Aging of surface anchoring and surface viscosity of a nematic liquid crystal on photoaligning poly-(vinyl-cinnamate) - art. no. 061709

Dynamic light scattering was used to measure the azimuthal anchoring energy coefficient W-phi of nematic liquid crystal (5CB) on photoaligning poly-(v inyl-cinnamate) layer. Measurements were repeated several times within two months. The results show that W-phi increases in the first few days after f illing the cell with liquid crystal. Then it remains approximately constant at W-phi = 5 x 10(-6) J/m(2) for at least two months. Also, presence of ve ry large effective surface viscosity is observed. This phenomenon is of tra nsient nature and attributed to swelling and dissolving of photosensitive p olymer into the liquid crystal. which gives rise to an inhomogeneity of vis coelastic properties. Numerical modeling of the fluctuation spectrum shows that an inhomogeneous surface layer can account for the observed effective surface viscosity.