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Computer Simulation of Hybrid Organic-Inorganic Nanocomposites

Maurizio Fermeglia1, Sabrina Pricl2, Paola Posocco3, Marek Mály4, and Martin Lisal4. (1) Molecular Simulation Engineering Laboratory, Department of Chemical Engineering, University of Trieste, Piazzale Europa 1, Trieste, 34127, Italy, (2) Molecular SImulation Engineering (MOSE) Laboratory - DICAMP, University of Trieste, Piazzale Europa 1, Trieste, 34127, Italy, (3) University of Trieste, Piazzale Europa 1, Trieste, 34127, Italy, (4) E. Hala Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, 6-Suchdol, Prague, 165 02, Czech Republic

A current challenge of physical, chemical and engineering sciences is to develop theoretical tools for predicting structure and physical properties of hybrid organic inorganic nanocomposite from the knowledge of a few input parameters. However, despite all efforts, progress in the prediction of macroscopic physical properties from structure has been slow. Major difficulties relate to the fact that (a) the microstructural elements in multiphase material are not shaped or oriented as in the idealizations of computer simulations, and more than one type can coexist; (b) multiple length and time scales are generally involved and must be taken into account, when overall thermodynamic and mechanical properties wish to be determined, and finally (c) the effect of the interphases/interfaces on the physical properties is often not well understood and characterized. As a consequence, their role is often neglected in the development of new theoretical tools or they are treated in a very empirical way. In this work, we focused on issues (b) and (c) in a multiscale molecular simulation framework, with the ultimate goal of developing a computationally-based nanocomposite designing tool.

In this work a computational procedurewas developed, which allowed to obtain atomistic models of hybrid organic/inorganic networks based on 3-glycidyloxypropyltrimethoxysilane (GPTMS), an organofunctional alkoxysilane monomer that can undergo both the sol-gel polymerization of the alkoxy groups and curing of the epoxy functionality to form an I/O hybrid network with covalent bonds between organic and inorganic phases. The actual procedure, however, could be applied with minor modifications to any similar system. The simulation allowed also to estimate several thermophysical properties of the 3D network, such as mechanical moduli and constant pressure specific heat, whose values were found to be in the range of the corresponding experimental evidence for similar systems. These results confirm both the accuracy of the 3D model structure generated by the script procedure, and the quality of the force field used. Therefore, the proposed computational recipe can constitute a useful tool for the design and development of new hybrid I/O systems with improved structural/chemico-physical properties.