CHARACTERIZATION SEVERAL NOVEL PHASE-TRANSITIONS IN A UNIQUE LOWER DIMENSION SYSTEM OF FREESTANDING LIQUID-CRYSTAL FILMS

Motivated by the defect-mediated two-stage melting theory, extensive e xperiments have been concluded on free-standing films of a liquid-crys tal sample which exhibits the isotropic-smectic-A-hexatic B-crystal-B bulk phase sequence. For a two-layer film, which is virtually two-dime nsional, our calorimetric measurement shows an apparently divergent an omaly near the smectic-A-hexatic-B transition. Its anomaly has a domin ant fluctuation contribution and can be fitted to a power law with an exponent alpha approximate to 0.37 +/- 0.05, in disagreement with the theoretical prediction. Thicker films exhibit surface-initiated layer- by-layer (LBL) wetting transition upon cooling. Moreover, these films also exhibit interesting LBL thinning transitions above the bulk clear ing temperature.