title: Contrast variation by dynamic nuclear polarization and time-of-flight small-angle neutron scattering. I. Application to industrial multi-component nanocomposites.
abstract: Dynamic nuclear polarization (DNP) at low temperature (1.2 K) and high magnetic field (3.3 T) was applied to a contrast variation study in small-angle neutron scattering (SANS) focusing on industrial rubber materials. By varying the scattering contrast by DNP, time-of-flight SANS profiles were obtained at the pulsed neutron source of the Japan Proton Accelerator Research Complex (J-PARC). The concentration of a small organic molecule, (2,2,6,6-tetramethylpiperidine-1-yl)oxy (TEMPO), was carefully controlled by a doping method using vapour sorption into the rubber specimens. With the assistance of microwave irradiation (94 GHz), almost full polarization of the paramagnetic electronic spin of TEMPO was transferred to the spin state of hydrogen (protons) in the rubber materials to obtain a high proton spin polarization (PH). The following samples were prepared: (i) a binary mixture of styrene-butadiene random copolymer (SBR) with silica particles (SBR/SP); and (ii) a ternary mixture of SBR with silica and carbon black particles (SBR/SP/CP). For the binary mixture (SBR/SP), the intensity of SANS significantly increased or decreased while keeping itsqdependence forPH= -35% orPH= 40%, respectively. Theqbehaviour of SANS for the SBR/SP mixture can be reproduced using the form factor of a spherical particle. The intensity at lowq(∼0.01 Å-1) varied as a quadratic function ofPHand indicated a minimum value atPH= 30%, which can be explained by the scattering contrast between SP and SBR. The scattering intensity at highq(∼0.3 Å-1) decreased with increasingPH, which is attributed to the incoherent scattering from hydrogen. For the ternary mixture (SBR/SP/CP), theqbehaviour of SANS was varied by changingPH. AtPH= -35%, the scattering maxima originating from the form factor of SP prevailed, whereas atPH= 29% andPH= 38%, the scattering maxima disappeared. After decomposition of the total SANS according to inverse matrix calculations, the partial scattering functions were obtained. The partial scattering function obtained for SP was well reproduced by a spherical form factor and matched the SANS profile for the SBR/SP mixture. The partial scattering function for CP exhibited surface fractal behaviour according toq-3.6, which is consistent with the results for the SBR/CP mixture.
authors.affiliation: Institute of Quantum Beam Science, Ibaraki University, Ibaraki, 316-8511, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Noda
authors.affiliation: Institute of Quantum Beam Science, Ibaraki University, Ibaraki, 316-8511, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Koizumi
authors.affiliation: Sumitomo Rubber Industries Ltd, Kobe, 651-0072, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Masui
authors.affiliation: Sumitomo Rubber Industries Ltd, Kobe, 651-0072, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Mashita
authors.affiliation: Sumitomo Rubber Industries Ltd, Kobe, 651-0072, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kishimoto
authors.affiliation: Materials Science Research Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yamaguchi
authors.affiliation: Materials Science Research Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kumada
authors.affiliation: J-PARC Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Takata
authors.affiliation: Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Ibaraki, 319-1106, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ohishi
authors.affiliation: Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Ibaraki, 319-1106, Japan.
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Suzuki
keywords: contrast variation; dynamic nuclear polarization; nanocomposites; small-angle neutron scattering (SANS); ternary mixtures