Recombination of dimers as a mechanism for the formation of several nematic phases.

A mixture of nonelongated monomers A and B capable of formation of three kinds of mesogenic dimers AA, BB, and AB is investigated. We show the possibility of a temperature-induced transition from one nematic phase consisting mostly of dimers AB composed of dissimilar monomers to a different nematic phase consisting mostly of dimers AA and BB composed of similar monomers. The binding energy of dimers AB is supposed to be lower (the binding of monomers A and B is more preferable) than that of dimers AA and BB (the binding of monomers A with each other and monomers B with each other is less preferable).