Length scale of mechanical heterogeneity in a glassy polymer determined by atomic force microscopy

Using dynamic force microscopy, nanoscale mechanical heterogeneity in glassy polymer was characterized. The correlation length of heterogeneous viscoelasticity was measured to be similar to 2.1 nm, consistent with the length scale of cooperatively rearranging regions at glass transition and is independent of molecular weight. Apparent energy dissipation with the variation of similar to 57%, originating from non-uniform distribution of local viscoelasticity, was revealed. The results provide definite experimental evidences on the nanoscale heterogeneity in glassy polymers and bear important insights in understanding the puzzling glass transition. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729931]