Bulg. J. Phys. vol.31 no.3-4 (2004), pp. 118-129



Thermal and Electroconvective Dendrites in the Nematic Phase with Short Range Smectic Order of 4,n-Heptyl and 4,n-Octyloxybenzoic Acids

H. Naradikian1, B. Katranchev1, E. Keskinova1, M.P. Petrov1, J.P. Marcerou2
1Institute of Solid State Physics, Bulgarian Academy of Sciences, 72, Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria
2Centre de Recherche Paul Pascal CNRS-UPR8641, Avenue A. Schweitzer, 33600 Pessac, France
Abstract. We found two kinds of dendritic textures (thermal and electroconvective (EC)) in the nematic phase of 7-OBA and 8-OBA, with different morphological and dynamical characteristics, but both possessing the basic elements of an weak first order phase transition – interface, which propagate and an underlined hysteresis. The dynamics of the dendrite growth is that typical for non-equilibrium nonlinear dissipative systems, driven outside of equilibrium. The EC dendrites, contrary to the thermal, characterize with convective flow. The observed subcritical (hysteretic) behavior of the EC dendrites refers this phenomenon to a first order phase transition, but in a thermodynamically monophase system.

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