pH-responsive self-assembly by molecular recognition on a macroscopic scale.

Macroscopic pH-responsive self-assembly is successfully constructed by polyacrylamide(pAAm)-based gels carrying dansyl (Dns) and β-cyclodextrin (βCD) residues, which are represented as Dns-gel and βCD-gel, respectively. Dns-gel and βCD-gel assemble together at pH ≥ 4.0, but disassemble at pH ≤ 3.0. The adhesion strengths for pairs of Dns-gel/βCD-gel increase with increasing pH. The fluorescence study on the model system of pAAm modified with 1 mol% Dns moieties (pAAm/Dns) reveals that Dns residues are protonated at a lower pH, which results in the reduction in binding constant (K) for Dns residues and βCD.