Vapor‐Based Initiator Coatings for Atom Transfer Radical Polymerization

Abstract

AbstractA novel polymeric initiator coating for surface modification via atom transfer radical polymerization (ATRP) is reported. The synthetic approach involves the chemical vapor deposition of [2.2]paracyclophane‐4‐methyl 2‐bromoisobutyrate and can be applied to a heterogeneous group of substrates including stainless steel, glass, silicon, poly(dimethylsiloxane), poly(methyl methacrylate), poly(tetrafluoroethylene), and polystyrene. Surface analysis using X‐ray photoelectron spectroscopy and Fourier‐transformed infrared spectroscopy confirmed the chemical structure of the reactive initiator coatings to be consistent with poly[(p‐xylylene‐4‐methyl‐2‐bromoisobutyrate)‐co‐(p‐xylylene)]. Appropriate reactivity of the bromoisobutyrate side groups was confirmed by surface initiated atom transfer radical polymerization of a oligo(ethylene glycol) methyl ether methacrylate. After solventless deposition of the CVD‐based initiator coating, hydrogel films as thick as 300 nm could be conveniently prepared within a 24 h timeframe via ATRP. Moreover, the polymerization showed ATRP‐specific reaction kinetics and catalyst concentration dependencies. In addition, spatially controlled deposition of the initiator coatings using vapor‐assisted microstructuring in replica structures resulted in fabrication of spatially confined hydrogel microstructures. Both protein adsorption and cell adhesion was significantly inhibited on areas that were modified by surface‐initiated ATRP, when compared with unmodified PMMA substrates. The herein described initiator coatings provide a convenient access route to controlled radical polymerization on a wide range of different materials. While demonstrated only for a representative group of substrate materials including polymers, metals, and semiconductors, this method can be expected to be generically applicable – thereby eliminating the need for cumbersome modification protocols, which so far had to be established for each substrate material independently.