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Diffusion NMR of Poly(acrylic acid) Solutions : Molar Mass Scaling and pH‐Induced Conformational Variation

Title data

Lenoch, Arthur ; Schumacher, Marcel ; Gröschel, André H. ; Cramer, Cornelia ; Schönhoff, Monika:
Diffusion NMR of Poly(acrylic acid) Solutions : Molar Mass Scaling and pH‐Induced Conformational Variation.
In: Macromolecular Chemistry and Physics. Vol. 224 (2023) Issue 22 . - 2300286.
ISSN 1521-3935
DOI: https://doi.org/10.1002/macp.202300286

Abstract in another language

Self-diffusion of poly(acrylic acid) (PAA) in dilute solution is studied by pulsed field gradient (PFG)-NMR, also known as DOSY, and correlated to molecular weight with scaling laws at varying pH. Fitting a diffusion coefficient distribution model to PFG-NMR data, the molecular weight polydispersity of commercial PAA samples is quantified. Due to good agreement with GPC data, diffusion measurements offer a viable alternative to estimate chain length properties with minimal sample preparation. Similar results are achieved by dynamic light scattering (DLS), however, with lower precision. The evolution of the scaling exponent with increasing pH indicates a transition from a globular state in highly acidic conditions (ν = 0.46) to a partially stretched conformation with a maximum at pH 5 (ν = 0.67). At higher pH, counterion screening counteracts chain expansion, while an unexpected increase in the width of the diffusion coefficient distribution occurs. A universal scaling law of the diffusivity applies for a chain length range of 25 ≤ N ≤ 1585, albeit with distinctly different scaling exponents. While opposing arguments are brought forward in recent literature concerning the pH-dependence of short-chain conformations, analysis supports the view that chain conformation is significantly affected by pH, even for short chains.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Polymer Materials for Electrochemical Storage > Chair Polymer Materials for Electrochemical Storage - Univ.-Prof. Dr. André Gröschel
Research Institutions > Central research institutes > Bayerisches Zentrum für Batterietechnik - BayBatt
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Polymer Materials for Electrochemical Storage
Research Institutions
Research Institutions > Central research institutes
Result of work at the UBT: No
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 11 Oct 2023 05:16
Last Modified: 21 Dec 2023 13:20
URI: https://eref.uni-bayreuth.de/id/eprint/87097