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

摘要

The interactions between negatively charged diblock polyelectrolyte PDMA_(71)-b-PAA_(59) 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 (D_h), and finally to the stable complexes with a smaller D_h. Accordingly, the value of D_h 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.