Surface Interaction Forces of Well-Defined, High-Density Polymer Brushes Studied by Atomic Force Microscopy (ORGANIC MATERIALS CHEMISTRY-Polymeric Materials)

Abstract

Direct force measurements were made by atomic force microscopy (AFM) at surfaces of polymer brushes comprising low-polydispersity poly(methyl methacrylate) chains densely end-grafted on a silicon substrate by living radical polymerization. These brushes are characterized by an exceptionally high graft density. The AFM force measurements revealed that the repulsive force rapidly increased with decreasing separation in toluene. The equilibrium thickness of the brushes was found to be proportional to the chain contour length. This indicates formation of a homogeneous polymer layer with highly stretched graft chains. Unlike the previously reported results for lower density polymer brushes, longer brushes were more resistant to compression. It is believed that these are the first observations of “polymer brushes” in the true sense of the words.