Blank micelles formulation of surfactant X are transparent, however when preparing the correspondent drug-loaded micelles through solvent evaporation/nanoprecipitation method, the medium turns cloudy. Why?
If you are taking ionic surfactant, then please read about "coacervation" of surfactant solution. That may be one of possibility. In coacervation there will be cloudiness of surfactant and two distinct phases can be observe.
If the whole solution is cloudy, then the answer given by Yuri Mirgorod sir possible.
Try one experiment by adding excess surfactant into solvent/ aqueous solution to check whether cloudiness of solution occurs.
the cloudiness shows that the micellar solution changes into dispersion either solid/liquid or liquid/liquid. Adding a third component to a nonionic surfactant solution changes the cloud point, i.e., may be lowered below room temperature.