In this work we report the effect of the polar solvent entrapped on benzyl-nhexadecyldimethylammonium chloride (BHDC) reverse micelles (RMs), as nanoreactors for gold nanoparticles (AuNPs) synthesis. We have evaluated how the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) and water inside RMs, can control the interactions at the interface as a key factor on nanoparticles finals properties. The results showed the bmimBF4 supramolecular network under confinement plays an important role on the nucleation and growth mechanism of AuNPs. The results showed how the polar solvent can induce a specific interaction at the interface, including an ionic segregation, which affects the BHDC counterion chloride (Cl-) availability at interface, the droplets size, the interface flexibility and thus the material exchange rate between droplets. These facts strongly influence the AuNPs size, polydispersity, morphology and crystallinity. The RTIL bmimBF4 in BHDC RMs induces an ionic segregation decreasing of the Cl- ions availability at interface which favors sphericity and monocrystallinity on AuNPs formed, meanwhile water do not disturb the Cl- ions availability at interface, and the insertion of these ions on the earlier layer?s crystallinity is a key fact on the anisotropy and polycrystallinity of AuNPs obtained. As we concerned this is the first which compared the influence of the polar solvent entrapped in BHDC RMs as nanoreactors for gold nanoparticles synthesis, also is the first time bmimBF4/BHDC/toluene RMs is used as reaction media for this particular reaction.