Miniemulsion Polymerization Monitoring Using Off-Line Raman Spectroscopy and In-Line NIR Spectroscopy

Abstract

Miniemulsion polymerization has been extensively studied in the last decade due to its advantages when compared with conventional emulsion polymerization. In this work, monomer conversion and particle size are monitored during miniemulsion polymerization of styrene using in-line near-infrared (NIR) spectroscopy and at-line Raman spectroscopy. Gravimetric analysis and dynamic light scattering have been used as off-line reference measurements. Good agreement has been found between off-line data and the values predicted by NIR and Raman spectroscopy for conversion. The values of average particle size are well predicted from the NIR spectra with the respective calibration model, but the predictions from Raman spectra present some slight discrepancies for particle size. The results show a decrease of the average particle size during the initial period of the polymerization, indicating the occurrence of nucleation mechanisms other than the classical droplet nucleation. These results indicate that insightful information can be obtained by monitoring miniemulsion polymerizations with the use of spectroscopic techniques. (Figure presented.).