title: pH-responsive behavior of selectively quaternized diblock copolymers adsorbed at the silica/aqueous solution interface.
abstract: 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 copolymer-free 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 zeta 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, zeta 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.
authors.affiliation: School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT, UK. k-sakai@rs.noda.tus.ac.jp
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sakai
authors.forename: Emelyn G
authors.initials: EG
authors.lastname: Smith
authors.forename: Grant B
authors.initials: GB
authors.lastname: Webber
authors.forename: Murray
authors.initials: M
authors.lastname: Baker
authors.forename: Erica J
authors.initials: EJ
authors.lastname: Wanless
authors.forename: Vural
authors.initials: V
authors.lastname: Bütün
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
authors.forename: Simon
authors.initials: S
authors.lastname: Biggs