摘要:

The radiation-induced cationic oligomerization of α-methyl-styrene was carried out in dilute hydrocarbon solutions at 0°C. Under rigourously dry conditions, oligomers are produced with relatively high yields in branched alkanes such as neopentane, 3-methylpentane, and dimethylbutanes. The oligomers contain alkyl groups derived from the solvent molecules. The average molecular weight of the oligomers decreases with decreasing monomer concentration. The formation of the oligomers is explained in terms of the chain transfer to the solvent molecules.

ISSN:0022-233X    

DOI:10.1080/00222338408056581

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Biphenylene end-capped polyquinoline pre-polymers (DP = 3,11 and 22) were melt processed in the presence of a nickel catalyst at 325–340°C under 500 psi to give high quality transparent films. Very short cure times (∼ 5 min) were realized, and the resulting films were insoluble, had increased Tg's, and showed improved mechanical properties both above and below the Tg as compared with the uncured resins. The main curing reaction is a chain extension by the conversion of the biphenylene ends to tetrabenzocyclooctatetraene, while a smaller amount of crosslinking takes place. Biphenylene end-capped polyimide, poly(keto-ether-sulfone) and polyphenylquinoxaline pre-polymers also were synthesized. The polyimide pre-polymer (DP=3) was melt processed at 325°C and 500 psi (Ni catalyst) for 15 min to give films that showed good mechanical properties. Friedel Crafts polymerization to yield the biphenylene end-capped poly(keto-ether-sulfone) could not be adequately controlled to give reproducible oligomers. Polyphenylquinoxaline pre-polymers were similarly melt processed to give insoluble films with good mechanical properties. Graphite reinforced composites were prepared from biphenylene end-capped polyquinoline and polyimide pre-polymers. The composites showed excellent initial properties and low weight loss after oxidative aging at 316°C. However, the mechanical properties were severely diminished after aging for 50–100 h at 316°C in air.

ISSN:0022-233X    

DOI:10.1080/00222338408056582

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Various linear and three-arm star end-reactive prepolymers carrying one, two or three terminal functions have been prepared by carbocationic techniques. The higher molecular weight varieties of these materials are valuable intermediates for the synthesis of block copolymers, whereas the low molecular weight telechelics (liquid oligomers) are useful starting materials for extension by end-linking. This presentation outlines the synthesis of some new polyisobutylene-based linear and three-arm star, symmetric and asymmetric end-reactive prepolymers such as, α-phenyl-ω-tertchloro-PIB, αω-diaryl-PIB's, and their derivatives carrying the -C6H/NO2, -C6H4NH2, etc. end groups. Telechelic PIB's with -C6H4NH2end groups react with diepoxy compounds (EPON 826) to give rise to hydrolytically and thermally stable flexible networks. An efficient semicontinuous synthesis procedure is outlined that leads to well-defined linear and three-arm star tert.-chloro-telechelic PIB's with close to theoretical end group functionalities and molecular weight distributions. Three-arm star hydroxyl-telechelic PIB's in conjunction with OCN-C6H4,-CH2-C6H4-NCO give new model polyurethane networks exhibiting outstanding hydrolytic and thermal properties.

ISSN:0022-233X    

DOI:10.1080/00222338408056583

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Living methacrylate polymers are obtained at room temperature and above by initiation with ketene silyl acetals in the presence of a soluble bifluoride catalyst. During the polymerization, a trialkylsilyl group is transferred from the living chain end to incoming monomer. The new procedure has thus been named group transfer polymerization (GTP). Monodisperse polymers with predetermined molecular weights as high as 100,000 can be obtained by adjusting the monomer/initiator ratio. Telechelic poly(methyl methacrylate) with hydroxy or carboxy ends can be obtained by using an initiator containing a protected hydroxy or carboxy group and coupling the resulting living polymer.

ISSN:0022-233X    

DOI:10.1080/00222338408056584

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Benzyl N-ethyldithiocarbamate(BEDC) and xylylene bis(N-ethyl-dithiocarbamate)(XEDC) were prepared, and used as mono- and bi-functional photoiniferters, respectively, of the polymerization of styrene and methyl methacrylate. These photopolymerizations were performed via a living radical polymerization mechanism in homogeneous system. The polymers obtained by BEDC and XEDC still contained one and two reactive N-ethyldithiocarbamate end groups, respectively, bonded at their chain ends. When these polymers were reacted with nucleophiles and copper(n) ion, the chain extension reactions were observed to occur depending on their functionality. By using the polymers obtained by BEDC and XEDC as mono- and bi-functional polymeric photoiniferters, the AB and ABA block copolymers were also obtained, respectively. Similar results were obtained by using benzyl N,N-diethyldithiocarbamate(BDC) and xylylene bis(N,N-diethyldithiocarbamate)(XEDC) as mono- and bifunctional photoiniferters, respectively. These results were also compared and discussed.

ISSN:0022-233X    

DOI:10.1080/00222338408056585

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Since free radical ring-opening polymerization made it possible to introduce functional groups, such as esters, carbonates, thioesters, and amides, into the backbone of an addition polymer, it was reasoned that simple hydrolysis of these copolymers would produce the desired oligomers that could be terminated with various combinations of hydroxyl, amino, thiol, and carboxy1 groups. Thus the copolymerization of 2-methylene-1,3-dioxepane and styrene (r1=0.021 and r2=22.6) gave a copolymer containing 10 mole-percent of an ester-containing unit with 100% ring opening at 120°C. Hydrolysis of this copolymer gave an oligomer terminated with a hydroxyl group and a carboxylie acid group. Similarly the copolymerization of 2-methylene-1,3-dioxepane and ethylene gave a series of biodegradable polyethylene copolymers containing 2.1 to 10.4% ester-containing units. Hydrolysis of these copolymers gave a series of ethylene oligomers with nine to forty-seven ethylene units and terminated with a hydroxyl group and a carboxylic acid group. By the same general method oligomers of various monomers that are terminated with a methylandno group and a carboxylic acid group from N-methyl-Z-methylene-1,3-oxazolidine and with a thiol group and a carboxyl group from Z-methylene-1,3-oxathiolane.

ISSN:0022-233X    

DOI:10.1080/00222338408056586

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Comb graft copolymers prepared by macromonomer technique has become applicable for permanent modification of polymer surfaces. In this paper the association and adsorption behavior in solution of the well designed graft copolymer prepared from polystyrene macromonomer and various hydrophilic comonomer was studied and the mechanism of surface accumulation of hydrophilic segment was clarified by surface analysis of polystyrene containing the graft copolymers. Wetting of modified polymer surfaces and the permeability of gases through the film was also discussed.

ISSN:0022-233X    

DOI:10.1080/00222338408056587

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

(2-Bromoethyl)oxirane is converted in 39% yield to poly-[(2-bromoethyl)oxirane] of inherent viscosity 1.99 dL/g. The AlEt3/H2O/AcAc system is a very effective initiator for the polymerization of (2-bromoethyl)oxirane. Poly[(2-bromoethyl)-oxirane] is a white elastomer, soluble in CHCl3and insoluble in CH3OH. Polyether-urethane hydrogels are prepared by the room temperature crosslinking of poly[(3-hydroxypropyl)oxirane] with aliphatic or aromatic diisocyanates. These networks absorb 100–200% of their weights in water, and can be prepared in transparent form with potential application as biomaterials or contact lenses.

ISSN:0022-233X    

DOI:10.1080/00222338408056588

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

This paper describes the synthesis and properties of oligomer chains derived from 2-oxazolines. First, poly(styrene-g-N-acetyl-ethylenimine) was prepared, and its hydrolysis gave poly(styrene-g-ethylenimine) which showed good chelating properties. Secondly, ABA type triblock copolymers were prepared in which anN-acylethylenimine chain is used as A block and ethylene oxide chain is employed as B block. These triblock copolymers showed good compatibility with Nylon 6, which were shown to posecess effective anti-electrostatic properties for Nylon 6. Thirdly, AB type block copolymers from 2-oxazolines have been prepared by using living polymerization technique. These block copolymers are soluble in water and showed good surfactant nature as reflected by surface tension (γ), when A block is consisted fromN-acetyl- orN-propionylethylenimine chain (hydro-philic) and B block is made ofN-tridecanoyl orN-aroylethylenimine chain (lipophilic). Finally, graft copolymers of cellulose diacetate havingN-acetylethylenimine chain were prepared. It has been found by using a rheovibron that these graft copolymers are compatible with poly(vinyl chloride).

ISSN:0022-233X    

DOI:10.1080/00222338408056589

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

α, β, γ δ-Tetraphenylporphinatoaluminum carboxylate (TPPA10COR) and phenoxide (TPPA10Ar) bring about the polymerization of β-lactone and epoxide to give polymers with controlled chain length having a carboxylic ester or phenoxy group at the end of each polymer molecule. Acrylate (TPPA10COCH=CH2) and p-vinylphenoxide (TPPA1-OC6H4,CH˭CH2(p)) as initiator give polyester or polyether macromer with narrow molecular weight distribution.

ISSN:0022-233X    

DOI:10.1080/00222338408056590

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor