Controlled radical copolymerization of β-pinene and acrylonitrile

The feasibility of the radical copolymerization of beta-pinene and acrylonitrile was clarified for the first time. The monomer reactivity ratios evaluated by the Fineman-Ross method were r(beta-pinene) = 0 and r(acrylonitrile) 0.66 in dichloroethane at 60 degrees C with AIBN, which indicated that the copolymerization was a simple alternating copolymerization. The addition of the Lewis acid Et2AlCl increased the copolymerization rate and enhanced the incorporation of beta-pinene. The first example for the synthesis of an almost perfectly alternating copolymer of beta-pinene and acrylonitrile was achieved in the presence of Et2AlCl. Furthermore, the possible controlled copolymerization of beta-pinene and acrylonitrile was then attempted via the reversible addition-fragmentation transfer (RAFT) technique. At a low beta-pinene/acrylonitrile feed ratio of 10/90 or 25/75, the copolymerization with 2-cyanopropyl-2-yl dithiobenzoate as the transfer agent displayed the typical features of living polymerization. However, the living character could be observed only within certain monomer conversions. At higher monomer conversions, the copolymerizations deviated from the living behavior, probably because of the competitive degradative chain transfer of beta-pinene. The beta-pinene/acrylonitrile copolymers with a high alternation degree and controlled molecular weight were also obtained by the combination of the RAFT agent cumyl dithiobenzoate and Lewis acid Et2AlCl. (c) 2006 Wiley Periodicals, Inc.