Thermochromic polymer opals

Large-scale shear-ordered photonic crystals are shown to exhibit unusual thermochromic properties. By balancing the refractive index of the polymer core and composite shell components at room temperature, transparent films are created, which become colored on heating to 150 degrees C. Since this scattering-based structural color depends only on resonant Bragg scattering of the unpigmented components, it can be tuned to any wavelength. The observed color shifts with temperature are not simply accounted for by theory and are sensitive to the constituents. (C) 2009 American Institute of Physics. [doi:10.1063/1.3256193]