The thermal degradation of 2-hydroxy-3-ionene chloride polymer (HICP) and 3,22-ionene bromide (3,22) was studied in nitrogen atmosphere by thermogravimetry (TG) and infrared spectroscopy (FTIR). For the two polymers, a different profile in the TG/DTG curves was observed which was probably associated with the structural and functional differences between HICP and 3,22. The E-values decreased from 150 to 105 kJ mol −1 for the HICP and increased from 110 to 140 kJ mol −1 for the 3,22 in the same range of weight loss fraction. The observed behaviour in terms of the TG/DTG curves and the activation energy values suggested that the 3,22 is more stable thermally than the HICP. This conclusion was supported by the FTIR spectra of the residues and evolved gas products of degradation. The mechanism of degradation was apparently associated with the scission of weak bonds and random scission of the polymer chain. Evolved gas products such as CO 2 and NH 3 in HICP and unsaturated hydrocarbons in 3,22 confirm the above mechanism.