A random copolymer of（poly（vinyl） acetate-co-isopropenyl acetate）（PVIPA） with number-average molecular weight（M

n

） of 9600 and relatively narrow molecular weight distribution（MWD

M

w

/M

n

=2.03）was prepared by free radical copolymerization of vinyl acetate with isopropenyl acetate using AIBN as initiator.Then

the cationic polymerizations of isobutylene were carried out by using the above copolymer PVIPA as macroinitiator in conjunction with coinitiator TiCl

4

in the absence of an external nucleophilic additive.The effects of [TiCl

4

]

[PVIPA]

the ageing temperature and time on monomer conversion and initiation efficiency of PVIPA

molecular weight and molecular weight distribution were investigated.Both PVIPA and H

2

O in the polymerization system would complex with Lewis acid TiCl

4

to form the two different active centers（A） and（B）.（A） and（B） initiated the cationic polymerization of isobutylene（IB） in competition and led to PVIPA-g-PIB and homopolymer PIB

respectively.The copolymerization product was extracted by methanol to remove unreacted macroinitiator.The initiation efficiency of PVIPA was dependent on [TiCl

4

]

the ageing temperature and time.The polymerization could be started under the condition of enough concentration of TiCl

4

and the initiation efficiency of PVIPA increased with increases in [TiCl

4

] and or a decrease in or at lower ageing temperature or for longer ageing time.However

the initiation from（B） increased when TiCl

4

was at high concentrationc.The initiation efficiency of PVIPA increased up to around 90% under the appropriate conditions.The graft copolymer PVIPA-g-PIB with M

n

of 163700 and polydispersity of 2.17 could be obtained under proper reaction conditions.Furthermore

the initiation efficiency was also increased by introduction of small amount of 2

6-dimethyl pyridine（DMP）.