The effect of molecular weight on thermal characteristics and thermal degradation of poly(ethylene glycol) (PEG) and poly(ethylene oxide)s (PEO) was investigated by differential scanning calorimetry, FT-IR spectroscopy and dynamic thermogravitnetry. Kinetic analysis of the non-isothermal degradation was performed using isoconversional (Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Friedman) and the invariant kinetic parameters method. The empirical kinetic triplets (E, A, and f(alpha)) as well as the rate constants have been calculated. The relation between the heating rate, the degradation rate and molecular weight for all investigated samples has been established. (C) 2009 Elsevier B.V. All rights reserved.