Syntheses and chiroptical studies of optically active polymethacrylates and polyisocyanides

A series of optically active block polymethacrylates, azo-containing random polymethacrylates, azo-containing polyisocyanides and (5) helicene-based polyisocyanides were synthesized by atropogenic (screw-sense-selective) polymerization. A film of trityl methacrylate-block-methyl methacrylate copolymer containing 1 wt% of diphenyl-p-tolylsulfonium triflate can undergo a partial racemization upon UV (254 nm) irradiation and baking (125{dollar}spcirc{dollar}C). Under the similar conditions, a film cast from cyclohexyldiphenylmethyl methacrylate-block-methyl methacrylate copolymer can undergo a complete racemization catalyzed by photogenerated acid. These results have demonstrated that the chemical process initiated by irradiation (writing) involves the photogeneration of an acid which catalyzes thermal cleavage of the bulky ester groups. The permanent change in optical rotation of these polymer films can be detected (reading). Photoisomerization of some optically active, azo-containing random polymethacrylates and polyisocyanides in solution indicated that configurational change of side-chain azo chromophore (trans to cis) under UV (300 nm) irradiation could induce conformational change of the polymer backbone to a certain extent. The main-chain chirality of a (5) helicene-based polyisocyanide was achieved by a chiral transfer from a remote chiral side group during polymerization of a chiral (5) helicene-based isocyanide.