Direct polymerization of surface-tethered polyelectrolyte layers in aqueous solution via surface-confined atom transfer radical polymerization

The direct polymerization of deprotonated acidic monomers in aqueous solutions was achieved via surface-confined atom transfer radical polymerization (SC-ATRP) to produce surface-tethered polyelectrolyte brushes. Layers of poly(itaconic acid), poly(methacrylic acid), and sodium poly(styrene sulfonate) were grown by SC-ATRP from self-assembled initiator monolayers of [BrC(CH3)(2)COO(CH2)(11)S](2) on gold substrates. The polymer layers were characterized with variable-angle ellipsometry and external-reflection Fourier transform infrared spectroscopy. Without intervention, atom transfer radical polymerization catalysts were deactivated by complexation with the deprotonated acidic monomers, disproportionation, and dissociation during the polymerization of these monomers in water; the result was the cessation of polymer growth. The addition of an alkali salt to the reaction media suppressed catalyst deactivation, allowing polymer layers to increase in thickness linearly for longer periods of time with respect to salt-free conditions. This result suggested an improved degree of polymerization control. (c) 2006 Wiley Periodicals, Inc.