Polymerization of acetylenic derivatives. XXX. Isomers of polyphenylacetylene

Abstract

Abstract Cis ‐transoidal (orange, soluble, and of low crystallinity) and cis ‐cisoidal (red, insoluble, and highly crystalline) polyphenylacetylenes (PPA) were prepared by Ziegler‐Natta catalysts and trans ‐cisoidal (yellow, soluble, and amorphous) polyphenylacetylenes were prepared by using phosphine complexes, TiCl 4 and by thermal initiation. The cis ‐transoidal and cis ‐cisoidal structures isomerize thermally in the solid state above 100°C. In solution the cis ‐transoidal structure isomerizes above 80°C. The polymers obtained by thermal isomerization are soluble, amorphous, and have a trans ‐cisoidal structure. At temperatures higher than 120°C the cis–trans isomerization is accompanied by cyclization and by scission of the polymer chain. A method was developed for determination of cis content of cis ‐transoidal and cis ‐cisoidal polyphenylacetylenes.