Interaction of normal and reverse pluronics (L44 and 10R5) and their mixtures with anionic surfactant sodium N-dodecanoylsarcosinate

•Interaction of monomeric pluronic (L44 and 10R5)-surfactant (SDDS) was studied.•L44 showed critical aggregation concentration, CAC and extended CMC; CAC absent for 10R5.•Free energy, enthalpy and entropy of CAC and extended CMC formation were evaluated.•Mixed L44 and 10R5 behaved like 10R5 with respect to interaction with SDDS.•Morphologies of pluronics and their complexes with SDDS were assessed.

Interaction of monomeric normal L44 [(PEO)10(PPO)23(PEO)10]) and reverse 10R5 [(PPO)8(PEO)22(PPO)8] pluronics designated as L and R, respectively, and their mixtures with the anionic surfactant sodium N-dodecanoylsarcosinate (SDDS) in aqueous medium has been studied by tensiometry, conductometry, calorimetry and dynamic light scattering methods. The critical aggregation concentration (CAC), concentration of maximum binding (CS), and the extended critical micelle concentration (CMCe) of SDDS resulted from the interaction have been presented. L has shown the formation of CAC, CS and CMCe, whereas R has shown the absence of CAC but the presence of both CS and CMCe. Micellization of SDDS is an endothermic process whereas the formation of CAC and CMCe is exothermic events, the formation of CS is endothermic. The hydrodynamic diameter (Dh) and zeta potential of L and R, and their SDDS interacted species have been determined. Dh decreased with increasing SDDS concentration for L whereas it was invariant for R. Mixed L and R in varied proportions have been also examined in the solution state to probe into their mutual interaction, and interaction with SDDS. The formation of CAC of their mixtures was absent; CMCe formation was exothermic while that of CS was endothermic like their individuals.

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