摘要:

When reacting ethylene-vinyl acetate copolymers (EVA) with sodium alcoholates in alcohol, the alcoholysis of EVA is accompanied by crosslinking reactions. Crosslinking can be detected by the increase in torque in a plastograph. This paper reports on investigations on the mechanism of the crosslinking reaction. Both crosslinking via C˭C bonds and formation of a thermally reversible network via polymer alcoholate structures can be found. If an ethylene-vinyl alcohol copolymer is obtained by complete saponification of EVA, however, only thermally reversible crosslinking can be demonstrated. This leads to the conclusion that irreversible crosslinking is established through a reaction of the acetate side chains. The reaction products of the low-molecular weight model substances, pentanol-3-acetate and sodium isopropylate in isopropanol, are analyzed by means of gas chromatography. These results suggest a partial Claisen condensation as a mechanism of the irreversible crosslinking process.

ISSN:0022-233X    

DOI:10.1080/00222339108052092

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

As with ethylene-vinyl ester copolymers, crosslinking reactions are observed with ethylene-acrylic acid ester copolymers in the presence of sodium alcoholates. The reaction mechanism was examined by means of infrared spectroscopic characterization of the cross-linked products and kinetic measurements. In comparative investigations with methyl methacrylate polymers and sodium alcoholates, a reaction was not observed. This leads to the conclusion that the course of the reaction is determined by the hydrogen atom positioned alpha to the carbonyl group. When diethyl acetic acid ethyl ester (as the model substance) was reacted with sodium iso-propylate, only isopropanol could be found by means of gas chromatography. Ethanol could not be detected, as it should have been in the case of ester condensation. Therefore, the crosslinking can be attributed to an aldol addition.

ISSN:0022-233X    

DOI:10.1080/00222339108052093

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The relationship between the structures and properties of solid polymer electrolytes formed by poly(tetramethylene succinate) and alkali metal salts is investigated in this article. The complexation between ions and polar groups, e.g., ester groups in the polymer chains, is determined by FT-IR and XPS techniques. The complexes are semicrystalline materials with the crystallites similar to pure polyester. Inorganic salts do not enter the crystal lattice of the polymer, whereas they do mainly dissolve in the amorphous domains of the polymer. The addition of salts depresses the melting temperature and crystallinity of the polyester. On the contrary, it increases the glass transition temperature. The conductivity of the polyester complexes varies with the concentration, species, solubility of salts in the polyester, temperature, etc. Ionic migration in the amorphous regions of the polymer contributes to the conduction of the electrolytes to a great extent. The conductive behavior could not simply be described either by the Arrhenius equation based on classical theory or by the WLF equation based on free volume theory.

ISSN:0022-233X    

DOI:10.1080/00222339108052094

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Aspects of the living polymerization of isobutylene (IB) initiated by the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4combination have been investigated in the presence and absence of di-tert-butylpyridine (DtBP) and various electron donors (ED), such as pyridine, tri-n-butylamine, di-n-butylamine,N,N-dimethylacetamide,N,N-dimethylformamide, urea, nitromethane, acetonitrile, acetone, acetyl chloride, tetrahydrofuran, tri-n-butyl phosphine, triethylphosphite, dimethyl sulfide, and dimethylsulfoxide. All these EDs, commonly regarded as “poisons” of cationic polymerizations, exert, in fact, beneficial effects; for example, they cause the narrowing of molecular weight distributions (MWD). The active agents are TiCl4-ED complexes which in some systems may be partially insoluble and precipitate from the charges. A detailed series of experiments with the TMPCl/TiCl4/IB/pyridine system demonstrates the living nature of these polymerizations.

ISSN:0022-233X    

DOI:10.1080/00222339108052095

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The objectives of this research were the synthesis and characterization of the following linear and three-arm star cyanoacrylate polyi-sobutylenes:

ISSN:0022-233X    

DOI:10.1080/00222339108052096

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The novel polyaminimide polymer, poly[sodium dimethyl(3-propyl)amine-4-methacrylamidobenzimide sulfonate] (PSDM), was prepared. This polymer contains a pendant sulfonate group in addition to the dipolar aminimide moiety. The dilute solution viscosity and light-scattering behavior of PSDM were studied as a function of salt concentration. It was found that the polymer exhibited typical polyelectrolyte behavior in spite of the presence of the dipolar aminimide group.

ISSN:0022-233X    

DOI:10.1080/00222339108052097

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A simple treatment of gelatin granules with aqueous glutaraldehyde (GLA) yields a versatile crosslinked matrix. The crosslinking involves the ε-amino groups of the lysine residues of the protein and the aldehyde functionality of the GLA. Grafting of this matrix with methyl acrylate results in a very interesting material which has a hydrophilic core but anchors hydrophobic grafts. Here we report the preparative details and essential characteristics of this versatile graft copolymer.

ISSN:0022-233X    

DOI:10.1080/00222339108052098

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0022-233X    

DOI:10.1080/00222339108052091

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor