Online Low-Field ¹H NMR Spectroscopy: Monitoring of Emulsion Polymerization of Butyl Acrylate

Abstract

The emulsion polymerization of butyl acrylate was monitored by online nuclear magnetic resonance spectroscopy at 20 MHz 1H frequency. The reaction progress could be followed, monitoring the conversion of the reactant time-resolved without any need of sample preparation. Experimental data were analyzed with kinetic models for free-radical polymerization. The data comprised the polymerization rate in seeded batch emulsion polymerizations of butyl acrylate with doubly deionized water and D2O as solvent. The polymerization rate versus conversion curve behaves compatible with the three rate intervals model, typically observed in emulsion polymerizations. Zero−one kinetics explains the experimental results appropriately, leading to the determination of entry and termination rate coefficients.

Online Monitoring of Polymerizations: Current Status

“…[51,52] Guthausen and coworkers monitored the emulsion polymerization of nBA in batch. [53] Multiple setups are reported where NMR spectroscopy is coupled with a flow reactor to follow the reactions in real-time. Duchateau and coworkers prepared Grignard reagents under continuous flow conditions with online NMR spectroscopy.…”

Medium Resolution NMR at 20 MHz: Possibilities and Challenges

“…First examples are described in literature 17,[20][21][22] . In this work the modified minispec mq20 19 was used to monitor the reaction progress in an emulsion polymerization 26 . This reaction type is of special interest in food processing science because of the above mentioned encapsulation possibility of active agents in droplets.…”

“…All spectra were fitted in a MATLAB ® routine resulting in graphs for intensities and widths 26 . The significant parameters are the intensity of the olefinic peak and the line width in the aliphatic region.…”

“…The significant parameters are the intensity of the olefinic peak and the line width in the aliphatic region. These two parameters can be described by kinetic models, revealing typical rate constants for the emulsion polymerization 26 . Please note the time shift between the start of integral decrease and width increase, which is caused by different physical phenomena reflected by the two NMR spectral parameters.…”

Real-time Detection of Polymerization Reactions with Hyperpolarized Xenon at Low Magnetic Fields

“…Recently an emulsion polymerization reaction was investigated online with proton NMR at 0.5 T [1]. Due to the fact that averaging during the measuring process was necessary we were looking for a method to detect a polymerization reaction in real-time.…”