Poly(iminoethylene)-b-poly(oxyethylene)-b-poly(iminoethylene) (PEI-b-PEO-b-PEI) polymers were synthesized and used as a "dual" matrix for polymer electrolytes having selectivity for "hard" cations (Li+/PEO) in one phase and for "soft" cations (Cu++/PEI) in the other. Both blocks are phase-separated, but each segment tends to crystallize, influenced by water and salt. The synthesis and characterisation, including AFM imaging before and after the perfluorosulfonimide salts loading is being addressed. The new block copolymer electrolytes with solvating affinities for different cations could be used either as a reference electrode or in the fabrication of electrochromic devices. (c) 2005 Published by Elsevier B.V.