We have developed new high heat resistant styrenic polymers. These new polymers are comprised of styrene, maleic anhydride, and methacrylic monomer and produced by our unique technologies based on free radical polymerizations. These new polymers are miscible with poly(methyl methacrylate) (PMMA) and have higher heat resistant more than 20 degrees C than that of PMMA. The heat resistance of PMMA can be easily improved by melt blending with these new polymers using extruder. Furthermore, an excellent transparency of PMMA is not degraded by blending with these new polymers. These new polymers have lower surface hardness than PMMA. However, surface hardness of these polymer blends are kept to be same level as PMMA if a ratio of this new polymer is to 50%. These unique properties are worth a lot for the industrial materials and can provide high heat resistant PMMA.