Preparation And Properties Of Glutathione-responsive Pesticide Microcapsules

In the process of using pesticides,there are problems such as low utilization rate,short duration of validity and low environmental safety.At the same time,the country's promotion of environmental protection in recent years has also put forward new requirements for the pesticide formulation industry.It is imperative to develop green,safe and efficient pesticide formulations.Intelligent responsive pesticide controlled-release agents have the advantages of controllable and precise release,improved efficacy,reduced application times,and reduced environmental pollution,and have been widely studied.In this paper,glutathione-responsive polyurethane microcapsules were prepared by interfacial polymerization with polyurethane as the microcapsule wall material,pyraclostrobin as the model pesticide,and 2-hydroxyethyl disulfide as the chain extender.The synthesis conditions were optimized using single-factor and multi-factor orthogonal experiments.At the same time,the physical and chemical properties,controlled release properties and biological activity tests of microcapsules such as morphology,particle size distribution were explored,and the following conclusions were obtained:(1)Microcapsule preparation experiment:The optimal solvent and emulsifier types in the emulsion preparation process were screened by single factor experiment,combined with the analysis of emulsion morphology and particle size,it was determined that butyl acetate was used as the solvent and EL-40 was the optimal solution.emulsifier.At the same time,through orthogonal experimental design,using the microcapsule particle size and encapsulation efficiency as evaluation indicators,the effects of solvent dosage,emulsifier dosage,chain extension temperature,and core-to-wall ratio on microcapsules were explored,and the optimal process formula was determined as solvent The dosage of 12g,the dosage of emulsifier was 8g,the chain extension temperature was 60?,and the ratio of core to wall was 1:2.The microcapsules with uniform particle size distribution and size of 480 nm were synthesized.The synthesis of polyurethane microcapsules was confirmed by characterization of microcapsules by scanning electron microscope,infrared and thermal analysis.(2)Pyraclostrobin controlled-release experiment:Pyraclostrobin was selected as the sustained-release model agent,and the microparticles were treated with different concentrations of glutathione(0 m M,1 m M,2 m M,3 m M,4 m M).The research on the release properties of capsules found that with the increase of glutathione concentration,the faster the sustained release of pyraclostrobin,the higher the cumulative release rate.When the glutathione concentration was 0 m M,the cumulative release rate of pyraclostrobin was 61%.When the glutathione was 4 m M,the cumulative release rate was 94%,which indicated that the microcapsules were responsive to glutathione,which also proved the successful preparation of the disulfide bond-containing microcapsules.The fitting results of the sustained-release kinetic model of the microcapsules showed that the release mechanism of the microcapsule formulations conformed to Ficker diffusion.(3)Wetting performance measurement experiment:By measuring the contact angle and surface tension of the agent on the target crop(wheat),it was found that the surface tension of the agent was 30.8 m N/m when undiluted,and the contact angle of the agent on wheat leaves was 32.°,far less than 90°,indicating that the microcapsule preparation has good wetting performance,which will help to improve the retention ability of pesticide droplets in target crops and improve the utilization rate of pesticides.(4)Preparation stability test experiment:Through the research on the rheological properties of microcapsules in thermal storage and normal storage,it is found that the microcapsules show shear-thinning rheological properties,and the thixotropy of the microcapsules is studied.The structure recovery rate was 97.88%,and the structure recovery rate after thermal storage was 96.4%,confirming that the microcapsules had good suspension stability and thermal stability.(5)Biological activity test experiment:Fusarium graminearum was selected as the antibacterial experimental object,and the experimental object was treated by the growth rate method to evaluate the bactericidal performance of pyraclostrobin-loaded polyurethane microcapsules and its glutathione Responsiveness.The results of antibacterial experiments showed that the microcapsules themselves had good antibacterial properties,and the EC₅₀ value was 23.4?L/L.When in the presence of 2m M glutathione,its EC₅₀ value was 13.5?L/L,and the antibacterial properties of the microcapsules were better.It shows that the microcapsules have good glutathione responsiveness.(6)Test experiment of anti-photolysis performance:By comparing the photolysis experiments of the original pyraclostrobin original drug and the pyraclostrobin-loaded polyurethane microcapsule preparation at 274 nm,it was found that within 30 hours,the pyraclostrobin preparation in the The photolysis speed of pyraclostrobin was significantly lower than that of the original pyraclostrobin itself,which effectively improved the photolysis resistance of pyraclostrobin.