A water-free solid polymer electrolyte containing poly(ethyle oxide) (PEO) and poly(ethyle oxide) with sulfonic acid dianion end groups (PEO sulfonic acid dianion) is constructed using periodic boundary conditions by atomistic molecular modelling. The vibrational frequencies are calculated and found to be in agreement with the measured spectra. The structure of the PEO sulfonic acid dianion is studied by calculating the dihedral angle distributions and the intramolecular pair correlation functions between the carbon atoms and the ether oxygen atoms. The dimensional analysis is made. Results concerning the PEO sulfonic acid dianion in the water-free system are compared to the results obtained in the water containing systems and in vacuum. The structure of the PEO sulfonic acid dianion in water-free system is found to be rather similar to its structure in water and PEO containing system but different from its structure in vacuum. (C) 2000 Elsevier Science Ltd. All rights reserved.