Thermally Induced Pitch Gradients in Side-Chain Cholesteric Liquid Crystalline Polymers
It is reported that a pitch gradient is formed in a side chain cholesteric liquid crystalline polymer (ChLCP) through a novel method. Heating up the ChLCP within the temperature range of the cholesteric (Ch) phase leads to the first availability of its planar texture. Then, the ChLCP film with the planar texture is cooled down to its glassy (G) state in line with the temperature difference between the upper and the bottom substrates. The SEM image indicates clearly a pitch gradient perpendicular to the substrates, and the results of transmission spectra show that the reflective bandwidth of the ChLCP film with the pitch gradient is greatly broadened.
J. M. Xiao et al., "Thermally Induced Pitch Gradients in Side-Chain Cholesteric Liquid Crystalline Polymers", Advanced Materials Research, Vols. 311-313, pp. 1323-1326, 2011