Electro-Opto-Mechanical Effects in Swollen Nematic Elastomers - Liquid Crystal Elastomers: Materials and Applications - page 118

Electro-Opto-Mechanical Effects in Swollen
Nematic Elastomers

Kenji Urayama

Abstract Nematic elastomers swollen by low molecular weight nematogens (nematic
gels) exhibit fast response to electric fields with a large change in optical birefringence
together with macroscopic deformation. This electro-opto-mechanical (EOM) effect
is a direct consequence of the deformation coupled to electrically driven director
rotation in nematic gels under a mechanically unconstrained geometry. This article
describes the static and dynamic features of the EOM effects of nematic gels. We
will discuss recent investigations into the influences of field strength, frequency,
and external mechanical constraints on the EOM effects. The relation between
director rotation and macroscopic deformation is elucidated on the basis of optical
and mechanical data in a steady state. The dynamics of the EOM effects are also
discussed, on the basis of optical and mechanical response times to field imposition
and removal. We also introduce a simple model to capture the main features of the
static and dynamic aspects of the EOM effects.

Keywords Electro-mechanical effect Electro-optical effect Liquid crystal

elastomers Nematic gels

Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
2 Materials and Observation Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
2.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
2.2 Observation Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
3 Static Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
3.1 Electro-Mechanical Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
3.2 Electro-Optical Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
3.3 Director Rotation Characterized by Polarized FTIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
3.4 Correlation Between Director Rotation and Macroscopic Deformation . . . . . . . . . . . . 131