Polymer nanodroplets adsorbed on nanocylinders: A Monte Carlo study

The structure and the shape of polymer droplets of nanoscopic size on ultrathin cylindrical fibers (with diameters in the range of nanometers) is investigated by Monte Carlo simulation of a coarse-grained bead-spring type model. The interaction between atoms in the solid nanocylinder and the effective monomers is assumed to be of Lennard-Jones-type, but the detailed atomistic structure of the nanofiber is ignored, using a homogeneous cylinder with a perfectly smooth surface. Depending on the size of the droplet, the fiber radius, and the strength of the adsorption potential, droplets have either the (axially symmetric) "barrel shape," or the asymmetric "clamshell shape," or are unstable against spreading out along the fiber. For the barrel-shaped droplets, the dependence of the contact angle on the parameters mentioned above is estimated. For comparison, using the same model also the case of droplets on a flat horizontal surface and in a wedge with opening angle of 90degrees has been studied. When appropriate, the simulation results are interpreted in terms of current theoretical predictions. (C) 2002 American Institute of Physics.