Polymethacrylontrile (PMAN)-based electrolytes were recently proposed as polymer matrix for ambient temperature applications. The living anionic polymerization of methacrylonitrile allowed PMAN–POE–PMAN triblock copolymers to be prepared from different starting PEGs. In order to appreciate the salt/polymer interactions, solvent-free polymer electrolytes were prepared by dissolution of lithium imide (LiTFSI) in PMAN homopolymer and copolymers. Despite the high T g of PMAN host polymer, conductivities as high as 10−4 S cm−1 were obtained around 90°C. Infra-red spectroscopy allowed the nitrile/salt interaction to be characterized. In particular, PMAN solvation number was determined from the homopolymer complexes. The investigation on the triblock copolymer complexes allowed the solvating competition between nitrile and ether functions to be highlighted.