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Molecular Dynamics Simulation of Polyimide-Polyhedral Oligomeric Silsesquioxane Mixed Matrix Nanocomposites

Yin Yani and Monica H. Lamm. Chemical and Biological Engineering, Iowa State University, 2114 Sweeney Hall, Ames, IA 50011

Nanocomposite blends containing polyimide and polyhedral oligomeric silsesquioxanes (POSS) are a promising class of mixed matrix membranes for highly selective transport of small gas molecules such as hydrogen in high temperature applications. In this work, we use atomistic molecular dynamics simulations to model blends of polyimide and either octahydrido silsesquioxane (OHS) or octaaminophenyl silsesquioxane (OAPS). The glass transition temperature of the model polyimide-OAPS blends increases with the incorporation of OAPS, an observation consistent with recent experiments on these systems.[1] We present intermolecular radial distribution functions for POSS-POSS and POSS-PI atoms to show how packing between the two species in the mixed matrix varies as a function of POSS loading and POSS functional group. These results provide molecular insight about the thermal property enhancements afforded by POSS-based additives.

[1] P. Iyer and M. R. Coleman, J. Appl. Pol. Sci., 2008, Vol. 108, 2691-2699.