“…Previously, we reported that 3‐methylenecyclopentene (MCP) as a cyclic 1,3‐diene monomer with a reactive exomethylene moiety produced an alternating copolymer during radical copolymerization with RMIs in a high yield because Diels–Alder reaction of this cyclic diene monomer was totally suppressed due to its fixed s‐trans conformation ( Scheme ) . We also succeeded in the synthesis of alternating copolymers of MAn and N ‐phenylmaleimide (PhMI) with 2,4‐dimethyl‐1,3‐pentadiene (DMPD) as noncyclic 1,3‐diene monomers . Anhydride moiety and carbon‐to‐carbon double bond in the repeating unit of MAn/DMPD copolymer were available for several postpolymerization reactions; for example, crosslinking using epoxy compounds, alcohols, and amines as polyfunctional crosslinkers, and oxidative ozonolysis of carbon‐to‐carbon double bonds in the main chain, leading to polymer chain scission, decrosslinking of cured resins, and polymer surface modification ( Scheme ) .…”