The cationic polymerization of isobutylene（IB）by utilizing difunctional initiator p-dicumyl chloride（DCC）in conjunction with coinitiator AlCl

3

was carried out in CH

2

Cl

2

/Hex（40/60

V/V）solvent mixtures.The effects of concentrations of 2

6-di-tert-butylpyridine（DtBP）

triphenylamine（TPA）and AlCl

3

on monomer conversion

molecular weight and molecular weight distribution（MWD）of polyisobutylene（PIB）were investigated.The small amount of water in the polymerization system in conjunction with AlCl

3

could induce a conventional uncontrolled rapid polymerization of IB and lead to polyisobutylene with broad molecular weight distribution（M

w

/M

n

=4.55）.It was found that the GPC trace of resultant polymers obtained by DCC/H

2

O/AlCl

3

systems exhibited a bimodal distribution

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

i.e.

H+AlCl

<

sub

>

3OH-（a）and AlCl-+

4

C（CH

3

）

2

C

6

H

4

（CH

3

）

2

C +-AlCl

4

（b）even at high DCC concentrations.The initiation by active center（b）was increased whereas the molecular weight of the polymer decreased with a decrease in AlCl

3

concentration.The addition of proton trap DtBP in the monomer solution could obviously decrease or even suppress the initiation from active center（a）and the chain transfer reaction to monomer

leading to the polymers with unimodal molecular weight distribution.The initiation from active center（a）could be suppressed by introduction of TPA and DtBP even at low DCC concentrations.A desirable cationic polymerization of IB would be achieved with the DCC/AlCl

3

initiation system in the presence of TPA and DtBP

and the telechelic tert-Cl-polyisobutylene with relatively high molecular weight（M

w

=103200）and unimodal molecular weight distribution（M

w

/M

n

=2.09）could be obtained.