Study of the interaction between a diblock polyelectrolyte PDMA-b-PAA and a gemini surfactant 12-6-12 in basic media

The interactions between negatively charged diblock polyelectrolyte PDMA71-b-PAA59 and oppositely charged gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) in basic media were studied using dynamic light scattering, fluorescence spectroscopy, surface tension, and 1H NMR. With increased addition of surfactant, the conformation of polyelectrolyte experienced changes from the initial unimer with open-extended PAA block, to the nano-scaled aggregates/complexes with a maximum hydrodynamic diameter (DhDh), and finally to the stable complexes with a smaller DhDh. Accordingly, the value of DhDh during the whole process of increasing the surfactant concentration changed from 14–17 nm, to 184 nm, and to the final 70 nm, respectively. This transformation was driven by the electrostatic attractive/repulsive interactions, the hydrophobic interaction between hydrophobic surfactant tails, and the hydrophilicity of PDMA block.

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