In the field of sensing, there is a need for stimuli-responsive materials that produce visible changes in aqueous environments. One strategy to address this issue is to incorporate the small molecules into a larger assembly, which can respond to stimuli at the interface between water and a solid film. It is hypothesized that by synthetically modifying an azo-benzene dye with mesogenic groups, the material will exhibit a liquid crystal phase that can visibly switch in response to aqueous salts. As a proof of the concept, a family of azo-benzenes with electronically diverse urea groups was synthesized. Some of the compounds showed evidence of LC thermal transitions in polarized optical microscope images at elevated temperatures and differential scanning calorimetry analysis. Also, when heated and exposed to aqueous sodium fluoride solutions, some of the compounds (e.g. compound <b>4 </b>in Figure 1) showed visible color changes that were observable in the UV-vis spectrum of thin films. We have also studied compounds that lack mesogen units as a control for these studies.

It’s just a phase: Visibly-switchable liquid crystals

251st National Meeting (2016)

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