PROPERTIES OF UNIAXIAL NEMATIC LIQUID-CRYSTAL OF SEMIFLEXIBLE EVEN AND ODD DIMERS

A microscopic model is developed to describe statistical properties of a nematic phase consisting of semiflexible dimers. The effect of the spacer chain bonding the two mesogens is described by the local condit ional probability in terms of a bare stiffness parameter OMEGA is simi lar to E(B)/kT and a bare equilibrium angle theta0 between mesogenic m onomers. In the framework of a molecular field approximation, taking i nto account long-range attraction and steric repulsion between monomer s, we obtain a complete statistical description of the nematic phase w ith expressions for order parameter, mean-field potential, phase trans ition parameters and Frank elastic constants depending on details of s pecific molecular structure. Comparison of results for dimers that are straight and bent in equilibrium and for corresponding monomers revea ls the effect of molecular biaxiality and biaxial fluctuations.