Copolymerization (Sch. 1) of VAC and the ring-substituted ECPP resulted in formation of copolymers (Table ) with weight-average molecular masses 8.8 to 12.6 kD. According to the nitrogen elemental analysis, between 42.1 and 49.5 mol% of TSE monomer is present in the copolymers prepared at VAC/ECPP = 3 (mol), which is indicative of relatively high reactivity of the monomers towards VAC. The structure of VAC-ECPP copolymers was characterized by IR and NMR spectroscopy.