Surface properties of the derivatives of lysosomotropic substances against other quaternary ammonium salts

Equilibrium adsorption at the air/water interface of cationic surfactants belonging in the group of quaternary ammonium bromides was studied. Quaternary ammonium salts, derivatives of lysosomotropic substances with different alkyl chain numbers and hydrophobicities were investigated. Surface properties of considered compounds, were examined and presented against other quaternary ammonium bromides of different chemical structure and with different number of alkyl chains in the molecule. The Frumkin equation and reorientation model were used for a quantitative description of the process of their adsorption. It was found that considered biologically active derivatives reveal strong surface activity. Chemical structure–surface activity relationship was analyzed and referenced to biological activity. Symmetry of the molecules resulting from the number of alkyl chains is the factor determining the behavior of the surfactants at the air/water interface as well as in the bulk. Surfactants with asymmetrical structure show a strong tendency to reorientation, in opposite to tetraalkylammonium bromides and double chain surfactants. Furthermore, the role of ester bond was emphasized.