Several Anomalous Thermal Behaviors in Free-Standing N-(4-n-butoxybenzylidene)-4-n-octylaniline Films

P. J. Wu ； Y. C. Shen ； Y. H. Liu ； C. R. Lo ； A. J. Jin ； C. C. Huang ； C. Y. Chao

《Chinese Journal of Physics》 38卷3期 (2000/06) Pp. 471-477

並列摘要

Entirely novel phenomena associated with the phase transitions of N-(4-nbutoxybenzylidene)-4-n-octylaniline (4O.8) free-standing liquid-crystal films are discovered. The hexatic-B ordering transition of the outermost surfaces has only a small thermal hysteresis and exhibits a predominant pretransitional heat-capacity anomaly, in disagreement with the predictions of two-dimensional melting theory. In light of our recently established results of the surface-enhanced two-stage freezing transformation, even a single interior layer shows a smectic-A-crystal-B transition and exhibits a drastic thermal hysteresis (about 10℃). The melting transitions are also unique in which, even though the interior crystal-B phase can unusually melt at a much higher temperature than the surfaces, the surface anomaly peaks occur in a layer-by-layer fashion with about the same sizes as in the cooling.