Process analytical approaches for the coil-to-globule transition of poly(N-isopropylacrylamide) in a concentrated aqueous suspension

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• 作者：Peter Werner ; Marvin Münzberg ; Roland Hass…
• 关键词：Poly(N ; isopropylacrylamide) ; Photon Density Wave spectroscopy ; Focused Beam Reflectance Measurement ; Turbidity measurement ; Particle Vision Microscope measurement ; Rate ; dependent lower critical solution temperature
• 刊名：Analytical and Bioanalytical Chemistry
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：409
• 期：3
• 页码：807-819
• 全文大小：3540KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Analytical Chemistry; Biochemistry, general; Laboratory Medicine; Characterization and Evaluation of Materials; Food Science; Monitoring/Environmental Analysis;
• 出版者：Springer Berlin Heidelberg
• ISSN：1618-2650
• 卷排序：409

文摘

The coil-to-globule transition of poly(N-isopropylacrylamide) (PNIPAM) microgel particles suspended in water has been investigated in situ as a function of heating and cooling rate with four optical process analytical technologies (PAT), sensitive to structural changes of the polymer. Photon Density Wave (PDW) spectroscopy, Focused Beam Reflectance Measurements (FBRM), turbidity measurements, and Particle Vision Microscope (PVM) measurements are found to be powerful tools for the monitoring of the temperature-dependent transition of such thermo-responsive polymers. These in-line technologies allow for monitoring of either the reduced scattering coefficient and the absorption coefficient, the chord length distribution, the reflected intensities, or the relative backscatter index via in-process imaging, respectively. Varying heating and cooling rates result in rate-dependent lower critical solution temperatures (LCST), with different impact of cooling and heating. Particularly, the data obtained by PDW spectroscopy can be used to estimate the thermodynamic transition temperature of PNIPAM for infinitesimal heating or cooling rates. In addition, an inverse hysteresis and a reversible building of micrometer-sized agglomerates are observed for the PNIPAM transition process.