Synthesis and Characterization of Oxazolone-Based Cationic Surfactants: Aggregation Behavior, Surface Properties, and Antimicrobial Activity

A novel series of oxazolone (OXZ)-derived cationic surfactants bearing decyl, dodecyl, and hexadecyl hydrophobic tails were synthesized via the green multicomponent Erlenmeyer–Perkin reaction using 4-dimethylaminobenzaldehyde as a key precursor. FT-IR, HRMS, and ¹H NMR spectroscopy were used to confirm the structures of the purified ammonium surfactants, and their self-assembly in aqueous media was studied through conductometry, tensiometry, and fluorimetry. Surface parameters such as the effectiveness of surface tension reduction, maximum surface excess concentration, minimum area per molecule, surfactant efficiency, and thermodynamic adsorption and micellization parameters were determined. Dynamic light scattering and transmission electron microscope images revealed an inverse correlation between micelle size and alkyl chain length, highlighting the role of hydrophobicity in controlling aggregate architecture. Fluorescence spectroscopy was used to evaluate aggregation numbers. Notably, these OXZ-derived surfactants displayed significant antimicrobial activity against a panel of six pathogens, including Gram-positive and Gram-negative bacteria and fungi, with a distinct cutoff effect observed against three species.