The tertiary chlorine (Cl-t) content of vinyl chloride/2-chloropropene copolymers [P(VC-co-2CP)] was determined by NMR spectroscopy. Copolymers containing 6.8-47.0 Cl-t's per P(VC-co-2CP) chain were used to initiate the cationic grafting of alpha-methylstyrene, norbornadiene, indene, and norbornene with Et2AlCl under various conditions. Grafting was demonstrated by selective solvent extraction, and the effect of the experimental conditions on the grafting efficiency was examined. Select rheological and thermal characteristics of P(VC-co-2CP) grafts, including the glass-transition temperature, heat deflection temperature, and discoloration upon heating, were studied. P(VC-co-2CP) carrying 7-11 poly(alpha-methylstyrene) or polynorbornadiene branches per chain raised the glass-transition temperature to, or above, that of a blend control. P(VC-co-2CP)s fitted with polyindene or polynorbornene branches were less effective in raising the mechanical properties.