A novel characterization technique for hydrogels - in situ rheology-Raman spectroscopy for gelation and polymerization tracking

The interest in hydrogels has grown considerably across a number of disciplines, including but not limited to the immobilization of (bio)catalysts in matrices and in the medical sector, for example, in drug delivery systems, contact lenses, biosensors, electrodes, and tissue engineering. Consequently, the characterization of these materials is frequently the subject of cutting-edge research. However, hydrogels are often insoluble, which precludes the use of many analytical methods, such as nuclear magnetic resonance (NMR). Consequently, other established analytical techniques, such as attenuated total reflection (ATR), infrared spectroscopy (IR), Raman spectroscopy, or rheological measurements, are frequently employed. These methods are generally straightforward to use and can be completed rapidly. However, IR spectroscopy, for instance, is inherently limited by the interference of water's vibrational bands. In this study, we present a method for the characterization of hydrogels that can simultaneously observe the gelation and polymerization of hydrogels.