Synthesis, characterization and swelling behaviour of poly(methacrylic acid) brushes synthesized using atom transfer radical polymerization

• DOI: 10.1016/j.polymer.2008.11.051
• Publication Date: 2008-12-10T15:21:00Z
• Authors: Andrew J. Parnell; Simon J. Martin; Cheen C. Dang; Mark Geoghegan; Richard A.L. Jones; Colin J. Crook; Jonathan R. Howse; Anthony J. Ryan
• Keywords: Poly(N-isopropylacrylamide); Atom-transfer radical-polymerization; Molar mass distribution

abstract Poly(methacrylic acid) brushes have been prepared utilizing the ‘‘grafting from’’ technique and a livingradical synthesis route using a two stage process. Firstly a poly(1-ethoxyethyl methacrylate) brush wassynthesized by atom transfer radical polymerization and then thermally decomposed to poly-(methacrylic acid). The swelling behaviour of the weak polyacid brush was investigated as a function ofpH and salt concentration in aqueous solutions using atomic force microscopy. Force pulling measure-ments were used to establish the molecular weight and the grafted chain density. The swelling transitionwas found to be at pH 9; which is significantly different to the pK a (5.5) of untethered poly(methacrylicacid). We attribute this large shift in pK a to the high grafting density of these brushes. This can beexplained as a resultof the Coulombic repulsion of neighbouring charges. High salt concentrations (0.3 MNa þ ) also collapse the brush layer. Conversely low salt concentrations cause an increase in the thicknessof the brush, a behaviour expected for osmotic brushes. 2008 Elsevier Ltd. All rights reserved.