Creating surface patterns of polymer brushes by degrafting via tetrabutyl ammonium fluoride

Abstract

We demonstrate the use of tetrabutyl ammonium fluoride (TBAF) for creating spatial patterns of poly(methyl methacrylate) (PMMA) brushes on a flat silica support by degrafting PMMA grafted chains from selected regions on the substrate. We generate a gradient in grafting density of PMMA brushes by dipping substrates featuring homogeneous PMMA brush assemblies into TBAF solution. Desired in-plane patterns in the PMMA brush layer in millimeter scale are created by using a microcontact printing TBAF with a stamp made of agarose gel. The use of TBAF for degrafting is appealing because it cleaves selectively Si–O bonds and activates hydroxyl groups on silicon surfaces to enable deposition of organosilane-based initiators for growth of a fresh polymer brush layer. The latter is verified by using ellipsometry, X-ray photoelectron spectroscopy, and water contact angle measurements. The reusability of the substrate allows us to create diblock copolymer brushes on selected portions of the substrate not exposed to TBAF while decorating the TBAF-treated sections of the substrate with homopolymer brushes.