Self-assembling systems based on ionic surfactants are highly sensitive to the additives of small molecules capable of hydrogen bonding, dipole-dipole, electrostatic interactions and other forces affecting water structure. Two types of such additives are known to be differentiated, i.e. chaotropic and kosmotropic ones. According to simplified interpretation the former disrupt the water structure, while the latter stabilize it. Meanwhile the influence of small molecules on surfactant solutions is markedly determined by chemical structure of additives and may be realized via different mechanisms. Apart from their effect on the water structure low molecular weight additives may modify charge character and surface curvature, thereby affecting critical micelle concentration, size and morphology of aggregates.
In this work, effect of small nonionic molecules and organic electrolytes on the solution behavior of cationic surfactants is studied. Different amphiphiles including typical cationic surfactant cetyltrimethyl ammonium bromide, its gemini analogs and amphiphilic phosphonium salts are involved. As additives organic electrolytes are explored, such as acetic acid salts, sodium tosylate, salicylate, benzoate, etc. Besides, organic and bioorganic nonionic molecules (glucamine, thymol, isosteviol) of different polarity are also used. Aggregation properties, solubilization capacity, viscoelastic behavior and functional activity (catalytic, antimicrobial) of surfactant-additives systems are studied by methods of tensiometry, conductometry, fluorescence spectroscopy, dynamic light scattering, etc. It was found that some of organic electrolytes are able of associating with the formation of their own nanosized aggregates, while such uncharged species as thymol may markedly modify the viscosity of solution.
Acknowledgements. We thank the RFBR (Grants 13-03-97075, 14-03-31141) for financial support.
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