  In this work we study the spreading dynamics of tiny liquid droplets on solid
surfaces in the case where the ends of the molecules feel different
interactions with respect to the surface. We consider a simple model of dimers
and short chainlike molecules that cannot form chemical bonds with the surface.
We use constant temperature Molecular Dynamics techniques to examine in detail
the microscopic structure of the time dependent precursor film. We find that in
some cases it can exhibit a high degree of local order that can persist even
for flexible chains. Our model also reproduces the experimentally observed
early and late-time spreading regimes where the radius of the film grows
proportional to the square root of time. The ratios of the associated transport
coefficients are in good overall agreement with experiments. Our density
profiles are also in good agreement with measurements on the spreading of
molecules on hydrophobic surfaces.
