Phase transition in surface-aligned nematic films

Properties of the nematic-isotropic phase transition in surface-aligned nematic films are calculated using the Landau-de Gennes theory. It is shown that there is a critical thickness Dc of the film below which the transition from the nematic phase to the isotropic phase becomes continuous. At the critical thickness the transition is second order and exhibits critical behavior. For N-[e-methoxybenzylidine] p-butylaniline, Dc is calculated to be about 1000, and the critical temperature is 0.17 K above the bulk first-order transition temperature. Magnetic and dimensional effects are discussed.