Communication: X-ray scattering from ionic liquids with pyrrolidinium cations

We report the structure functions obtained from x-ray scattering experiments on a series of four homologous ionic liquids. The ionic liquids are 1-alkyl-1-methylpyrrolidinium cations paired with the bis(trifluoromethylsulfonyl)amide anion, with alkyl chain lengths of n = 4, 6, 8, and 10. The structure functions display two intense diffraction peaks for values of the scattering vector q in the range from 0.6 to 1.5 ?(-1) for all samples. Both diffraction peaks shift to lower values of q for increasing temperature. First sharp diffraction peaks are observed in the structure functions for q < 0.5 ?(-1) for liquids with n = 6, 8, and 10.