Fundamental Properties of Liquid Crystals From Multiscale Simulations

Thursday, October 20, 2011: 12:46 PM
103 D (Minneapolis Convention Center)
Abhijeet A. Joshi, Nicholas L. Abbott and Juan J. de Pablo, Chemical engineering, University of Wisconsin, Madison, WI

The thermophysical behavior of liquid crystals is an inherently multiscale problem, where molecular details lead to precise molecular arrangements whose consequences are amplified over macroscopic length scales. That attribute of LCs has been used in the past to design biosensors capable of amplifying molecular binding events at interfaces over micrometer and even millimeter domains. Past efforts to arrive at a complete, bottom up prediction of liquid crystal behavior from molecular considerations have met with limited success. In this work, we present a hierarchical formalism that enables complete parameterization of coarse grained theories or models on the basis of atomistic and coarse grain advanced sampling simulations. Our simulations rely on a recently proposed simulation approach that enables facile prediction of free energy surfaces as a function of distinct order parameters. Through judicious application of external fields, one can then extract in an unambiguous manner distinct molecular descriptors of relevance to molecular or continuum theories for the free energy of the system. The usefulness and validity of such formalism is demonstrated in the context of 5CB (4-Cyano-4'-pentylbiphenyl), where we present results for the elastic constants, phase behavior, defect energies, and anchoring energies at various interfaces.

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