3D Orientation Imaging of Polymer Chains with Polarization-Controlled Coherent Raman Microscopy
Shuyu Xu, Young Jong Lee
Despite the ubiquity of three-dimensional (3D) anisotropic materials, their 3D molecular alignment cannot be measured using conventional two-dimensional (2D) polarization imaging. Here, we present images of the 3D angles of molecular orientations with submicrometer spatial resolution acquired through polarization-controlled coherent anti-Stokes Raman scattering microscopy. The hyperspectral Raman data of a polyethylene (PE) film were converted into images, showing the polymer chains' 3D angles and order parameters. The 3D orientation images of PE chains in ring-banded spherulites show that the azimuthal angles of the chains are perpendicular to the crystal growth direction, while the out-of-plane angles display limited-range oscillations synchronous with ring banding. The prevailing crystal growth model of fully twisting lamellae is inconsistent with the observed restricted oscillations of the out-of-plane direction, which are unobservable through conventional 2D projected imaging. This high-resolution, label-free, quantitative imaging of 3D molecular orientation can become a standard measurement tool for the microscopic structures of complex synthetic and biological materials.
and Lee, Y.
3D Orientation Imaging of Polymer Chains with Polarization-Controlled Coherent Raman Microscopy, Journal of the American Chemical Society, [online], https://doi.org/10.1021/jacs.2c10029, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934584
(Accessed September 25, 2023)