The cationic polymerization of isobutylene (IB) by utilizing six functional initiator hexaepoxy squalane (HES) in conjunction with TiCl4 was carried out in CH2Cl2/n-Hex (40/60

V/V) solvent mixtures in the absence or in the presence of 2

6-dimethylpyridine (DMP) respectively.The effects of concentrations of HES

DMP on monomer conversion

molecular weight and molecular weight distribution (MWD) of the product polyisobutylene (PIB) were investigated.A small amount of water in the polymerization system in conjunction with TiCl4 could induce a conventional uncontrolled rapid polymerization of IB and led to polyisobutylene with broad molecular weight distribution.It is found that the GPC trace of resultant polymer obtained by HES/H2O/TiCl4 system exhibit a bimodal distribution

which is attributed to the competition of initiation from two different active centers

i.e.

H+TiCl4OH- (A) and HES+TiCl4OH- (B).The initiation from active center (B) increased with an increase in HES concentration.A large dosage of HES (［HES］＝2.24×10-3 mol/L) was needed to decrease the initiation from active center (A) to some extend but it was still difficult to suppress the initiation from (A) and the chain transfer reaction.According to the GPC and NMR characterization results of polymers，the controlled initiation from (B) could almost be achieved and the GPC traces exhibited relatively narrow unimodal MWD by addition of small amount of DMP.The mechanistic role of DMP is suggested to decrease the initiation from (A) and chain transfer to monomer.A desirable cationic polymerization of IB would be achieved with HES/TiCl4 initiation system in the presence of adequate amount of DMP

and the star-branched telechelic polyisobutylenes with relatively narrow MWD and tert-chloride end-groups could be prepared.