Polymers from pine gum components: Radical and coordination homo and copolymerization of pinenes

The present work is aimed at studying the reactivity of α- and β-pinenes in radical polymerization. The pinene homopolymers obtained were oligomers, showing both isomers similar reactivities. In order to achieve products of higher molecular weight, the radical copolymerization of α- and β-pinene with methyl methacrylate and styrene was performed, giving rise to polymers with M̄_w varying from 11 500 to 53 000. In radical copolymerization α-pinene showed to be more reactive than β-pinene. All the radical reactions performed were carried out with a Ziegler-Natta catalyst, TiCL₄/Et₃Al, and with Et₃Al. Under the conditions tested, β-pinene did not undergo any polymerization reaction and the cocatalyst showed a pronounced catalytic effect. The coordination polymers obtained at 5 h had chain lenghts of the same order of magnitude of the corresponding radical copolymers obtained at 50 h, although for much lower overall conversion.