title: Direct evidence for structural transition promoting shear thinning in cylindrical colloid assemblies.
abstract: In this paper, we describe stimuli-responsive hydrogels prepared from a rigid rod-like polyelectrolyte 'imogolite' and a dicarboxylic acid. The hydrogel exhibited thixotropy in response to mechanical shock within the order of seconds or sub-seconds. Here, using the latest structural/rheological characterisation techniques, the relationship between the structural transition processes and the shear thinning was estimated. The evidence obtained by the experiments revealed for the first time the direct relationship between the microscopic structural change and the macroscopic thixotropic behavior that have been extensively discussed. The thixotropic hydrogel has the hierarchical architecture in the combination of imogolite and dicarboxylic acid, i.e., sheathed nanotubes/hydroclusters of cross-bridged nanotubes/frameworks. The formation and disintegration of the network structure upon resting and agitating, respectively, were the origin of gel/sol transition (thixotropy), although the hydroclusters of cross-bridged nanotubes were maintained throughout the transition.
authors.affiliation: Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16, Naka-cho, Koganei, Tokyo, 184-8588, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shikinaka
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kaneda
authors.forename: Saori
authors.initials: S
authors.lastname: Mori
authors.forename: Tei
authors.initials: T
authors.lastname: Maki
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Masunaga
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Osada
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Shigehara
keywords: colloids; gels; nanotubes; phase transition; self-assembly