Radical Copolymerization of Spiro–substituted Cyclopentadienes

Radical copolymerizations of spiro[2,4]hepta–4,6–diene(SHD) and spiro[4,4]nona–1,3–diene(SND) were carried out. They gave only Diels–Alder adducts when maleic anhydride was used as comonomer, and styrene homopolymer was obtained in the presence of SHD and SND. On the other hand, true copolymers were formed when acrylonitrile(AN) and methacrylonitrile(MAN) were used as comonomers, and the following reactivity ratios were obtained. Although the radical reactivity of SHD monomer did not differ much from that of SND monomer, the structures of these units in copolymers were quite different. The SND unit was formed by the conventional 1,2– and 1,4–additions, while the SHD unit mainly consisted of the structures which were formed by the opening of the cyclopropyl ring. The structure of the SHD unit varied slightly with comonomers. This result was discussed on the basis of the competitive monomer addition and rearrangement of the growing SHD radical.