Cationic polymerization of isobutylene with H2O/TiCl4 initiating system in the presence of electron pair donors

Cationic polymerization of isobutylene (IB) in a mixture of methylene dichloride (CH2Cl2) and n-hexane (n-Hex) was conducted by using H2O as initiator, TiCl4 as co-initiator in the presence of strong external electron pair donor (ED), such as pyridine (Py), dimethylacetamide (DMA) or triethylamine (TEA). The effects of ED concentration, TiCl4 concentration, solvent polarity, polymerization temperature (T) and time on IB polymerization, molecular weight (MW) and molecular weight distribution (MWD, Mw/Mn) of polyisobutylene (PIB) products were investigated. The relative amount of polymer formed via uncontrolled initiation by conventional active species (I) decreased with increasing the solvent polarity, TiCl4 concentration and ED concentration in the polymerization. The desirable polymerization of IB with apparent absence of chain transfer reactions could be obtained by H2O/TiCl4 initiating system in the presence of ED under the appropriate reaction conditions. The external electron pair donors and TiCl4 did specially play important and effective roles on polymerization.