Photo-responsive Polymeric Propesticide Nanomicelles Based On PEG And Their Application In Controlled Release Of Pesticide

Due to the low efficacy of and environmental pollution of conventional pesticides,design of polymeric propesticide has a leading edge significant meaning.Smart responsive polymeric micelles as a new carrier drug delivery system,has attracted increasingly widespread attention and concern.Smart responsive polymeric micelles can be responsive to such as pH,temperature,enzymes,reduction potential,light and so on.Compared with other stimuli,the light stimulus is a clean and convenient stimulation source,light stimulation can be set from the outside,and additional time,location and strength of light can be precisely controlled,so the design of the light stimulus responsive polymeric propesticide micelles is significant to achieve controlled release of the pesticide.We used 3-nitro-4-bromomethyl benzoic acid as the connecting arm grafting 3-nitro-4-bromomethyl benzoic acid on polyethylene glycol(PEG)to obtain PEG derivative,and then the carboxyl group of PEG derivative was reacted with bromomethyl of herbicide-dichlorophenoxyacetic acid to obtain the light-responsive amphiphilic polymeric propesticide,which could be used as raw materials for preparing light-responsive micelles.The main research work and results are as follows:?.PEG derivatives and Light-responsive polymeric propesticide were prepared,their structures were determined,and their related properties were studied.Using 3-nitro-4-bromomethyl benzoic acid as the connecting arm,grafting3-nitro-4-bromomethyl benzoic acid on polyethylene glycol(PEG)to obtain PEG derivative(PEG-NBA),and then the carboxyl group of PEG derivative was reacted with bromomethyl of herbicide dichlorophenoxyacetic acid to obtain the light-responsive amphiphilic polymeric propesticide.Structures of derivatives and polymeric propesticide were detected by FT-IR and ~1H NMR methods.Light-responsiveness of the intermediate and polymeric propesticide were determined by UV and ~1H-NMR and other inspection techniques.?.Light-responsive polymeric propesticide micelles was prepared,and the morphology and particle size,light-responsive,critical micelle concentration and the effect of PEG to critical micelle concentration and particle size were studied.(1)The polymeric propesticide were uniformly dispersed into deionized water,and by ultrasound treatment,the light-responsive micelles were prepared,TEM showed light-responsive polymeric propesticide micelles had obvious core-shell structure,neat and clear morphology,equal distribution,the particle size was 35nm;Malvern particle size analyzer showed relatively uniform particle size,the particle size was 50nm.(2)The polymeric propesticide micelles had a good property of light-responsive.TEM and Malvern particle size analyzer comfirmed that the particle size of micelles was smaller after light irradiation,but not too much.The result can attribute to after light irradiation,the herbicide-dichlorophenoxyacetic acid is released from micelles,the macromolecular chains still maintain amphiphilic,and can self-assemble to smaller micelles.(3)When the molecular weight of the PEG chain grew,the critical micelle concentration of polymeric propesticide micelles was increased,it can be seen that the molecular weight of hydrophobic segment was constant and the molecular weight of hydrophilic segment grew,CMC would increase,too.In summary,smaller molecular weight PEG was more useful to prepare light response micelles.(4)When the molecular weight of the PEG chain grew,the particle size of polymeric propesticide micelles was increased.?.The photoresponsive release of polymeric propesticide micelles was studied,whcih provided a theoretical support for the development of nanocarriers in the application of nano-pesticide.The influence of light stimulus on the pesticide release of micelles:When under365nm UV stimulation,approximately 99.5%of dichlorophenoxyacetic acid was released from the micelles within 9 min.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 9 h.Therefore,unlike physical embedding methods may occur drug burst release,the photosensitive propesticides bonded on the chain maintained relatively stabilized,the drug will not released unless in UV irradiation.