Complexing salts, like lithium perchlorate, form interesting polymer electrolytes with terpolymers containing branched ether derivatives, which can be cross-linked, depending on the allyl glycidyl ether group content. Using thermal and electrochemical techniques, the effect of polymer cross-linking upon the properties of the resulting electrolytes has been estimated. It is shown that increasing the salt concentration intensifies the stiffness of the terpolymer network or the linear/branched one and the glass transition temperature consequently rises. Both electrolyte systems investigated in this work present good thermal stabilities up to 270 degreesC and ionic conductivities of 10(-4) S cm(-1) at 30 degreesC with 8 wt.% of LiClO4. Cross-linking does not severely affect the electrolyte conductivity but very significantly enlarges the electroactivity window (from 3 to 5 V) and improves the mechanical stability. The thermal dependence of the conductivity revealed a particular conduction mechanism attributed to the presence of short mobile chains due to the high polydispersity of the terpolymer. Thermal, electrical and special electrochemical properties suggest the inclusion of this material into the available polymer electrolytes for developing new electrochemical applications. (C) 2003 Elsevier Science B.V. All rights reserved.