Liquid Crystals

Paul H. Keyes

	Atoms and simple molecules have solid, liquid and vapor phases.  Large 
symmetric molecules, however may also exhibit a cascade of transitions involving
new types of phases between the solid and liquid phases.  The study of the 
material properties of these liquid crystal "mesophases", which have attributes 
of both the liquid and solid phases, has been of great interest to physicists, 
chemists, and materials scientists in recent years.  Many fundamental questions 
regarding the nature of  phase transitions have also arisen during the 
investigation of the changes that take place on going from one to another of 
these partially ordered structures.
	In the liquid crystal laboratory at Wayne State we are presently involved in 
the study of two types of novel mesophases: the cholesteric blue phase, 
fascinating materials which may truly be called "cubic liquids", and nematic 
liquid crystals which arise in certain soap solutions and are closely related to
structures having biological significance.
	The techniques we employ in the study of these materials are chiefly optical.  
Laser light scattering and photon correlation spectroscopy are used to study the
statics and dynamics of phase transitions.  Polarization microscopy is employed 
to elucidate the structures of these phases.  The response of these phases to 
external fields, particularly in the vicinities of transitions are measured 
through Kerr effect and Cotton-Mouton effect studies.  The influence of high 
pressures on these phases is also measured.

"Dynamics of Order-Parameter and Director Fluctuations in the Nematic Phase of 
the Lyotropic Liquid Crystal", J.P. McClymer and P.H. Keyes, Phys. Rev. E 48, 
2838 (1993).
"The Cholesteric Blue Phases", P.H. Keyes, Material Research Society Bulletin, 
Jan. 1991, p. 32.
"High Chirality Blue Phase Lattices Are Unstable:  A Theory for the Formation of
Blue Phase III", P.H. Keyes, Phys. Rev. Lett. 65, 436 (1990).