Synthesis of some amino acid based surface active molecules and investigation of their physicochemical properties

In this thesis, firstly, the synthesis and characterization of cationic amino acid based surface active molecules (S-OPAH and S-DPAH), whose hydrophilic group consists of L-phenylglycine moiety and hydrophobic part consisting of octyl and decyl hydrocarbon chains, has been carried out. Then, micellization, adsorption, volumetric, and antibacterial properties of the aqueous solutions of the obtained surfactants have been determined by conductivity, density, surface tension, and disk diffusion methods. The values of critical micelle concentration (CMC) obtained for S-OPAH and S-DPAH from conductivity, surface tension, and density measurements were found to be consistent with each other. From the results, it was observed that both micellization and surface properties increased with an increasing hydrocarbon chain and the addition of a phenyl ring to the surface active molecule. Although S-OPAH was active against all Gram-positive (S. pyogenes, S. aureus, and S. epidermidis) and Gram-negative (E. coli, E. cloacea, S. typhimurium, S. marcescens, K. pneumoniae, P. vulgaris, and P. aeruginosa) bacteria, S-DPAH showed activity only against S. aureus and S. pyogenes. It is well known that surfactants are used together with many additives, especially electrolytes. Therefore, the micellization and adsorption properties of the studied surfactants have been also investigated in the presence of some inorganic salts (LiCl, NaCl, KCl, NaBr, and NaI) to get a better idea of their performance in these environments. All the salts used were found to promote micelle formation by reducing the electrostatic repulsion between S-OPAH and S-DPAH head groups. For both S-OPAH and S-DPAH, the decrease in CMC was greatest in the presence of NaI. It was also seen that with increasing salt concentration, the electrostatic repulsion between the ionic head groups was further suppressed, resulting in increased surface activity and micelle formation.