On the thermolysis of poly(chloroalkyl methacrylates) and poly(chloroalkyl acrylates): Part 1-Poly(2,2,2-trichloroethyl methacrylate)

Abstract

The thermal degradation of poly(2,2,2-trichloroethyl methacrylate). PTCMA, in the absence and presence of O2 was studied and compared with that of poly(ethyl methacrylate), PEMA. In the absence of O2 the two polymers behaved quite differently. Apart from unzipping, PTCMA became partially insoluble due to intermolecular crosslinking at T < 240°C in contrast to PEMA which remained soluble. At T > 240°C both polymers degraded effectively by depolymerization. O2 prevented crosslinking of PTCMA and retarded unzipping (shift of onset to higher temperature). It was inferred from product analysis that at T < 240°C the thermolysis of PTCMA is initiated by decomposition of pendant groups. Primary bond cleavage at various positions in the side groups, {A figure is presented} results in the formation of free radicals. In the presence of O2, hydrogen abstraction from CH2 groups in the polymer backbone generates carbon centered radicals {A figure is presented} which can be converted into oxyl radicals {A figure is presented}. The latter can give rise to main-chain scission. Apart from the monomer, the main volatile compounds formed in the presence of O2 are: 2,2,2-trichloroethyl pyruvate, CH3COCOOCH2CCl3 and 2-methyl-oxirane carbonic acid 2,2,2-trichloroethyl ester, {A figure is presented} Mechanisms concerning the initiation of thermolysis of PTCMA are proposed on the basis of the various thermolysis products.