Photoinitiated polymerization of 4-methylene-2-phenyl-1,3-dioxolane (1) was carried out using either tris(4-methylphenyl) sulfonium hexafluoroantimonate or 4-decyloxyphenyl phenyliodonium hexafluoroantimonate as initiators. H-1-NMR analyses confirmed exclusive ring-opening while DSC and SEC were used to determine the glass transition temperatures (T(g)s) and molecular weights, respectively. Photoinitiated cationic copolymerizations of 1 were investigated with several acyclic and cyclic monomers. Copolymerization of 1 with vinyl ethers and a spiroorthoester resulted in copolymers whose thermal properties were dependent on comonomer ratios. Copolymers of 1 and dihydrofuran or dihydropyran afforded soluble polymers with T(g)s significantly higher than the homopolymer of 1.