Thermosensitive gels are polymers that modify their conformation in response to temperature change. Many polymers exhibit this property, including N-isopropylacrylamide (NiPAAm). NiPAAm polymer gels are perhaps the most studied thermosensitive polymer because it has a low critical solution temperature (LCST) at 32 �C, and the transition period from a homogenous mixture to a phase-separated polymer is small, within 1-2�C. The LCST is close to a human's body temperature, making it particularly desirable for drug delivery and tissue engineering. Even with this popularity, the water environments above and below the LCST are not completely understood. In this poster, 1H high-resolution magic-angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy was used to identify and characterize the different water environments present near the LCST. The improved spectral resolution afforded by HRMAS NMR allowed the identification of multiple water environments in these gels, which were observed to depend on the temperature and cross-link ratios. By coupling HRMAS NMR with pulse field gradient (PFG) experiments, it was also possible to measure the self-diffusion rates for these different water environments. Spin-spin relaxation times (T2), and self-diffusion results were obtained as a function of temperature for two different gels preparation protocols. These HRMAS NMR results provide additional insights to develop describe the water environments in thermo-responsive gels such as NiPAAm. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Security Administration under contract DE-AC04-94AL8500.

Characterization of the water environments in thermosensitive NiPAAm gels using <sup>1</sup>H HRMAS NMR

247th National Meeting (2014)

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Characterization of the water environments in thermosensitive NiPAAm gels using 1H HRMAS NMR

Characterization of the water environments in thermosensitive NiPAAm gels using ¹H HRMAS NMR