Abstract: In this study bulk polymerization of methacrylic derivative of thiophenol (PSM) with commercial monomers styrene (St) and methyl methacrylate (MMA) was presented. This monomers had been chosen because of their good thermal and optical properties, which make them useful in optical fibres technology. Copolymerization MMA or St with PSM in glass form, with different weight ratio of monomers (1:10, 1:20; MMA or St : PSM) was performed. As a initiator α,α’-azoiso-bis-butyronitrile (AIBN) was used. This process was carried out in water bath at 60 oC for 2 h and 90 oC for 12 h. As an analytical method coupled TG/DTG/QMS was used.