| Abstract: | The thermal degradation of some polythiocarbonates obtained from bisphenol A bischloroformate and dithiols have been investigated by thermogravimetry and by direct pyrolysis in the mass spectrometer operating both in electron and chemical ionization. Poly(bisphenol A-co-tri-methylenedithiocarbonate) decomposes by an intramolecular exchange process (back-biting) producing trimethylene-1,3-dithiocarbonate and bisphenol A polycarbonate. The latter undergoes further thermal degradation at higher temperature yielding cyclic oligomers. Polymers containing tetramethylene-1,4-dithiocarbonate and hexamethylene-1,6-dithiocarbonate units decompose by the same mechanism, but the elimination of the dithiocarbonate units is not as fast and selective as the previous case. Some bisphenol A units are eliminated in the first thermal degradation stage and a rearrangement reaction producing ether linkage also occurs. Poly(phenylene-1,3-dithiocarbonate) decomposes by CO and COS loss with formation of sulfide and disulfide bridges along the polymer chains, which undergo further thermal degradation by a back-biting process yielding a series of cyclic compounds. The thermal degradation of Poly(bisphenol A-co-phenylenedithiocarbonate) takes place through an interchange reaction producing phenylene-1,3-dithiocarbonate sequences which further decompose as the corresponding polymer. The remaining bisphenol A polycarbonate decomposes at higher temperature producing cyclic carbonates. |
