Degradation of polydimethylsiloxane-block-polystyrene copolymer

Thermal decomposition of polydimethylsiloxane-(azobiscyanopentanoyl ester)s (PDMS-ACP) in the presence of styrene (St) monomer yielded polydimethylsiloxane-polystyrene block copolymers (PDMS-b-PSt). The thermal and thermo-oxidative degradation of these copolymers was investigated by thermogravimetry, and compared with that of unmodified polystyrene (PSt). The apparent activation energies E-a in the degradation process for PSt and PDMS-b-PSt were determined by Ozawa's method. The values of E-a in thermal degradation for copolymers increased with increasing initial conversion, and were comparable with the values for PSt. The incorporation of PDMS segments in the block copolymers improved the thermo-oxidative stability of PSt. However, the degradation of PSt segments in the copolymers was not affected greatly by the siloxane content. (C) 1997 Elsevier Science Limited.