Bicontinous cubic structures

Many single-chain amphiphiles form cubic phases when added to water in a given composition. Two of the most well known are didodecyl-phosphatidyl ethanolamine, and mono-olein. Figure 9.18 shows some idealized bicontinous cubic structures of the former, including typical inverse ones. This is also highly viscous and optically transparent as are most of the other cubic phases. 

Related to these structures and also of relevance for the preparation of nanoparticles are some amphiphile-based nanostructured phases which do not possess any long range order. For example, another type of bicontinuous phase with relation to the inverse bicontinous cubic phases is the so-called sponge phase (L3). Its curved bilayer structure is disordered so that the water channels adopt a sponge-like structure. Sometimes this phase is referred to as a "melted cubic (v2) phase". Moreover, also dispersions of inverse micellar phases (L2) have been described which may be regarded as "melted I2 phase". Although such disordered phases do not represent a liquid crystalline phase in a strict sense they are included here since they are of relevance for nanoparticulate drug delivery purposes. 

Micellar cubic (OD), hexagonal columnar (ID), lamellar (2D), and bicontin-uous cubic (3D) nanostructures are formed by self-assembly of 13. For the complexes with IiC104, the ionic conductivities show discontinuous changes following the phase transitions with change of temperature or molecular structure of the dendritic moiety. For example, the conductivity of the complex of 13 with LiC104 drops from 4.6 x 10 6 to 1.2 x 10 9 S cm, along the phase transition from crystalline lamellar to micellar cubic phases. 

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