Novel Approach for Metallic Surface-Initiated Atom Transfer Radical Polymerization Using Electrografted Initiators Based on Aryl Diazonium Salts

Abstract

This paper reports on the preparation of poly(methyl methacrylate) (PMMA), poly(n-butyl acrylate) (PBA), and polystyrene (PS) brushes at the surface of conducting materials that were modified by the electrochemical reduction of a brominated aryl diazonium salt BF4-, +N2-C6H4-CH(CH3)-Br (D1). The grafted organic species -C6H4-CH(CH3)-Br was found to be very effective in initiating atom transfer radical polymerization (ATRP) of vinyl monomers. This novel approach combining diazonium salts and ATRP allowed PMMA, PBA, and PS brushes to be grown from the surface of iron electrodes. The polymer films were characterized in terms of their chemical structure by infrared reflection absorption spectroscopy and X-ray photoelectron spectroscopy. Atomic force microscopy studies indicated that the polymer brushes are densely packed. Contact angle measurements of water drops on PS and PMMA brushes were 88.1 +/- 2.0 and 70.3 +/- 2.1 degrees, respectively, which is consistent with the published wettability data for the corresponding polymer sheets.

Hydrophilic polymers grafted surfaces: preparation, characterization, and biomedical applications. Achievements and challenges

“…A few years ago, in a series of papers, Matrab et al [31,32] demonstrated that polymerization of vinyl monomers can be initiated by electrografted aryl derivatives of diazonium salts covalently bound to various solid supports (e.g. stainless steel, gold, and glassy carbon).…”

Interfacial aspects of polymer brushes prepared on conductive substrates by aryl diazonium salt surface‐initiated ATRP

“…The general procedure for grafting polystyrene (PS) and poly(methyl methacrylate) (PMMA) chains from the surface of iron disks and GC plates modified by electrochemical reduction of D2 is adapted from Refs [10,13].…”

“…[8] We have recently shown that controlled ATRP of vinylic monomers can be initiated on metals and carbon by electrografted brominated aryl species based on diazonium salts. [10,11] The use of aryl diazonium salts is indeed an elegant way of modifying conducting substrates, particularly carbon. [12] The interest of using aryl diazonium salts to surface-initiate ATRP (SI-ATRP) is that this class of organic salts leads, after electrochemical reduction, to the covalent attachment of functional aryl groups, [12] thereby, ensuring a covalent link between the polymer chains and the support.…”

“…Taking into account the chemistry of diazonium salts and the principles of surface-confined ATRP, we have designed BF 4 − , + N 2 -C 6 H 4 -CH(CH 3 )-Br (D1), a diazonium salt which is an analog for 1-phenylethyl bromide, a bulk solution ATRP initiator. [10] D1 can be readily electrochemically reduced on glassy carbon (GC) and iron to yield the attached -C 6 H 4 -CH(CH 3 )-Br (1) aryl group for surface-initiated ATRP. We have also designed another salt, BF 4 − , + N 2 -C 6 H 4 -CH 2 -CH 2 -Br (D2), and found it suitable for modifying the surface of multi-walled carbon nanotubes.…”

Atom transfer radical polymerization (ATRP) initiated by aryl diazonium salts: a new route for surface modification of multiwalled carbon nanotubes by tethered polymer chains

“…initiator-functionalized silanes [5], thiols [11,12], plasma-treated polymers [13], polyelectrolyte macroinitiators [ 14] and streptavidin-biotin conjugates [15]. Recently, we have proposed that ATRP of vinyl monomers can be initiated by electro-grafted brominated aryl species based on diazonium salts at the surface conductive materials such as iron [16], doped ultrananocrystalline diamond [17] and glassy carbon [18]. The use of aryl diazonium salts is indeed a simple and elegant way of modifying conductive substrates such as metals, semi-conductors and carbon in view of elaborating molecular junctions in electronic circuits, biosensors, and protective layers against corrosion [19].…”