Well-defined poly(2-isopropenyl-2-oxazoline) brushes provide fouling resistance and versatility in surface functionalization

Abstract

Poly(2-isopropenyl-2-oxazoline) (PIPOx), a biocompatible polymer amenable to clean and orthogonal post-polymerization modifications, has recently emerged as a suitable candidate for the preparation of functional polymer brushes via surface-initiated reversible-deactivation radical polymerization (SI RDRP). However, the field currently lacks a universal SI RDRP method that would provide a straightforward control over the PIPOx brush thickness and be applicable to non-planar surfaces. Herein, we designed an aqueous, metallic copper-mediated RDRP (Cu(0)-RDRP) protocol for SI grafting of IPOx that manifests an excellent degree of temporal control over the PIPOx brush thickness up to more than 100 nm. The superior kinetic control was achieved through the use of an all-chlorine initiation/catalytic Cu(0)-RDRP system and careful ligand selection, demonstrating a clear advantage over previous approaches based on brominated initiators. Additionally, we found that using neat water as a reaction medium for the Cu(0) catalyst generation in the standard disproportionation step significantly accelerates the brush growth. Importantly, a surface plasmon resonance analysis demonstrated for the first time the high resistance of PIPOx brushes against non-specific protein fouling, as documented by a significant (96%) decrease in protein deposition from undiluted blood plasma and negligible adsorption from fetal bovine serum and other protein solutions. Finally, we showcased in model scenarios the versatility of the prepared well-defined PIPOx brushes by modifying them with suitable functional carboxylic acids under mild conditions in order to subsequently synthesize graft copolymer brushes or trigger a CuAAC click reaction. Our results highlight PIPOx brushes as an attractive platform for the fabrication of low-fouling, multifunctional surfaces.