"A model system for random field effects:
Liquid crystal + aerosil dispersions"
Germano S. Iannacchione
Department of Physics
Worcester Polytechnic Institute
Abstract
The study of quenched disorder by random-fields on phases and phase transitions continues to be an active area of condensed matter research. Previous studies of liquid crystals confined in rigid aerogels have yielded results dominated by elastic-strain effects, which either destroy or strain-smear all phase transitions. Suspensions of 70 Å diameter silica particles in LCs form hydrogen-bonded thixotropic gels similar in structure to that of aerogels, which can relax (anneal) severe elastic strains while preserving the quenched disorder of randomly oriented silica strands. Thus, the LC+sils system provides an attractive physical model for random-field effects.
Current, high-resolution x-ray scattering studies in 8CB+sils coupled with results from previous calorimetric studies reveal behavior showing the interplay of random-fields, elastic-strains, and finite-size effects. The experimental situation will be reviewed as well as recent theoretical and computer simulation work. This theoretical work predicts a nematic elastic glass (NEG) and smectic Bragg glass (SBG) phases and Isotropic-NEG as well as NEG-SBG transitions for a similar system. Detailed theoretical work is in progress while many attractive new experiments are possible with broad implications.
Elizabeth K. Mann