Healing surface defects with nanoparticle-filled polymer coatings: Effect of particle geometry
Smith, KA; Tyagi, S; Balazs, AC
MACROMOLECULES, 38 (24): 10138-10147 NOV 29 2005
Using computational models, we investigate how the aspect ratio of nanoparticle fillers within a polymer coating affects the ability of the film to heal nanoscale defects in the underlying substrate. We first consider the interactions between the filled polymer melt and a flat surface and show that the depletion attraction between the nanoparticles and this substrate depends strongly on this aspect ratio. In particular, the rodlike particles experience a significantly stronger attraction to the substrate than spherical fillers. 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 that contains a nanoscopic notch, which represents the damaged region. We show how tailoring the particles' aspect ratio provides a means of optimizing the localization of the particles into the notch. Morphologies obtained from molecular dynamics simulations are then used as input to a lattice spring model, which allows us to determine the mechanical properties of the coated surfaces. The results show that coatings filled with rodlike particles significantly reduce the stress concentrations at the notch. The application of such nanocomposite coatings could potentially yield defect-free surfaces that exhibit enhanced mechanical properties.
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