Ring-opening metathesis copolymerizations (co-ROMPs) of norbornene derivatives bearing five- or six-membered ring cyclic carbonate and cyclooctene were carried out with a ruthenium catalyst under various polymerization conditions. All co-ROMPs smoothly gave the corresponding copolymers in good yields, and the glass-transition temperatures of the resulting polymers and the degrees of volume change during the copolymerizations were simultaneously controlled by the amount of the comonomer.