Thermodynamic parameters, like change in free energy of activation (?G?t*), enthalpy of activation (?H?t*), and entropy of activation (?S?t*) of poly(ethylene glycol) with average molecular mass 400 Delton (PEG 400) in dilute solution of benzene were computed on the basis of theory of Eyring rate process. To estimate these, the dielectric relaxation time (t), determined at various temperatures adopting Whiffen and Thompson model have been used. X-band microwave bench working at 9.59 GHz was employed to find temperature dependent real part e' of the complex dielectric permittivity e* and dielectric loss e?. The values of these e' and e? are used to find t values. Based on the results reported, the relaxation behavior of the stated polymer in nonpolar solvent is discussed. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012