Self-Assembly of Soft Materials: A Multiscale Computational Approach @ Princeton University

Author(s):

Seed and IRG 2: Maria Sammalkorpi, Mikko Haataja, and Athanassios Panagiotopoulos

Surfactant adsorption at solid-liquid interfaces is important in many industrial processes, including corrosion inhibition, dispersion stabilization, and lubrication. Furthermore, surfactant adsorption may provide novel and exciting means to guide soft materials to self-assemble into a myriad of tailored shapes. Recently, PCCM researchers have made a breakthrough in elucidating the physical mechanisms behind surfactant self-assembly on a graphite surface [1]. Their simulations reveal that graphite-hydrocarbon chain interactions favor specific molecular orientations along the crystallographic directions, leading to the formation of oriented hemimicellar aggregates as observed in previous experiments [2] from PCCM's IRG2. The results suggest that manipulating the structure of the graphite surface can be employed to tune the orientational order of the hemimicellar aggregates Top left: snapshot of a C₁₂ aggregate on graphite. Top middle: orientational distribution for varying surface coverage. Top right: schematic of the orientations in the middle panel. Bottom left: snapshot of an SDS aggregate on graphite. Bottom right: orientational distribution for varying surface coverage. Both C₁₂ and SDS molecules display strong orientational bias the single molecule level, while bias disappears at intermediate coverages only to re-emerge at complete filling.

Related publication(s):

1. M. Sammalkorpi, A. Z. Panagiotopoulos, and M. Haataja, â€Å“Structure and Dynamics of Surfactant and Hydrocarbon Aggregates on Graphite: A Molecular Dynamics Simulation Study‒, <em>J. Phys. Chem. B</em>, submitted (2007).
2. D.A. Saville, J. Chun, J.L. Li, H.C. Schniepp, R. Car, and I.A. Aksay, â€Å“Orientational Order of Molecular Assemblies on Inorganic Crystals‒, <em>Phys. Rev. Lett.</em>, <strong>96</strong>, 018301 (2006).