\end{document} is found to be dimensionally and numerically unity (\documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \nu _2 $\end{document}: partial specific volume of polymer; ρ1 : density of solvent): \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{R \cdot T}}{{1 - \tilde \nu _2 \cdot \rho _1 }} \cdot K_s \cdot K_D^{ - 1} = 1 $$\end{document}The experimental validity of this “Product of Constants” to be unity is proven by evaluating 26 different s versus M and D versus M relationships of 8 different polymer/solvent (temperature) systems from literature, which are based on mutually independent measurements of s, D, and M.
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  • 89
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermally prepared polyacenaphthylene when irradiated in solution undergoes random chain scission. The photodegradation is solvent- and temperature-dependent and leads to a lower limit of the degree of polymerization. Polymeranalogous reactions and crosslinking can be found to occur simultaneously. A certain fraction of „weak links“ was detected in the polymer.
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  • 90
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Primary amine and pyridine-initiated polymerizations of L-proline-N-carboxyanhydride (Pro-NCA) at 20 or 100°C yield exclusively or predominantly 103-helices. Only primary amine-initiated polymerizations in 1,4-dioxane at 100°C result in partial formation of 31-helices. The stability of both 103- and 31-helices against conformational transitions was investigated in various organic non solvents or salt solutions at 100 or 150°C. A 103 → 31 transition was only observed in protic non solvents such as formamide, water, or propionic acid, but not in alcohols. A 31 → 101 helix transition was observed in alcohols and most aprotic solvents but not in formamide, water, or propionic acid. Hence, it is concluded that the formation of 31 helices by primary amine-initiated polymerizations in 1,4-dioxane at 100°C is a kinetically controlled consequence of the reaction mechanism. The usefullness of 13C NMR CP/MAS spectra and Fourier-Transform IR spectra for the quantitative analysis of composed secondary structures is compared and discussed.
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  • 91
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The state of Ti3+ ions formed at various steps of preparation and activation of highly active titanium-magnesium catalysts of various composition (dry milling of TiCl3 with MgCl2; reduction of TiCl4 by nonsolvated magnesium dialkyl; interaction of the TiCl4/MgCl2 system with an organoaluminium compound) was studied by the ESR method. It was found that in all systems studied the same three types of Ti3+ ions in the chlorine environment are formed, differing in coordination and localization sites in MgCl2. The content of these ions depends on the composition and preparation conditions of the catalysts, and does not exceed 20% of the total content of titanium. Most of the Ti3+ ions formed in all systems enter the composition of particles or surface aggregates of TiCl3 and appear in the ESR spectra only after dissolution of the sample in pyridine. The active centers of titanium-magnesium catalysts are supposed to be constituents of these particles or of surface aggregates.
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  • 92
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    Die Makromolekulare Chemie 185 (1984), S. 1219-1228 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The precipitation behaviour of polystyrene from solution was studied for the ternary system of polymer/solvent/precipitant, the solvent being toluene or ethyl methyl ketone and the precipitant methanol. The relationships between the efficiency of precipitation and temperature of precipitation, concentration of the solution, molecular weight of the polymer, and the solvent system were investigated. The optimum volume ratio of the polymer solution to precipitant, in order to obtain maximum efficiency of precipitation for a particular system, was derived from graphical plots. The results indicated that the efficiency increases with increasing concentration of the solution, molecular weight of polymer, and thermodynamically “poorer” solvent, but decreases with increasing temperature between 200 K and 300 K. It was also observed that a plot of the efficiency of precipitation versus the volume ratio of polymer solution to precipitant passes through a maximum for all the systems studied. The optimum volume ratio of polymer solution to precipitant exhibits a similar behaviour just as in the case of the efficiency of precipitation. Information obtained from this study enables one to select the best combination of the parameters affecting precipitation, in order to produce a high yield of precipitate of polystyrene at a relatively low cost of solvent and precipitant for a particular temperature of precipitation.
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  • 93
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    Die Makromolekulare Chemie 185 (1984), S. 1277-1284 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The products resulting from the reaction of PVC with sodium benzenethiolate were degraded to 0,3% at 180°C in the solid state and at 160°C in solution in trichlorobenzene. The polyene distribution of the polymers after degradation was studied by both UV-visible and resonance Raman spectroscopies, as a function of the degree of substitution. The results show that there are two types of behaviour: that of the PVC sample prior to the substitution reaction together with the samples modified up to a definite degree of substitution which depends on the starting isotactic content, and that of samples with higher degrees of substitution. The former group exhibits not only a steady improvement in thermal stability but also a preferential formation of polyenes of 7 - 9 double bonds whose concentration decreases with increasing degree of substitution. Conversely, for the second group of samples the thermal stability decreases with the degree of substitution and no specific absorption bands are observed. On the basis of earlier work on the selective substitution of the isotactic GTTG and heterotactic TTTG triads during the first stage of the reaction, the present results show that the bands at 393, 416, and 437 nm are related to specific polyenes which result from initiation by the above quoted conformations in PVC, a conclusion for which confirmatory evidence was obtained by resonance Raman spectroscopic examination of the samples. There is, therefore, clear evidence for the occurrence of two distinct degradation mechanisms, one involving initiation by the unstable triad conformations and the other via random initiation at stable and normal structures. To this may be added the initiation by defect structures, which have been extensively documented in the literature.
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  • 94
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    Die Makromolekulare Chemie 185 (1984), S. 1327-1334 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis and phase behaviour of azo dye containing liquid crystalline side group copolymers are described. These Copolymers show the same electro-optical effects as low molar mass guest-host systems. Their macroscopic oriented nematic structure can be frozen in below the glass transition temperature resulting in a polymer film with dichroic properties. The behaviour of the copolymers (phase behaviour, surface and electric field orientation) can be improved via mixtures with low molar mass liquid crystals.
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  • 95
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    Die Makromolekulare Chemie 185 (1984), S. 1855-1866 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A convenient method for binding saccharides to natural and synthetic substances, polymers and low molecular weight compounds, consists in coupling via an amide linkage. For this purpose aldonolactone or amino groups are introduced at the reducting end of the saccharides which allows coupling to a great variety of amino and carboxyl groups containing compounds. Purification with the usual ion-exchange resins based on polystyrene proved unsatisfactory for oligosaccharides due to adsorption effects and reduced ion-exchange capacity. Excellent results on each step of conversion are obtained by chromatography on a cross-linked poly(acrylamide) gel (Bio-Gel P-4 and P-10) containing a small amount of carboxylic groups introduced by moderate saponification. The new procedure combining the effect of molecular size fractionation and ion-exchange chromatography offers a wide field of application.
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  • 96
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    Die Makromolekulare Chemie 185 (1984), S. 1881-1895 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three polymeric amines, poly(1-aminoethylene) (polyvinylamine) (PVNH2) and linear and branched poly(iminoethylene)s (polyethylene(imines)) (1-PEI and b-PEI) as well as their dodecyl (D) and imidazolylmethyl (Im) substituted derivatives were used for the hydrolysis of p-nitrophenyl acetate (PNPA), 4-acetoxy-3-nitrobenzoic acid (ANBA) and some of their homologues in order to elucidate the relations between their overall structures and their catalytic activities. In each series polymers of similar degree of substitution were compared, namely PVNH2-D18 and PVNH2-D18-Im16; b-PEI-D20 and b-PEI-D20-Im18; 1-PEI-D20 and 1-PEI-D20-Im16. The degree of branching of b-PEI was 41%. All reactions were carried out at 28,7°C in aqueous solution, and followed spectrometrically. Using a catalyst concentration in large excess with respect to the substrate concentration (10-4 mol · l-1) the reactions were found to obey pseudo-first order kinetics. By plotting log [Substrate] against time, k2 (cat) and consequently k2 rate constantes were evaluated. For each series of polymers, k2 increases considerably by dodecyl substitution (hydrophobic-), imidazolylmethyl substitution (catalytic-) and by the use of a charged substrate (electrostatic effects). At similar degree of substitution the catalytic activity is always in the following order: l-PEI 〈 PVNH2 〈 b-PEI. Using the method of Kosower-Mikes the polarity of the microenvironment of l-PEI and b-PEI was found to be almost equal. Substitution of l-PEI with ethyl or 2-diethylaminoethyl side groups (40% substitution) modifies only slightly the catalytic effect of l-PEI. It is, therefore, concluded that the primary amino groups of the side chains in b-PEI are reponsible for its much higher reactivity than that of l-PEI and PVNH2. Experiments with [Substrate] 〉 [Catalyst] were carried out with b-PEI, b-PEI-D20-lm18 and l-PEI-D20-Im16. Under these conditions the reactions follow Michaelis-Menten kinetics and permit the comparison of the complexation constant and rate constant of hydrolysis for the three systems. In the case of b-PEI hydrolysis, reactions towards PNPA carried out at different temperatures, indicate a low enthalpy of activation, ΔH≠ = -196 j · mol K-1 is strongly negative. On the contrary the enthalpy and entropy of complexation are low, indicating low hydrophobic effects.
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  • 97
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    Die Makromolekulare Chemie 185 (1984), S. 1607-1611 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of temperature on the chemical healing of poly(ethylene terephthalate) (PET) - healing as a result of chemical reactions between neighboring macromolecules located in the interface surface  -  was studied. The healing process was carried out in vacuum on pressed partially overlapped strips of commercial PET, previously annealed at 258°C, at temperatures between 140 and 250°C for 24 h. It is demonstrated that the fracture behavior of the welded samples depends strongly on the healing temperature Th. At Th 〉 200°C the strips break beyond the contact area, at 160 〈 Th 〈 200°C debonding occurs, and at Th 〈 160°C no bonding is observed. It is assumed that the bonding effect is mainly a result of chemical reactions (solid state postcondensation and transreactions) taking place during the healing procedure.
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  • 98
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electric birefringence (or Kerr effect) measurements can give, in principle, important informations on the optical, electrical and hydrodynamical properties of macromolecules. The theoretical basis of the Kerr effect is reviewed here so as to be applied to the determination of some molecular parameters of DNA such as optical and electrical polarizability anisotropies, permanent dipole moment, and rotatory diffusion constant. It is necessary to conduct the measurements at very low electric fields. The original device used and the methods for the analysis of the experimental data are described.
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  • 99
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    Die Makromolekulare Chemie 185 (1984), S. 1699-1717 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molar mass distribution of polyethylenes synthesized at pressures up to 2500 bar and temperatures to 255°C with thermal and partly with photochemical initiation is determined by GPC. In the limiting situation of high pressure, low temperature, and small conversion a distribution function based on a limited set of kinetic equations provides a fair representation of the experimental data. The transfer constant with the monomer is derived as a function of pressure and temperature. The logarithmic normal distribution reasonably represents the molar mass distribution of the high pressure polyethylenes if the conversion is low and if both empirical parameters are taken as temperature dependent. The degree of long chain branching is analyzed for the ethylene polymerization as a function of pressure and temperature and to maximum conversions of 30%. It turns out that even at conversions as low as 2% long chain branching is not negligible.
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  • 100
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends of poly(vinyl butyral) (PVB) and of a copolymer of bisphenol A and epichlorohydrin (Phenoxy) with poly(N-vinyl-2-pyrrolidone) (PVP) were prepared by solution casting. The glass transition temperatures Tg for different compositions of the blends were measured by differential scanning calorimetry (DSC). The Tg behaviour of PVB/PVP blends suggests the existence of a single phase for blends containing less than 50 wt.-% PVP, and of two phases in blends containing more than 50 wt.-% PVP. Phenoxy/PVP blends showed to be miscible over the entire composition range. It was found that the Gordon-Taylor equation predicts adequately the Tg-composition dependence with a K parameter equal to 0,5 and 1,25 for PVB/PVP and Phenoxy/PVP blends, respectively.
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