The Steric Course of the Cationic Polymerization of Vinyl and Related Monomers. The Counterion Effect
作者:
Toyoki Kunitake,
期刊:
Journal of Macromolecular Science: Part A - Chemistry
(Taylor Available online 1975)
卷期:
Volume 9,
issue 5
页码: 797-816
ISSN:0022-233X
年代: 1975
DOI:10.1080/00222337508065895
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Polymerization with many triphenylmethyl salts was conducted for α-methylstyrene, isobutyl vinyl ether, t-butyl vinyl ether, and spiro[2,4]hepta-4,6-diene (SHD). The variation of polymer structure (the isotactic unit content for the first three monomer systems and the amount of the 1,4-addition structure for SHD) showed fairly simple correlations with the counteranion size. The results can be interpreted in terms of the tightness of the propagating ion pair within the framework of a theory of the cationic propagation which had been proposed. When the counteranion radius was greater than 3.5 Å, the counteranion exerts a parallel influence on the tightness of the growing ion pair without regard to the monomer structure. However, in the case of smaller counterions, the tightness appears to be determined by the relative sizes of counteranion and monomer. The penta-coordinated counteranions gave rise to the polymer structure which would arise from tighter ion pairs than expected from their sizes alone. The polymer structure was also affected by the initiator concentration in these cases. These results are attributed to peculiar characteristics of penta-coordinated anions.
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