Ellipsometry at the nematic-isotropic phase transition in a confined geometry

Small, parallel, cylindrical pores in a thin polymer film were impregnated with the liquid crystal pentylcyanobiphenyl Optical retardation measurements, performed around the bulk nematic-isotropic phase transition temperature, are reported. Relative to the bulk, a depression Delta T-NI of the phase transition temperature region was observed, although for the smallest diameter pores (d = 150 Angstrom), Delta T-NI was found to be larger than expected. The profile of the optical retardation vs temperature was also found to be anomalously sharp for the d = 150 Angstrom pores. The results are discussed in terms of current models.