Surface properties and premicellar aggregation behavior of cationic gemini surfactants with mono- and di-(2-hydroxypropyl)ammonium head groups

Abstract Novel cationic gemini surfactants - pentanediyl-1,5-bis[mono(2-hydroxypropyl) alkylammonium] dibromide and pentanediyl-1,5-bis[di(2-hydroxypropyl) alkylammonium] dibromide {in the abbreviation form - C n C 5 C n [iso-Pr(OH)] and C n C 5 C n [iso-Pr(OH)] 2 ; alkyl - C n H 2n+1 with n = 8, 9, 12 and 16} were synthesized. Surface tension, electroconductivity and dynamic light scattering methods were applied to study aggregation properties of these surfactants in aqueous medium. By tensiometric method it was established that, at two studied concentrations in water, the synthesized gemini surfactants form aggregates. This occurs well below the critical micelle concentrations (CMC) of these surfactants. The influence of the length of the surfactants alkyl chain and the number of the 2-hydroxypropyl fragments in the head group on the surface activity parameters and binding degree of the counterion has been studied. By dynamic light scattering method, the impact of the number of the 2-hydroxypropyl groups in the gemini surfactants with C 12 –chain on the micelles sizes at the concentrations higher than CMC has been investigated. It was revealed that the synthesized surfactants possess an antimicrobial property.