title: In situ small-angle neutron scattering and rheological measurements of shear-induced gelation.
abstract: The microscopic structure of shear-induced gels for a mixed solution of 2-hydroxyethyl cellulose and nanometer-size spherical droplets has been investigated by in situ small-angle neutron scattering (SANS) with a Couette geometry as a function of shear rate gamma. With increasing gamma, the viscosity increased rapidly at gamma approximately 4.0 s(-1), followed by a shear thinning. After cessation of shear, the system exhibited an extraordinarily large steady viscosity. This phenomenon was observed as a shear-induced sol-gel transition. Real-time SANS measurements showed an increase in the scattering intensity exclusively at low scattering angle region. However, neither orientation of polymer chains nor droplet deformation was detected and the SANS patterns remained isotropic irrespective of gamma. It took about a few days for the gel to recover its original sol state. A possible mechanism of gelation is proposed from the viewpoint of shear-induced percolation transition.
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan. shibayama@issp.u-tokyo.ac.jp
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Shibayama
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Kawada
authors.forename: Takuji
authors.initials: T
authors.lastname: Kume
authors.forename: Takuro
authors.initials: T
authors.lastname: Matsunaga
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Iwai
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Sano
authors.forename: Noboru
authors.initials: N
authors.lastname: Osaka
authors.forename: Sho
authors.initials: S
authors.lastname: Miyazaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okabe
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endo