Mechanisms of Thermal Decompositions of Polysulfones: A DFT and CBS-QB3 Study

The thermal stabilities of polysulfones with different lengths of the carbon-linker between sulfone groups have been explored. B3LYP and CBS-QB3 calculations on possible thermal decomposition mechanisms of model compounds show that even carbon-linked polysulfones copolymers of alkenes and SO 2 decompose by a radical chain mechanism involving facile depolymerization after initial homolysis. Sulfinate impurities [−S( O)−O−CH 2 −], formed as a minor component in polysulfone synthesis, can serve as good initiators for the radical mechanism. Polysulfones with odd-carbon linkers do not readily depolymerize in this fashion owing to high barriers of depropagation; these polymers undergo thermal degradation by the slower cyclic β-elimination processes.