The living carbocationic polymerization of isobutylene(IB) has been investigatedby the 2-chloro-2

4-

4-trimethylpentane (TMPCl)/TiCl4 initiating system in the presence of N

N-dimethylaniline (DMAB) and Et3Nas electron pair donors (EDs) by use ofthe mixedsolvent dichloromethane hexane (40/60 V/ V)/ at -80℃under conventional laboratoryconditions. It is demonstrated that living polymerization can be achieved when theconcentration of electron pair donors such as DMAB or Et3N is higher than that of trace water in the polymerization system

and that polymers with narrow moleculat weightdistribution can be obtained. The rate of polymerization is also reduced because of adding EDs which indicates that stabler active centers are formed.