Surface and micellar properties of the mixtures containing esterquats

The main goal of the presented study was to analyze the adsorption properties of mixed surfactant systems containing the esterquats which are biologically active and show strong surface activity in the single surfactant solutions. The subjects of investigations were following cationic surfactants: fatty acids N,N-dimethylaminoethylesters methobromides (DMM-n), fatty acids N,N-dimethylaminopropylesters methobromides (DMPM-n), and fatty acids 1-dimethylamino-2-propyl methobromides (DMP2M-n) with different alkyl chain length. Sodium dodecylbenzenesulfonate (DBSNa) was used as anionic surfactant. Two types of mixed equimolar systems were considered: mixturescontaining two esterquats as well as cationic + anionic mixtures i.e. systems containing an esterquat and DBSNa. The equilibrium and dynamic surface tension data for all the binary systems considered were studied and interpreted. Moreover, dynamic light scattering method was used to determine micelles size. In the case of some mixed systems the synergism in reduction of the surface tension and critical micelle concentration was evidenced. Kinetics of micelle dissociation was found substantially different for the mixtures of the surfactants and for the single components. The presented results can be useful from the standpoint of biological applications.