Atomistic investigation of Poly(3-hexylthiophene) adehesion on nanostructured titania

We studied the adhesion of poly(3-hexylthiophene) on a nanostructured titanic surface in vacuo by means of model potential molecular dynamics. We generated large-scale atomistic models of nanostructured titania surfaces [consisting of spherical nanocaps on top of a (110) rutile surface] and we studied the adhesion of an oligothiophene as a function of local curvature and roughness. In the limit of a perfect planar Surface, the maximum adhesion energy is calculated to be as large as 0.6 eV/monomer, and it corresponds to the oligothiophene oriented along the [(1) over bar 10] direction of the surface. Deformations of the polymer are observed due to incommensurability between the titanic and the polymer lattice parameters. When the surface is nanostructured, adhesion of the polymer is affected by the local morphology and it nonmonotonic dependence on the surface curvature is observed. The atomistic results are explained by a simple continuum model that includes the strain energy of the polymer and its electrostatic interaction with the local surface charge.