"Living" Cationic Polymerization of Indene. 3. Kinetic Investigation of the Polymerization of Indene Initiated with Cumyl Methyl Ether and Cumyl Chloride in the Presence of Titanium Derivatives

Abstract

The kinetics of the polymerization of indene in dichloromethane solution, initiated with cumyl methyl ether and cumyl chloride, in the presence of titanium derivatives (TiCl 4 and TiCl 3 OBu), at variable temperatures (0 to -62 °C), have been investigated by adiabatic calorimetry under vacuum. At -40 °C, with cumyl methyl ether as an initiator, an internal first-order plot with respect to the monomer is observed after 60% yield, and initiation is completed before the end of the polymerization. The polymerization is apparently living or living, which means only that the molecular weight increases linearly with polymer yield. With the CumCl/TiCl 4 initiating system, complete initiation is obtained only in the presence of dimethyl sulfoxide (DMSO). Addition of DMSO increases the initiation rate, decreases the apparent propagation rate constant, and allows the observation of a first-order plot and an apparently living process. The use of a common ion salt (tetra-n-butylammonium pentachlorotitanate) has a similar effect. With the CumCl/TiCl 3 OBu initiating system, an apparently living polymer is obtained without additive. These data, and the negative apparent activation energies observed, imply that several types of chain ends are present in variable concentrations in the solution (covalent inactive species, ions pairs, and free ions), involving a reversible termination. These results, as well as the occurrence of transfer reactions, may be explained, as in conventional carbocationic polymerization, by a propagation involving ionic active centers.