Features of the Thermal Degradation of Sodium Hyaluronates with Different Molecular Weights

Hyaluronic acid and hyaluronates are polysaccharide of considerable interest for medicine and pharmaceuticals, and the area of their specific applications is determined by molecular weight. Samples of hyaluronans (sodium hyaluronates) in the molecular weight range 11.2–1800 kDa were studied by thermal analysis methods (differential scanning calorimetry and thermogravimetry with mass spectrometric recording of volatile degradation products) and Fourier IR spectroscopy using the ATR variant. The processes of the thermal and thermooxidative degradation of hyaluronans were characterized; these can be subdivided into two stages. In the first stage, degradation processes affect the side substituents, i.e., N-acetyl and ester groups, while the main macromolecular chain of hyaluronan is exposed to actions at the second stage. These processes are more clearly separated from each other when degradation is carried out in the absence of atmospheric oxygen. The results obtained here are employed to substantiate a method for rapid assessment of the molecular weight of hyaluronan using differential scanning calorimetry data for the primary selection of components for medical and pharmaceutical formulations.