Analysis of Surface Dynamics of Polymer Films by Lateral Force Microscopy

Abstract

We here introduce how surface dynamics in polymer films can be examined by lateral force microscopy. Since the manifestation of lateral force is strongly related to energy dissipation during a tip sliding, lateral force can be regarded as an index of dynamic loss modulus at the surface. As a sample, monodisperse polystyrene (PS) films were used. On the basis of the temperature dependence of lateral force, glass transition temperature at the surface was determined. In addition, by measuring scanning rate vs. lateral force curves at various temperatures, activation energy of the surface segmental motion corresponding to glass transition could be successfully obtained via time-temperature superposition principle. The results of these experiments made it clear that thermal molecular motion at the surface was much more vigorous than that in the interior bulk region. Finally, it is also described that LFM was applied to surface segregation phenomenon in polydisperse PS films.