  We have developed a coarse-grained (CG) model of a polymer-clay system
consisting of organically modified montmorillonite nanoclay as the nanoparticle
in accordance with the MARTINI forcefield. We have used mechanical properties
and cleavage free energy of clay particle to respectively parameterize bonded
and nonbonded interaction parameters for an organically modified
montmorillonite (oMMT) clay particle where intergallery Na+ ions are replaced
by tetramethylammonium (TMA) ions. The mechanical properties were determined
from the slope of stress-strain curve and cleavage free energy was determined
by allowing for full surface reconstruction corresponding to a slow equilibrium
cleavage process. Individual dispersive and polar contributions to oMMT
cleavage energy were used for determination of appropriate MARTINI bead types
for CG oMMT sheet. The self-consistency of developed MARTINIFF parameters for
TMA-MMT-polymer system was verified by comparing estimates for select
structural, thermodynamic, and dynamic properties obtained in all-atomistic
simulations with that obtained in coarse-grained simulations. We have
determined the influence of clay particle on properties of three polymer melts
(polyethylene, polypropylene, and polystyrene) at two temperatures to establish
transferability of the developed parameters. We have also shown that the effect
of clay-polymer interactions on structure-property relationships in this
nanocomposite system is well captured by Rosenfeld's excess entropy scaling.
