Comonomers contraining the phenyl t-butyl carbonate moiety have previously been incorporated into acid-producing polymers to act as traps for acid evolved and thereby lend stability to the polymer. To better understand the thermal fragmentation of such materials, a homopolymer, poly([4-(t-butyoxycarbonyloxy)phenyl]merthyl acrylate)(PBPMA), has been prepared, fully characterized, and subjected to examination by thermogravimetry (TGA). In the main, this polymer undergoes multistep degradation to evolve isobutylene and carbon dioxide, to extrude a quinoid aryl fragment and to form a residue of poly(acrylic acid) which may degrade further with the evolution of water, carbon dioxide, and carbon monoxide.