For a novel corrosion inhibitor for copper, the free radical copolymerization of vinyl imidazole(VI) and vinyl trimethoxy silane(VTS) was carried out in benzene at 68 degrees C using azobisisobutyronitrile(AlBN) as an initiator. The reactivity ratios of the two monomers were determined from instantaneous composition diagram : r(VT) = 3.22 and r(VTS) = 0. Thermal stability of poly(VI-co-VTS) depended on VTS mole fraction in the feed rather than the molecular weight of the copolymer, due to the disiloxane bond linkages formed during heating.