TRI-ARMED STAR POLYMERS BY LIVING CATIONIC POLYMERIZATION .1. TRIFUNCTIONAL INITIATORS FOR LIVING POLYMERIZATION OF ISOBUTYL VINYL ETHER

Tri-armed star polymers of isobutyl vinyl ether (IBVE) were synthesized by living cationic polymerization with a mixture of EtAlCl2 and a trifunctional initiator [CH3C(C6H4OCH2CH2OCH-(CH3)OCOCF3)3 (1) or C6H3(COOCH2CH2OCH(CH3)OCOCF3)3 (2)] at 0-degrees-C in the presence of 1,4-dioxane (an added base for carbocation stabilization). The tris(trifluoroacetate)-type initiators, 1 and 2, were obtained from the corresponding trifunctional vinyl ethers. The number-average molecular weights (M(n))BAR of the polymers thus prepared increased in direct proportion to monomer conversion and were close to the calculated values, assuming that each molecule of 1 or 2 produces one living chain; the molecular weight distribution (MWD) was very narrow (M(w)BAR/M(n)BAR < 1.1) throughout the polymerizations. The generation of three living ends per molecule of 1 or 2 was confirmed by comparing the polymerization with that by its monofunctional analogue [C6H5OCH2CH2OCH(CH3)OCOCF3 (3) or C6H5COOCH2CH2OCH(CH3)OCOCF3 (4), respectively], as well as by end-capping analysis with sodiomalonic ester. When the ester-type core of the poly(IBVE) obtained by 2 was hydrolyzed under alkaline conditions, the M(n)BAR was reduced to one-third with the narrow MWD unchanged, thus indicating that the polymer possesses exactly three arm chains with a uniform and controlled length.