Emulsion-polymerized copolymers of methyl methacrylate and N-cyclohexylmalemide were synthesized and used for blending with poly(vinyl chloride) (PVC) to improve the heat resistance of PVC. The thermal stabilities of the blends with different copolymer contents were characterized by thermogravimetric analysis, torsional braid analysis, and the Vicat softening temperature. The mechanical properties and rheological behavior of the blends were also determined. (C) 2003 Wiley Periodicals, Inc.