Effects of stretching on microstructures of polymer-immobilized non-close-packed colloidal crystalline array

Non-close-packed silica colloidal crystalline array was immobilized by polymer, and effects of stretching on the change of the optical properties and microstructure of the colloidal crystalline arrays have been demonstrated. The immobilization was a two-step polymerization process: the first step was with hydrophilic polyethylene glycol acrylate (PEGA) polymer gel, and the second step was with 2-hydroxyethyl acrylate polymer matrix. The structure of the three-dimensional array was maintained during the immobilizing process with lock in periodic order. The peak wavelength of Bragg diffraction of the polymer-immobilized colloidal crystalline array shifted to shorter wavelength with stretching. The peak shift was caused by the compression of the polymer proportional to the stretching ratio, and the compression was homogeneous throughout the polymer-immobilized colloidal crystalline arrays. These results show that by using polymer-immobilized non-close-packed colloidal crystalline array, mechanically tunable photonic crystals can be realized, and they open the possibility of tuning the microstructure of colloidal crystalline array for photonic crystal.