Numerical Methods in Studies of Liquid Crystal Elastomers.

Madjid Soltani,Arman Nokhosteen,Kaamran Raahemifar,Elham L Zoudani,Farshad Moradi Kashkooli

doi:10.3390/polym13101650

Abstract

Liquid crystal elastomers (LCEs) are a type of material with specific features of polymers and of liquid crystals. They exhibit interesting behaviors, i.e., they are able to change their physical properties when met with external stimuli, including heat, light, electric, and magnetic fields. This behavior makes LCEs a suitable candidate for a variety of applications, including, but not limited to, artificial muscles, optical devices, microscopy and imaging systems, biosensor devices, and optimization of solar energy collectors. Due to the wide range of applicability, numerical models are needed not only to further our understanding of the underlining mechanics governing LCE behavior, but also to enable the predictive modeling of their behavior under different circumstances for different applications. Given that several mainstream methods are used for LCE modeling, viz. finite element method, Monte Carlo and molecular dynamics, and the growing interest and reliance on computer modeling for predicting the opto-mechanical behavior of complex structures in real world applications, there is a need to gain a better understanding regarding their strengths and weaknesses so that the best method can be utilized for the specific application at hand. Therefore, this investigation aims to not only to present a multitude of examples on numerical studies conducted on LCEs, but also attempts at offering a concise categorization of different methods based on the desired application to act as a guide for current and future research in this field.

Highlights

Liquid crystal elastomers (LCEs) are a type of synthetic materials with specific features that make them appropriate for use in many applications [1,2,3,4,5]
LCEs are made of polymers that have been cross-linked with liquid crystalline molecules
According to the structure of LCEs, as they consist of a polymeric network with mesogenic units with a strong coupling between these two, any change in mesogenic orientational order can result in a considerable change in the network of the elastomer, and in turn any stress in the polymeric network has an effect on orientational order of the liquid crystal [9]

Summary

Introduction

LCEs are made of polymers that have been cross-linked with liquid crystalline molecules (known as mesogens). They possess both the elasticity of polymers and the properties of liquid crystalline materials [6]. A monodomain sample with aligned mesogenic orientation can be generated by applying an appropriate external field through the second stage of the polymerization, while without such precautions, polydomain LCE with opaque appearance is created [7]. In a nematic LCE, isotropic phase transition produces dramatic strain changes to the nematic LCE, this phenomenon makes it a good candidate for artificial muscles and soft actuators applications, applying strain to the nematic elastomer, induces changes in the magnitude of the orientational order, providing the interesting phenomenon of semi-soft elasticity [10]

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