Photoresponsive polymers based on a coumarin moiety for the controlled release of pesticide 2,4-D

We report an excellent photoresponsive controlled release formulation based on a coumarin copolymer for pesticide 2,4-D. In the present work, acrylate and polyethylene glycol (PEG) based coumarin photoresponsive polymers were synthesised. The newly synthesised coumarin based polymers exhibited dual functionalities, namely as fluorophores and phototriggers for the controlled release of pesticide 2,4-D. The fluorescence properties of coumarin based polymers helped us to monitor the release of 2,4-D from the polymeric formulation. Release of the pesticide by coumarin based polymers was achieved on exposure to UV light. TGA results indicated that the coumarin polymer encapsulated pesticide has a good thermal stability compared to the free pesticide 2,4-D. A further leaching experiment also showed that the polymer encapsulated pesticide leaches slowly compared to the free pesticide 2,4-D. Bioassay studies in a plant suggest that the coumarin polymer encapsulated pesticide efficiently delivered 2,4-D inside the plant tissues (pumpkin plant Cucurbita maxima) improving its herbicidal activity. Our results indicated that use of a fluorescent coumarin polymer based delivery device for controlled release of pesticide by light holds great interest for field application.