In situ Monitoring of Polymers via Low-frequency Raman Spectroscopy: Samuel Lofland

Polymers are among the most used materials in manufacturing so it is essential to understand their structure-processing-property relationships. While polymer properties can be evaluated by various techniques, the process analytical technology used in production requires real-time (and preferably remote) monitoring. This is inherently difficult to implement for most experimental methods, the exception being optical approaches. Raman and infrared spectroscopies are sensitive to chemical bonding, and changes therein provide pertinent insight into the state of the polymer; however, both techniques suffer from signal-to-noise issues that arise depending upon the type of bond. However, recent advances in photonics technology have made it possible to measure the low-frequency (< 100 cm^‑1) Raman signal with spectrometers that are smaller, cheaper, and significantly easier to use. In the low-frequency region, low-lying structural excitations dominate the Raman response, and for amorphous materials the resulting spectra relate to the phonon density of states and the conformational entropy. These spectra display universal features that can be followed for real-time and spatially localized monitoring of polymer properties and kinetics.