Scrutinizing self-assembly, interfacial properties and antimicrobial behavior of pyrrolidinium-based monomeric surfactants

Pyrrolidine surfactants are environmentally friendly compounds that exhibit good surface activity and have a wide range of applications. In this study, two monomeric pyrrolidinium surfactants (1-methyl-1-hexadecylpyrrolidin-1-ium bromide and 1-methyl-1-octadecylpyrrolidin-1-ium bromide) were synthesized and characterized by 1 H NMR, 13 C NMR, ESI MS, FTIR and TGA. Furthermore, the conductivity, density, viscosity, and surface tension of the synthesized surfactants were studied at four temperatures ((i.e. 288.15, 298.15, 308.15, and 318.15) K) using distilled water as the solvent. The conductivity results comfirmed that these surfactants are weak electrolytes. The strong interactions between the surfactant and the solvent molecules were confirmed by the constant values obtained from the density (A and B using Root equation) and the viscosity ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:mover accent="true"> <m:mi>V</m:mi> <m:mo>‾</m:mo> </m:mover> </m:mrow> </m:math> V̄ using the Einstein equation and M and K using the Moulik equation) data. The surface tension parameters such as the critical micelle concentration (CMC), surface excess concentration ( τ max ), minimum area adsorbed ( A min ) and adsorption efficiency (pC 20 ) confirmed that these surfactants are good candidates for lowering the surface tension. Thermogravimetric analysis (TGA) revealed that the compounds are thermally stable at 663.15 K with an activation energy for thermal decomposition in the range of (28.27–26.14) kJ mol −1 . Additionally, the antimicrobial action of both pyrrolidinium monomeric surfactants has been confirmed.