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Advances in Condensed Matter Physics
Volume 2013, Article ID 752060, 11 pages
http://dx.doi.org/10.1155/2013/752060
Research Article

Polar Liquid Crystal Elastomers Cross Linked Far from Thermodynamic Phase Transitions: Dislocation Loops in Smectic Clusters

1Physics Department, Faculty of Mathematics and Natural Sciences, Gadjah Mada University, Yogyakarta 55281, Indonesia
2Department of Applied Quantum Physics and Nuclear Engineering, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395, Japan
3Makromolekulare Chemie, Universität Freiburg, 79104 Freiburg, Germany
4Advanced Liquid Crystal Technologies, P.O. Box 1314, Summit, NJ 07902, USA
5Department of Life Engineering, Graduate School of Systems Life Sciences, Kyushu University, Fukuoka 819-0395, Japan

Received 5 February 2013; Accepted 16 June 2013

Academic Editor: Michael C. Tringides

Copyright © 2013 Yusril Yusuf et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Nematic networks with three different concentrations of polar and nonpolar mesogens and the same concentration of a novel cross-linking agent give rise to unusual liquid single crystal elastomers (LSCEs) that are transparent monodomain nematic networks with smectic clusters. The largest spontaneous length change is observed in the sample with 70 mol% of the polar mesogen which also has the highest glass transition temperature and smectic clusters with a slowly increasing but nearly constant layer spacing on cooling from 90°C to 25°C. X-ray scattering intensity from smectic clusters with layer spacings that monotonically increase on cooling first increases to a maximum at C corresponding to clusters of about 30 layers. Below , the scattering intensity decreases as the number of layers in a cluster decreases. To account for this surprising nonlinear behavior that correlates with nonlinear features of the networks’ macroscopic spontaneous shape change and birefringence, a model is proposed where dislocations form in the layers at . Below , more dislocations form to break down the layer structure. The possibility of dislocation formation at independent of mesogenic concentrations is attributed to a conformational change in the crosslinker which is present at the same concentration in the three LSCEs.