Biomedical subjects

Tung-Cheng Pan

Publications and source records attributed to Tung-Cheng Pan.

3 recordsLinked to original sources

PubMed2004

Thickness-dependent smectic-A-smectic-C* transition in chiral smectic free-standing liquid-crystal films.

We have conducted heat-capacity measurements near the smectic-A -smectic-C* phase transition in free-standing films of a chiral liquid-crystal compound. The heat-capacity behavior confirms the evolution of the transition in the interior layers from first to second order as a function of film thickness suggested earlier in tilt angle measurements. The asymmetry in the heat-capacity anomaly exhibits an interesting crossover in thinner films. We also observed the phase transitions leading to the crystallization to the tilted crystal-G phase in these films at lower temperatures. The surface ordering strength in these films is found to be much larger than that in other orthogonal-smectic films, which we speculate is due to the molecular tilt.

Journal Article↗

PubMed2003

Multiple electron diffraction and two-dimensional crystalline order in liquid-crystal thin films.

Electron diffraction in freestanding thin films in the crystal-B phase reveals extensive multiple diffraction in films of 14S5 but not of 4O.8, suggesting an important difference in the structural order in these films despite the similarities in their positional correlations found in earlier experiments. The result in a two-layer 14S5 film indicates surprisingly that secondary diffraction can occur in a crystal with only pseudo-long-range positional order.

Journal Article↗

PubMed2003

Surface phase transitions in free-standing films of nonchiral tilted hexatic liquid crystals.

Surface freezing transitions in free-standing films of achiral Schiff's-base liquid crystals 5O.6 and 7O.7 exhibiting tilted hexatic phases have been studied using optical textures. The evolution of textures with temperature in 5O.6 films is qualitatively similar to that reported earlier in the ferphenyl ester FTE1, suggesting the existence of the surface smectic-L phase, except that the stripe texture in 5O.6 consists of alternating light and dark stripes of unequal widths. No stripe texture is observed in 7O.7.

Journal Article↗