SynopsisCis-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, T i c 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.
Solution and solid‐state thermal cis‐trans isomerization of cis–transoidal polyphenylacetylene was investigated. At temperatures higher than 120°C, cis‐trans thermal isomerization in solution is accompanied by cyclization, aromatization, and scission of the polymer chain. Both spectral and kinetics data showed that at temperatures lower than 120°C, not only cis‐trans thermal isomerization takes place but also intramolecular cyclization.
Considerable confusion exists in the literature concerning the structure and properties of polyarylacetylenes. Taking into account the significant structural aspects from the literature data with our recent results on the polypentadeuterophenylacetylene isomers, we present our findings concerning this class of polymer.
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