Amphiphilicity-driven octaphenyl polyoxyethylenes regulate soft microcapsules flexibility for better foliar adhesion and pesticide utilization

Pesticide-loaded flexible carriers that allow for deformation and adhesion on crop leaves is an effective way to improve pesticide utilization. In interfacial polymerization, the addition of octaphenyl polyoxyethylene (OP) with different hydrophile lipophilic balances (HLBs) into the oil phase can regulate the flexibility of pyraclostrobin-loaded microcapsules (MCs). Due to differences in amphiphilicity and molecular structure, OP redistributed on the oil-water two-phases and oil-water interface. With increasing HLB, the proportion of OP entering the aqueous phase increased. Furthermore, more OP with low HLB remained in the oil phase and occupied the oil-water interface, and these OPs participated in and regulated the interfacial polymerization to increase the thickness, reduce the compactness of the shell, and increase the hydroxyl and ether bond contents in the shell. Therefore, pyraclostrobin-loaded MCs with low HLB (11.5–12.5) OP-7 exhibited flexible deformation, strong foliar adhesion, good scouring resistance, and a high control effect on peanut leaf spot, which the disease severity was 3.67. For high HLB (16), OP-21-prepared MCs with compact shells were safer to zebrafish, which the safety index was 23.81. Using the amphiphilicity of OP molecules to drive their redistribution in an encapsulation system to regulate interfacial polymerization is an effective way to control the structure and performance of pesticide-loaded MCs.