Online Monitoring of Styrene Polymerization in Miniemulsion by Hyperpolarized¹²⁹Xenon NMR Spectroscopy

Abstract

Online monitoring of a miniemulsion polymerization of styrene by hyperpolarized 129 Xe NMR spectroscopy is presented. The chemical shift of 129 Xe directly reports on the monomer/polymer ratio in the reaction mixture and therefore on the conversion of the reaction. The method allows for monitoring the progress of a polymerization with high time resolution and without sample extraction. The results obtained by 129 Xe NMR spectroscopy were successfully validated by comparison with results of calorimetry. Further characterization of the polymer dispersions with regard to the solids content and the particle diameters proved the comparability of both methods. Small deviations in the kinetic data and the properties of the polymer suspension from both methods are explained by the loss of monomer during the 129 Xe NMR experiments due to the used setup. In the future, 129 Xe NMR might also be applied for online monitoring of other chemicals reactions, e.g., allowing for determining the kinetics of thermoneutral reactions.

Hyperpolarized 1H long lived states originating from parahydrogen accessed by rf irradiation

“…This lifetime issue limits the application of hyperpolarization to the observation of sufficiently fast processes, e.g. fast chemical reactions 15,16 or metabolism pathways. [17][18][19] Thus, during the last few years, a lot of research was conducted to overcome this issue.…”

In situ monitoring of styrene polymerization using Raman spectroscopy. Multi‐scale approach of homogeneous and heterogeneous polymerization processes

“…Raman spectroscopy appeared as one of the most promising spectroscopic methods because of its fast response, its very low sensitivity to water, its applicability to both homogeneous and heterogeneous reaction media and the relative easiness of its use both at the laboratory scale and in industrial environment . Other spectroscopic techniques like nuclear magnetic resonance or fluorescence have been reported for monitoring polymerization reactions either in homogenous or in heterogeneous reaction media but mainly at the laboratory scale. It has been shown that Raman spectroscopy allowed in situ determination of monomer consumption in free radical polymerization reactions carried out with different processes: several examples have been reported for bulk polymerization and emulsion polymerization while there is only one example for miniemulsion process .…”

Online Monitoring of Polymerizations: Current Status

“…[48] Zakharov and coworkers introduced in situ CT MAS NMR spectroscopy under continuous flow conditions to monitor the dynamics of propene polymerization over a supported Ziegler catalyst. [49] Landis and coworkers investigated the kinetics of the catalyst polymerization of 1-hexene by utilizing stopped-flow NMR spectroscopic measurements.…”