Synthesis and Properties Evaluation of Eco‐Friendly Cardanol‐Derived Anion‐Nonionic Surfactant

ABSTRACT

Herein, a series of novel cardanol polyoxyethylene ether sulfates (NESn, n  = 3, 5, 7, 9) were synthesized via chlorosulfonic acid sulfation of commercial cardanol polyoxyethylene ethers (NSFn), and the effect of sulfation/sulfonation and EO number on solution properties was systematically studied. Compared with NSFn, sulfonation modification not only retains the advantages of nonionic surfactants but also endows the product with the characteristics of ionic surfactants. The introduction of anionic headgroup significantly enhances the water solubility by eliminating the cloud point. Meanwhile, NESn demonstrates excellent salt and alkali resistance. Specially, NES7 exhibits the highest alkali resistance (100 g/L NaOH), while NES7 and NES9 maintain stability even at 300 g/L NaCl or CaCl ₂ . Increasing EO number raised the HLB value, γ _cmc , and A _min , while lowering cmc and Γ _max due to the enhanced steric hindrance. Diffusion coefficients, both at short time and long time, decreased with EO length and concentration, indicating higher adsorption barriers, as verified by the smaller t *. Adsorption kinetics of NESn followed a mixed diffusion‐kinetic controlled adsorption mechanism. Small EO number decreases foaming but enhances foam stability. Emulsification favored NES3 for liquid paraffin and NES5 for soybean oil. This work provides key insights for designing green, high‐performance biomass‐based surfactants.