Living cationic polymerization of beta-pinene with 1-phenylethyl chloride/TiCl4/Ti(OiPr)(4)

The cationic polymerization of beta -pinene was carried out with l-phenylet hyl chloride as an initiator and the mixture of TiCl4 and tetraisopropoxyti tanium [Ti(OiPr)(4)] as a Lewis acid activator in CH2Cl2 at -40 degreesC. T he polymerization with strong Lewis acid TiCl4 alone completed instantaneou sly and gave the polymers with broad molecular weight distributions. The ad dition of weak Lewis acid Ti(OiPr)(4), which alone had no catalytic activit y for beta -pinene, retarded the polymerization by TiCl4 and led to polymer s with narrower molecular weight distributions. When [Ti(OiPr)(4)](0)/[TiCl 4](0)=1/3, the number-average molecular weight of the polymers increased in direct proportion to monomer conversion, and the molecular weight distribu tion of the polymers was narrow. The living nature of the polymerization wa s further demonstrated by monomer-addition experiments. H-1 NMR analysis of the polymers obtained at [Ti(OiPr)(4)](0)/[TiCl4](0)=1/3 showed that l-phe nylethyl chloride served as an initiator and generated poly (beta -pinene) chains with the CH3CH(C6H5) head group and a tert-Cl tail group.