Substituents chiral-achiral substituent copolymers

UV and CD Spectra of Copolymers Bearing Chiral-Achiral Substituents... 

The nature of the helical conformation of poly(phenylacetylene) has been studied in detail (74). The stabihty of the helical conformation of poly(phenylacetylenes) was estimated by the chiroptical properties of the copolymers from chiral and achiral phenylacetylenes. When the monomer possesses sterically less bulky ring substitnents, a clear cooperative nature on the copolymerization is not observed. A chiral amplification phenomenon is attainable only when the monomers have bulky ring snbstitnents. This result coincides with the poor chiroptical property of poly(42) (73) and also with the very intense CD effects of poly(44) having bulky chiral silyl groups (256). Computational simulations verified that, unlike polyisocyanates which have a long persistence length of helical structure because of their stiff main chain, the main chain of poly(phenylacetylene) is quite fiexible and that, unless bulky substituents are incorporated, poly(phenylacetylene) exists in essentially randomly coiled conformation or in a helical conformation with very short persistence length. 

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