PROTECTION AND POLYMERIZATION OF FUNCTIONAL MONOMERS .15. ANIONIC LIVING POLYMERIZATIONS OF 2-(3-VINYLPHENYL)-1,3-DIOXOLANE AND RELATED MONOMERS

Anionic polymerizations of the three acetal-protected styrene derivatives 2-(2-vinylphenyl)-(3a), 2-(3-vinylphenyl)- (3b), and 2-(4-vinylphenyl)-1,3-dioxolanes (3c) were carried out in THF at -78-degrees-C with a variety of initiators. The meta isomeric monomer, 3b, underwent anionic living polymerization to produce polymers of controlled molecular weights and narrow molecular weight distributions. New well-defined block copolymers of both the ABA and the BAB types were readily synthesized by the sequential polymerizations of 3b and styrene and vice versa. On the contrary, complications were observed in the polymerization of the ortho and para isomers, 3a and 3c. Soluble polymers with very broad molecular weight distributions from 3a and insoluble polymers from 3c were obtained in low yields by these polymerizations. Thus, the anionic polymerization behavior was significantly influenced by the difference in placement of the acetal group on the aromatic ring of the monomer. To explain these results, we propose a reaction mechanism based on the base-induced 1,6(or 1,4)-elimination of the acetal to generate the very reactive p(or o)-xylene intermediate. This is the first clear example that shows the positional effect of this substituent in the anionic polymerization of styrene derivatives. The anionic polymerizations of some related styrene derivatives containing acetal functionalities are also described.