Visualization of Structural Deformation of Polymer Additives in Oil Under High Shear Flow

Using a powerful synchrotron radiation X-ray source, we developed a cell that can perform Small Angle X-ray Scattering (SAXS) measurements under high shear (~ 10⁵ s⁻¹). We successfully and quantitatively visualized the deformation of polymer chains as polymer additives in oil under high shear. We found that poly(alkylmethacrylate) (PMA) with the lowest molecular weight was not deformed by the shear flow and did not show the shear thinning behavior. On the other hand, the other PMAs were deformed and exhibited shear-thinning behaviors. We compared the experimental results with the simulation by Ryder et al.( The Journal of Chemical Physics 45: 194906 (2006)) and found the shrink perpendicular to the flow direction in the experiment is stronger than that in the simulation, indicating that the rigidity of the polymer chains enhanced by long side groups induced the alignment of the chain along the flow direction. The decrease in viscosity was less than that estimated from the rate of deformation estimated by SAXS due to the effects of polydispersity of PMA polymers.