Interactions of tetradecyldimethylaminoxide with polyacrylic and polymethacrylic acids in aqueous solution

The interactions between the zwitterionic surfactant tetradecyldimethylaminoxide (C14DMAO) and the polyelectrolytes polyacrylic (PAA-205 and PAA-250) or polymethacrylic (PMA-100) acids have been investigated in aqueous solution. The physico-chemical properties of these systems have been monitored by measuring the solution pH, electric birefringence, zero-shear viscosity and density for increasing surfactant concentrations. The experimental results have shown that significant change in the physico-chemical properties of the polyacid/surfactant system occurs only in a narrow pH range and when the amphiphile forms rod-like micelles. Moreover, they clearly reveal the important role played by both hydrogen bonding and hydrophobic forces in governing polyacid–surfactant interactions. The change in the physico-chemical properties of the polyacid solutions upon addition of C14DMAO has been attributed to both the conformational transition of the polyelectrolyte chains and the polyacid/rod-like micelles complex formation. The suggestion is made that the C14DMAO induces a progressive conformational transition in the polyelectrolyte chains much akin to that produced by NaOH.