The carbocationic polymerization of isobutylene (IB) with H2O/TiCl4 as initiating system in the presence of pyridine (Py)

triethylamine (TEA) or N

N-dimethylacetamide (DMA) was conducted in a mixture of methylene dichloride (CH2Cl2) and n-hexane (Hex).The effects of solvent polarity

polymerization temperature and monomer concentration on the conversion

molecular weight (MW) and molecular weight distribution (MWD

Mw/Mn) of polyisobutylene (PIB) were investigated.The polymerization rate increased greatly with an increase in solvent polarity.The polymerization rate and the molecular weight of PIB obtained increased obviously with decreasing the polymerization temperature.The corresponding active energy of propagation (ΔE) was calculated to be -28.8 kJ/mol

-25.8 kJ/mol and -29.0 kJ/mol in the presence of Py

DMA and TEA respectively.The chain transfer side-reaction decreased and molecular weight distribution of PIB products became narrow with decreasing polymerization temperature.The polymer with tert-chlorine end group were obtained at -60℃.Both the monomer conversion and molecular weight of PIB increased with isobutylene concentration (［IB］0≤2.5 mol/L) while molecular weight distribution kept relatively narrow and the polydispersity (Mw/Mn) is around 1.4 and 1.5 for the carbocationic polymerization of IB in the presence of Py and TEA respectively.The constant of chain transfer reaction to monomer (CM) was calculated to be 5.5×10-4 and 6.6×10-4 for the carbocationic polymerization of IB in the presence of Py and TEA respectively.A desirable polymerization of IB with apparent absence of chain transfer reactions could be obtained by H2O/TiCl4 initiating system in the presence of Py or DMA at -60℃ under the appropriate reaction conditions.