  We report on a molecular dynamics investigation of the wetting properties of
graphitic surfaces by various solutions at concentrations 1-8 wt% of
commercially available non-ionic surfactants with long hydrophilic chains,
linear or T-shaped. These are surfactants of length up to 160 [\AA]. It turns
out that molecular dynamics simulations of such systems ask for a number of
solvent particles that can be reached without seriously compromising
computational efficiency only by employing a coarse-grained model. The MARTINI
force field with polarizable water offers a framework particularly suited for
the parameterization of our systems. In general, its advantages over other
coarse-grained models are the possibility to explore faster long time scales
and the wider range of applicability. Although the accuracy is sometimes put
under question, the results for the wetting properties by pure water are in
good agreement with those for the corresponding atomistic systems and
theoretical predictions. On the other hand, the bulk properties of various
aqueous surfactant solutions indicate that the micellar formation process is
too strong. For this reason, a typical experimental configuration is better
approached by preparing the droplets with the surfactants arranged in the
initial state in the vicinity of contact line. Cross-comparisons are possible
and illuminating, but equilibrium contanct angles as obtained from simulations
overestimate the experimental results. Nevertheless, our findings can provide
guidelines for the preliminary assessment and screening of surfactants. [See
pdf file for full abstract]
