Polymer electrolytes with high ionic conductivity and good elasticity were prepared by mixing nitrite rubber (poly(acrylonitrile-co-butadiene) rubber; NBR) with ionic liquid, N-ethylimidazolium bis(trifluoromethanesulfonyl)imide (EImTFSI). The NBR/EImTFSI composites were obtained as homogeneous and transparent films when the ionic liquid content was less than 60 wt%. Raman spectroscopy suggested the interaction between nitrile group of NBR and TFSI anion. Sample with ionic liquid content of 50 wt% showed the ionic conductivity of 1.2 x 10(-5) S cm(-1) at 30 ° C. Addition of lithium salt to this NBR/EImTFSI composite further enhanced the ionic conductivity to about 10(-4) S Cm-1 without spoiling mechanical properties. DSC studies showed two glass transition temperatures for composites indicating microphase separation. © 2005 Elsevier Ltd. All rights reserved.