Maleimide-containing polymer inverse opals: a new kind of reactive photonic structure with significant extendibility

In this work, maleimide-containing polymer inverse opals have been successfully prepared by utilization of an acrylate monomer bearing a masked (protected) maleimide unit. As an ideal clickable functional group, maleimide can promote the Michael addition of thiol-containing molecules and the thermoreversible Diels-Alder reaction of furan derivatives, providing tremendous opportunities to produce various functional materials from one maleimide-containing polymer. As a demonstration, four chemical systems were facilely evolved from the prepared maleimide-containing inverse opal. By exploiting the nucleophilic thiol-ene reaction of maleimide, the zwitterionic pH-responsive inverse opal and electroactive inverse opal were first fabricated by reacting with cysteine and thiol-containing ferrocene derivatives, respectively. Based on the same reaction, it was also found that the maleimide-containing inverse opal could serve as a self-reporting sensing platform to sensitively detect the reduction of oxidized glutathione by specific enzymes. On the other hand, the thermoreversible nature of the Diels-Alder reaction of the maleimide groups made it possible to construct a dynamic molecule gating system by reacting with alkyl-chain-substituted furan derivatives from the prepared interconnected macroporous film. In fact, due to the unlimited variety provided by the two kinds of reactions mentioned above, the described photonic material exhibits a significant extendibility and could be easily post-modified for special purposes with maintenance of the opaline structure. Thus, this novel clickable maleimide-containing polymer inverse opal could serve as a reactive platform for producing a variety of functional photonic materials.