FREE-RADICAL COPOLYMERIZATION OF ELECTRON-RICH VINYL MONOMERS WITH ACRYLONITRILE COMPLEXED TO ZINC-CHLORIDE

The spontaneous free radical copolymerizations of a series of electron-rich olefins with acrylonitrile (AN) complexed to zinc chloride (ZnCl2) have been investigated in solution. With styrene (St) and 2-vinylnaphthalene, an alternating copolymerization occurred without added initiator at 40-degrees-C. Using p-methylstyrene as the electron-rich olefin, no-initiator spontaneous alternating copolymerization was observed at 30-degrees-C. Copolymer formed in an amount equal to that of the ZnCl2 used. With p-methoxystyrene (pMeOSt) and with isobutyl vinyl ether (IBVE), the copolymerizations were conducted in the presence of ethyldiisopropylamine (EDIA) to inhibit cationic homopolymerization of these monomers. The copolymerization with pMeOSt proceeded to high yield, but the copolymers were rich in pMeOSt and the rates were slow presumably due to competitive complexation of ZnCl2 with the methoxy-substituent. Using IBVE only low yields of a random copolymer were obtained, and again competitive coordination with ZnCl2 appears responsible. The small molecules accompanying these spontaneous copolymerizations were shown by GC/MS to possess cyclobutane and Mayo adduct structures. The mechanism of these spontaneous copolymerizations cannot be decided on the basis of the small molecules formed, but the increase of copolymer molecular weight with time at constant yield speaks for a diradical mechanism.