TRANSFERABILITY OF FIRST-PRINCIPLES DERIVED TORSIONAL POTENTIALS FOR MESOGENIC MOLECULES AND FRAGMENTS

The transferability of torsional potentials governing molecular flexib ility is investigated using first principles density functional calcul ations. We aim to define the criteria required for transferability bet ween different molecular systems and to quantify the mechanisms which reduce it. We begin by examining the influence that polar and lateral substituents have on the torsional potentials for the liquid crystal m olecular fragments, biphenyl and phenyl cyclohexane. We also determine the flexibility of alkyl and alkoxy tail groups attached to both benz ene and cyclohexane units. For the systems investigated, we find that the transferability depends sensitively on steric factors and molecula r electronic structure particularly through the degree of electron del ocalization and dipolar interactions. Finally, we explore the transfer ability of fragment-derived potentials to liquid crystal forming molec ules, by examining the coupling between the inter-ring torsion and fle xible alkyl tail for the liquid crystal molecule 4-n-pentyl-4'-cyanobi phenyl (5CB).