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Article

A Process Analytical Concept for In-Line FTIR Monitoring of Polysiloxane Formation

1
School of Applied Chemistry, Reutlingen University, 72762 Reutlingen, Germany
2
Reutlingen Research Institute, 72762 Reutlingen, Germany
*
Author to whom correspondence should be addressed.
These authors contributed equally.
Polymers 2020, 12(11), 2473; https://doi.org/10.3390/polym12112473
Received: 6 October 2020 / Revised: 23 October 2020 / Accepted: 23 October 2020 / Published: 25 October 2020
(This article belongs to the Special Issue Silicon-Containing Polymers)
The chemical synthesis of polysiloxanes from monomeric starting materials involves a series of hydrolysis, condensation and modification reactions with complex monomeric and oligomeric reaction mixtures. Real-time monitoring and precise process control of the synthesis process is of great importance to ensure reproducible intermediates and products and can readily be performed by optical spectroscopy. In chemical reactions involving rapid and simultaneous functional group transformations and complex reaction mixtures, however, the spectroscopic signals are often ambiguous due to overlapping bands, shifting peaks and changing baselines. The univariate analysis of individual absorbance signals is hence often only of limited use. In contrast, batch modelling based on the multivariate analysis of the time course of principal components (PCs) derived from the reaction spectra provides a more efficient tool for real-time monitoring. In batch modelling, not only single absorbance bands are used but information over a broad range of wavelengths is extracted from the evolving spectral fingerprints and used for analysis. Thereby, process control can be based on numerous chemical and morphological changes taking place during synthesis. “Bad” (or abnormal) batches can quickly be distinguished from “normal” ones by comparing the respective reaction trajectories in real time. In this work, FTIR spectroscopy was combined with multivariate data analysis for the in-line process characterization and batch modelling of polysiloxane formation. The synthesis was conducted under different starting conditions using various reactant concentrations. The complex spectral information was evaluated using chemometrics (principal component analysis, PCA). Specific spectral features at different stages of the reaction were assigned to the corresponding reaction steps. Reaction trajectories were derived based on batch modelling using a wide range of wavelengths. Subsequently, complexity was reduced again to the most relevant absorbance signals in order to derive a concept for a low-cost process spectroscopic set-up which could be used for real-time process monitoring and reaction control. View Full-Text
Keywords: polysiloxane; process analysis and process control; FTIR spectroscopy; multivariate data analysis; batch modelling; reaction trajectories polysiloxane; process analysis and process control; FTIR spectroscopy; multivariate data analysis; batch modelling; reaction trajectories
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MDPI and ACS Style

Steinbach, J.C.; Schneider, M.; Hauler, O.; Lorenz, G.; Rebner, K.; Kandelbauer, A. A Process Analytical Concept for In-Line FTIR Monitoring of Polysiloxane Formation. Polymers 2020, 12, 2473. https://doi.org/10.3390/polym12112473

AMA Style

Steinbach JC, Schneider M, Hauler O, Lorenz G, Rebner K, Kandelbauer A. A Process Analytical Concept for In-Line FTIR Monitoring of Polysiloxane Formation. Polymers. 2020; 12(11):2473. https://doi.org/10.3390/polym12112473

Chicago/Turabian Style

Steinbach, Julia C., Markus Schneider, Otto Hauler, Günter Lorenz, Karsten Rebner, and Andreas Kandelbauer. 2020. "A Process Analytical Concept for In-Line FTIR Monitoring of Polysiloxane Formation" Polymers 12, no. 11: 2473. https://doi.org/10.3390/polym12112473

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