NONLINEAR DIELECTRIC STUDIES OF INTERMOLECULAR INTERACTIONS AND STRUCTURE OF 4-HEPTYL-4-CYANO-BIPHENYL IN BENZENE

The energies of intermolecular interactions in benzene solutions of 4- heptyl-4'-cyano-biphenyl (7CB) in concentration range 0-0.4 mole fract ion have been determined from the experimental data of linear and nonl inear electric polarisation. The theory of the nonlinear dielectric ef fect for associated solutions is discussed. To achieve the agreement b etween theoretical calculations and experimental data the Flory atherm al model of association was used. The results show that the dimerisati on, so important in very diluted solutions, is only the first step to a more complex process of molecular association. The low polar cluster s with even number of molecules (mainly dimers and tetramers) are the dominant. Beside the distinctly preferred antiparallel orientation, th e concentrations of highly polar, chain multimers are also significant . The possible reasons why the model does not work for concentrated so lutions are also discussed. (C) 1997 Elsevier Science B.V.