Sodium polymer electrolytes, as much safer electrolytes, are expected to be applied in sodium batteries. Here we present a systematic analysis of the NaTDI-PEO electrolytes. Their relatively high conductivity is explained by means of detailed structural, thermal and spectroscopic studies. On the basis of these results and with help of the database obtained for NaTDI-glyme system, we propose the coordination modes for polymer-salt complex phases. Thanks to this, it is possible to simulate intramolecular interactions both in crystalline and amorphous phases and explain the influence of formed crystalline phases on the observed conductivity relationship. (C) 2018 Elsevier Ltd. All rights reserved.