title: Small-Angle X-ray Scattering Study on Internal Microscopic Structures of Poly(N-isopropylacrylamide-co-tris(2,2'-bipyridyl))ruthenium(II) Complex Microgels.
abstract: Internal microscopic structures of poly(N-isopropylacrylamide-co-tris(2,2'-bipyridyl))ruthenium(II) complex microgels were investigated using small-angle X-ray scattering (SAXS) in the extended q-range of 0.07 ≤ q/nm(-1) ≤ 20. The microgels were prepared by aqueous free-radical precipitation polymerization, resulting in formation of monodispersed, submicrometer-sized microgels, which was confirmed by transmission electron microscopy and dynamic light scattering. To reveal the changes in the microscopic structures of the microgels during swelling/deswelling or dispersing/flocculating oscillation, the redox state of Ru(bpy)3 complexes was fixed in the microgels using Ce(IV) or Ce(III) ions under high ionic strength (1.5 M) during the SAXS measurements. The scattering intensity of the microgels manifested five different structural features. In particular, the correlation length (ξ), which was obtained from the fitting analysis using the Ornstein-Zernike equation, of the microgels both in the reduced and oxidized Ru(bpy)3 states exhibited divergent-like behavior. In addition, a low-q peak centered at q ≈ 5 nm(-1) did not appear clearly in both the reduced [Ru(bpy)3](2+) and oxidized [Ru(bpy)3](3+) states, indicating that the formation of a polymer-rich domain was suppressed; thus, Ru(bpy)3 complexes can be active even though the microgels are deswollen or flocculated during the oscillation reaction.
authors.forename: Shusuke
authors.initials: S
authors.lastname: Matsui
authors.forename: Takuma
authors.initials: T
authors.lastname: Kureha
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Nagase
authors.affiliation: §School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi 923-1292, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Okeyoshi
authors.affiliation: ∥Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yoshida
authors.forename: Takaaki
authors.initials: T
authors.lastname: Sato
authors.forename: Daisuke
authors.initials: D
authors.lastname: Suzuki