Living cationic isomerization polymerization of beta-pinene .2. Synthesis of block and random copolymers with styrene or p-methylstyrene

Block copolymers of beta-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 3-chloroethyl vinyl ether (1a: HCl-CEVE), respectively, in the presence of isopropoxytitanium trichloride [TiCl3(OiPr)] and tetra-n-butylammonium chloride (nBu(4)NCl) in CH2Cl2 at -40 degrees C. As for the beta-pinene-St pair, both AB and BA block copolymers (<(M)(w)over bar>/<(M)(n)over bar> similar to 1.3) were obtained by this method. With pMeSt, the addition of beta-pinene to the living pMeSt polymers gave block copolymers with narrow molecular weight distributions (MWDs) ((M) over bar(w)/(M) over bar(n) similar to 1.2), whereas the reverse order of addition led to block copolymers with broad MWDs (<(M)(w)over bar>/<(M)(n)over bar> - similar to 1.9). In the polymerization of a mixture of beta-pinene and St, the former was consumed faster to give tapered copolymers. In contrast, beta-pinene and pMeSt were copolymerized nearly at the same rate to give random or statistical copolymers.