Mechanical hole burning spectroscopy in polymeric systems - A novel technique to characterize dynamic heterogeneity

Mechanical Spectral Hole Burning (MSHB) is a novel rheological technique to probe dynamic heterogeneity for polymeric materials, which exhibit relatively weak dielectric responses. In the present work, mechanical spectral hole burning (MSHB) was applied to a block copolymer and a series of polystyrene solutions in order to investigate its capability of detecting the heterogeneity and the possible relationship between the length scale of heterogeneity and hole properties. The results illustrate the power of MSHB to probe the dynamic heterogeneity of polymeric systems as evidenced by the presence or absence of mechanical holes in the vicinity of the order-disorder transition of a block copolymer. The results also suggest the hole properties are not governed by the length scale of the heterogeneity, rather they are dominated by the dynamics, i.e., whether the MSHB is performed in close to Rouse regime, rubbery plateau regime, transition regime from plateau to terminal region or the terminal flow regime.