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    pH-responsive behavior of selectively quaternized diblock copolymers adsorbed at the silica/aqueous solution interface

    Year: 2007

    Journal: Journal of Colloid and Interface Science 314 (2007) 381–388, 20100827

    Authors: Sakai K. 1 *, Smith E.G. 2, Webber G.B. 1 2, Baker M. 2, Wanless E.J. 2, Bütün V. 3, Armes S.P. 4, Biggs S. 1 *

    Last authors: Simon Biggs

    Organizations: 1 School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT, UK 2 School of Environmental and Life Sciences, The University of Newcastle, Callaghan, N.S.W. 2308, Australia 3 Department of Chemistry, Eskisehir Osmangazi University, Campus of Meselik, Eskisehir 26040, Turkey 4 Department of Chemistry, Dainton Building, The University of Sheffield, Brook Hill, Sheffield S3 7HF, UK

    Country: UK, United Kingdom

    The desorption and subsequent pH-responsive behavior of selectively quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2- (diethylamino)ethyl methacrylate) (PDMA–PDEA) films at the silica/aqueous solution interface has been characterized. The copolymer films were prepared at pH 9, where micelle-like surface aggregates are spontaneously formed on silica. The subsequent rinse with a copolymerfree electrolyte solution adjusted to pH 9 causes partial desorption of the weakly or non-quaternized copolymers, but negligible desorption for the highly quaternized copolymers. Further rinsing with a pH 4 electrolyte solution results in additional desorption and extension (swelling) of the remaining adsorbed copolymer film normal to the interface. This pH-responsive behavior is reversible for two pH cycles (9–4–9–4) as monitored by both quartz crystal microbalance with dissipation monitoring (QCM-D) and also ζ potential measurements. The magnitude of the pH-responsive behavior depends on the mean degree of quaternization of the PDMA block. Moreover, a combination of contact angle data, ζ potential measurements and in situ atomic force microscopy (AFM) studies indicates that the pH-responsive behavior is influenced not only by the number of cationic binding sites on the adsorbed copolymer chains but also by the adsorbed layer structure.