A Macroscopic Model of a Liquid Crystal Phase Transition
Mentor:Bradley McCoy, Associate Professor of Physics, Azusa Pacific University
A nematic phase is a state of matter between the solid and liquid states, whose constituent (usually rod-like) molecules show average orientational ordering but random positional ordering. On the other hand, molecules in an isotropic phase show neither positional nor orientational ordering. We have attempted to observe an isotropic-nematic phase transition in a liquid crystal model consisting of macroscopic rods suspended in a sucrose solution. We have developed a technique for measuring the positions and angles of these rods. In order to create a stable suspension, the concentration of the sucrose solution is adjusted until the solution density approximately equals the density of the plastic used in the rods. The solution is then frozen, and we use video analysis and direct height measurements to extract the position and angles of each rod as the ice block melts. This method can be used to examine the nonequilibrium phase behavior of aggregations of hard rods in three dimensions, as well as to investigate the presence of liquid crystal ordering as a function of volume density and particle anisotropy. At a volume fraction of 38±2%, preliminary results show evidence of nematic ordering.