Europhys. Lett.
Volume 71, Number 6, September 2005
Page(s) 945 - 951
Section Condensed matter: structural, mechanical and thermal properties
Published online 12 August 2005
Europhys. Lett., 71 (6), pp. 945-951 (2005)
DOI: 10.1209/epl/i2005-10180-5

Unusual thickness-dependent thermal behavior due to molecular tilt coupling strength in free-standing $\chem{7O.7}$ thin films

C.-Y. Chao, M.-T. Hsu and W.-J. Hsieh

Department of Physics, National Taiwan University - Taipei 10617, Taiwan, ROC

received 11 April 2005; accepted in final form 19 July 2005
published online 12 August 2005

We report the results of thermal and structural studies near the $\chem{Sm}$-C-$\chem{Sm}$-I critical point in free-standing thin films of $\chem{7O.7}$. The profiles of the $\chem{Sm}$-C-$\chem{Sm}$-I heat-capacity anomalies are found to exhibit an unexpected crossover behavior with film thickness in reduced dimensions, which is qualitatively similar to that seen in by Yao et al. in the bulk. Moreover, we observe the existence of a surface hexatic $\chem{Sm}$-L phase in $\chem{7O.7}$ films of less than eight layers whose phase sequence is, however, dramatically different from that observed in thicker films.

61.30.Eb - Experimental determinations of smectic, nematic, cholesteric, and other structures.
64.70.Md - Transitions in liquid crystals.

© EDP Sciences 2005