Detection of the Order-to-Disorder Transition in Block Copolymer Electrolytes Using Quadrupolar 7 Li NMR Splitting.

The order-to-disorder transition temperature ( T ODT ) in a series of mixtures of polystyrene- b -poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is identified by the disappearance of a quadrupolar 7 Li NMR triplet peak splitting above a critical temperature, where a singlet is observed. The macroscopic alignment of ordered domains required to produce a quadrupolar splitting occurs due to exposure to the NMR magnetic field. Alignment is confirmed using small-angle X-ray scattering (SAXS). The T ODT determined by NMR is consistent with that determined using SAXS.