(255b) Healing Surface Defects with Polymer Nanocomposites Containing Spheres and Rods

We use molecular dynamics (MD) simulations to investigate the benefits of applying a nanocomposite coating to substrates containing scratches and other defects. We consider a nanoparticle filled polymer film and show that the polymer melt induces a depletion attraction between nanoparticles and a flat surface. The nature of this force depends strongly on the particle shape, rodlike particles have a much stronger attraction than spherical particles. We quantify these interactions by measuring the effective potential between a particle and surface, as well as between two particles in the melt. We then consider the case of a surface notch, where the attraction is stronger due to the proximity of two surfaces. Here we show how tailoring the particle shape is a means of optimizing the tendency of particles to fill the notch. Morphologies obtained from the MD simulations are used as input to a lattice spring model which allows us to determine mechanical properties of the coated surfaces. The results show that the coating significantly reduces stress concentration at a notch. The application of such nanocomposite coatings could potentially yield defect-free surfaces that exhibit enhanced mechanical properties.