Kinetic Investigation of the Carbocationic Polymerization of Isobutylene with the H₂O/TiCl₄/ED Initiating System

Abstract

The cationic polymerizations of isobutylene (IB) initiated by the H 2 O/TiCl 4 in dichloromethane (CH 2 Cl 2 ) at −30 °C were carried out in the absence and presence of various external electron pair donors (EDs). Controlled polymerization with a slow polymerization rate and a narrow molecular weight distribution (MWD, M w / M n = 1.11−1.28) of the polymer was achieved by using certain appropriate H 2 O/TiCl 4 /ED systems. The kinetics of the IB polymerization with the H 2 O/TiCl 4 /ED initiating system was investigated. It indicated that the polymerization rate was first-order with respect both to monomer and to initiator concentrations in the presence of strong or weak EDs. Polymerizations exhibited a second-order dependence on TiCl 4 concentration in those cases where weak EDs, such as methyl acetate (MAC), methyl acrylate (MA), sulfolane (HDF), or methyl benzoate (MB), were used. On the other hand, first order in TiCl 4 concentration was observed when strong EDs, such as dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), pyridine (Py), or triethylamine (TEA), were used.