Four-armed biobased glycyrrhizic acid-tailored AIE fluorescent gelator

Abstract

Benefiting from the intrinsic amphiphilic feature, natural glycyrrhizic acid (GL) has attracted increased attention in recent years as a supramolecular gelator. Nevertheless, these works often mix GL as a gelator with other components directly without any functionalization of GL, which limits its further applications. In this work, a four-armed biobased AIE fluorescent gelator (TPE- 4GL) was designed and synthesized, where four glycyrrhizic acids were linked to a tetraphenylethene (TPE) core via amide bonds. The four substituted-amphiphilic GLs render TPE-4GL the potential to gel, while the hydrophobic TPE core makes TPE-4GL own the aggregation-induced emission (AIE) feature. The results demonstrated that TPE-4GL can form stable gels in DMSO/water and 1,2-propanediol/water, respectively, the morphology of which was flower-like microstructures and regular nanospheres. In addition, the gelator TPE-4GL exhibited the typical AIE behavior as we expected, despite the specific process in DMSO/water and 1,2-propanediol/water were not exactly the same, i.e. there was a hypochromic shift of the emission from 481 to 463 nm as the water fraction (fw) in DMSO increased from 0 to 40%, whereas no shift was observed in 1,2-propanediol/water. This work provides a straight forward way to obtain the AIE featured biobased gelator, which will enrich the library of functional gels based on natural products. 2021 Elsevier Ltd. All rights reserved.