Shape self aggregation

A tennis-ball-shaped molecular aggregate can be constructed by the self-assembly of curved molecule I. Tetrameric assembly of II generates a pseudo-spherical capsule. Dimeric assembly of III can be induced by the encapsulation of smaller molecules of appropriate size and shape at the center of a spherical complex. 

Two characteristics determine the shape of molecular aggregates. The first is the shape of the constituent molecules, which sets the curvature of the aggregate. The second is coupled to the chirality of the molecules, which also determines the curvature of the aggregate, via the geodesic torsion. The bulk of this chapter is devoted to an exploration of the effect of molecular shape on aggregation geometry. An account of the theory of self-assembly of chiral molecules is briefly discussed at the end of this chapter. 

It has been shown that micelles forming just above CMC take a spherical or near-spherical shape note that this occurs within the bulk of the continuous phase. As the amphiphile concentration increases, the architecture of self-aggregation changes and follows more complex geometries than simple spheres [ 3,41]. When in addition a dispersed phase is available in the system (which now changes from... 

Due to their strongly anisometric particle shape, triglyceride SLN tend to self-aggregate and build-up stacked lamellae at higher concentrations. The formation of such stacked lamellae was found to be reversible upon dilution and did not lead to an accelerated physical instability of the dispersions. The anisometric particle shape also determines the flow properties of SLN dispersions and high lipid contents (up to 40%) led to the formation of an elastic gel with viscoelastic properties comparable to standard dermal preparations. ... 

While flattened vesicles are sometimes observed with the more hydrophobic amphiphiles, recently however we have discovered a route to disc shaped self assemblies (Fig. 11.6(a)) and found that branched polymers because of their lower hydrophilic head group area give rise to disc shaped self assemblies in the presence of cholesterol. The difference in hydrophilic head group area is also evidenced by the lower CMC values exhibited by the branched polymer (Fig. 11.6(b)). A lower hydrophilic head group area would favour molecular aggregation in aqueous media as stabilisation of the individual molecules in water via hydrogen bonding would be less likely. 

A special case of a miktoarm star copolymer with many arms are so-called Janus Micelles, which are formed by cross-linking the short middle block of a triblock terpolymer in the microphase separated bulk state, in which the center block self-assembles in spherical [ 189,190] or cylindrical domains [191]. By this procedure the two different outer blocks are oriented to the two opposite hemicoronas around the center block domain and subsequent dissolution leads to amphiphilic particles (Figure 14). While spherical Janus Micelles form superstructures in solution, the cylindrically shaped Janus Micelles seem to have a lower tendency of self-aggregation to higher superstructures. 

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