Amphiphilic film mean curvature

However, using double-chain ionic surfactants, e.g. sodium-bis-ethylhexylsulfo-succinate (AOT) [9, 67] and didodecyl dimethyl ammonium bromide (DDAB) [68], no co-surfactant is necessary to time the mean curvature of the amphiphilic film from positive to negative. In the following the quaternary (pseudo-ternary) system H20/NaCl (A)-n-decane (B)-AOT (D) will be discussed to show the main features of ionic microemulsions. Subsequently, the knowledge gained for alkylpolyglucoside micro emulsions (see Section 1.2.3) will be applied to understand the complex behaviour of five component ionic mixtures. 

Ionic surfactants with only one alkyl chain are generally extremely hydrophilic so that strongly curved and thus almost empty micelles are formed in ternary water-oil-ionic surfactant mixtures. The addition of an electrolyte to these mixtures results in a decrease of the mean curvature of the amphiphilic film. However, this electrolyte addition does not suffice to drive the system through the phase inversion. Thus, a rather hydrophobic cosurfactant has to be added to invert the structure from oil-in-water to water-in-oil [7, 66]. In order to study these complex quinary mixtures of water/electrolyte (brine)-oil-ionic surfactant-non-ionic co-surfactant, brine is considered as one component. As was the case for the quaternary sugar surfactant microemulsions (see Fig. 1.9(a)) the phase behaviour of the pseudo-quaternary ionic system can now be represented in a phase tetrahedron if one keeps temperature and pressure constant. 

The space-averaged mean curvatures ternary amphiphilic system is related to the water-surfactant interfacial area A , the oil-surfactant interfacial area Ag, the interfacial area at the mid-plane of surfactant film and... 

Section 3 then reviews the behavior of diblock copolymers in mixed micelles with surfactants. Section 4 discusses other polymer surfactant mixtures, such as mixtures of amphiphilic poly(para-phenylenes) (PPP) with nonionic surfactants [48]. The packing parameter and the curvature of an amphiphilic BCP are not only influenced by means of co-micellization with a surfactant. Both parameters can also be influenced by changing the solvent quality for one of the blocks, e.g., by adding alcohol or salt. Denkova et al. have shown that this also leads to structural changes [49], However, despite the similarity of both approaches, the present review will only focus on aqueous BCP surfactant mixtures. Surfactants can also be used to assist structure formation in BCP thin films [50], This is an area of growing importance, but is beyond the scope of the present contribution. 

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