Reversible Photorheological Lyotropic Liquid Crystals

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• 作者：Shuhua Peng ; Qipeng Guo ; Timothy C. Hughes ; Patrick G. Hartley
• 刊名：Langmuir
• 出版年：2014
• 出版时间：January 28, 2014
• 年：2014
• 卷：30
• 期：3
• 页码：866-872
• 全文大小：402K
• ISSN：1520-5827

文摘

We describe novel lyotropic liquid-crystalline (LLC) materials based on photoresponsive amphiphiles that exhibit rapid photoswitchable rheological properties of unprecedented magnitude between solidlike and liquidlike states. This was achieved through the synthesis of a novel azobenzene-containing surfactant (azo-surfactant) that actuates the transition between different LLC forms depending on illumination conditions. Initially, the azo-surfactant/water mixtures formed highly ordered and viscous LLC phases at 20鈥?5 wt % water content. Spectroscopic, microscopic, and rheological analysis confirmed that UV irradiation induced the trans to cis isomerization of the azo-surfactant, leading to the disruption of the ordered LLC phases and a dramatic, rapid decrease in the viscosity and modulus resulting in a 3 orders of magnitude change from a solid (20鈥?00 Pa) to a liquid (50 Pa) at rate of 13鈥?00 Pa/s. Subsequent exposure to visible light reverses the transition, returning the viscosity essentially to its initial state. Such large, rapid, and reversible changes in rheological properties within this LLC system may open a door to new applications for photorheological fluids.