NMR Spectroscopy in the Study of the Structure and Dynamics of Gels

Abstract

Nuclear magnetic resonance (NMR) spectroscopy in combination with FTIR, X-ray diffractometry, electron microscopy and other instrumental techniques is rewarding in the study of the morphology, molecular structure and component dynamics of gel networks. For example, structural quantities such as the composition of polymers, microtacticity, sequence distribution, branching, crosslinking and molecular weight can be determined from the chemical shifts and signal intensities in NMR spectra, while more sophisticated experiments, i.e., measurements of spin relaxation times, nuclear Overhauser enhancement (NOE), magnetization transfer (MT), chemical exchange saturation transfer (CEST), multiple-quantum (MQ) coherencies, and the pulsed field gradient (PFG) technique, can give detailed information on the molecular organization and morphology of gels, as well as the internal mobility of the constituents of the gel. In this chapter, the capabilities of all these NMR methods will be discussed in the context of comprehensive studies of hydrogels and organogels. A special emphasis is put on the interplay between the morphology of the gel systems, the molecular mobility of their constituents and the intermolecular interactions.