A monomer having a 2,4,5-triphenylimidazole moiety was prepared by the reaction of benzoin and 3-vinylbenzaldehyde with ammonium acetate and 1-butylimidazolium tetrafluoroborate in moderate yield. The radical copolymerization of the obtained monomer and MMA were carried out at 60 degrees C for 24 h by using AIBN (5 mol %) as an initiator to give a copolymer in good yield. The cross-linking reaction of the obtained copolymer proceeded with K-3[Fe(CN)(6)] and KOH. The obtained cross-linked polymer was de-cross-linked by visible light or pressure. The signal of imidazolyl radical was detected by ESR spectroscopy. This signal showed that a linear polymer was generated.