Nanoscale phase segregation in tailored graft copolymer electrolyte is probed by microscopy and small-angle scattering, and modeled by a stochastic technique. Based on stochastic modeling, we describe the percolation and connectivity of the ion-rich phase, and propose boundaries for the graft length and graft density to obtain favorable phase segregation potentially relevant for operation at low levels of hydration. The approach can be adapted for other copolymer systems, and points out new aspects in the structure-property relationships for polymer electrolytes. (c) 2013 Elsevier Ltd. All rights reserved.