Please cite this article in press as: R. Montazami, et al., Enhanced thermomechanical properties of a nematic liquid crystal elastomer doped with gold nanoparticles, Sens. Actuators A: Phys. (2012), doi:10.1016/j.sna.2012.01.026 ARTICLE IN PRESS G Model SNA-7683; No. of Pages 4 Sensors and Actuators A xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Sensors and Actuators A: Physical jo u rn al hom epage: www.elsevier.com/locate/sna Enhanced thermomechanical properties of a nematic liquid crystal elastomer doped with gold nanoparticles Reza Montazami a,∗ , Christopher M. Spillmann b , Jawad Naciri b , Banahalli R. Ratna b a Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, United States b Naval Research Laboratory, Center for Bio/Molecular Science and Engineering, 6900, Washington, DC 20375, United States a r t i c l e i n f o Article history: Received 8 February 2011 Received in revised form 1 September 2011 Accepted 12 January 2012 Available online xxx Keywords: Liquid crystal Elastomer Doped Nanoparticles Thermomechanical a b s t r a c t Here we report the development of a thermomechanical nematic liquid crystal elastomer (LCE) actuator containing gold nanoparticles (AuNPs). Embedding a low concentration of AuNPs enhances the thermal conductivity of the actuator with minimal effect on the elasticity of the cross-linked polymer. Doping LCEs with AuNPs provides a means to improve the material response time to external stimuli. Under fast heating conditions, the AuNP-doped LCE actuators exhibited more than a 100% increase in the rate of change of strain with respect to time. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Development of biomimetic, stimuli responsive, smart mate- rials has attracted significant experimental [1–7] and theoretical [8–12] interest from the materials research community. There have been considerable efforts to mimic the fiber structure of skeletal muscle by developing soft linear electromechanical and/or ther- momechanical actuators as the building blocks of artificial muscles [13,14]. Liquid crystal elastomers (LCEs) have been shown to exhibit a linear, anisotropic mechanical response to electrical and/or ther- mal stimulation due to a reversible change in orientation of the liquid crystal director, which is tightly coupled to the underly- ing polymer network. Nematic LCEs are particularly attractive for biomedical applications since they are soft, elastic materials that have been shown to exert stress and strain comparable to that of human skeletal muscle ( = 350 kPa and ε = 25%). Nematic LCEs consist of pendent liquid crystal mesogens attached to a polymer network. Previous studies have demon- strated that the actuation properties of LCEs may be enhanced by doping these materials with colloidal particles. Addition of micron- sized particles was shown to produce defects in the elastomer network that may deform the director, causing the formation of complex structures [15–17]. Effective dispersion of submicron par- ticles in LCEs is a delicate task, yet provides a means to improve the material response to external stimuli while preserving the elas- ∗ Corresponding author. E-mail address: reza@iastate.edu (R. Montazami). tomer network. Incorporating a high concentration of submicron particles disturbs the elastic network of the elastomer and creates rigid compounds [18,19], while embedment of low concentrations introduces several interesting properties to the LCEs [20–22]. For instance, Reznikov et al. embedded ferroelectric thiohypodiphos- phate particles in nematic LCE matrices and enhanced the dielectric anisotropy without significantly perturbing the director field [20]. Matuo et al. studied the dynamic behavior of nematic LCEs doped with ferromagnetic particles using linear optical techniques and verified that ferromagnetic particles reduced the volume fraction of the magnetic material in the sample [21]. Courty et al. induced a large electromechanical response in nematic LCEs filled with very low (∼0.01%) concentration of carbon nanotubes aligned along the director, which is particularly significant since pure nematic LCEs do not respond to electric field [22]. In this work, we embed dispersed AuNPs in nematic LCEs. Due to the high thermal conductivity of gold (300 W/(m K)), the presence of AuNPs in the elastomer was expected to enhance the inher- ently low thermal conductivity of the nematic LCE [14]. We report the effects of incorporating low amounts of AuNPs into a nematic LCE and quantify the mechanical properties, thermoelastic proper- ties and response time of the resultant material at different AuNP concentrations. 2. Materials 2,5-Dihydroxybenzoic acid, benzyl bromide, 4- pentylcyclohexylcarboxylic acid, 4-hydroxybutyl acrylate, and anhydrous dichloromethane were purchased from Sigma Aldrich. 0924-4247/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.sna.2012.01.026