NIRT: Multiscale Simulation of the Synthesis, Assembly and Properties of Nanostructured Organic/Inorganic Hybrid Material

This proposal was submitted in response to the solicitation 'Nanoscale Science and Engineering' (NSF-00-119). The resulting grant is co-funded by the Divisions of Materials Research and Chemical and Thermal Systems. The proposed research will be carried out at the Universities of Tennessee, Michigan and Virginia. Also participating are NIST, Hybrid Plastics and Tal Materials.

Polyhedral oilgomeric silsesquioxane (POSS) molecules are unique nanometer-sized structures. POSS molecules have a polyhedral core which can be multifunctional and serve as platforms that can be synthetically modified to contain groups for polymerization, adhesion, light sensitization, binding catalyst species, and improved solubility. The ability to independently functionalize each corner of a POSS cube with different organic or inorganic groups confers a nearly infinite array of possible hybrid nanostructures made of assemblies of POSS molecules. Depending on the functionalization of the POSS cages, the resulting systems can be solid or liquid, or on crosslinking turned into a network. They are a truly nanostructured building block, which, through self-and guided-assembly, can be transformed into a remarkable array of products, and due to recent breakthroughs in rapid synthesis technology, are only just now becoming available to industry on a commercial scale.

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 systems has not been studied. In this grant a multiscale computational framework will be developed to simulate the synthesis and self-and guided-assembly of POSS systems.

In order to address POSS systems at many levels, beginning at the quantum mechanical through to the mesoscale and macroscopic, the principal investigators (PI's) have the requisite expertise ranging from electronic structure calculations to molecular simulation. This expertise will be applied to three initial problems: (1) structure of cross-linked POSS networks; (2) nanostructured phase prediction; and, (3) templated nanostructured thin films. Feasible multiscale modeling routes to describing these systems have been developed, based on the expertise and codes available among the PI's. Modifications will be made as the modeling effort evolves. The simulation codes developed will be in the public domain, documented in user manuals and technical reports, and distributed to the user community. These techniques will enable the prediction, essentially from first principles, of the physical and structural properties of hybrid inorganic/organic nanostructured systems.

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