Electrophilic trisubstituted ethylene monomers, ring-substituted methyl 2-cyano-3-phenyl-2-propenoates, RC6H4CH˭C(CN) CO2CH3(where R is 4-C2H5O, 4-C3H7O, 4-C4H9O, 3-C6H5O, and 3-CN), were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and methyl cyanoacetate, and characterized by CHN elemental analysis, IR,1H- and13C-NMR. All the propenoates were copolymerized with styrene (M1) in solution with radical initiation (AIBN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR,1H- and13C-NMR. The order of relative reactivity (1/r1) for the monomers is 3-CN (1.21) > 3-C6H5O (1.16) > 4-C2H5O (0.94) > 4-C3H7O (0.8305) > 4-C4H9O (0.616). The highTg's of the copolymers (> 130°C) in comparison with that of polystyrene indicate a substantial decrease in the chain mobility of the copolymers due to the high dipolar character of the trisubstituted monomer unit. Gravimetric analysis indicated that the copolymers decompose in the range 300–400°C.