The carbocationic polymerization of isobutylene (IB) in a mixture of methylene dichloride (CH2Cl2) and hexane (Hex) was conducted by using H2O as initiator

TiCl4 as co-initiator in the presence of a small amount of oxygencontaining additive

such as methanol(MeOH)

isopropanol or ethyl ether.The effects of MeOH concentration

TiCl4 concentration

monomer concentration

solvent polarity and polymerization time on the IB carbocationic polymerization

polyisobutylene (PIB) yield

molecular weight (MW) and molecular weight distribution(MWD

Mw/Mn) and endgroups of PIB chains were investigated.The polymerization products were characterized by gel permeation chromatography (GPC) and 1H-NMR spectroscopy.The carbocationic polymerization of IB in C4 fractions including 2-butane

butane

isobutylene

1-butene and 1

3-butadiene by using H2O/TiCl4/MeOH as initiating system was also investigated.MeOH did play important and effective roles in polymerization initiated by H2O/TiCl4 system.The relative amount of polymers formed via uncontrolled initiation by conventional active species decreased with increasing the concentration of MeOH.MeOH and/or its complexe with TiCl4 interacted with the growing chain end to reduce its cationicity and thus to decrease the propagation rate

decrease MW

suppress the uncontrolled chain transfer and termination reactions

and thus to narrow MWD.The desirable polymerization of IB with relatively slow polymerization rate could be obtained by H2O/TiCl4 initiating system in the presence of MeOH under the appropriate reaction conditions

and PIB products with low molecular weight (Mn=1600～4600) and narrow unimodal molecular weight distribution (Mw/Mn=1.35～2.05) could be obtained.It is found that MeOH also played an extra important role in increasing the content of vinylidene (α-double bonds) in polymer chain ends.The tert-chlorine in PIB chain end obviously decreased with increasing MeOH concentration.The content of α-double bonds increased with decreasing H2O concentration and monomer concentration or prolonging polymerization time.The highly reactive polyisobutylene (HRPIB) with the content of α-double bonds more than 70% could be synthesized by using H2O/TiCl4 initiating system in the presence of MeOH

isopropanol and ether under the appropriate reaction conditions.Furthermore

the preliminary investigation on the IB polymerization in C4 fractions shows that the molecular weight

molecular weight distribution and the content of tert-chlorine end groups of PIB products decreased while the content of α-double bonds at end groups increased with MeOH concentration in the polymerization system.The polymer with Mn of 2000

Mw/Mn of 2.59 and vinylidene isomer content of 38.9% could be obtained.