just dissolve the AOT in hexane ( 1 or 2 molal). Finally add the water drop by drop taking care to mix thoroughly between additions.

The amount of water you can add before separation depends on the molality of your AOT solution on hexane.

thank you , my problem is : I want to have the droplets with about 20 nanometer or below this size, what should i do?what should be the molar rathio of surfactant/water / oil to get this size? I need to accurate information , do you can introduce a article or document ?

then you should use the lower concentration solution. And add a very small amount of water

See J. Chem Soc Faraday Trans 1984,80 13 and J.Chem Ed 1994, 71,446