The Microstructure of Di-alkyl Chain Cationic/Nonionic Surfactant Mixtures:  Observation of Coexisting Lamellar and Micellar Phases and Depletion Induced Phase Separation

Abstract

The evolution of the microstructure and composition occurring in the aqueous solutions of di-alkyl chain cationic/nonionic surfactant mixtures has been studied in detail using small angle neutron scattering, SANS. For all the systems studied we observe an evolution from a predominantly lamellar phase, for solutions rich in di-alkyl chain cationic surfactant, to mixed cationic/nonionic micelles, for solutions rich in the nonionic surfactant. At intermediate solution compositions there is a region of coexistence of lamellar and micellar phases, where the relative amounts change with solution composition. A number of different di-alkyl chain cationic surfactants, DHDAB, 2HT, DHTAC, DHTA methyl sulfate, and DISDA methyl sulfate, and nonionic surfactants, C12E12 and C12E23, are investigated. For these systems the differences in phase behavior is discussed, and for the mixture DHDAB/C12E12 a direct comparison with theoretical predictions of phase behavior is made. It is shown that the phase separation that can occur in these mixed systems is induced by a depletion force arising from the micellar component, and that the size and volume fraction of the micelles are critical factors.

SANS, SAXS, and light scattering investigations of pH-responsive dynamic combinatorial mesophases

“…The possibilities of coexistence between different morphologies of aggregates in one system have been discussed in the literature for copolymers or surfactants largely different in geometry, charge, and size. 38,39 More recently, Li et al showed the coexistence of copolymers in solution with similar composition (but with different PEG lengths: 10 and 18 units) that leads to the formation of coexisted mixed objects. Experimentally, 40 the authors found that small vesicles can coexist with a large amount of spheres for a specific mixing ratio R confirmed by molecular modelling.…”

Physicochemical Properties and Phase Behavior of Didecyldimethylammonium Chloride/Alkyl Polyglycoside Surfactant Mixtures

“…Previous work has indicated that double-tailed cationic surfactants have been widely used as fabric softeners, antimicrobials, and antistatic agents [20] in many formulations because of their strong absorbability onto negative surfaces. APG and didecyldimethylammonium chloride (DDAC) mixtures, combining the advantages of pure APG and DDAC, are of particular interest and importance in the development of multi-functional disinfection and washing products [21][22][23][24].…”

Micellar and Interfacial Behavior of Mixed Systems Containing Glycoside‐Based Surfactant and Cationic Didecyldimethylammonium Chloride

“…Hence, knowledge of the behavior of surfactant mixtures in solution and at the interface is very necessary. Among different types of mixed surfactant systems, cationic/nonionic surfactant mixtures are an important class because they are the major components of cosmetics, especially for hair and clothing conditioners [3][4][5][6]. Cationic surfactants are good fabric softeners, antimicrobials, and antistatic agents, while nonionic surfactants are biodegradable and mild in nature.…”