Multi-modal vibrational analysis of blend polymers using mid-infrared photothermal and Raman microscopies

Chemical characterization of polymeric samples, such as blend polymers is a fundamental analytical approach for advancement of polymer science and polymer technologies. Vibrational imaging is a promising technique to analyze chemical compositions of materials in a wide range of fields. Raman scattering and infrared (IR) absorption reflect complementary molecular vibrations; therefore, Raman and IR imaging provide rich information of the spatial distributions of chemical compositions of samples, revealing their complicated chemical structures. However, the discrepancy of spatial resolution in Raman and conventional IR imaging makes it difficult to merge these techniques. In the present study, we performed chemical characterization of polymeric samples using Raman and IR imaging enabled by mid-infrared photothermal (MIP) microscopy. The chemical compositions of blend polymer films were visualized based on both Raman scattering and IR absorption with the spatial resolution of the sub-micrometer scale. We found that the varying contrasts in Raman and MIP imaging enabled the investigation of averaged and surface-sensitive compositions of polymer blends. Raman and MIP imaging holds a promise of unique applications in a wide range of current research fields, such as polymers, two-dimensional materials, and biology.