Phase transitions in lyotropic colloidal and polymer liquid crystals

An overview is given of theory and experiments on liquid crystal phases which appear in solutions of elongated colloidal particles or stiff polymers. The Onsager (1949) virial theory for the isotropic-nematic transition of thin rodlike particles is treated comprehensively along with extensions to polydisperse solutions and soft interactions. Computer simulations of liquid crystal phases in hard particle fluids are summarized and used to assess the quality of statistical mechanical theories for stiff particles at higher volume fraction-like the inclusion of higher virial coefficients, y-expansion, scaled particle theory and density functional theory. Both computer simulations and density functional theory indicate formation of more highly ordered smectic phases. The range of experimental applicability is strongly widened by the extension of the virial theory to wormlike chains by Khokhlov and Semenov (1981,1982). Finally, experimental results for a number of carefully studied, charged and uncharged colloids and polymers are summarized and compared to theoretical results. In many cases the agreement is semi-quantitative.