Three-Dimensional Molecular Orientation Imaging of a Semicrystalline Polymer Film under Shear Deformation

The 3D molecular orientations of polymer chains are imaged and compared for a quiescent spherulite region and a shear-deformed region of a semicrystalline poly(ε-caprolactone) film. To acquire the images of 3D orientation, we used a newly developed hyperspectral imaging method based on the orthogonal-pair polarization IR (OPPIR) analysis. Polymer chains in spherulites are azimuthally aligned perpendicular to the crystal growth direction and axially tilted from the film normal direction. By contrast, polymer chains in a sheared region are azimuthally aligned along the shear direction but axially tilted from the shear direction. The unexpected out-of-plane tilted orientation indicates that orientational relaxation followed shear deformation and occurred predominantly in the out-of-plane direction. Furthermore, incorporating peak deconvolution into the OPPIR analysis shows that the crystalline and amorphous chains are oriented aligned at different angles, possibly due to different orientational relaxation between the two chain configurations.