Cationic grafting of olefins from PVC: The effect of reaction conditions

The cationic grafting of isobutylene, styrene, ol-methylstyrene, and beta - pinene from a poly(vinyl chloride) (PVC) backbone was investigated. Graftin g-from was induced by Et2AlCl in 1,2-dichloroethane and methylene dichlorid e solutions from 20 to -70 degreesC. The effects of temperature and proton trap [2,6-di-tert-butylpyridine (DtBP)] on grafting-from efficiency (G(eff) ), extent of grafting, branch length (molecular weight), and number of bran ches per PVC molecule were determined. Reducing the temperature invariably increased the G(eff) and the molecular weight of polyisobutylene, polystyre ne, poly(alpha -methylstyrene), and poly(beta -pinene) branches attached to PVC. The magnitude of the effects was different with the various olefins a nd depended on the reaction conditions. The effect of DtBP was examined in the 5 x 10(-4)-4 x 10(-3) mol/L range. By increasing the DtBP concentration the G(eff) increased; however, the number-average molecular weight of the grafted branches decreased. The lengths of the grafted branches can be cont rolled, and G(eff)'s close to 100% were obtained. The fact that the proton trap reduced the molecular weights of grafted branches suggests that beside s proton scavenging, DtBP may also abstract protons from the growing carben ium ion site. (C) 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chern 3 9: 1675-1680, 2001.