Improving Droplet Retention on Hydrophobic Leaf Surfaces via Nonionic Hyperbranched Surfactants

Massive pesticide loss during field application leads to severe environmental contamination and low utilization efficiency, while existing mitigation strategies are often operationally complex or limited to a single spraying stage. In this work, a nonionic hyperbranched surfactant was rationally designed to simultaneously regulate droplet deposition, diffusion-wetting, and retention on hydrophobic plant surfaces, thereby improving pesticide utilization. Specifically, a terminal alkene-functionalized hyperbranched PEG-PPG copolymer was synthesized via in situ RAFT polymerization and further grafted with amino-functionalized fluorinated hydrocarbons through Michael addition. The resulting surfactant effectively suppressed droplet bouncing, enhanced spreading, and delayed evaporation. Among the synthesized variants, HB-M-F1 exhibited the best interfacial regulation performance. As a tank-mix adjuvant for glyphosate isopropylammonium (41% AS), only 0.1 wt% HB-M-F1 significantly improved herbicidal efficacy, increasing the inhibition rate and mortality of Echinochloa crus-galli from 98.00% and 81.25% to 99.70% and 93.75%, respectively, and those of Portulaca oleracea from 88.76% and 62.50% to 90.63% and 75.00%. These results highlight the potential of hyperbranched surfactants to enhance pesticide deposition, uptake, and herbicidal performance at low dosages.