We report the controlled synthesis of micrometre-sized thermally labile PMMA particles. This was achieved by a combination of dispersion polymerization and chain transfer techniques. The dispersion polymerization allows for the synthesis of spherical micrometre-size particles of PMMA, whereas the use of cobalt chain transfer agents results in vinylidene end-functionalized PMMA. Furthermore, the vinylic end-groups facilitate thermal depolymerization and this consequently limits the thermal stability. We anticipate that these PMMA particles could further serve as useful modifiers to generate porous polymers, including siloxane elastomers.