Vanderbilt University, Nashville, TN, USA.

The broad goal of our work is to apply molecular simulation and molecular theory to the prediction of the thermodynamic and transport properties of chemical, biological and nanostructured systems. A brief overview of our work will be given and then selected topics discussed in detail. In particular, work on model development and molecular simulations of polyhedral oligomeric silsesquioxanes will be discussed and more recent work on simulating skin lipids highlighted.

Polyhedral oligomeric silsesquioxane (POSS) molecules are unique nanometer-size inorganic/organic hybrid structures based on a (SiO_1.5)₈ core. While much is known experimentally about the chemical synthesis of POSS systems, very little theoretical understanding exists at the molecular level or beyond. In particular, the way in which individual POSS molecules can be assembled and manipulated at the nanoscale to form meso- and macro-scale materials, with properties that depend on the functionality of the cage, has not been investigated. The overall goal of this project has been to develop a multiscale computational framework to enable the prediction of the structure, properties and behavior of POSS-based systems, leading to structure-property relationships for these materials. Results will be presented from atomistic simulations of POSS systems and the development of a mesocale model discussed.

While much is known about the nature of the skin lipids, a detailed picture of the molecular organization of lipids in the stratum corneum (SC, the outermost layer) has not been elucidated. We are developing both atomistically detailed and coarse-grained molecular models for the lipids of the SC that can then be used to probe the molecular arrangement of the lipid molecules. Results will be presented for a number of pure and mixed lipid systems to demonstrate the suitability of the proposed force field for modeling crystalline and melt phases as well as the transferability of the coarse-grained potentials.