Amino Acid Ionic Liquids as a Potential Adjuvant for Fungicide Formulations: COSMO-RS Prediction and Dissolution Mechanism Elucidation

Screening green solvents to improve the solubilityof insoluble pesticides in water is a significant developmentdirection for pesticide formulations in the future. Amino acid ionicliquids (AAILs) have strong dissolution properties and are widelyused in dissolution. In this work, the conductor-like screeningmodel for real solvents (COSMO-RS) as a solvent screening toolwas used to screen AAILs with good solubility for two insolublefungicides (fludioxonil and cyprodinil) and the physicochemicalproperties (viscosity, density, and CMC) of AAILs werecharacterized. The results showed that the selected AAILs hadgood solubility effects on fungicides, wherein the solubility offludioxonil and cyprodinil in 1-ethyl-1-methyl-pyrrolidiniumglycinate ([Empy][Gly]) was 115.78 and 67.17 g/L, respectively.The mechanism of the AAIL dissolving the fungicide was explored by theoretical calculation and IR characterization, indicating thatthe hydrogen bond interaction was the main driving force for AAILs to dissolve fungicides. The solubilization effects of AAILs indifferent systems were explored, and the results showed that the solubilization effect in aqueous solution was positively correlatedwith the content of AAILs, which was not only related to the interaction between fungicides and AAILs, but also the formation ofmicelles as an essential factor. Moreover, the impact of the biosurfactant rhamnolipid (Rha) and AAILs on the solubilization effectwas explored, and most AAILs demonstrated a synergistic solubilization effect after adding Rha, which was expected. Finally, theinhibitory effects of organic solvent adjuvant methanol and eight AAILs on wheat growth were measured. Three [Empy] ILs showedless inhibitory effects on wheat than methanol under the same concentration. The research results indicated that AAILs had apromising research prospect as cosolvents in pesticide formulations