Synthesis of photoresponsive polymeric propesticide micelles based on PEG for the controlled release of a herbicide

A novel amphiphilic polymer–pesticide conjugate was synthesized by conjugation of PEG with the photolabile o-nitrobenzyl group followed by grafting dichlorophenoxyacetic acid (2,4-D), which can self-assemble into photoresponsive micelles in aqueous solutions for a controlled release of the herbicide. 1H NMR and FT-IR confirmed the structure of the synthesized conjugate. TEM observations showed that the micelles had a core–shell configuration. DLS and TEM measurements showed that the average diameters of the micelles decreased by about 40 nm after 365 nm UV irradiation. 1H NMR and UV-Vis studies confirmed that the photoresponse may be ascribed to the photolytic cleavage of o-nitrobenzyl as the connecting arm in the polymeric chain. No release of the micelles was detected without light, while the cumulative release rate from the micelles increased gradually upon solar-simulating radiation, reaching 99.6% in 8 h.