Local chemical composition of nanophase-separated polymer brushes

Using scattering scanning nearfield infrared microscopy (s-SNIM), we have imaged the nanoscale
phase separation of mixed polystyrene–poly(methyl methacrylate) (PS–PMMA) brushes and
investigated changes in the top layer as a function of solvent exposure. We deduce that the
top-layer of the mixed brushes is composed primarily of PMMA after exposure to acetone, while
after exposure to toluene this changes to top layers dominated by PS. Access to simultaneously
measured topographic and chemical information allows direct correlation of the chemical
morphology of the sample with topographic information. Our results demonstrate the potential of s-SNIM for chemical mapping based on distinct infrared absorption properties of polymers with a high spatial resolution of 80 nm .