The electrochemistry of polymers is reviewed, in comparison with solid or liquid electrolytes. It is shown that the coordination chemistry leading to the formation of conductive complexes is very general with specific interactions (e.g. transition metal-nitrogen). While the transference numbers are still the subject of controversies, a coordination chemistry akin to that of water for PEO or ammonia with PEI exists. Also, the possibility of redox conduction, through microphase separation leads to mixed conductivity (ions + electrons).