Computationally toward novel self-assembling materials
When a disorganized group of molecules assembles to form an ordered structure in the absence of external forces, as a result of internal interactions of the molecular system, the material is a self-assembling molecular material. Common examples of self-assembling molecular materials include polymer films, liquid crystals, and various interfacial surfactant films. In biology, the cell membrane (lipid bilayer), protein folding, or DNA double helix result also from molecular self-assembly.
Self-assembling molecular materials have an enormous number of applications not only in biology but also in technology: synthetic molecular films function as filters, as ion membranes in energy applications, or self-assembling coatings. Self-assembling molecular materials are used also in drug transport, as molecular sensors, solvation agents, and protective coatings.
In the Department of Chemistry, the Novel Materials via Self-Assembly research group studies computationally and theoretically self-assembling molecular materials. Molecular self-assembly is a new and interdisciplinary field. In biology and chemical engineering, a vast amount of experimental knowledge and empirical understanding of the structure, properties and usage of self-assembling molecular materials exists but a predictive level understanding of self-assembly does not exist. For example, the amino acid sequence of a protein is known exactly, and the structure of a folded protein can be probed from protein crystals but deducing the folded structure, dynamics, or function based on the sequence is not possible at the moment. Polymer films grow and are stable but why? Experimentally these molecular systems are challenging. Thermodynamics bulk properties and mainly macroscopic characteristics, as well as, different transition points can be measured but the self-assembly is often microstructure dependent in a subtle way.
Additionally, charge correlations are typically important in polyelectrolyte and ionic surfactant behavior which makes mean field approximations insufficient theoretical approaches. Computer simulations on the other hand are a powerful tool for describing such systems, and creating understanding on them, because it enables taking into account both microstructure and charge distribution explicitly in calculating the structures and their dynamics.
At the moment, in the group, we study surfactant and charged polymer (polyelectrolyte) self-assembly in bulk water solution and at water-solid-interface. As a research example, Figure 1 (at the top of the page) visualizes ion ordering around charged polymers described in both atomistic and in molecular level coarse-grained description detail.
Figure 2 provides another example of research performed in the group; in this figure surfactant behavior at liquid-crystal interface is presented. In the figure, the surfactants self-assemble into micelles in water solution and on a carbon nanotube surface. Such molecular self-assembly enables the solvation of otherwise insoluble, extremely hydrophobic carbon nanotubes into water. The behavior is subtly dependent on the interplay of the surfactant and interface characteristics.
The group is funded by Academy of Finland, EU 7th framework programme, and National Doctorate Programme in Materials Physics. The computer resources for our computationally intensive research are provided by CSC IT Centre for Science, Finland, and Yale University High Performance Computing Center, USA.
The group has an opening at the level of Master's thesis work:
Homepage of the group: http://chemistry.aalto.fi/en/research/physical/novelmaterials/index/
Inquiries and additional information: Research group leader, Academy of Finland Research Fellow Maria Sammalkorpi, Department of Chemistry