Exploring the role of MgO nanoparticles in the mechanical properties of the MgO/PE composite: a tight-binding and molecular dynamics simulation study†

Metal oxide nanoparticles have been widely used as reinforcing agents in polyethylene (PE)-based composites but the reinforcing mechanism is not yet fully understood. Here we report a study of the interfacial and mechanical properties of a composite composed of magnesium oxide (MgO) particles and an amorphous PE (a-PE) matrix using ab initio density functional tight binding (DFTB) and classical molecular dynamics (CMD) simulations. Through the DFTB calculations of the MgO/a-PE composite models, we reveal that the oxygen-rich termination of the MgO surface not only exhibits a much stronger attractive interaction between the MgO particles and the PE chains than the Mg-rich ones, due to the formation of interfacial O–H covalent bonds, but also provides a more favourable condition for the cross-linking between the a-PE chains. Furthermore, we demonstrate via DFTB and CMD simulations that the elastic moduli and yield stress of the MgO/a-PE composite models are obviously enhanced compared to those with a-PE, verifying the role of MgO particles as a reinforcing agent in the composite. Highlighting the importance of controlling the size and distribution of MgO nanoparticles, we believe that the present work contributes to getting atomistic insights into interfacial and mechanical properties of MgO/a-PE composites and providing a guide for developing advanced PE-based composites.