TIME-RESOLVED SAXS TECHNIQUE FOR STUDYING BLOCK COPOLYMERS UNDER SHEAR DEFORMATION. S. Suehiro, K. Saijo, T. Seto, M. Kakiuchi, T. Hashimoto, Department of Polymer Chemistry, Kyoto University, Kyoto 606-01, Japan, and Y. Amemiya, Photon Factory, National Laboratory for High Energy Physics,

Tsukuba 305, Japan.

The investigation of pattern formation in block copolymers has become a fascinating research topic in statistical mechanics of complex fluids in recent years. In-situ, time-resolved scattering experiments under shear are essential to understanding the structural mechanisms of shear deformation of block copolymers and other mesostructured materials, owing to the fact that such systems are expected to have numerous kinds of microscopic responses to applied stress.

A synchrotron-radiation dynamic small-angle X-ray scattering (SR-DSAXS) system has been developed at the Photon Factory, National Laboratory for High Energy Physics, Japan, in collaboration with the Department of Polymer Chemistry, Kyoto University, Japan, utilizing an imaging plate (IP) as a two-dimensional X ray detecting system, and a hydraulic driving system as a sample deformation device in order to study time-resolved structural changes in polymer specimens, especially block copolymers, subjected to a mechanical stimulus.

The specimen is sandwiched between two metal plates and subjected to a large amplitude oscillatory shear strain. The time resolved small-angle X-ray detecting system consists of an IP mounted on a YZ stage driven by a pair of stepping motors and an intelligent stepping motor controller. There is a 100 mm x 100 mm square aperture for the scattered X-rays in front of the IP stage. An IP (400 mm x 200 mm in size) divided into eight sections (100 mm x 100 mm) is used for detecting the SAXS patterns. Each section is moved to the position of the aperture in turn by the two stepping motors to record the X-ray pattern. The time required for the translational movement of the IP stage along the Y-axis or the Z-axis is ca. 0.5 s/100 mm. Therefore, this system can follow the change of structures at a mesoscopic level on a time scale as short as one second. DSAXS studies were performed on polystyrene-block poly(ethylene-alt-propylene) copolymers concerning the dynamic deformation of a body-centered-cubic (bcc) lattice of spherical microdomains, as well as the dynamic orientation and deformation of alternating lamellar microdomains, under a large oscillatory shear deformation.