Reconfigurable Supramolecular Hydrogel for Light-Triggered Pesticide Release via Reversible Gel−Sol−Gel Transition

Abstract

Conventional pesticide application often results in the premature loss of active ingredients through runoff, degradation, and nontarget dispersion, highlighting the need for delivery systems capable of externally regulated release. Herein, we report a proof-of-concept reconfigurable supramolecular hydrogel based on the self-assembly of cetyltrimethylammonium bromide (CTAB) and azobenzene-4,4′-dicarboxylic acid (ADA), enabling light-triggered release through a reversible gel−sol−gel transition. The hydrogel network was systematically tuned using composition and concentration, establishing well-defined correlations between molecular assembly, rheological properties, and release behavior. Upon UV irradiation, trans−cis isomerization of ADA induces a transient gel−sol transition, triggering the release of the encapsulated model pesticide thiamethoxam (TMX). Importantly, the system undergoes spontaneous network reassembly upon cessation of irradiation, recovering the gel state. This reversible reconfiguration is achieved without disruption of the underlying supramolecular interactions, as confirmed by spectroscopic and rheological analyses. The adaptive release behavior enables controlled pesticide release while minimizing uncontrolled diffusion. By integrating dynamic molecular switching with recoverable supramolecular network organization, this work establishes the design principles of a photoresponsive supramolecular platform for externally regulated pesticide release, providing a foundation for the future development of adaptive controlled-release materials.