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 conditional probability in terms of a bare stiffness parameter $\Omega\sim E_{\rm B}/kT$ and a bare equilibrium angle $\theta_{0}$ between mesogenic monomers. In the framework of a molecular field approximaiton, taking into account long-range attraction and steric repulsion between monomers, we obtain a complete statistical description of the namatic phase with expressions for order parameter, mean-field potential, phase transition parameters and Frank elastic constants depending on details of specific molecular structure. Comparison of results for dimers that are straight and bent in equilibrium and for corresponding monomers reveals the effect of molecular biaxiality and biaxial fluctuations