Calorimetric and Structural Characterization of Thin Liquid-Crystal Films Exhibiting the Smectic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">A</mml:mi></mml:math>–Hexatic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">B</mml:mi></mml:math>–Crystal-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">B</mml:mi></mml:math>Transitions

Abstract

High-resolution heat-capacity and electron-diffraction measurements have been conducted on thin free-standing films of a liquid-crystal compound exhibiting the smectic- $A$--hexatic- $B$--crystal- $B$ transitions. Despite the absence of herringbone order, the liquid-hexatic transition in extremely thin films has nevertheless been found to show a pronounced pretransitional heat-capacity anomaly, in disagreement with the predictions of two-dimensional melting theory.