Fabrication of PAM/PMAA inverse opal photonic crystal hydrogels by a 'sandwich' method and their pH and solvent responses

摘要

This paper presents fabrication of polyacrylamide (PAM) and PAM/poly(methacrylic acid) (PMAA) inverse opal photonic crystal hydrogels (IOHs) based on poly(styrene-acrylic acid) (PSA) template by a "Sandwich" method. SEM images showed the obtained IOHs had a three-dimensional ordered structure and extremely uniform pore size without over-layers and defects. The IOHs exhibited brilliant structural color by controlling the PSA particle size, MAA and cross-linker compositions. The color and Bragg diffraction peak of the IOHs responded to external stimuli such as pH, methanol and ethanol. The reflectance was red-shifted in low pH and blue-shifted in high pH and in the presence of methanol and ethanol. The effects of the MAA and cross-linker composition on the response properties of the IOHs were investigated. The PMAA in the IOHs provided -COOH groups that are apt to form hydrogen bonds with water, enhancing the response sensitivity.