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Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
* Author to whom correspondence should be addressed.
Received: 25 June 2013; in revised form: 24 July 2013 / Accepted: 25 July 2013 / Published: 8 August 2013
Abstract: We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the centre of mass. Even for isotropic attractive interactions, the resulting overall inter-particle potential is anisotropic, due to the orientation-dependent excluded volume of the underlying hard core. An algebraic equation of state for attractive disc particles is developed by adopting the Onsager trial function to characterize the orientational order in the nematic phase. The theory is then used to represent the fluid-phase behaviour (vapour-liquid, isotropic-nematic, and nematic-nematic) of the oblate attractive particles for varying values of the molecular aspect ratio and parameters of the attractive potential. When compared to the phase diagram of their athermal analogues, it is seen that the addition of an attractive interaction facilitates the formation of orientationally-ordered phases. Most interestingly, for certain aspect ratios, a coexistence between two anisotropic nematic phases is exhibited by the attractive disc-like fluids.
Keywords: equation of state; discotics; attractive cylindrical disc; nematic-nematic equilibria; anisotropic square well; phase diagrams
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Wu, L.; Jackson, G.; Müller, E.A. Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles. Int. J. Mol. Sci. 2013, 14, 16414-16442.
Wu L, Jackson G, Müller EA. Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles. International Journal of Molecular Sciences. 2013; 14(8):16414-16442.
Wu, Liang; Jackson, George; Müller, Erich A. 2013. "Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles." Int. J. Mol. Sci. 14, no. 8: 16414-16442.