Acceleration effect of N-allyl group on thermally induced ring-opening polymerization of 1,3-benzoxazine

Abstract

Thermally induced ring-opening polymerization of monofunctional N-allyl-1,3-benzoxazine 1a was compared with that of N-(n-propyl)-1,3-benzoxazine 1b to clarify an unexpected effect of allyl group to promote the polymerization, that is, in spite of the comparable bulkiness of allyl group to n-propyl group, the polymerization of 1a was much faster than that of 1b. Such a difference in polymerization rate was also observed similarly in the comparison of thermally induced polymerization of a bifunctional N-allyl-benzoxazine 2a with that of a bifunctional N-(n-propyl) analogue 2b. These observations implied a certain contribution of an electron-rich CC double bond of the N-ally group to promotion of the ring-opening reaction of 1,3-benzoxazine into the corresponding zwitterionic species, which would involve a mechanism to stabilize the cationic part of the zwitterionic species based on “neighboring group participation” of the CC double bond. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010