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Title: Characterization of Free Surface-Bound and Entrapped Water Environments in Poly(N-Isopropyl Acrylamide) Hydrogels via 1H HRMAS PFG NMR Spectroscopy

We found that different water environments in poly(N-isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using 1H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro-gels. For photo-initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spin R2 relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. Furthermore, by combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self-diffusion rate for these different water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described.
 [1] ;  [1] ;  [2] ;  [2]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Univ. of Oklahoma, Norman, OK (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0887-6266; 534159
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Polymer Science. Part B, Polymer Physics
Additional Journal Information:
Journal Volume: 52; Journal Issue: 23; Journal ID: ISSN 0887-6266
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
National Science Foundation (NSF), Arlington, VA (United States)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; diffusion; HRMAS; hydrogels; NMR; PFG; stimuli-sensitive polymers; thermoresponsive polymer; water