We review the evidence indicating that ion transport can be decoupled from structural relaxations of the host material in polymer electrolytes. Particular emphasis is given to side group liquid crystal polymer electrolytes consisting of poly(ethylene oxide)-based backbones and pendent mesogenic groups. In salt complexes of these materials appreciable ionic conductivities are observed below the glass transition temperature, Thus, truly solid polymer electrolytes have been obtained. Structural similarities are discussed between these materials and rigid polymers containing powerful ion solvating groups which also appear to exhibit a decoupled conductivity mechanism. The conductivity mechanism in solid polymer electrolytes is compared to that proposed for inorganic glasses.