Improved chemical resistance of polymer-based composites
such as
coatings remains a significant challenge for many defense applications
and technologies. In particular, composites with high concentrations
of large, micrometer-size particles present a complex microstructural
landscape of competing processes that influence the transport of penetrant
molecules. We present results of molecular dynamics calculations designed
to model micrometer-size particle surfaces that have been modified
by the addition of functional groups. The effect of the functionalized
surfaces on the surrounding polymer binder and the diffusive transport
of penetrant molecules is examined for different chemistries through
a polymer–particle composite system designed to represent an
interfacial region. We directly calculate penetrant diffusion coefficients
and polymer–penetrant properties within the composite interface
and compare with simulations of the same polymer in bulk systems.
In the simulations of the composite interface, the equilibrated polymer
density is 10–15% less than in the corresponding bulk system,
and at room temperature the penetrant diffusivity is found to be more
than an order of magnitude greater in the composite interface. In
the systems studied here, amine functional groups are seen to have
only a secondary effect on transport while no change is observed by
the presence of carboxyl groups.