CATIONIC RING-OPENING POLYMERIZATION OF 2-ISOPROPENYL-4-METHYLENE-1,3-DIOXOLANE IN DONATIVE SOLVENTS

2-Isopropenyl-4-methylene-1,3-dioxolane (1) undergoes cationic polymer ization in donative solvents without crosslinking to afford poly(ether -ketone) 2 having two unit-structures. When solvents having medium don or number (DN = 14,1-17,1), such as acetonitrile, dioxane, ethyl aceta te, and propylene carbonate, were used, 2 was obtained in high yields. When solvents having higher DN (>19,2), such as diethyl ether, DMF, a nd DMAc, were used, the rate of polymerization decreased considerably, although polymerization proceeded even in the most donative solvent, DMAc (DN = 27,8). The ratio of the unit-structures was independent of the solvent used. When ethanol was used as the solvent, ethoxyacetone and methacrolein were obtained instead of 2. It was concluded that har d nucleophiles such as ethanol attack at the alpha'-position of termin al oxyallyl cation, while soft nucleophiles such as monomer 1 attack a t the alpha- or gamma-position.