Emulsion polymerization remains a challenging system for in situ Raman spectroscopic analysis, despite extensive research in the necessary instrumentation and chemometric data analysis methods. In this study we demonstrate a new and facile data analysis method, making in situ Raman spectroscopy a more versatile research tool for monitoring the concentrations of monomers in reactions spanning a wide range of compositions. The method improvement stems from the use of the homopolymer as an internal standard for the corresponding monomer. Classical least squares or indirect hard modeling is used for the spectral analysis to determine the spectral responses of major monomers and polymers within the system. Once the relative response factor ratios for a number of monomerhomopolymer pairs are determined in the calibration, they can be used to calculate the concentration ratio for such pairs based on reaction spectra. This approach offers two important advantages in determining the conversion of monomer to polymer. First, because the polymer internal standard will always be present for the corresponding monomer, it is straightforward to compensate for variable signal intensity due to changes in light scattering or instrumental fluctuations. Second, it is possible to calibrate based on a small set of monomer and homopolymer standards. The appropriate pairs can then be selected to establish a calibration method for any polymer product involving a combination of monomers from this set without the need for re-calibration. To demonstrate this technique, examples of in situ Raman monitoring for both batch and semi-batch emulsion polymerizations are provided.
Notes 2795 barrel and the surrounding liquor, but large enough to permit ready flow between them when desired. The pipet is fitted at the top with an ordinary glass stopcock, leaving a mouthpiece of glass about 2.5 cm. above the cock. Its total length is not longer than a stirring rod.The sample to be analyzed is secured in a beaker, diluted suitably, and indicator added if necessary. The portion is adjusted when possible to require a set amount of standard solution. The stirring rod is introduced and the barrel filled. The pipet stopcock is closed and the standard solution run into the beaker as rapidly as possible from the buret to a slight excess, the buret stopcock being full open until the end-point is signaled. The pipet meanwhile functions as a stirring rod. Half of the withdrawn barrel portion is now drained into the beaker and titration repeated to excess, this time by additions of say twenty drops each. This cycle is repeated with say five drop portions. The rod is then rinsed in the solution by running liquid in and out several times. The final titration in one drop portions is rapid. The color variation or other indication of the end-point is fresh in the memory. Judgment is not strained. It was found even when duplicates were being run that it was quicker and easier to titrate by this method. A medicine dropper arrangement is similar but not satisfactory. It is not precise and not readily cleaned.If the sample can be adjusted approximately to require a set volume of standard solution the titration (with a set procedure) will always occur in a fixed time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.