The effect of solvents on asymmetric induction cationic copolymerization of l-menthyl vinyl ether with indene

Cationic copolymerization of l-menthyl vinyl ether (l-MVE) with indene (IN) was carried out in several solvents with BF₃OEt₂ as catalyst at 0°C. The solvents used in this study were selected toluene (Tol), chloroform (CHCl₃), chlorobenzene (BzCl), 1,2-dichloroethane (EtCl₂), and nitrobenzene; (BzNO₂)/Tol = 65/35 mixture solvent. l-Methyl residue, which is an optically active side chain of copolymer produced by cationic copolymerization, was removed with dry hydrogen bromide gas by ether cleavage reaction. The copolymer vinyl alcohol(VA)–lN], produced by the ether cleavage reaction, also showed optical rotation. From this result, therefore, it was concluded that asymmetric induction takes place in the copolymer main chain. The efficiency of asymmetric induction was determined by the measurement of optical rotation of VA–IN copolymer after the ether cleavage reaction. The efficiency of asymmetric induction in the copolymer main chain developed from the variation on polymerization solvents; the order was Tol > EtCl₂ > BzCl > CHCl₃ > BzNO₂/Tol (65/35) mixture solvent.