Bio-Based Cationic Surfactants from 5-(Hydroxymethyl)furfural for Antimicrobial Applications: The Role of Cationic Substitutes, Alkyl Chains, and Ester Linkages

A novel series of bio-based cationic surfactants, synthesized from the platform chemical 5-(hydroxymethyl)furfural (5-HMF), fatty acids, and bio-based amines, has been developed, offering a sustainable alternative to conventional surfactants. These compounds, referred to as surface-active ionic liquids (SAILs), have critical micelle concentration (CMC) values lower compared to conventional quaternary ammonium cationic surfactants, indicating enhanced surface activity. The surface properties of the SAILs are predominantly influenced by the type of substitution in the cationic head group, with morpholinium-based surfactants having significantly lower CMC values than diethyl ammonium ones. The length of the alkyl chain also plays a significant role in determining the physicochemical and biological characteristics of these surfactants, which vary depending on the chain length. Surfactants with longer alkyl substituents demonstrate enhanced thermal stability and surface activity. The newly synthesized amphiphiles exhibit antimicrobial activity comparable to known quaternary ammonium cationic agents but with lower cytotoxicity. Importantly, these surfactants show controlled degradation under temperature-driven hydrolysis and basic conditions while maintaining stability in acidic environments. These findings highlight the potential of developed bio-based surfactants to deliver high performance with reduced environmental impact, positioning them as potential candidates for antimicrobial applications and industrial uses focusing on sustainability goal.