A series of carboxylate-terminated monochelic polystyrenes were synthesized by anionic polymerization of styrene initiated with sec-butyllithium, followed by reaction with CO2, acidification, and neutralization with different bases, i.e., alkali-metal hydroxide and tetraalkylammonium hydroxide. These functionalized polymers were studied by viscometry and light scattering. They were found to form aggregates or reverse micelles in solvents of low dielectric constant, i.e., cyclohexane, carbon tetrachloride, toluene, chloroform,etc. Well-defined aggregation numbers and critical micelle concentrations (cmc’s;) were determined by curve fitting of light-scattering data. The aggregation numbers vary between 3 and 17 and cmc’s between <10(-6) and 10(-4) M, depending on the polystyrene chain length, the size of the counterion, and the dielectric constant of the solvent. Compared to linear polystyrene, the THETA temperature of these aggregates is reduced in cyclohexane, and the second virial coefficient is depressed in the other solvents.