Self-assembly three-dimensional "spherical" structures

Time-resolved in situ Small Angle Neutron Scattering (SANS) investigations have provided direct experimental evidence for the initial steps in the formation of the SBA-15 mesoporous material, prepared using the non-ionic tri-block copolymer Pluronic 123 and TEOS as silica precursor. Upon time, three steps take place during the cooperative self-assembly of the Pluronic micelles and the silica species. First, the hydrolysis of TEOS is completed, without modifications of the Pluronic spherical micelles. Then, when silica species begin to interact with the micelles, a transformation from spherical to cylindrical micelles takes place before the precipitation of the ordered SBA-15 material. Lastly, the precipitation occurs and hybrid cylindrical micelles assemble into the two-dimensional hexagonal structure of SBA-15. 

Defects seem to be inevitable in all three-dimensional opaline lattices of spherical colloids because a thermodynamic equilibrium is seldom accomplished in the self-assembly process. The presence of defects could have a profound influence on the structure and thus photonic band gap properties... 

The liquid gelators, Span 80-Tween 80 also forms emulsion organogels and emulsion hydrogels by fluid-filled fiber mechanism. It has been reported that Span 80 (sorbitan monooleate) and Tween 80 (polyoxyethylene sorbitan monooleate) mixed in the ratio of 1 2 w/w forms organogel with better firmness and architecture as compared to the other surfactant mixture ratios.When water is added dropwise into the homogenous surfactant mixture and oil, it forms spherical reverse-micellar droplets. These droplets/fibers self-assemble to form three-dimensional architecture to immobilize apolar solvent. " Similarly, in case of hydrogels micellar structures are formed, which entraps the external liquid phase to flow and form hydrogel. 

Surfactant micelles and bilayers are the building blocks of most self-assembly structures. One can divide the phase structures into two main groups [1) (1) those that are built of limited or discrete self-assemblies, which may be characterized roughly as spherical, prolate or cylindrical. (2) Infinite or unlimited self-assemblies whereby the aggregates are connected over macroscopic distances in one, two or three dimensions. The hexagonal phase (see below) is an example of onedimensional continuity, the lamellar phase of two-dimensional continuity, whereas the bicontinuous cubic phase and the sponge phase (see later) are examples of three-dimensional continuity. Figure 3.8 illustrates these two types schematically. 

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