Non-isothermal depolymerisation kinetics of poly(ethylene oxide)

The depolymerisation of low molecular weight poly(ethylene oxide) (PEO) under mild conditions was studied using a linear temperature ramped non-isothermal technique and the results compared with those obtained from a conventional isothermal technique. The analysis of the non-isothermal kinetic (NIK) data was performed using an original computer program incorporating an algorithm that systematically minimizes the sum of the squares of the residuals between the experimental data and the calculated theoretical kinetic profile in order to extract the kinetic parameters. The results revealed that the depolymerisation of PEO proceeds in accordance with the Ekenstam model and follows the Arrhenius equation over the temperature range of ca. 40-130 °C. The NIK analysis resulted in a two-dimensional convergence to produce a unique solution set for the kinetic parameters of E_a = 89.4 kJ mol⁻¹ and A = 9.6 × 10⁶ h⁻¹. These data are consistent with the results obtained from the isothermal experiments. It is proposed that NIK analysis is a quick and reliable means of obtaining kinetic parameters relevant to lifetime predictions in polymers whose degradation behaviour can be considered to be close to ideal.