Synthesis and radical ring-opening polymerization of 1-phenyl-2-vinylcyclopropane in the presence of TEMPO

Synthesis and radical ring-opening polymerization behavior of 1-phenyl-2-vinylcyclopropane (PhVCP) were examined. PhVCP was synthesized by the coupling reaction of butadiene with phenyldiazomethane, where cis and trans isomers were obtained with the ratio 78 : 22. Radical polymerization of PhVCP was carried out in bulk at 60–180°C with 2,2′-azoisobutyronitrile, benzoyl peroxide, or di-tert-butyl peroxide as initiator to obtain a 1,5-ring-opened polymer with M_n ≈ 1 900. When PhVCP was polymerized in the presence of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), M_n of the obtained polymer increased with time. The radical polymerizability of PhVCP is much lower compared with that of styrene. From the molecular-orbital calculation of both monomers, it has been suggested that this is not caused by an electronic factor of the vinyl group but by side reactions such as the abstraction of a hydrogen atom from the allylic position of PhVCP.