Networked polymers that had poly(ethylene glycol) (PEG) chains and lithium sulfonylimide salt structures were prepared by curing a mixture of poly(ethylene glycol) diglycidyl ether and lithium 3-glycidyloxypropanesulfonyl-trifluoromethanesulfonylimide with poly(ethylene glycol) bis(3-aminopropyl) terminated. The obtained flexible self-standing networked polymer films showed high thermal and mechanical stability with relatively high ionic conductivity. The room temperature ionic conductivity under a dry condition was in the range of 10(-5) similar to 10(-4) S m(-1), which is one order of magnitude higher than the corresponding networked polymers having lithium sulfonate salt structures (10(-6) similar to 10(-5) S m(-1)). The film sample became swollen by immersing in propylene carbonate (PC) or PC solution of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). The sample swollen in PC showed higher ionic conductivity (7.2 x 10(-3) S m(-1) at room temperature), and the sample swollen in 1.0 M LiTFSI/PC showed much higher ionic conductivity (8.2 x 10(-1) S m(-1) at room temperature). (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49:1874-1880, 2011