Bundle structureformation on a polymer film at various temperatures andscanning velocities

Abstract

The structures formed by atomic force microscopic tipscanning on a 133 nm thick poly(tert-butylacrylate) (PtBuA) film were examined attemperatures ranging from room temperature to 58 °Cwith various scanning velocities from 1 to20 µm s-1. It was observed that bumps were created atlow temperatures and high scanning velocities. As thetemperature was increased and the scanning velocity wasdecreased, bundles were produced through aggregation of the bumps. The width of the bundles was about 100 nm. As thetemperature was further increased to higher than theglassy-rubbery phase transition temperature, Tg~50 °C, of the PtBuA polymer, no bundle structures were formed at low scanning velocities. Our results clearlyindicate that the formation of bumps and bundles occurs fromthe interplay of polymer peeling and relaxation. With polymerpeeling taking place on soft polymer surfaces, slowerrelaxation favours the accumulation of polymer coil displacementand the formation of the bump and bundle structures, while fast relaxation results in the recovery of the polymer perturbationand no formation of surface structures.