Liquid Crystal Phase Transitions of Monodisperse and Bidisperse Suspensions of Rodlike Colloidal Virus

Liquid Crystal Phase Transitions of Monodisperse and Bidisperse Suspensions of Rodlike Colloidal Virus A dissertation presented to the Faculty of the Graduate School of Arts and Sciences of Brandeis University, Waltham, Massachusetts by Kirstin Rachael Purdy We experimentally study the role of steric and electrostatic interparticle interactions in monodisperse and bidisperse suspensions of rodlike colloids. For our model system we used aqueous suspensions of the charged semiflexible filamentous bacteriophages fd and M13. In solution, these particles undergo entropically driven liquid crystal phase transitions from isotropic to cholesteric ( or chiral-nematic) to smectic phases with increasing concentration. For the monodisperse suspensions, we present as a function of ionic strength, measurements of the role of flexibility and surface charge on the transitions between these phases. We also present the evolution of the helical pitch of the cholesteric phase with concentration as a function of solution ionic strength and particle surface charge in order to understand the coupling between ionic strength and surface charge in the expression of chirality in the nematic phase. Unwinding and aligning the chiral-nematic phase in a magnetic field allowed us to measure the nematic ordering of fd as a function of rod concentration and solution ionic strength. The nematic orientational distribution function was measured using x-ray diffraction and birefringence techniques. Results