Both vinyl methacrylate (VMA) and vinyl acrylate (VA) were homopolymerized by n‐butyllithium catalyst at −78°C. Both of the anionic polymers were soluble in common organic solvents, and only vinyl group was contained in the polymers. Both of the monomers were homopolymerized by free‐radical catalysts under different conditions. The soluble polymers were obtained under low monomer concentrations and at low conversions. It was estimated by NMR and infrared spectroscopy that both the soluble polymers contained mainly a vinyl group, similar to the anionic polymers. The soluble VMA polymers comprised 10–20% cyclic units for monomer concentrations ranging from 1.8 to 0.5 mole/I. The soluble VA polymers comprised 50–60% cyclic units for monomer concentrations ranging from 0.9 to 0.3 mole/l. It was suggested that the cyclic units did not consist of γ‐lactone but of larger‐membered rings than δ‐lactone or of ladder structural units. The difference between the cyclization content of poly‐VMA and that of poly‐VA might be explained by the copolymerization data of the reference monomers.