Amphoteric polymeric photonic crystal with U-shaped pH response developed by intercalation polymerization

Amphoteric one-dimensional photonic crystal (PC) based on polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) block copolymer was developed by intercalation polymerization of acrylic acid and 2-hydroxyethyl methacrylate in the partly quaternized P2VP (QP2VP) layers. The amphoteric PC reversibly exhibits a high first Bragg peak position (λmax > 700 nm) at both acidic and basic pH values where the QP2VP layers are positively and negatively charged respectively. The minimum λmax (300 nm) at pH 5.5 can be observed due to charge screening. The PC with a U-shaped pH response also shows good durability.