Rheological behavior of PAA-C^sub n^TAB complex: influence of PAA charge density and surfactant tail length in PAA semidilute aqueous solution

Interactions between anionic polyelectrolyte, poly(acrylic acid) (PAA), and cationic surfactant, alkyltrimethylammonium bromide (CnTAB), were investigated by rheological measurements in semidilute PAA solution. The dependences of the rheological behavior on the chain length of the surfactant, PAA neutralization degree, and temperature were discussed. The results revealed that both dodecyl and cetyltrimethylammonium bromides (C12TAB and C16TAB) could increase the viscosity of PAA solution when the surfactant amounts surpassed a critical surfactant concentration (C c), and C c of C16TAB was lower than that of C12TAB at same PAA neutralization degree. The increase of viscosity is attributed to the surfactant micelles bridging of the polymer chains and confine the mobility PAA chain. On the other hand, it is found that the hydrogen bonding also played an important role in the PAA-CnTAB system, especially in lower neutralization degree PAA solution, which results in the viscosity increase rapidly with the added surfactant into lower neutralization degree PAA solution.