Bicontinuous phases aggregates

The difference between direct ordering of molecules and the indirect ordering of molecules via supermolecular aggregates is one of the distinctions between different types of soft material. Thermotropic liquid crystal phases result from partial orientational and translational order of the molecules. In contrast, the symmetry of lamellar, micellar and bicontinuous phases is specified by the location of supermolecular aggregates. The molecules within the aggregate do not have the same orientational and translational order as the mesoscopic structure itself in fact, they can be relatively disordered . 

Bicontinuous phases. Surfactant aggregate stmctures related to liquid crystalline phases or mesophases that exhibit bicontinuous (two interwoven continuous phases) behavior. The most common is the cubic bicontinuous strucmre, often referred to today as cubosome, although other stmctures are possible. 

Like biological systems, however, the vesicle is by nature compartmentalized, which makes it amenable to the inclusion of additives in the three phases present the external aqueous phase, the hydrophobic interior of the bilayer, and the aqueous internal phase. That availability of carrying capacity has made vesicles natural candidates as delivery systems in pharmaceutical, cosmetic, and various other industrial applications. Who hasn t heard of the magical liposomes that make the wrinkles of aging disappear As will be seen below, other newer mesophases, such as the cubic bicontinuous phase or cubosomes, are now beginning to join the corps of amphiphile aggregate workhorses. 

It is generally accepted that surfactant-polymer interactions may occur between individual surfactant molecules and the polymer chain (i.e., simple adsorption), or in the form of polymer-surfactant aggregate complexes. In the latter case, there may be a complex formation between the polymer chain and micelles, premiceUar or submiceUar aggregates, liquid crystals, and bicontinuous phases—that is, with any and all of the various surfactant aggregate structures described in Chapters 4 and 5. Other association mechanisms may result in the direct formation of what are sometimes called hemimicelles along the polymer chain. The term hemimicelle may be defined, for present purposes, as a surfactant aggregate formed... 

Figure 16.1 Relationship between molecular shape, aggregate structure in dilute dispersions, phase behavior and packing parameter. Micellar phase (L,), cubic micellar phase (I), hexagonal phase (H), bicontinuous cubic phase (Q), La lamellar phase. Subscripts I and II indicate normal and inverted phases, respectively. From M. Scarzello, Aggregation Properties of Amphiphilic DNA-Carriers for Cene Delivery, Ph. D. Thesis University of Groningen, p 6, 2006...

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