Molecular Dynamics Simulation of Organically Functionalised Nanoparticles Applicable to Polymer Nanocomposite Systems*

We present a molecular simulation study a series of organically functionalised polyhedral oligomeric silsesquioxanes (POSS) systems and use these to elucidate the thermomechanical capabilities of POSS-containing materials. Since they inherently comprise both organic and inorganic components, POSS systems can exhibit a wide range of possible behaviours through variation of the geometry of their central inorganic cores. In simulation, it is also straightforward to systematically explore i) the range of ligands appended (either uniformally or asymmetrically to the central cores), ii) mixing ratios of various POSS forms and iii) their influence on polymer matrices.

These systems are amenable to simulation via atomistic MD methods, with gross system-wide behaviours (most obviously, the glass transition temperature of pure POSS systems) proving sensitive to a range of model inputs, such as geometry and choice of force-field. We also identify the key molecular degree of freedom which freezes in at Tg, thereby providing important insight for synthetic control of this key property. Finally, we present initial steps towards more ambitious systems of functionalised POSS cubes incorporated into polymeric melts.