Polymers and copolymers of pentabromobenzyl acrylate (PBBA) with styrene were synthesized and characterized. Poly(PBBA) exhibits a rather high glass transition temperature (T-g) and good solvent resistance. The incorporation of PBBA moiety into polystyrene (PSt) enhances T-g, improves the thermal stability, and also does not adversely affect polystyrene’s mechanical properties. Copolymers prepared through both emulsion semibatch and batch processes exhibit random chain structures and possess similar properties such as T-g, inherent viscosity, and mechanical properties. Blends of poly(PBBA) and PSt demonstrate immiscible phase behavior, however their thermal stabilities are similar to the copolymers’ stability at the same PBBA content. It is thus shown that the thermal stability of the systems investigated in this work is essentially affected by composition, regardless of the distribution and dispersion of the PBBA polymer or copolymers.