The thermal decomposition of hydrogels based on N-maleoyl chitosan and poly(acrylic acid-co-ethyl acrylate) (NMACs-P(AA-co-EA)) and its precursors (chitosan and N-maleoyl chitosan) was studied by thermogravimetric analysis coupled to Fourier transform infrared spectroscopy and mass spectrometry (TGA/FTIR/MS). These coupled techniques allow collecting simultaneous information about the decomposition process as well as of the composition of gas-phase evolved from samples, identifying the structures for all degradation products. The effect of ethyl acrylate ratio on thermal stability and degradation mechanism of hydrogels is also discussed. An increase of ethyl acrylate monomer ratio resulted in a slightly decreased weight loss, indicating a low thermostability for NMACs-P(AA-co-EA) hydrogels. Also, the main thermal degradation pathways followed dehydration and condensation of comonomers with anhydride formation, chitosan depolymerization, decarboxylation, fragmentation and chain scission. (C) 2015 Elsevier B.V. All rights reserved.