Hydrogels represent heterogeneous systems that consist of a large amount of water retained by a three-dimensional network. The hydrogel network is the result of assembly through physical interactions or chemical cross-linking of polymers or small molecules. The applications of hydrogels (water purification, tissue regeneration, therapeutic delivery, bio-detection or bio-imaging, etc.) depend on their physicochemical properties and structural features. Although electron microscopy and viscoelastic measurements provide general information about a gel material, the spectroscopic methods complement these methods and also afford a deep insight into the gel structure. In this chapter, the applications of several spectroscopic methods for characterizing polymeric or supramolecular hydrogels are discussed. Thus, this review highlights the particular application of vibrational spectroscopy, circular dichroism, fluorescence (these providing information on assembly in the network), interactions that occur between network and solvent (water), pulsed-field gradient NMR (determination of mesh size) and EPR spectroscopy (a method that can provide extensive information regarding the assembly process, diffusion and release).
Part of the book: Emerging Concepts in Analysis and Applications of Hydrogels