Scanning Electron Microscopy Investigation of Molecular Transport and Reactivity within Polymer Brushes

Scanning electrochemical microscopy (SECM) allows investigation of the transport of redox probes within polymer brushes grown by atom-transfer radical polymerization (ATRP) from gold electrodes. By combination with cyclic voltammetry, the permeation of aqueous or organic redox probes is described and quantified in poly(glycidyl methacrylate) (PGMA) and polystyrene (PS). It is related to the chemical nature of both the probe and its environment (the solvent and the polymer phases). This study anticipates the permeation of reactive species within polymer brushes for further etching. The SECM reductive etching of the terminal C-Br bond of PGMA or PS macroinitiator layers is then investigated for different polymer thicknesses. The incomplete reductive etching of the macroinitiator layers is in agreement with the low permeability of the etchant within such polymer brushes and with the distribution of the terminal C-Br bonds throughout the brush. SECM proves to be a convenient tool for patterning such macroinitiator surfaces to form channels in block-copolymer structures. The combination of both analytical and patterning investigations enables one to anticipate and understand the reactivity of grafted macromolecules.