In spite of their apparently similar structures, fluorocarbons (FC) and hydrocarbons (HC) possess very different properties, and their mixtures produce experimental evidences for the formation of microdomains in the solid and in the liquid state as well. Some theoretical treatments have been proposed to explain the surprising and highly non-ideal phase separation behavior of fluorocarbons/hydrocarbons mixtures, but none of them can exhaustively offer a general and realistic framework in agreement with the experimental results. The addition of semifluorinated copolymers to FC/HC mixtures enhances their mutual solubility, and leads to the formation of supramolecular structures in the liquid state.