ISSN:0022-233X    

DOI:10.1080/10601326708053965

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Aldehyde polymers were prepared long before the true nature of a macromolecule was recognized. Polyaldehydes made important contributions in crucial phases of the development of our knowledge of polymers. They have the distinction of providing several first discoveries that added to the understanding of addition polymerization and to the determination of the structure of polymers.

ISSN:0022-233X    

DOI:10.1080/10601326708053966

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A review is presented that covers the chemistry of various routes from formaldehyde to high-molecular-weight polyoxymethylenes, and emphasizes recent developments. The requirements of a feasible addition polymerization system are enumerated. The variety of possible polymerization mechanisms is illustrated by discussions of representative anionic, organometallic, and cationic initiator systems.

ISSN:0022-233X    

DOI:10.1080/10601326708053967

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Stable high-molecular-weight polyacetals can be prepared from formaldehyde or from its trimer trioxane.

ISSN:0022-233X    

DOI:10.1080/10601326708053968

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Polyacetals of higher aliphatic aldehydes have been prepared as amorphous, elastomeric polymers and as crystalline, isotactic polymers. They are prepared by solution polymerization or bulk polymerization with appropriate cationic and anionic initiators at low temperature. The polyaldehydes obtained are thermally unstable and must be end-capped.

ISSN:0022-233X    

DOI:10.1080/10601326708053969

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The field of poly(haloaldehydes) is reviewed, with emphasis on recent developments. The poly(chloroaldehydes) described by the early investigators had the common characteristics of being formed “spontaneously” from the monomer, and dissociating on being heated. Characterization of thesemetapolymers by Novak and Whalley showed them to be crystalline and of low molecular weight and to have an OH-ended substituted polyoxymethylene structure.

ISSN:0022-233X    

DOI:10.1080/10601326708053970

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The large differences in chemical shifts that result from oxygen's being incorporated into the polymer backbone yield more accurate qualitative and quantitative analysis through NMR than those polymers that do not have oxygen in the backbone. Configuration effects are observed without interference from methylene groups that frequently interfere in the analysis of polymers. However, the results obtained on polyacetaldehyde with the new 200-MHz Varian Instrument at ambient temperature show a much more complete definition of the configuration than can be obtained with lower-frequency instruments. They show that there are more isotactic triads than syndiotactic triads for the methyl group in “atactic” polyacetaldehyde and that this polyacetaldehyde is nearly a random polymer. By means of the new 220-MHz Varian Instrument and heating of the samples to elevated temperatures for better-resolved lines complete configurational analysis of polyacetaldehyde should become possible.

ISSN:0022-233X    

DOI:10.1080/10601326708053971

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Recently it was shown that the C˭S group in fluorothiocarbonyl compounds readily undergoes addition polymerization. This review describes polymers obtainable from such compounds as CF2˭S, CF3CF˭S, ClCF2CF˭S, HCFClCF˭S, and hexafluorothioacetone. The polymerization of CF2˭S is readily brought about in anionic systems at low temperatures, giving a high-molecular-weight poly(thiocarbonyl fluoride) with a number-average molecular weight in the range of 300,000 to 400,000. It is believed that the major portion of this polymer is composed of chains of CF3–-S—(—CF2S—)n–CF˭S. Poly(thiocarbonyl fluoride) is a highly resilient elastomer in the amorphous form but suffers the disadvantage of slow crystallization at temperatures below 35°C and concomitant loss of rubbery properties. Above 175°C it depolymerizes. Fluorothioacyl fluorides also undergo anionic polymerization, but the products are logy elastomers. Copolymers of fluorothioacyl fluorides with CF2˭S have better thermal stability but poorer resilience than poly(thiocarbonyl fluoride). Hexafluorothioacetone has been polymerized at—110°C to give a white elastomer that slowly depolymerizes at room temperature to regenerate monomer. Thiocarbonyl fluoride is also susceptible to free-radical polymerization, and in free-radical systems it copolymerizes with conventional vinyl monomers, giving a wide variety of new elastomeric products.

ISSN:0022-233X    

DOI:10.1080/10601326708053972

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Crystalline polymers of formaldehyde were recognized by Staudinger (1) in 1927 as having a polyacetalic structure.

ISSN:0022-233X    

DOI:10.1080/10601326708053973

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

This paper reviews published data on the morphology of polyoxymethylene crystallized from the solution and melt. Recent work in these areas as well as the mechanism of deformation, effect of annealing, and structure of solid-state polymerized polymer are also described.

ISSN:0022-233X    

DOI:10.1080/10601326708053974

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor