Living Cationic Isomerization Polymerization of β-Pinene. 2. Synthesis of Block and Random Copolymers with Styrene or p-Methylstyrene

Block copolymers of β-pinene with styrene (St) or p-methylstyrene (pMeSt) were prepared by the sequential living cationic polymerizations initiated with the HCl adducts of styrene (1b: HCl−St) or 2-chloroethyl vinyl ether (1a: HCl−CEVE), respectively, in the presence of isopropoxytitanium trichloride [TiCl3(OiPr)] and tetra-n-butylammonium chloride (nBu4NCl) in CH2Cl2 at −40 °C. As for the β-pinene−St pair, both AB and BA block copolymers (M̄w/M̄n ∼ 1.3) were obtained by this method. With pMeSt, the addition of β-pinene to the living pMeSt polymers gave block copolymers with narrow molecular weight distributions (MWDs) (M̄w/M̄n ∼ 1.2), whereas the reverse order of addition led to block copolymers with broad MWDs (M̄w/M̄n ∼ 1.9). In the polymerization of a mixture of β-pinene and St, the former was consumed faster to give tapered copolymers. In contrast, β-pinene and pMeSt were copolymerized nearly at the same rate to give random or statistical copolymers.