Terpolymers of N-cyclohexylmaleimide, methyl methacrylate, and acrylonitrile (AN) at different AN feed content were synthesized by suspension polymerization. The thermal properties of the terpolymers such as glass transition temperature (T-g) and Vicat softening temperature (T-Vicat) were determined by torsion braid analysis and Vicat softening temperature tester, respectively. The value of T-g and T-Vicat decreased with increasing AN feed content. Thermogravimetric analyses were carried out with the results that the incorporated AN units enhanced the thermal stability of the resulting polymers and a second degradation step appeared with the addition of AN. The mechanical properties (tensile strength and impact strength) of the terpolymers were also detected and the results show that the tensile strength and impact strength of terpolymers increase with increasing AN feed content. The rheological results illustrated that the terpolymers showed rheological behavior similar to that of pseudoplastic liquid. The apparent shear viscosity decreased with the increasing of AN feed content. The flow power index n increased with increasing AN feed content. (c) 2007 Wiley Periodicals, Inc.