摘要:

AbstractA dehydrohalogenation reaction between THF solution of PVC and alcoholic KOH has been studied in the temperature range from 18 to −12°C using UV and visible spectroscopy. The absorption spectra of dehydrohalogenated PVC consist of a series of absorption maxima between 260 and 450 mμ due to the formation of conjugated polyene sequences. The presence of oxygen has no effect on the dehydrohalogenation. The kinetics and mechanism of this reaction are discussed and the over‐all activation energy is determined. The proposed mechanism is an ionic elimination reaction similar to the dehydrohalogenation of alkylhalide with a basic reagent in solution. The preferable conditions for this reaction are proposed. It is also suggested that the conjugated polyene sequences are distributed rather selectively among the polymer

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550101

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractThe melting behavior of stretched polyoxyethylene networks was examined. Polyoxyethylene networks were prepared by reacting the chain ends of fractions of polyoxyethylene having a molecular weight of 15,000. The apparent melting temperatures are given by stress‐temperature plots, following a modified version of a method described by GENT. True thermodynamic temperatures were determined using the HOFFMAN and WEEKS method; the experimental data were analyzed following the FLORY and ROE‐KRIGBAUM treatme

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550102

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractPolyacrylonitrile prepared by gamma‐ray irradiation to urea‐canal complex of acrylonitrile (U‐PAN) was fractionated from a solution in dimethylsulfoxide (DMSO) at 25°C, using toluene as a precipitant. Viscosities of fractions, thus prepared, in DMSO and in ethylenecarbonate (EC), were measured for elucidating the unperturbed‐chain dimensions together with the long‐range polymer/solvent interaction parameter. In conclusion, U‐PAN which is comparatively isotactic has almost the same value (the K value is 2.95·10−3) of the unperturbed‐chain dimensions as the atactic polyacrylonitrile prepared by conventional, radical polymerization (R‐PAN), whilst the long‐range parameter of U‐PAN is extremely smaller than R‐PAN in a poor solvent. The conclusions reached from these experimental facts are in very good consistence with those of other polymers with less differenc

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550103

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractThe reaction ofp‐xylylene dichloride (XDC) and N.N.N′.N′‐tetramethylethylenediamine (TED) in several solvents proceeds by nucleophilic bimolecular substitution (SN2), just as in a normal MENSCHUTKIN reaction, to form a polycation polymer of the integral type. However, the rate of the reaction decreases as the polymerization proceeds. This may be attributed to the decrease in the functional concentrations and, especially to the rapid decrease in the rate constant, for the reactivities of the end functional groups,i.e., the nucleophilicity of the end amino groups becomes much lower than the nucleophilicity of the monomers because of the inductive effect of the charge sites formed during the propagation. The influence of the solvent is measured and di

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550104

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractIt was found that the oxidative polymerization of aromatic amines in the presence of oxygen with ferric chelate in aqueous solutions proceedsviaa mechanism similar to that of the MICHAELIS‐MENTEN reaction, the steady state being maintained during the polymerization. On the basis of this mechanism, a kinetic analysis was carried out.The rate constant of the polymerization ofp‐phenylenediamine (p‐PD) with Fe(III)EDTA (ferric ethylendiaminetetraacetic acid) (k2) reaches its maximum at pH 7–8, but K1(the reciprocal of the MICHAELIS constant (Km)) exhibits a minimum in this pH region. From the fact that the rate constant of the oxidation reaction of Fe(II)EDTA alone with oxygen (k0) is very small compared with k2, it was assumed that oxygen is part of the activated radical complex composed of the iron chelate and the monomer. When different ferric chelates are used, the k2values vary in this order: Nitrilotriacetic acid (NTA)

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550105

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractThe variation with pH of the viscosities of aqueous solutions of the following polyvinylpyridine oxide derivatives has been studied,viz.atactic poly(2‐vinylpyridine 1‐oxide), poly(2‐methyl‐6‐vinylpyridine 1‐oxide), poly(3‐methyl‐2‐vinylpyridine 1‐oxide), poly(5‐ethyl‐2‐vinylpyridine 1‐oxide), poly(4‐vinylpyridine 1‐oxide), poly(3‐methyl‐4‐vinylpyridine 1‐oxide) and poly(2‐methyl‐5‐vinylpyridine 1‐oxide), and mainly isotactic poly(5‐ethyl‐2‐vinylpyridine 1‐oxide).When the vinyl group is in the 3 or 4 position, viscosity is maximal between pH 6 and 10, probably because polymer chains are cross‐linked by water molecules attached to N‐oxide groups. Poly(methyl‐2‐vinylpyridine 1‐oxides) give a pH/viscosity curve that is roughly the inverse of this with a minimal viscosity within this pH range. These polymers probably take up a tightly packed conformation near neutrality due to bonding between N‐oxide and α‐H of the polyvinyl chain. More than one conformation is possible and an attempt has been made to interpret the p

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550106

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractCopolymerization of carbon dioxide (CO2) and propylene oxide (PO) was carried out by using diethylzinc/water and diethylzinc/methanol catalyst systems. A remarkable amount of polycarbonate was obtained using the former system, but hardly any polymer was formed with the latter catalyst. The difference between these two systems was examined in relation to the elementary processes of the copolymerization. Both the catalysts react with CO2to produce XZnOCOOR, where X = OCH3for the diethylzinc/methanol system and X = (OZn)nOH or (OZn)nC2H5for the diethylzinc/water system. The reactivity of XZnOCOOR with PO depends on X and the difference between the two systems can be explained by the presence or absence of repeating ZnO bonds.Diethylzinc/primary amine systems produced copolymers while diethylzinc/secondary amine systems were inefficient yielding only small quantities of polymer. This can also be explained by the presence or absence of repeating ZnNR bo

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550107

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractGel permeation chromatography calibrations for polystyrene standards and poly‐(dimethyl siloxane) fractions have been obtained with polystyrene gel usingo‐dichlorobenzene at 87°C. Intrinsic viscosity‐molecular weight data show that, at this temperature,o‐dichlorobenzene is a theta solvent for poly(dimethyl siloxane) but a good solvent for polystyrene. The KUHN‐MARK‐HOUWINK exponents are 0.50 and 0.73 for poly(dimethyl siloxane) and polystyrene respectively. This significant difference in polymer/solvent interaction allows assessment of various universal calibration procedures. Comparison of the experimental poly(dimethyl siloxane) data with curves calculated from a polystyrene calibration suggests that the most suitable calibration procedures use the hydrodynamic volume or the perturbed dimensions given by the FLORY‐FOX equation. Calibration procedures based on the unperturbed dimensions or on the perturbed dimensions derived from the PTITSYN‐EIZNER equation are not valid when the difference in the KUHN‐MARK‐HOUWINK exponents is large. For experimental calibrations with fractions, the position of molecular weight and hydrodynamic volume calibrations may depend on the choice of average molecular weight. The influence of fraction polydispersity on th

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550108

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractDie Einwirkung einer Reihe aromatischer Aldehyde auf die mit α.α‐′Azobisisobuttersäurenitril gestarteten Polymerisationen von Styrol und Methacrylsäuremethylester wurde untersucht (a) durch Vergleich der Polymerausbeuten; (b) durch quantitative Analyse der UV‐Spektren der gereinigten Polymeren und (c) durch Vergleich ihrer M̄n‐ und M̄n‐Werte. Bei der Styrolpolymerisation zeigen 4‐Phenyl‐benzaldehyd und Indol‐3‐aldehyd keine Einwirkung. 4‐Phenylazo‐benzaldehyd, Benzaldehyd, Anthracen‐9‐aldehyd undm‐(2.4‐Dinitrophenoxy)‐benzaldehyd verzögern die Polymerisation. Bis auf Benzaldehyd wird hierbei ihr kovalenter Einbau in das Polystyrol nachgewiesen. Für 4‐Phenylazo‐benzaldehyd konnte eine scheinbare Übertragungskonstante bestimmt werden. Bei der Polymerisation von Methacrylsäuremethylester wird entweder inhibierende, verzögernde oder keine Einwirkung der Aldehyde beobachtet; sie werden sämtlich nicht eingebaut. Jedoch zeigen die Molekulargewichte der Polymethacrylsäuremethylester eine Er

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550109

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY

摘要:

AbstractIn the course of further investigations of ring‐opening polymerizations we have studied the bulk polymerization of β‐methylglycidaldehyde (βMG) by aluminum isopropoxide at 20 and 50°C.The polymerization proceeds in two distinct stages. In the first stage the α.β‐epoxybutyl ester of α.β‐epoxybutyric acid (2.3‐epoxy‐n‐butyl‐1′.2′ ‐epoxybutyrate) (DßMG) is formed by a TISHCHENKO‐CLAISEN reaction.In the second stage this ester gives a polyether (PßMG) by polymerization of the epoxy groups adjacent to the ester carbonyl. The pendent epoxy‐butyl groups are attached to the polyether by an ester linkage. Mechanisms are proposed for

ISSN:0025-116X    

DOI:10.1002/macp.1972.021550110

出版商:Hüthig&Wepf Verlag    

年代:1972

数据来源: WILEY