Solvent-tunable colors in imprinted helical structures on polymer template via multiple UV-induced polymerization

A solvent tunable single-layer polymer film with a multipitched photonic structure as a new photonic band gap material has been developed by imprinting the helical structures on polymer matrices through multiple photocrosslinking in an induced chiral nematic mesophase. Here, the polymer matrices themselves served as a chiral template, which exhibited Bragg reflections in the absence of both a chiral dopant and anisotropic materials because of the memory effects of the polymer network. Tuning of colors was achieved by making a refractive index contrast in the two periodic media of imprinted solid helical structure and the isotropic liquids that fill it. On incorporation of various isotropic liquids in the imprinted matrices, a sharp peak in the reflection spectrum shifted drastically, which indicated that the wavelength shifts strongly depended on the sort of liquids that filled the matrices. The effects of temperature on the imprinted polymer template feeding the various liquids were studied through the reflectance spectra.