DEGRADATION OF POLYDIMETHYLSILOXANE-BLOCK-POLYSTYRENE COPOLYMER

Thermal decomposition of polydimethylsiloxane-(azobiscyanopentanoyl es ter)s (PDMS-ACP) in the presence of styrene (St) monomer yielded polyd imethylsiloxane-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 proces s for PSt and PDMS-b-PSt were determined by Ozawa's method. The values of E-a in thermal degradation for copolymers increased with increasin g initial conversion, and were comparable with the values for PSt. The incorporation of PDMS segments in the block copolymers improved the t hermo-oxidative stability of PSt. However, the degradation of PSt segm ents in the copolymers was not affected greatly by the siloxane conten t. (C) 1997 Elsevier Science Limited.