Mechanism and strategy of self-assembly of quaternary ammonium surfactant molecules to regulate pesticide droplet impact and wetting of hydrophobic surfaces.

BACKGROUND

Surfactants regulate the interaction between pesticide droplets and the surfaces of plants on which they are sprayed. The influence of the key structural functional groups of surfactants on the interaction between pesticide droplets and hydrophobic pear leaves has not been explored. The behavior of Imidacloprid (Imid) droplets regulated by cationic quaternary ammonium surfactants with different structures on hydrophobic pear leaves and their bouncing dynamics were studied.

RESULTS

The properties of pesticide droplets regulated by rosin-based bicationic quaternary ammonium salt and ethylene (dodecyl polyoxyethylene/tetradecyl polyoxyethylene) chloride/ammonium bromide were well matched with those of pear leaves with a waxy layer. This structure was closely related to the double-chain structure corresponding to that of double N-head groups in quaternary ammonium surfactants. Quaternary ammonium surfactants regulate the wetting of droplets by forming semi-micellar structures near the three-phase contact line, which drives the droplets to wet and spread on the leaf. The quaternary ammonium surfactant containing the double N-head structure enabled strong wetting and adhesion of pesticide droplets on the hydrophobic surface. The key structural functional groups of different quaternary ammonium surfactants directionally modified the impact kinetics of Imid droplets on the leaf surfaces and their changing trend.

CONCLUSION

The double N-head structure played a key role in the molecular structure of quaternary ammonium surfactants, and the hyperbranched ethylene oxide (EO) chain played a small role in the molecular structure. These results clearly indicate how the structure of key functional groups of quaternary ammonium surfactants regulated the interface adhesion of pesticide droplets on the leaf surfaces and explain the microscopic mechanism of their interaction. © 2024 Society of Chemical Industry.