A Cationic Polymerization of Phenylcyclopropane

A cationic polymerization of phenylcyclopropane (I) yielded a polymer, which have the benzene ring in the backbone chain, instead of the expected ring-opening polymer. The structure of the polymer and the reaction mechanism was studied.(I) was polymerized with cationic initiators such as AlCl3 in methylenechloride at above 0°C to yield a low molecular weight polymer. Polymerization was found to proceed stepwise, and a growth reaction was observed even between growing polymers. The infrared, NMR and UV spectra, C-methyl chemical analysis and oxidation of the polymer suggested the following structure. _??_ The growth reaction was considered to be the repetition of a Friedel-Crafts substitution on the benzene ring by the ethylbenzyl cation which was derived by the opening of the cyclopropyl group. The UV spectra and the existence of fluorescence in polymer suggests the formation of anthracene group in the polymer, and this might explain at least a part of the termination reactions.