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Advances in Materials Science and Engineering
Volume 2017 (2017), Article ID 4762379, 8 pages
Research Article

Effects of Cooling Rates on Self-Assembling Structures of 12-Hydroxystearic Acid in an Ionic Liquid

Department of Chemistry and Chemical Biology, School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan

Correspondence should be addressed to Hiroyuki Takeno

Received 20 June 2017; Accepted 1 August 2017; Published 13 September 2017

Academic Editor: Andrey E. Miroshnichenko

Copyright © 2017 Hiroyuki Takeno and Mai Kozuka. 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.


We investigated effects of cooling rates on self-assembling structures and mechanical and electrochemical properties of 12-hydroxystearic acid (12-HSA) in an ionic liquid (IL), 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl) imide ([ABIm][TFSI]). The mixture of 12-HSA with [ABIm][TFSI] had an upper critical solution temperature (UCST) above the sol-gel transition temperature, and the microstructure of the ionogel was significantly affected by cooling rates, where it was prepared. The twisted self-assembling structure was formed during a slow cooling process at a rate of 0.4°C/min, whereas spherical domains caused by the liquid-liquid phase separation and radiate fibrous structure were observed for the quenched gel. The real-time small-angle X-ray scattering (SAXS) measurements for the ionogel during a slow cooling process at a rate of 0.4°C/min presented three different (001) peaks arising from long spacings of 46.5, 42.4, and 39.7 Å, which were also observed for SAXS curves of a neat 12-HSA. These results suggest that three polymorphic forms of 12-HSA are formed in the IL. The polymorphic form significantly affected the mechanical properties of the ionogel, whereas it did not affect the ionic conductivity. The ionic conductivity of the ionogel was close to that of a neat [ABIm][TFSI] irrespective of the polymorphic forms of 12-HSA.