Friction and Surface Dynamics of Polymers on the Nanoscale by AFM

Abstract

In this article the measurement and understanding of friction forces and surface dynamics ofpolymers on the one hand and the importance of molecular relaxation processes and viscoelasticityin polymers for advanced micro- and nanoscale applications on the other hand are discussed. Particularattention is paid to the nanoscale (surface) analysis by scanned probe microscopic approaches, includingatomic force microscopy (AFM), as a means to assess molecular relaxation processes that operateat a given temperature. Established AFM approaches, including lateral force and force modulationmicroscopy, are introduced and more recently developed techniques, such as torsional resonant modes,are briefly sketched. On the basis of the discussion of the techniques to measure friction and toprobe surface dynamics of polymers on the nanoscale, illustrative examples are reviewed. The examplesdiscussed address in particular the determination of values of the glass transition temperature (T g) and the difference of T gassessed in the bulk vs. at the free surface of polymers. Confinement and thin film effects on T g, but also on sub-T gtransitions and chain dynamics, are treated in detail. Finally, the mapping of multiphase systemsand anisotropic friction receive attention.