The polymerization of styrene in a 15-cm storage bottle and of methyl methacrylate (MMA) inside a 50-cm reactor cell was monitored non-invasively by stimulated Raman scattering (SRS) for spectroscopic analysis. A pulsed laser was required to stimulate Raman scattering while a photodiode array detector measured the monochromator-dispersed Stokes lines. The results demonstrate that SRS is a useful spectroscopic technique for the real-time probing of polymerization in a large sample volume. Its signal intensity is related to the average analyte concentration integrated over the laser interaction path, which can better represent the bulk property of extended sample dimensions.
Edward P. C. Lai and Hassan S. Ghaziaskar, "Noninvasive Spectroscopic Detection of Bulk Polymerization by Stimulated Raman Scattering," Appl. Spectrosc. 48, 1011-1014 (1994)