Styrenic copolymers comprising styrene, methyl methacrylate, and maleic anhydride were developed to improve the heat-resistance property of poly(methyl methacrylate) (PMMA). The optical, thermal, and mechanical properties were examined for the blend specimens prepared by an injection-molding machine using melt-mixed samples. It was found that the copolymers, which were miscible with. PMMA, increase the glass transition temperature and therefore the Vicat Softening temperature. Furthermore, the blends were completely transparent as similar to PMMA.