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We have succeeded in fabricating monodomain polymer cholesteric liquid crystal (PCLC) films by spin coating a polymer solution onto glass substrates with polyimide coated and rubbed unidirectionally. The thickness and helical pitch were well characterized by controlling the rotational speed of the spin coater and the chiral unit content of the polymer solution, respectively. Lasing from dye-doped PCLC films utilizing the photonic structure was confirmed.

The twist elastic constant K 22 in 5CB was determined as a function of temperature by the following four independent methods; (1) electric field static light scattering, (2) electric field dynamic light scattering, (3) angular dependence of the scattered light intensity combined with a K 11 or K 33 measurement, and (4) Frederiks transition detected by forced Rayleigh scattering. The first one is a measurement of relative scattered light intensity as a function of the applied voltage in a proper optical geometry, and was used to determine K 22 for the first time. Each measurement gave a K 22 value within an accuracy of ±4%. The collected values that were determined by the four methods were located within ±7% from each other. It was also confirmed that they agree with other recent measurements.

A system based on photon correlation spectroscopy has been constructed using a microcomputer to measure the spectral width of Rayleigh light scattered from nematic liquid crystals. Maps in the (α, φ, θ=0° ) space have been devised to find the most suitable scatterinu geometries for the determination of K 1/ηsplay, K 2/ηtwist and K 3/ηbend, where α, φ and θ specify the scattering angle and the director direction. The ratios have been obtained as a function of T NI–T for 4'-alkyl-4-cyanobiphenyls (n=5∼8).

A novel method for determining the twist elastic constant K 22 is proposed. A critical magnetic field strength due to a Frederiks transition was detected by utilizing the anisotropy of diffusion constants of a dye by means of forced Rayleigh scattering technique. Measurements were made for 5CB and were compared with those made by other methods. It was found that the obtained values are comparable with those from other recent measurements.