Tuning of the Reflection Properties of Templated Cholesteric Liquid Crystals using Phase Transitions

The magnitude of the color changes induced by heating chiral templated polymer structures formed in spatially heterogeneous cells is examined. The large blue and subsequent red tuning of the selective reflection wavelength, caused by deswelling/reswelling of the network at the transition temperatures, is affected by the network crosslink density, heating/cooling rates, and architecture of the cell. The system is stable to multiple heat/cool cycles and shows large scale coloration changes at heating rates up to 10°C/min. At higher heating rates, a distortion of the selective reflection notch shape occurs during tuning. The magnitude of the color change is not affected by rate. At both high and low crosslink density, no tuning is observed. A window of network elasticity and responsiveness is needed to enable the anisotropic contraction/expansion processes to be observed macroscopically. Finally, the magnitude of tuning relative to the cell thickness and spatial heterogeneity across the thickness direction i...