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This grant has been successfully allocated to support several graduate students as well as undergraduate interns to investigate finite-size effects on hydrophobic interactions in polymers. A supplementary summer research fellowship was to support Professor Samina Masood at the University of Houston at Clear Lake (non-Ph.D. granting institute) to participate research at the PI’s laboratory in the summer of 2008. We applied both all-atomistic molecular dynamics simulations and coarse-grained molecular simulations to address the thermodynamic and kinetic behavior of alkanes and polymers in nano-containers with different geometries. We produced two publications and one manuscript in a two-year period under the support of this grant.

In the paper of “Manipulating Biopolymer Dynamics by Anisotropic Nanoconfinement¹”, reported in Nano Letters in 2007, we investigated the geometrical effect of a nanocontainer on the kinetics of polymer collapse. The best geometry of a nano-container facilitating this process is the one that resembles the transition states of a polymer when it evolves from unfolded states to a fully collapsed state. We are the first to address the use of anisotropic nanoconfinement as a tool to manipulate chemical reactions in nano systems. This study was featured in the Research Highlights Nature Nanotechnology and its impact to the nanotechnology community was acknowledged.

We also investigated the characteristics of a hexane molecule in nano-sized water droplets using all-atomistic molecular simulations. The stability of a hexane molecule and the spatial and angular arrangement of water molecules surrounding individual hexane carbon atoms are investigated under varying sizes of water droplets. This work, “Hydrophobic Interactions of Hexane in Nanosized Water Droplet²”, is reported in the Journal of Physical Chemistry, B, 2009. It provided a quantitative insight into understanding the finite size effects on a broken network of hydrogen bonds of water molecules in the presence of hexane, which in turn affects the average conformation of hexane in a nano-sized droplet. In addition, our finding about the growing stability of hexane interacting with the interior of a pore as the pore size decreases addresses the need of efficient operations in the process of enhanced oil recovery. Noticeably, one of the co-authors, Mr. Byron Hoffman, an undergraduate research intern, was supported by this program when he joined the PI’s research group in the summer of 2008.

Supports from the ACS PRF award helped initiate new projects in the PI’s group and provided leverage for new grants. For example, one of our manuscripts entitled, “Studying polymer in different solvent conditions using a multiscale simulation scheme”, has attracted the attention of the DOE agency and a pending proposal derived from this work is under review. The PI recently received an NSF research award. We are very grateful to the generous support from your prestigious foundation.

Reference:
1. Zhang, S.-Q. & Cheung, M. S. (2007). Manipulating Biopolymer Dynamics by Anisotropic Nanoconfinement. Nano Letters 7, 3438-3442.

2. Homouz, D., Hoffman, B. & Cheung, M. S. (2009). Hydrophobic Interactions of Hexane in Nanosized Water Droplets. J. Phy. Chem. B. 113, 12337-12342.