Bio‐Based Surfactants Derived From Citronellol and Citronellic Acid: Synthesis, Aggregation Properties, and Cytotoxicity Assessment

The study presents the synthesis of terpene‐based novel biosurfactants derived from sodium and choline salts of citronellic acid (SC, CC) and citronellyl sulfate (SCS, CCS). Surface tension (ST) measurements, dynamic light scattering (DLS), and small‐angle neutron scattering (SANS) were used to examine their colloidal properties and thermodynamic parameters. The findings suggest that hydrophobic tail architecture, headgroup chemistry, and counterion identity significantly influence the micellization behavior of citronellol‐based amphiphiles. Sulfate‐containing surfactants (SCS and CCS) had lower critical micellar concentrations (CMCs) of 134 ± 9.4 and 88.8 ± 4.3 mM, respectively, than carboxylate analogs (SC and CC; ~200 mM). SANS analysis revealed spherical micelles with radii of 0.8–0.9 and 1.1–1.3 nm for SCS and CCS, respectively. DLS measurements further validated the presence of predominant nanoscale aggregates (< 5 nm) with reduced polydispersity, especially at higher concentration. The zeta potential data indicated that the choline counterion exhibited partial charge screening compared to sodium. All surfactants showed very low cytotoxicity (IC 50 = 1149–1400 μg/mL) against RAW264.7 macrophage immune cells and biocompatibility similar to that of lauryl glycoside and Tween 20 in HEK‐293 cells. Initial studies reveal their potential as safe insect repellents and as a part of crop‐protection formulations.