The effect of C12E6 nonionic surfactant on the solubilization of Eosin Y in unmodified- and hydrophobically modified poly(Acrylic acid) solutions

Abstract The effect of the hexaethylene glycol mono-dodecyl ether (C12E6) on the solubilization of Eosin Yellow (2,4,5,7-tetrabromofluorescein, disodium salt) in 0.1 % wt. solution of unmodified and hydrophobically modified poly(acrylic acid) (PAA) was investigated by steady-state and dynamic fluorescence. To this end, firstly the poly(acrylic acid) was hydrophobically modified with 3 % mol and, respectively, 10 % mol linear C16 alkyl chain graft. The behavior of the obtained polymers and that of the parent one in the appropriate solvents were investigated by several methods. It was revealed that the grafts associated with the formation of intra-coil hydrophobic nano-domains and that the polyacrylic acids had lower viscosity than their sodium polyacrylates counterparts, although the c*s were almost similar. The effect of C12E6 nonionic surfactant on 0.1 % wt. polymers solution was also investigated. In water, the addition of C12E6 to polyacid solution leaded to the decrease of the critical aggregation concentration (CAC or T1). On the contrary, in the water–ethanol mixture the interaction was delayed, thus the CAC increased. At the addition of Eosin Y to the surfactant or surfactant-polymer solutions, the dye interacted with each species present in the system, no matter the solvent was. It was also shown that, at higher surfactant concentration, the dye solubilized into bound or free micelles. Therefore, it was considered the nonionic surfactant helped the anionic dye Eosin Y to be incorporated in poly(acrylic acid) based polymers.