New monomer, methacryloyl toluenesulfonylhydrazide (MATSH) containing foamable sulfonylhydrazide functional group after decomposed by heating, was synthesized from p-toluenesulfonylhydrazide (TSH) with methacryloyl chloride, and used to obtain poly(MATSH) as a polymeric foaming agent (PFA) in dry THF at 70 A degrees C using AIBN as an initiator. The structures of synthesized MATSH and poly(MATSH) were identified by FT-IR and H-1-NMR spectroscopies. The decomposition temperature of poly(MATSH) was determined to be 224 A degrees C and this temperature was decreased into around 160 A degrees C by adding an activator such as surface-treated urea to polymer. The exothermic temperature and heat determined by the decomposition of the polymer were 260 A degrees C and 447 J/g. The amount of gas evolution for poly(MATSH) measured at decomposition temperature was 90 mL/g. Furthermore, the polymer incorporated with PFA showed better skin and fine cell structure as well as better mechanical properties such as elongation and compression set due to better compatibility of the developed PFA with polymers than those added with TSH.