Der Gegenionen-Effekt bei der durch Perchlorsäure initiierten Polymerisation von Styrol

The effect of various counter-ions has been investigated in the cationic polymerisation of styrene in 1,2-dichloroethane at different temperatures (238 K, 253 K). The soluble silver salts of the corresponding acids HBF₄, HClO₄, HPF₆, HAsF₆, and HSbF₆ were added to the reaction medium before initiation by perchlorid acid. Monomer consumption is seen to be incomplete under these circumstances. Initial polymerisation rates and the final degree of monomer conversion rise with decreasing nucleophilicity of the counter-ions.A kinetic scheme is proposed which is able to describe the course of polymerisation and gives the approximate values of the rate constants for propagation, termination and chain transfer reactions, respectively. The information obtained from GPC-measurements on the polymeric products supports the view that chain propagation takes place by at least two different forms of active species, the ratio of which is strongly determined by the nature of the added silver salt.