Fig. 13.

(a) pH-responsive sol-gel transition of the prepared gel. (I) The staining of hydrogel with rhodamine B, (II) hydrogel breakdown upon incorporating in the HCl solution, and (III) regenerated hydrogel after 4 cycles of gel-sol transition. (b) The redox-responsive sol-gel transition of the prepared gel. (I) The staining of hydrogel with methylene blue (MB), (II) hydrogel breakdown after addition of 1,4-dithio-dl-threitol (DTT), and (III) regenerated hydrogel after 5 cycles of gel-sol transition. (c) Representation of pH/redox dual-responsive sol-gel transitions [114]. Copyright 2017. Reproduced with permission from WILEY-VCH.