Surface-Initiated Atom Transfer Radical Polymerization of Oligo(ethylene glycol) Methyl Methacrylate from a Mixed Self-Assembled Monolayer on Gold

Abstract

This paper describes the in-situ synthesis of an oligo(ethylene glycol)-functionalized polymer brush in which the oligo(ethylene glycol) chains are presented as side-chains from a methacrylate backbone that is anchored to the surface. These polymer “bottlebrushes” have been synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of oligo(ethylene glycol) methyl methacrylate (OEGMA) from a mixed self-assembled monolayer (SAM) of an ATRP initiator-functionalized alkanethiol and a diluent, methyl-terminated thiol. The systematic control of the ATRP initiator surface density afforded by the mixed SAM on gold and the polymerization time enables the polymer chain length and surface density to be independently controlled. Surface plasmon resonance (SPR) spectroscopy of fibronectin (Fn) adsorption on poly(OEGMA) grown from the surface of the mixed SAMs on gold shows that above a threshold solution molar ratio of the ATRP-initiator thiol to methyl-terminated thiol of 0.2, and a dry film thickness of ∼ 4 nm, Fn adsorption on the surface-initiated poly(OEGMA) coatings was below the detection limit of SPR. The relatively low surface density of the ATRP initiator required to confer protein resistance to the surface suggests that SI-ATRP may be a viable strategy to create protein resistant polymer brushes on real-world materials.