STEREOREGULATION IN THE FREE-ION PROPAGATION OF OPTICALLY-ACTIVE ALKYL VINYL ETHERS

Trimethylvinyloxysilane (TMVO), (-)-menthyl vinyl ether (MVE), and (S)-l-methylpropyl vinyl ether (BVE) have been polymerized using tropylium hexachloroantimonate as cationic initiator under conditions in which free carbocations are the important propagating intermediates. The bulky and nonoptically active TMVO yielded highly syndiotactic polymers in accordance with current theories regarding stereoregulation in propagation by unassociated species such as free radicals. In complete contrast, the equally bulky but optically active MVE yielded highly isotactic polymers indicative of a pronounced chirality induced stereoregulation during the chain growth process. BVE yielded polymers having optical activity consistent with a degree of isotacticity approximately one half of that for the most isotactic fraction reported in the literature. Implications of these results for the mechanisms of cationic polymerization of alkyl vinyl ethers are discussed. © 1979, American Chemical Society. All rights reserved.