Engineering Elastic Responses of Liquid Crystalline Materials

Liquid Crystalline Elastomers
Image of the local orientational domains formed in a model for side-chain liquid crystalline elastomers. Upon the addition of elastic stress, these merge into a single orientationally aligned phase.

Liquid crystals (LCs) are a fascinating state of matter exhibiting ordering between that of a liquid and a solid. Importantly, the equilibrium state of a liquid crystal is characterized by a global orienting vector, the director \(\hat{\mathbf{n}}\). These have a wide range of technological applications which exploit their liquid-like flow and orientational ordering, with especially exciting applications as exquisitely responsive biological sensors. These applications result from the orientational elasticity of LCs---local perturbations of \(\hat{\mathbf{n}}\) cost energy, which may be phrased in terms of a local free energy density.

Motivated by the recent use of liquid crystalline phases as templates for self-assembly and in novel sensing devices, our group seeks to establish useful models and structure-property relationships for liquid crystalline materials. We utilize powerful free-energy computation techniques to analyse the elastic properties and thermodynamic response of liquid crystalline materials. This includes the incorporation of particulates, impurities, surface stresses and mechanical deformations.

Related Publications:

[1] A. A. Joshi, Whitmer, J. K., Guzman, O., Abbott, N. L., & de Pablo, J. J. (2014). Measuring liquid crystal elastic constants with free energy perturbations. Soft Matter, 10 882-893. Link
[2] Jonathan K. Whitmer, Chi-cheng Chiu, Abhijeet A. Joshi, and Juan J. de Pablo. "Basis Function Sampling: A New Paradigm for Material Property Computation." Physical Review Letters 113, 19 (2014): 190602. Link
[3] Hythem Sidky and Jonathan K. Whitmer. "Elastic response and phase behavior in binary liquid crystal mixtures." Soft Matter 12, 19 (2016): 4489-4498 Link
[4] Hythem Sidky and Jonathan K. Whitmer. "Elastic properties of common Gay-Berne nematogens from density of states (DOS) simulations." Liquid Crystals 43, 13-15 (2016): 2285-2299. Link
[5] Hythem Sidky and Jonathan K. Whitmer. "The Emergent Nematic Phase in Ionic Chromonic Liquid Crystals" The Journal of Physical Chemistry B 121, 27 (2017): 6691–6698 Link
[6] Hythem Sidky, Juan J. de Pablo, and Jonathan K. Whitmer. "Atomistic Molecular Simulations are a Direct Probe of Liquid Crystal Elasticity." Submitted, (2017).