A thermodynamic approach was used to characterise the formation of complexes between CTAB (hexadecyltrimethylammonium bromide) and some oxygenated aromatic compounds in aqueous surfactant solutions, promoting viscoelastic properties or thermo-reversible gels. At low temperature, a crystallized molecular surfactant complex is also formed, whose temperature of fusion is different from the Krafft temperature of CTAB. Through DSC study, the role of the nature and the position of substituted groups on the aromatic ring have been shown in the enhancement and stability of the solute-CTAB complexes. The selected solutes were phenol, p, o and m cresols, monochlorophenols and different substituted isomers of dichlorophenol.