Säckel, Christoph ; Klitzing, Regine von ; Siegel, Renée ; Senker, Jürgen ; Vogel, Michael (2024)
Water dynamics in solutions of linear poly (N-isopropyl acrylamide) studied by ²H NMR field-cycling relaxometry.
In: Frontiers in Soft Matter, 2024, 4
doi: 10.26083/tuprints-00027140
Artikel, Zweitveröffentlichung, Verlagsversion
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Kurzbeschreibung (Abstract)
We use ²H nuclear magnetic resonance to study the dynamics of deuterated water in a solution of linear poly (N-isopropyl acrylamide) (pNIPAM, 4 wt%) across its coil-to-globule transition at a lower critical solubility temperature (LCST) around 32°C. In agreement with previous studies, we find that the ²H spin-lattice (T₁) and, in particular, spin-spin (T₂) relaxation times abruptly decrease when heating through the LCST, indicating that the polymer collapse causes an emergence of a water fraction with strongly reduced mobility. To quantify the dynamics of this slow water fraction, we exploit the fact that ²H field-cycling relaxometry allows us to measure the spectral density of the water reorientation in a broad frequency range. We find that the slow water fraction is characterised by a broad logarithmic Gaussian distribution of correlation times (σ LG = 2.3), which is centred about τ LG ≈ 10⁻⁹ s near the LCST. Hence, the common assumption of a Debye spectral density does not apply. We argue that a minor water fraction, which is located inside the pNIPAM globules and shows dynamics governed by the disordered polymer matrix, accompanies a major water fraction with bulk-like dynamics above the LCST. The former fraction amounts to about 0.4 water molecules per NIPAM monomer. Several findings indicate fast exchange between these bound and free water fractions on the T₁ and T₂ time scales.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2024 |
| Autor(en): | Säckel, Christoph ; Klitzing, Regine von ; Siegel, Renée ; Senker, Jürgen ; Vogel, Michael |
| Art des Eintrags: | Zweitveröffentlichung |
| Titel: | Water dynamics in solutions of linear poly (N-isopropyl acrylamide) studied by ²H NMR field-cycling relaxometry |
| Sprache: | Englisch |
| Publikationsjahr: | 7 Mai 2024 |
| Ort: | Darmstadt |
| Publikationsdatum der Erstveröffentlichung: | 21 März 2024 |
| Ort der Erstveröffentlichung: | Lausanne |
| Verlag: | Frontiers Media S.A. |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Frontiers in Soft Matter |
| Jahrgang/Volume einer Zeitschrift: | 4 |
| Kollation: | 11 Seiten |
| DOI: | 10.26083/tuprints-00027140 |
| URL / URN: | https://tuprints.ulb.tu-darmstadt.de/27140 |
| Zugehörige Links: | |
| Herkunft: | Zweitveröffentlichung DeepGreen |
| Kurzbeschreibung (Abstract): | We use ²H nuclear magnetic resonance to study the dynamics of deuterated water in a solution of linear poly (N-isopropyl acrylamide) (pNIPAM, 4 wt%) across its coil-to-globule transition at a lower critical solubility temperature (LCST) around 32°C. In agreement with previous studies, we find that the ²H spin-lattice (T₁) and, in particular, spin-spin (T₂) relaxation times abruptly decrease when heating through the LCST, indicating that the polymer collapse causes an emergence of a water fraction with strongly reduced mobility. To quantify the dynamics of this slow water fraction, we exploit the fact that ²H field-cycling relaxometry allows us to measure the spectral density of the water reorientation in a broad frequency range. We find that the slow water fraction is characterised by a broad logarithmic Gaussian distribution of correlation times (σ LG = 2.3), which is centred about τ LG ≈ 10⁻⁹ s near the LCST. Hence, the common assumption of a Debye spectral density does not apply. We argue that a minor water fraction, which is located inside the pNIPAM globules and shows dynamics governed by the disordered polymer matrix, accompanies a major water fraction with bulk-like dynamics above the LCST. The former fraction amounts to about 0.4 water molecules per NIPAM monomer. Several findings indicate fast exchange between these bound and free water fractions on the T₁ and T₂ time scales. |
| Freie Schlagworte: | water, poly (N-isopropyl acrylamide), NMR, field cycling NMR, molecular dynamics |
| ID-Nummer: | Artikel-ID: 1379816 |
| Status: | Verlagsversion |
| URN: | urn:nbn:de:tuda-tuprints-271409 |
| Zusätzliche Informationen: | This article is part of the Research Topic: Editors’ Showcase 2023: Polymers |
| Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik 500 Naturwissenschaften und Mathematik > 540 Chemie |
| Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik 05 Fachbereich Physik > Institut für Physik Kondensierter Materie (IPKM) |
| Hinterlegungsdatum: | 07 Mai 2024 13:19 |
| Letzte Änderung: | 13 Mai 2024 08:09 |
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| Suche nach Titel in: | TUfind oder in Google |
Verfügbare Versionen dieses Eintrags
- Water dynamics in solutions of linear poly (N-isopropyl acrylamide) studied by ²H NMR field-cycling relaxometry. (deposited 07 Mai 2024 13:19) [Gegenwärtig angezeigt]
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