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As part of an ongoing study of the structure and properties of mixtures of ionic liquids in which one component has a hydrocarbon chain and the other a semiperfluorocarbon chain, we now report a study of the mixtures [C 8 MIM] 1- x [C 10 MIM-F 17 ] x [Tf 2 N], [C 10 MIM] 1- x [C 8 MIM-F 13 ] x [Tf 2 N] and [C 10 MIM] 1- x [C 10 MIM-F 17 ] x [Tf 2 N], where [C 8 MIM][Tf 2 N] is 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide, [C 10 MIM][Tf 2 N] is 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C 8 MIM-F 13 ][Tf 2 N] is 1-(1 H ,1 H ,2 H ,2 H -perfluorooctyl)-3-methylimidizolium bis(trifluoromethylsulfonyl)imide and [C 10 MIM-F 17 ][Tf 2 N] is 1-(1 H ,1 H ,2 H ,2 H -perfluorodecyl)-3-methylimidizolium bis(trifluoromethylsulfonyl)imide. The mixtures were investigated using small-angle X-ray (SAXS) and neutron (SANS) scattering complemented by molecular dynamics simulations (with viscosity and surface tension measurements also possible for the mixtures [C 10 MIM] 1- x [C 8 MIM-F 13 ] x [Tf 2 N]). Unlike previous studies of [C 8 MIM] 1- x [C 8 MIM-F 13 ] x [Tf 2 N], where no strong evidence of alkyl/fluoroalkyl chain segregation or triphilic behaviour was seen (Elstone et al. , J. Phys. Chem. B , 2023, 127, 7394-7407), these new mixtures show the formation of small aggregates of varying sizes of each component, even though all were co-miscible across the full range of compositions. Thus, while a clear polar non-polar peak (PNPP) was observed at large or small values of x , at intermediate compositions the small-angle neutron scattering at low q was dominated by scattering from these small aggregates, while at other compositions, there was little or no evidence of the PNPP. The origins of this behaviour are discussed in terms of inter-chain interactions.

A crossed beam velocity-map ion-imaging apparatus has been used to determine differential cross sections (DCSs) for the rotationally inelastic scattering of NO(A 2 Σ + , v = 0, j = 0.5) with CO 2 , as a function of both NO(A, v = 0, N ') final state and the coincident final rotational energy of the CO 2 . The DCSs are dominated by forward-peaked scattering for all N ', with significant rotational excitation of CO 2 , and a small backward scattered peak is also observed for all final N '. However, no rotational rainbow scattering is observed and there is no evidence for significant product rotational angular momentum polarization. New ab initio potential energy surface calculations at the PNO-CCSD(T)-F12b level of theory report strong attractive forces at long ranges with significant anisotropy relative to both NO and CO 2 . The absence of rotational rainbow scattering is consistent with removal of low-impact-parameter collisions via electronic quenching, in agreement with the literature quenching rates of NO(A) by CO 2 and recent electronic structure calculations. We propose that high-impact-parameter collisions, that do not lead to quenching, experience strong anisotropic attractive forces that lead to significant rotational excitation in both NO and CO 2 , depolarizing product angular momentum while leading to forward and backward glory scattering.