Influence of monomer concentration and dielectric constant on transfer reactions in the carbocationic polymerization of indene

The cationic polymerization of indene initiated with cumyl chloride and sta nnic chloride in solution in methylene chloride at -15 degrees C is control led up to M-n = 20 000, with a low transfer to monomer constant (k(trM)/k(p ) = 9 x 10(-4)). Experiments carried out in compensated media allowed kinet ic measurements and showed that the sharp decrease of the M-n at high inden e concentrations results from zero order transfer due to the change of diel ectric constant (k(tr)/k(p) = 1.5 x 10(-3) for a dielectric constant of 5.4 ). In methylene chloride, for indene concentrations higher than 2 mol.L-1, the heat release of the fast reaction adds up to the zero order transfer to lower the molar masses. Bimodal distributions result from propagation on f ree ions and ion pairs.