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Title: Water Dynamics in Polyacrylamide Hydrogels

Abstract

Polymeric hydrogels have wide applications including electrophoresis, biocompatible materials, water superadsorbents, and contact lenses. The properties of hydrogels involve the poorly characterized molecular dynamics of water and solutes trapped within the three-dimensional cross-linked polymer networks. In this study, we apply ultrafast infrared two-dimensional infrared (2D IR) vibrational echo and polarization-selective pump-probe (PSPP) spectroscopies to investigate the ultrafast molecular dynamics of water and a small molecular anion solute, selenocyanate (SeCN -), in polyacrylamide hydrogels. For all mass concentrations of polymer studied (5% and above), the hydrogen bonding network reorganization (spectral diffusion) dynamics and reorientation dynamics reported by both water and SeCN - solvated by water are significantly slower than in bulk water. As the polymer mass concentration increases, molecular dynamics in the hydrogels slow further. The magnitudes of the slowing, measured with both water and SeCN -, are similar. However, the entire hydrogen bonding network of water molecules appear to slow down as a single ensemble, without a difference between the core water population and the interface water population at the polymer-water surface. In contrast, the dissolved SeCN - do exhibit two-component dynamics, where the major component is assigned to the anions fully solvated in the confined water nanopools. Lastly, themore » slower component has a small amplitude which is correlated with the polymer mass concentration, and is assigned to adsorbed anions strongly interacting with the polymer fiber networks.« less

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [1]
  1. Stanford Univ., CA (United States). Department of Chemistry
Publication Date:
Research Org.:
Stanford Univ., CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1485138
Grant/Contract Number:  
FG03-84ER13251
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 30; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; hydrogels; dynamics; ultrafast infrared experiments; water dynamics in nanoconfinement

Citation Formats

Yan, Chang, Kramer, Patrick L., Yuan, Rongfeng, and Fayer, Michael D. Water Dynamics in Polyacrylamide Hydrogels. United States: N. p., 2018. Web. doi:10.1021/jacs.8b03547.
Yan, Chang, Kramer, Patrick L., Yuan, Rongfeng, & Fayer, Michael D. Water Dynamics in Polyacrylamide Hydrogels. United States. doi:10.1021/jacs.8b03547.
Yan, Chang, Kramer, Patrick L., Yuan, Rongfeng, and Fayer, Michael D. Mon . "Water Dynamics in Polyacrylamide Hydrogels". United States. doi:10.1021/jacs.8b03547. https://www.osti.gov/servlets/purl/1485138.
@article{osti_1485138,
title = {Water Dynamics in Polyacrylamide Hydrogels},
author = {Yan, Chang and Kramer, Patrick L. and Yuan, Rongfeng and Fayer, Michael D.},
abstractNote = {Polymeric hydrogels have wide applications including electrophoresis, biocompatible materials, water superadsorbents, and contact lenses. The properties of hydrogels involve the poorly characterized molecular dynamics of water and solutes trapped within the three-dimensional cross-linked polymer networks. In this study, we apply ultrafast infrared two-dimensional infrared (2D IR) vibrational echo and polarization-selective pump-probe (PSPP) spectroscopies to investigate the ultrafast molecular dynamics of water and a small molecular anion solute, selenocyanate (SeCN-), in polyacrylamide hydrogels. For all mass concentrations of polymer studied (5% and above), the hydrogen bonding network reorganization (spectral diffusion) dynamics and reorientation dynamics reported by both water and SeCN- solvated by water are significantly slower than in bulk water. As the polymer mass concentration increases, molecular dynamics in the hydrogels slow further. The magnitudes of the slowing, measured with both water and SeCN-, are similar. However, the entire hydrogen bonding network of water molecules appear to slow down as a single ensemble, without a difference between the core water population and the interface water population at the polymer-water surface. In contrast, the dissolved SeCN- do exhibit two-component dynamics, where the major component is assigned to the anions fully solvated in the confined water nanopools. Lastly, the slower component has a small amplitude which is correlated with the polymer mass concentration, and is assigned to adsorbed anions strongly interacting with the polymer fiber networks.},
doi = {10.1021/jacs.8b03547},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 30,
volume = 140,
place = {United States},
year = {2018},
month = {7}
}

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Cited by: 6 works
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