Heat triggered molecular restructuring results in triple gel-gel-gel transformations in a Li+-integrated metallogel

Abstract

Nature upholds many self-regulatory assemblies which adapt themselves according to the external adverse change and modulate their molecular and/or supramolecular structures to transform into another structural form through dynamic evolution. In a similar fashion, herein, we synthesized a Li+-induced chiral metallogel ensemble (S-TLG) which undergoes the process of self-adjusting strategy in response to thermal stimuli. The Li+-metallogel was obtained from an l-tartaric acid-based gelator (H4TL) and LiOH in DMSO. When S-TLG was heated up to ∼65 °C, it transformed into a stiffer translucent yellow metallogel (Y-TLG). Further, heating of Y-TLG in the temperature range of 75-95 °C followed by cooling to ambient room temperature (RT) transformed the yellow gel into an intense red-coloured metallogel (R-TLG). This thermo-responsive behaviour of the metallogel was also accompanied by a two-step dynamic transformation of fibre-rod-fibre morphology along with supportive changes in molecular structure. To the best of our knowledge, it is the first report of triple morphological transformations in metallogels under the influence of a single stimulus. The mechanism of triple macroscopic gel phase transformation, visible colour change, and morphological evolution along with gelation has been well established using UV-vis, FTIR, PXRD, FE-SEM, fluorescence, 1H NMR, ESI-mass, rheology and EIS techniques.