Poly(dimethylsiloxane) grafted with adhesive polymeric chains provide a route towards cost effective dry adhesives

Abstract

This study is aimed at developing an effective and potentially industrially applicable methodology for dry adhesion enhancement of bioinspired adhesive materials. Recently developed Activator Re-Generation through Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) was employed to graft poly(ethyl acrylate), poly(n-butyl acrylate) and poly(n-hexyl acrylate) polymer brushes on poly(dimethylsiloxane) (PDMS) substrates in presence of a structurally similar sacrificial initiator. Attenuated Total Reflection-Fourier Transformed Infrared spectroscopy (ATR-FTIR), Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance Spectroscopy (NMR), and ellipsometry were used to confirm the grafting and controlled growth of polymer chains on PDMS surfaces and in solution. A nanoindenter was used to measure adhesion on the PDMS samples at retraction rates of 10–50 nm/s and indentation depths of 100–500 nm. The polymer brushes were also grafted on PDMS micropillars of 20 μm in diameter with aspect ratio of 3, to test applicability of the developed method on bioinspired microstructured surfaces. A significant increase in adhesion was observed in all flat and micropatterned samples after the grafting resulting in achieving 20 kPa of adhesion strength in the flat samples. The study suggests that the investigated ARGET ATRP procedure can be used to produce cost effective dry adhesive surfaces.