Abstract
Colloidal liquid crystals are a useful experimental system for studying fundamental aspects of liquid crystal ordering, because the time, energy, and size scales involved allow one to interact with the system with laboratory scale probes and forces, in a way that is not possible in small molecule systems. In the colloidal systems, liquid crystalline ordering arises from simple particle shape and excluded volume effects, rather than more complex interactions that occur in molecular systems involving van der Waals attractions, dipolar effects, and more complicated molecular interactions. The study of hard rod systems has recently been a subject of intensive theoretical investigation [1, 2, 3] prompted by a series of remarkable computer simulations [4, 5, 6, 7]. For comparing this body of theoretical work to a real physical system, solutions of virus particles have provided the only suitable experimental tests [8, 9, 10]. These studies have implications for all liquid crystals, because the symmetry and the nature of the ordered phases being studied are universal to a wide range of systems, including low molecular weight thermotropics and polymer liquid crystals. In this chapter we will discuss experiments exploring the liquid crystalline properties of colloidal suspensions of virus particles. Since an article summarizing TMV research at Brandeis was published recently [11], we will focus on studies not reviewed previously. A second review article on TMV research by Wetter [12] is especially recommended for its abundance of splendid photographs.