Initiation of polymerization by ammonium trichloracetate in the presence of copper derivatives — A tracer study

Abstract

The mechanism of the initiation of the free-radical polymerization of methyl methacrylate by ammonium trichloracetate in the presence of copper derivatives has been studied with the aid of 14 C labelling of the salt in the two positions. An earlier suggestion that the mechanism depends critically on the salt concentration has been confirmed. At low salt concentrations in the presence of Cu(acac) 2 the initial radicals formed are exclusively ĊCl 3 [equation (2)]. At high salt concentrations, initiation by CuCl involves formation of ĊOO − predominantly, but some production of ĊCl 3 may also occur [equation (5)]. High salt concentrations together with Cu(acac) 2 yield ĊCl 3 radicals [equation (9)]. It is suggested that, with high salt concentrations, termination by derivatives of Cu II occurs, with formation of Cu I , which may then react further. In this way cyclic processes involving alternate oxidation and reduction of copper may arise.