Molecular dynamics simulation of mixed matrix nanocomposites containing polyimide and polyhedral oligomeric silsesquioxane (POSS)

Mixed matrix blends containing polyimide (PI) and polyhedral oligomeric silsesquioxanes (POSS) are studied with atomistic molecular dynamics simulation. To examine the effect of functional group, two types of POSS are considered, either octahydrido silsesquioxane (OHS) or octaaminophenyl silsesquioxane (OAPS). The glass transition temperature of the model PI–OAPS blends increases with the incorporation of OAPS, an observation consistent with recent experiments on these systems. A decrease in glass transition temperature is shown for the model PI–OHS blends. Radial distribution functions for both blends are presented to show how packing between the inorganic (POSS) and organic (PI) species in the mixed matrix varies as a function of POSS loading and POSS functionalization. In addition, we report the mobility of the PI chains and POSS molecules in the material by calculating the mean square displacement. These results provide molecular insight about thermal property enhancements afforded by POSS-based additives.