Controlling permeation in electrically deforming liquid crystal network films: A dynamical Landau theory

Liquid crystal networks exploit the coupling between the responsivity of liquid crystalline mesogens, e.g., to electric fields, and the (visco)elastic properties of a polymer network. Because of this, these materials have been put forward for a wide array of applications, including responsive surfaces such as artificial skins and membranes. For such applications, the desired functional response must generally be realized under strict geometrical constraints, such as provided by supported thin films. To model such settings, we present a dynamical, spatially heterogeneous Landau-type theory for electrically actuated liquid crystal network films. We find that the response of the liquid crystal network permeates the film from top to bottom, and illustrate how this affects the timescale associated with macroscopic deformation. Finally, by linking our model parameters to experimental quantities, we suggest that the permeation rate can be controlled by varying the aspect ratio of the mesogens and their degree of orientational order when crosslinked into the polymer network, for which we predict a single optimum. Our results contribute specifically to the rational design of future applications involving transport or on-demand release of molecular cargo in liquid crystal network films.

Automated summary

Liquid crystal networks combine the responsiveness of liquid crystalline mesogens to electric fields with the (visco)elastic properties of a polymer network. The study shows that the response of liquid crystal networks permeates throughout the film, impacting the timescale of macroscopic deformation. By adjusting the aspect ratio of the mesogens and their degree of orientational order in the polymer network, the permeation rate can be controlled to achieve optimal results for future applications involving molecular cargo transport or release in liquid crystal network films.