Elsevier

Analytica Chimica Acta

Volume 1238, 15 January 2023, 340635
Analytica Chimica Acta

Improving the accuracy of copolymer sequence length determination by pyrolysis gas chromatography: A comprehensive study

https://doi.org/10.1016/j.aca.2022.340635Get rights and content
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Highlights

  • Sequence determination of various styrene-acrylate copolymer systems was achieved, through a novel assignment strategy.

  • Correction values for trimer formation were established using 13C NMR for several copolymer systems.

  • In-depth analysis of MS spectra yielded specific fragments for formed trimers, aiding in identification.

Abstract

Many industrial polymers which find application in contemporary materials are copolymers. Copolymers feature multiple distributions, that govern their physical properties, including the sequence distribution. Styrene-acrylate copolymers are an important class of polymers, their monomer sequence is typically determined by 13C NMR which suffers from low sensitivity and spectral resolution. A series of studies have shown that Py-GC can be applied to determine the sequence length of copolymers. The accuracy of the trimer assignments and the appropriate calibration approaches yielding reliable data have however not yet been validated. In the present study we propose a comprehensive workflow to ensure the accuracy of the sequence determination by Py-GC, next to NMR. In-depth analysis of the trimers observed in the Py-GC pyrograms of model styrene-acrylate copolymers was performed and specific MS fragments relating to the trimer sequence were assigned. A comparison of a series of copolymers yielded reliable assignments for the trimer signals. The obtained sequence lengths were in agreement with those calibrated with the benchmark method, 13C NMR. Py-GC was found to consistently underestimate the acrylate sequence length. Py-GC calibration with 13C NMR was thus found to be indispensable for the accurate absolute quantification of the sequence length by Py-GC. The calculated randomness did not vary significantly after NMR calibration, indicating that NMR calibration might not be required in all cases to obtain (relative) information on the sequence of a copolymer.

Keywords

Polymer
Sequence
Pyrolysis-gas chromatography
Styrene-acrylate copolymers

Data availability

Data will be made available on request.

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