Chitosan and naproxen salts: preparation and characterization

• Published in: Journal of thermal analysis and calorimetry Vol. 148; no. 1; pp. 177 - 190
• Main Authors: Medeiros, R. S., Ferreira, A. P. G., Cavalheiro, E. T. G.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2023; Springer; Springer Nature B.V
• Subjects: Ammonia; Analytical Chemistry; Chemistry; Chemistry and Materials Science; Chitosan; Crosslinking; Decomposition; Dehydration; Differential thermal analysis; Epichlorohydrin; Epoxy resins; Exothermic reactions; Fourier transforms; Infrared spectroscopy; Inorganic Chemistry; Measurement Science and Instrumentation; Naproxen; NMR; Nuclear magnetic resonance; Physical Chemistry; Polymer Sciences; Reagents; Chitosan salts; Naproxen; Chitosan
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-022-11626-8

Chitosan (CTS) and naproxen (NAP) salts were prepared using different reaction parameters such as time, molar ratio and temperature. The salt was also synthesized from chitosan crosslinked with epichlorohydrin (EP). The starting reagents and salts were characterized by spectroscopic ( 1 H NMR and FTIR) and thermoanalytical (TG/DTG/DTA, DSC and TG-FTIR) techniques. Under dry air atmosphere, the CTS TG/DTG curve showed three mass loss events, one resulting from dehydration and the other two referring to the decomposition and burning of the carbonized material, with a residue of 5.95% at 1000 °C. Under the same conditions, the DTA curve exhibited an endothermic dehydration peak and an exothermic decomposition peak. TG/DTG curve of NAP shows two stages of mass loss, the first related to the drug decomposition and the other of burning the carbonized material. The DTA curve showed an endothermic peak at 156.7 °C (melting), in addition to other endo and exothermic peaks attributed to evaporation, decomposition and burning of the carbonized material. The TG/DTG/DTA curves of naproxen salts with non-crosslinked (CN) and crosslinked (CEPN) chitosan showed profiles similar to those of CTS; however, the mass loss events were observed at different temperature intervals, suggesting an interaction between CTS and NAP. The DSC curves of CNs and CEPNs showed salt formation, as the endothermic peak characteristic of NAP melt was not observed. These data are supported by spectroscopic techniques (FTIR and 1 H NMR). In experiments involving TG-FTIR, the release of gases was observed: CO, CO 2 , CH 3 CONH 2 , CH 3 COOH, NH 3 and CH 4 .