Surfactant microemulsions

A microemulsion comprising at least one surfactant, an oil phase, and an aqueous phase, wherein the surfactant is a compound of Formula (IV) or Formula (IVa):

• wherein
• R1 is C1-C6 alkyl;
• R2 is C10-C30 alkyl or C8-C30 alkenyl;
• M is a cation chosen from ammonium, an alkali metal, an alkaline earth metal, or a transition metal;
• k is an integer from 1 to 10;
• and
• n is an integer from 1 to 3;
• wherein the microemulsion has an interfacial tension from about 6×10−4 mN/m to about 10×10−2 mN/m.