Living cationic isomerization polymerization of beta-pinene. Initiation with HCl-2-chloroethyl vinyl ether adduct TiCl3(OiPr) in conjunction with nBu(4)NCl

The first example of living cationic isomerization polymerization of beta-pinene was achieved with an initiating system that consists of the HCl-2-chloroethyl vinyl ether adduct [1a; CH3CH(OCH2CH2Cl)Cl] and isopropoxytitanium trichloride [TiCl3(OiPr)] in the presence of tetra-n-butylammonium chloride (nBu(4)NCl) in CH2Cl2 at -40 and -78 degrees C. The number-average molecular weight of the polymers (<(M)(n)over bar> less than or equal to 5 x 10(3)) increased in direct proportion to monomer conversion,and the molecular weight distribution of the polymers was relatively narrow (<(M)(w)over bar>/<(M)(n)over bar> similar to 1.3). The living nature of the polymerization was further demonstrated by monomer-addition experiments. A similar living polymerization was also feasible with the HCl-styrene adduct or 1-phenylethyl chloride [1b; CH3CH(Ph)Cl] in conjunction with TiCl3(OiPr) and nBu(4)NCl. H-1 NMR analysis of the polymers from 1a showed that 1a serves as an initiator and generates poly(beta-pinene) chains consisting of the 1-(2-chloroethoxy)ethyl head group, a tert-chloride tail group, and isomerized beta-pinene repeat units with a cyclohexene ring.