Self-assembly and self-organization: Important processes, but can we predict them?

Two aggregation processes of amphiphilic molecules, i.e., molecules consisting of a hydrophilic head group and a hydrophobic tail, are presented. Self-assembly of these amphiphiles is based on non-directed and non-selective intermolecular interactions such as van der Waals attraction between hydrocarbon chains and repulsion between charged or hydrated head groups. Self-organization, on the other hand, is based on directed and selective interactions such as hydrogen bonds. The aggregation behavior of amphiphiles and surfactants is often explained using the molecule-specific packing parameter P = v/a(0)l(c), with a(0) being the optimal head group area, v the volume of the hydrocarbon chain, and 1, the critical chain length. The reliability of the packing parameter concept in predicting mesophases and molecular aggregates based on these geometrical considerations is evaluated, and shortcomings of this concept are illustrated with many examples. More reliable model simulations are presented, which provide reasonable to food agreement between calculated phase behavior and experimental results. A hands-on approach in predicting and tailoring self-assembly and self-organization is proposed using the monomer solubility as a measure. and its feasibility is demonstrated.