A polymer mixture of polystyrene (PS)/poly(vinyl methyl ether) (PVME) has been investigated by using a three-dimensional small-angle neutron scattering (3D-SANS) method. PS and PVME exhibit a large difference in the glass transition temperatureTg. Therefore, dynamical asymmetry is strongly enhanced in an intermediate temperature region between theTgvalues of neat PS and PVME. In the intermediate temperature region, a shear deformation was imposed on the polymer mixture to enhance the concentration fluctuations,i.e.shear-induced phase separation. By rotating the film specimen, which was rapidly quenched after deformation, 3D-SANS due to shear-induced phase separation was observed successfully. In theqx=qyplane of the sample coordinate system, whereqis a component of scattering vectorq, it was possible to observe SANS of `double-lobe' shape, with the minor axes of the lobes inclined towardsqx=qy, whereqx,qyandqz, denote the shear, velocity gradient and vorticity directions in reciprocal space, respectively. Abnormal `butterfly' scattering was observed in a section cut through the 3D-SANS in theqxqzplane. The 3D-SANS thus obtained is discussed in comparison with a model of dynamical coupling between stress and diffusion.
Interaction Parameters of Poly(vinyl methyl ether) in 2-Propanol-Water Mixture as Determined by Small-Angle Neutron Scattering.