Surface transitions by shear modulation force microscopy

With the increasing importance of thin film in various applications, there is a need for new techniques with high surface sensitivity to measure physi cal properties. In this paper, we report results using a recently developed technique based on atomic force microscopy, temperature-dependent shear mo dulation force microscopy (SMFM), to investigate the surface glass transiti on. We test the effects of pressure under the tip, modulation frequency, an d driving amplitude, which have been the subject of some controversy. The g lass transition measurements on polystyrene and poly(methyl methacrylate) w ith different sample geometries demonstrate that the active volume probed b y this technique has lateral dimensions on the order of the tip-sample cont act radius. Applications to thin film glass transition measurements and sur face segregation in long-chain/short-chain blends demonstrate the general u tility of this technique.