Temperature dependence of the polar anchoring strength of weakly rubbed polyimide films for the nematic liquid crystal (5CB)

We have succeeded in measuring the polar anchoring energy of a nematic liquid crystal (5CB) aligned on rubbed polyimide films. The polar anchoring energy gradually weakens with increasing temperature and tends to zero as the nematic-isotropic (NI) transition temperature (35.3°C) is approached. This indicates a strong correlation between the polar anchoring energy and the surface order parameter. Under the weakest rubbing condition, a polar anchoring energy of 8×10^-4 J/m² is obtained at a cell temperature T=30°C. This result indicates that, even with the weakest rubbing strength, the anchoring strength of the rubbed polyimide films is stronger than that of other alignment films.