Synthesis and characterization of aspartic acid-based tripeptide surfactants

Amino acid-based surfactants (AABSs) provide a more environmentally friendly option than traditional surfactants. The introduction of amino acids into the polar headgroup increases bioavailability and biodegradation. This study aimed to introduce three amino acids at the polar headgroup to form a tripeptide surfactant. However, this study used aspartic acid (Asp) as a central amino acid at the polar headgroup and utilized its dicarboxyl groups to form peptide bonds with auxiliary amino acids, thus forming bifurcated tripeptide surfactants. This study used stoichiometric coupling with diisopropylcarbodiimide (DIC) and n-hydroxysuccinimide (NHS) to aid in synthesis. Products were examined with proton NMR (1H-NMR) to analyze synthesis results. Then, solubility tests were performed to determine relative solubility and preliminary critical micelle concentration (CMC) studies were conducted. The 1H-NMR results revealed that the current method of bifurcated tripeptide surfactant synthesis should be amended to obtain desired products, as a mixture of bifurcated tripeptide surfactants and linear dipeptide surfactants formed. Solubility tests revealed the products formed organogels, while preliminary CMC tests revealed an estimated CMC of 51.20 mM.