Figure 21.

(A) Structure of the gelators; (B,C) optical micrographs of a gel formed by compound 33 (with n = 7, m = 8) in ethanol at 0.8 mg/mL. (a) Before treatment of the gel with UV light. (b) After irradiation with UV light for 1 min. (C): Temperature dependent ¹H-NMR study of the gelator from 20 to 55 °C. Note that the NH bond absorption shifted gradually from 5.87 to 5.78 ppm at 55 °C; (D) gel formed by compounds 33 (with n = 7, m = 8) and its responses to UV treatment. (a) An opaque gel formed by this compound in ethanol at 1.5 mg/mL. (b) The gel in vial (A) was treated with UV irradiation for 7 min through the top of the vial. (c) The gel in vial (B) turned purple-red when heating at 70 °C in a water bath. Reprinted with permission from [99]. Copyright 2015 American Chemical Society.