Described is a cyclobutene polymer comprising: monomeric units of cyclobutene, said cyclobutene having at least one fused ring system substituted thereon, said polymer comprising not more than 10 mol percent ring-opened units of said cyclobutene; and said polymer having a molecular weight of at least 1,000; said polymer optionally copolymerized with a comonomer to form a copolymer therewith. Compositions thereof and methods of making the same are also described.