Influence of molecular size and shape of the nematogenic substances on the liquid crystal phase equilibrium
Santiago Lago
Most chemical molecules with important applications are poorly modelled if considered as spherical because their principal moments of inertia are different. Hovewer, it is very frequent that one of them is markedly different from the other two moments and the molecules are called oblate or prolate whether the differing moment is the biggest or the least, respectively. For sake of simplicity, we call the corresponding liquids as oblate molecular liquids (OML) and prolate molecular liquids (PML). If the molecular anisotropy is large enough, mesophases (liquid crystals) between the solid and the liquid state may appear. The relation between the global phase diagram and the intermolecular potential is relatively well-known for prolate models and we can assign the features of the intermolecular potential to the appearance of different macroscopic phases. The behavior is far less understood for OML. Recently, we have performed Gibbs ensemble Monte Carlo (GEMC) simulations and proposed a perturbation theory for oblate fluids reproducing vapor-liquid equilibrium in a satisfactory way. Even more recently, we have applied a Parsons- Lee theory to OML obtaining very good results for hard OML not too thick. We present here the main results from our works, considering the possible extensions to more complicated systems.
References
- F.Gámez, B.Garzón, S. Lago, P.Merkling and C.Vega;Mol.Phys. 106,1331-1339, (2008)
- F.Gámez, S.Lago and P.J.Merkling ; Chem.Phys.Lett. (in press). doi:10.1016/j.cplett.2010.05.094