Morphology of Nanostructured Polymer Brushes Dependent on Production and Treatment

Abstract

The morphology of top-down and bottom-up nanostructured neutral brushes is studied as a function of the production process and the quality of solvent to which the brushes have been exposed. Neutral brushes of poly(tert-butyl methacrylate) (PtBuMA) were grafted from the substrate by surface-initiated radical-chain polymerization (SI-RCP). Brush patterning was conducted using deep ultraviolet (DUV) photolithography following either top-down (TD) or bottom-up (BU) approaches with patterned lines as small as 200 nm. The resulting brushes were immersed in toluene or methanol, and the change of morphology of the dried brushes was monitored using tapping mode atomic force microscopy (AFM). TD nanopatterned brushes (NPBs) exhibit a box-like and BU generated brushes a lens-like shape directly after the production process. We show that the pattern width for the BU brushed depends not only on the wetting properties of the areas adjacent to the pattern but also on the process history to which the sample has been exposed, especially the solvent quality. Furthermore, we show that TD NPBs are cross-linked on the edges of the pattern because of the high-energy process conditions during brush patterning and study the behavior of the thus-obtained structures.