We have studied the potential of friction and stiffness measurements w
ith high spatial resolution for the surface characterization of glassy
polymers. We present experimental evidence for quasi-chemical sensiti
vity on a heterogeneous surface consisting of polystyrene islands on a
poly(methyl methacrylate) base layer. Although similar in their bulk
mechanical properties, the two polymers are easily distinguished by th
eir different nanomechanical behavior. As an example, we characterize
the domain pattern formed after spinodal decomposition of a symmetric
blend of the two polymers.