ELLIPSOMETRY AT THE NEMATIC-ISOTROPIC PHASE-TRANSITION IN A CONFINED GEOMETRY

Small, parallel, cylindrical pores in a thin polymer film were impregn ated with the liquid crystal pentylcyanobiphenyl Optical retardation m easurements, performed around the bulk nematic-isotropic phase transit ion temperature, are reported. Relative to the bulk, a depression Delt a T-NI of the phase transition temperature region was observed, althou gh for the smallest diameter pores (d = 150 Angstrom), Delta T-NI was found to be larger than expected. The profile of the optical retardati on vs temperature was also found to be anomalously sharp for the d = 1 50 Angstrom pores. The results are discussed in terms of current model s.