摘要:

AbstractThe thermal oxidation of polyamide 6 and 6,6 gives rise to azomethine groups (Schiff's bases) as a result of the reaction of aldehyde and ketocarbonyl groups with amino end groups. During the course of degradation, these azomethine groups react with each other in an aldol‐type condensation to produce conjugated unsaturated oligoenimine structures that absorb in the UV/VIS range. During aldol condensation, the amino end groups are re‐formed, allowing them to react again with the carbonyl groups which are continuously supplied by thermal oxidation (auto‐oxidation) to form azomethine groups once more. The concentration and sequence length distribution of the oligoenimine structures can be correlated to the concentration profiles of the amino end groups, carboxyl end groups, and carbonyl groups, in a kinetic model. The concentrations of the individual oligo‐enimine species calculated with the aid of the model, are in agreement with the figures found experimentally with UV spectroscopy. Sterically hindered phenols inhibit the formation of carbonyl groups, and thus indirectly counteract the formation of oligoenimine structures (kinetic model for the autoxidation of po

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901201

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractNew cationic polymers (4and8) with‐defined separation of charges were obtained byN‐quaternization of epoxide‐amine addition polymers with benzyl chloride, butyl bromide and methyl iodide. The termal decomposition of4and8starts at temperatures between 320 and 370°C. Dielectric measurements in the frequency range 102to 107Hz show a dependence of the conductivity on the temperature. The cationic polymer4dexhibits a conductivity of δ = 10−6S/cm at 89°C

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901202

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractNew initiators for group transfer polymerization (GTP), triphenylphosphonium‐containing ketene silyl acetals, were synthesized by addition of triphenylphosphine and chlorotrimethylsilane to methyl acrylate or methyl methacrylate, respectively, giving 3‐methyoxy‐3‐trimethylsiloxy‐2‐propenyltriphenylphosphonium chloride (4a) and its 2‐methyl substituted derivative (4b), together with their corresponding oligomers (8). These phosphonium salts initiate GTP of ethyl acrylate using zinc halides as catalysts. The resulting polymers, containing a terminal triphenylphosphonium group, show a small polydispersity. In the presence of zinc halides, triphenylphosphine and chlorotrimethylsilane can be used directly to initiate GTP of acrylates and methacrylates. In this case triphenylphosphonium terminated polymers with a larger polydispersity

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901203

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAmphiphilic polyurethanes5a–c,6a–c,10a–cand11a–ccontaining hydrophilic amino or quaternary ammonium groups in the main chain, and hydrophobic ocatadecyl or docosyl groups in the side chain, were synthesized by polycondensation of 2,2′‐octadecyliminodiethanol (3a), 2,2′‐docosyliminodiethanol (3b), bis(2‐hydroxyethyl)methyloctadecylammonium bromide (8) and bis(2‐hydroxyethyl)docosylmethylammonium bromide (9) with a diisocyanate such a hexamethylene diisocyanate (4a), 2,4‐toluylene diisocyanate (4b) and 4,4′‐methylenediphenyl isocyanate (4c). Some of them show a thermotropic liquid‐crystalline state, as determined by DS

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901204

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe free‐radical copolymerization of ethylene (E) and acrylonitrile (A) was studied up to 275°C and 2900 bar in continuously and in discontinuously operated devices. Polymerization is induced by KrF excimer laser light at 248 nm. In addition, results for copolymerizations with thermal and with chemical (oxygen) initiation are presented. The ethylene reactivity ratio,rE, is derived as a function of temperature. At 2450 bar,rEincreases from 0,016 ± 0,003 at 150°C up to 0,055 ± 0,009 at 275°C.rEmeasured as a function of pressure, yields an activation volume of ΔV#(rE) = (−5,2 ± 3,5) cm3·mol−1. The kinetic information from the laser‐induced experiments is used to describe the measured overall quantum yield, ϕ0, which is found to be a few thousand monomer molecules polymerized by one absorbed laser photon. ϕ0decreases toward higher acrylonitrile content. The kinetic parameters are also used to predict overall and acrylonitrile conversion in continuous free‐radical E/A copolymerizations with various

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901205

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAnionic polymerizations of butyl cyanoacrylate by tetrabutylammonium salts (acetate, cyano‐ and chloroacetates, and bromide) in tetrahydrofuran and 1,2‐dimethoxyethane show definite ‘retardation periods’ in presence of strong acids. The back‐extrapolated ‘retardation times’ are proportional to [Acid] and inversely proportional to [Salt]and to [Monomer]1,5. The deduced rate of chain‐initiation increases with temperature, in contrast to the negative temperature dependence of initiation by covalent amines. A stationary‐state theory of the retardation is proposed, having a composite initiation process, involving a reversibl

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901206

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAnionic polymerizations of butyl cyanoacrylate were initiated in tetrahydrofuran (plus a few experiments in 1,2‐dimethoxyethane) by the salts tetrabutylammonium hydroxide, bromide, acetate and three substituted acetates. The hydroxide gives near‐ideal ‘living polymerization’ kinetics, withkpclose to 106l·mol−1. s−1at 20°C. The kinetics of the reactions initiated by the acetates and bromide are analysed by the slow‐initiation‐no‐termination theory, using values of the initiation rate constants evaluated in Part 1. Thekpvalues derived are in the same range as those from the OH‐initiated reactions and those of the zwitterionic polymerizations initiated with covalent bases, i.e., tertiary phosphines and amines. A ca. 4‐fold variation ofkpwith concentration of active species is given a speculative analysis in terms of dissociation from paired to free ions, yielding tentative estimates fork p±≈ 105andk p−≈ 107l·mol−1·s−1in THF at 20°C. Molecular w

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901207

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractPoly(3‐hexylthiophene) (PT6), poly(3‐octylthiophene) (PT8), poly(3‐decylthiophene) (PT10) and poly(3‐dodecylthiophene) (PT12) were synthesized by electrochemical and chemical polymerization. Investigation of these polymers by means of gel permeation chromatography indicates that the polymers prepared from the different monomers under similar conditions do not differ substantially considering molecular weight and molecular weight distribution. Bimodal distributions were found for electropolymerized polymers, and with increasing polymerization time, the high‐molecular‐weight and probably highly branched fraction increased relatively to the low‐molecular‐weight fraction. The microstructure of the polymers was investigated by nuclear magnetic resonance, and it has been found that the polymers exhibit more types of structural units than expected from a simple coupling of adjacent thiophene moieties in 2,5′‐positions. Chemical oxidation with iron trichloride in chloroform gave soluble, high‐molecular‐weight poly(3‐alkyl‐thiophene)s with a rather low amount of irregular couplings, and these more regular polymers exhibited a higher degree of crytallinity. Room temperature conductivities of the oxidized polymers were between 0,1 and 30 S/cm depending on the polymerization conditions, but these values were rather independent of the leng

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901208

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractCrosslinked copolymers from styrene, divinylbenzene and maleic anhydride were reacted with 4‐amio‐2,2,6,6‐tetramethylpiperidine to form imides, then oxidized to form polynitroxyles, and reduced to polyhydroxylamines. These resins form hydrogen peroxide when oxygen is blown through an aqueous slurry. The highest yield was found at

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901209

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractGraft polymerization of various vinyl monomers onto a polystyrene resin (6) containing azo groups having the ability to initiate the radical polymerization was performed. The graft efficiency of vinyl monomers onto6increases with time of polymerization and achieves more than 85%. The swelling of6affects remarkably the graft efficiency. Scanning electron microscopy (SEM) shows that considerable amounts of graft copolymers are located at the surface of6. The graft copolymer of chloromethylstyrene onto6was treated with (S)‐(−)‐2‐amino‐3‐(p‐hydroxyphenyl)‐1,1‐diphenyl‐1‐propanol to yield a resin (9) carrying chiral amino alcohol functions. Resin9/borane was used for asymmetric reductions of acetophenone oximeO‐methyl andO‐benzyl ethers, leading to 1‐phenylethylamine with 43% and 46% enantiomeric excess (e.e.), respectively. These values are higher than those obtained with the generally used polystyrene resin, suggesting that the enantioselectivity can be improved by modifi

ISSN:0025-116X    

DOI:10.1002/macp.1989.021901210

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY