The structures of a semidilute polymer solution, comprised of ultrahigh molecular weight polystyrene as a solute and dioctyl phthalate as a solvent, under oscillatory shear flow were investigated by means of small-angle light scattering. The system exhibited a double-winged anisotropic scattering pattern called “butterfly”, characteristic of shear-induced phase separation known to occur under a continuous shear flow. Under oscillatory shear flow the phase separation strongly depended on both a strain amplitude γ 0 and an angular frequency ω, being observed inside a quasi-parabolic line in the space of γ 0 vs log ω. The system was brought to a dynamically stationary state in about 20 min after applying the shear flow, and the shear-induced structures changed with a strain phase φ of the oscillatory shear. At a given φ and γ 0, the shear-induced structures strongly depended on ω:  the characteristic wavelength of the structures decreased with increasing ω, and the mean square of the concentration fluctuations was a maximum at a certain ω.

Structures induced by a steady shear flow in a semidilute polymer solution of high molecular weight deuterated polystyrene in dioctyl phthalate are investigated. By a combined use of small-angle light scattering (SALS) and small-angle neutron scattering (SANS), we are able to obtain scattering functions of the shear-induced structures over 3 orders of magnitude in wavenumber (q) and 7 orders of magnitude in intensity. The changes in the structures with shear rate (γ̇) at a given temperature and with temperature at a given γ̇ are explored. At a given temperature, the shear flow induces a structural change in the solution at γ̇ larger than a critical shear rate γ̇c, giving rise to a scattering pattern called “butterfly pattern” in the low q region of SANS, while keeping the same pattern as that in the quiescent state in the q region of SALS. As γ̇ increases, the butterfly patterns evolved not only in the low q region of SANS but also in the q region of SALS. This indicates that the shear-induced structures responsible for the butterfly pattern are developed over a wide q range (q ≤ 0.06 nm-1) with increasing γ̇. At a given γ̇ larger than γ̇c, both SALS and SANS scattering intensity increase with a decrease of temperature, indicating the shear-induced structures are more pronounced upon decreasing temperature. Especially, at the lowest temperature covered in this experiment, the scattering pattern observed in the low-q region of SANS is turned into an elliptical shape with a major axis perpendicular to the flow direction, while keeping the butterfly pattern in the SALS q region. A detailed analysis and discussion about the scattering functions are presented in the text.

Oscillatory-shear-flow-induced structures of a semidilute polymer solution of ultrahigh molecular weight deuterated polystyrene in dioctyl phthalate were investigated by using the small-angle light scattering (SALS) and the small-angle neutron scattering (SANS). Under a fixed strain amplitude of oscillatory shear flow at 4.8, we observed the shear-induced structures as a function of the angular frequency (ω) and the strain-phase. At low ω, butterfly patterns, which are the scattering patterns unique to the shear-induced structures formed in semidilute polymer solution, were observed by SALS and isotropic patterns with weak scattered intensities were obtained by SANS. At high ω, on the other hand, SANS showed butterfly patterns and SALS showed almost isotropic patterns. These results indicate that the anisotropic structures developed under oscillatory shear flow become smaller with increasing ω. From the SALS and SANS patterns, we obtained scattering profiles parallel and perpendicular to the flow direction. At ω higher than 0.6133 rad/s, the SANS profiles parallel to the flow direction could be reproduced by a linear combination of the squared Lorentzian (SQL) function, which reflects the scattering from the random two-phase structures, and the Ornstein−Zernike (OZ) function, which gives the scattering from concentration fluctuations in a single phase. This analysis suggests that the shear-induced structures are not just the concentration fluctuations in a single phase but kind of phase-separated structures having well-defined interfaces between two phases.

Nanodisk array with sandwich structure of Au/ ͓Co/ Pt͔ n / Au was fabricated by electron beam lithography combined with argon ion milling. Excitation of localized surface plasmon resonance ͑LSPR͒ was demonstrated for various disk diameters. Magneto-optical ͑MO͒ properties were measured by a home-made micro-Faraday system at wavelengths of 633 and 690 nm. Faraday ellipticity at 690 nm showed non-monotonic dependence on disk diameter and reached maximum for disk diameter of 84 nm, which was associated with LSPR at 690 nm. The experimental results show direct evidence for LSPR enhancement effect on MO properties. The optical and MO properties were fitted by average field approximation.