Preparation of Tunable Colloidal Crystals Based on Temperature-sensitive Hydrogel

Wet type colloidal crystals were fabricated on the temperature-sensitive hydrogel PNIPAAm by dip-coating method.Optical properties of the colloidal crystals were controlled by taking advantage of the water-releasing effect of PNIPAAm.It is found that monodisperse spheres could form ordered three-dimensional structure on the surface of PNIPAAm by lifting hydrogel-coated substrate from latex suspension.The colloidal crystal on hydrogel exhibited a sharp reflection peak originating from the diffraction of light.By raising the temperature over 34 ℃,phase transition occurred for PNIPAAm.Accompanying with the phase transition,water in PNIPAAm was released to the colloidal crystal,which diluted the concentration of the spheres and increased the interparticle distance.As a result,the reflection peak shifted to the long wavelength side.Such a change can be recovered by decreasing the temperature.