Shear modulation force microscopy study of near surface glass transition temperatures

We report results of glass transition (T-x) measurements for polymer thin films using atomic force microscopy (AFM). The AFM mode, shear modulation force microscopy (SMFM), involves measuring the temperature-dependent shear force on a tip modulated parallel to the sample surface. Using this method we have measured the surface T-g of thin (17-500 nm) polymer Films and found that T-g is independent of film thickness (t > 17 nm), strength of substrate interactions, or even presence of substrate.