Optimization of multifunctional polymer emulsifiers properties for lambda-cyhalothrin nanoemulsion fabrication

It is highly desirable to construct stimuli -responsive nanocarriers for improving pesticides targeting and preventing the pesticides premature release. In this study, five new amphiphilic polymer emulsifiers with stimuliresponsive properties were designed and prepared via esterifying ethylene maleic anhydride copolymer (EMA) with straight chain alkyl alcohols (including n-octanol, n-decanol, n-dodecanol, n-tetradecanol, and n-hexadecanol), followed by ionizing the esterification products. The alkyl ester side groups in the polymer structure gave the emulsifiers multiple characteristics, including adjustable amphiphilicity, affinity to pesticide, ability to form micelle in water, cleavable dynamic covalent ester linkages, and the possibility of temperature -induced phase transition. With these emulsifiers, especially for the one with dodecyl ester side groups (defined as HEMA-C12), lambda-cyhalothrin (LC) was fabricated into the nanoemulsion with nanosized particles (71.1 nm) via the phase inversion emulsification process. HEMA-C12 could also emulsify other hydrophobic pesticides, including avermectin, cyhalothrin, and bifenthrin, into nanoemulsions. The obtained LC nanoemulsion exhibited a series of advantages, including exceptional encapsulation efficiency (86.06%), high drug loading (52.10%),