The hydrophobic/hydrophilic or polar/apolar domain segregation in ILs is observed if the alkyl chain is long enough and is characterized experimentally by X ray or neutron scattering and rheology, as well as observed in computer simulations. The strength of the segregation and the size of the domains tends to increase with the cation alkyl group length, and so is the stabilization provided to a NP dispersion. Atomic force microscopy showed the presence of an oscillatory force between mica surfaces separated by films of both 1-butyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMIM][NTf2], and 1-hexyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide, [HMIM][NTf2], with both the intensity of the force peaks and the distance between peaks increasing as the cation alkyl group length increases. It was also observed that the increase of the alkyl group of the cation improves the stability of dispersions of both metallic and ceramic NPs in ILs. Besides the stabilization of nanomaterials, the formation of domains in ILs can also be explored as a template for the synthesis of nanoporous materials, providing smaller and more reproducible porous size than similar methods in surfactant solutions. Despite the undeniable importance of the hydrophobic/hydrophilic domain segregation in ILs for the stabilization of colloidal dispersions, it is not fully understood yet how this effect affects the interaction between NPs and controls the size and shape of formed NPs as well as the importance of specific interactions between the particle surface and the ions for the stabilization. Molecular dynamics simulations, Monte Carlo simulations and quantum chemical calculations had been employed for some years to elucidate the organization and interactions of ILs close to NPs, nanotubes, and solid substrates. However, to the best of our knowledge, no computer simulation work provided a direct calculation of how the domain segregation and the interaction between IL and NP modulates the aggregation thermodynamics and the kinetic stability of NPs dispersions since most of them consist of simulations with only one NP or only one solid substrate interacting with the IL. Some exceptions are the works of Frost et al In the present work, the potential of mean force was computed between pairs of NPs in two ILs that differ by the length of the cation alkyl chain: 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM][BF4] or C4) and 1-octyl-3-methyl-imidazolium tetrafluoroborate ([OMIM][BF4] or C8) and concentrated dispersions with several NPs were simulated with microseconds time scale simulations. To access how the interaction between the NPs and the IL affects the colloidal stability, two different models were compared for the particle: One NP that interacts well with the charged portion of the IL (imidazolium ring of the cation and the BF 4 ⁻ anion), which will be called the hydrophilic NP, and another NP that interacts better with the alkyl groups of the cation, hence being called the hydrophobic NP. To limit the effects involved, both NPs models were generated with the same crystalline structure, size and mass, with the only difference being the interaction parameters with the IL (see details in the Methods section).