  The structural features of polystyrene brushes grafted on spherical silica
nanoparticles immersed in polystyrene are investigated by means of a Monte
Carlo methodology based on polymer mean field theory. The nanoparticle radii
(either 8 nm or 13 nm) are held constant, while the grafting density and the
lengths of grafted and matrix chains are varied systematically in a series of
simulations. The primary objective of this work is to simulate realistic
nanocomposite systems of specific chemistry at experimentally accessible length
scales and study the structure and scaling of the grafted brush. The profiles
of polymer density around the particles are examined; based on them, the brush
thickness of grafted chains is estimated and its scaling behavior is compared
against theoretical models and experimental findings. Then, neutron scattering
spectra are predicted both from single grafted chains and from the entire
grafted corona. It is found that increasing both the grafting density and the
grafted chain molar mass drastically alters the brush dimensions, affecting the
wetting behavior of the polymeric brush. On the contrary, especially for
particles dispersed in high molecular weight matrix, variation of the matrix
chain length causes an almost imperceptible change of the density around the
particle surface.
