Preparation and properties of crystalline polystyrene III. Copolymerization

With mononuclear half-titanocenes such as CpTiCl₃, IndTiCl₃, Cp*TiCl₃ and a siloxane-bridged dinuclear half-titanocene, Cl₃Ti-CpSi(CH₃)₂-O-Si(CH₃) ₂-O-Si-(CH₃)₂Cp-TiCl₃ cocatalyzed by modified methylaluminoxane, the copolymerization of styrene (St) with ethylene(E), p-methylstyrene (PMS) and vinyl naphthalene (VN) was carried out, and copolymerization behavior as well as properties of the obtained polymer were examined for each catalyst. In copolymerization of St and E, the mixture of homopolymers, syndiotactic polystyrene and polyethylene, was obtained mainly with a less amount of copolymer, which intimated that these titanocenes are unsuitable for St/E copolymer preparation. By copolymerization of St with PMS, the copolymer was prepared with a enhanced catalyst activity. The melting temperature (T_m) and initial decomposition temperature (T_di) of copolymer decreased and the difference of T_m and T_di could be controlled with the amount of added PMS. For copolymerization of St and VN, the catalyst activity and T_m of copolymer decreased drastically even with a small amount of VN.