Effects of sodium halide on the interaction between polyvinylpyrrolidone and sodium oleate: Surface tension and oscillating barrier studies

The effects of sodium halide (NaX: X = Cl, I) on the interaction between polyvinylpyrrolidone (PVP) and sodium oleate (C17H33COONa) were studied via surface tension and oscillating barrier methods. The results of surface tension measurement indicate that there is an interaction between C17H33COONa and PVP. Both critical micelle concentration (CMC) of C17H33COONa and the saturation concentration of C17H33COONa on PVP (T2) decrease in the presence of NaX. It is found that the binding amount of C17H33COONa on PVP is enhanced after NaX is added. NaCl is more efficient than NaI in promoting the association of C17H33COONa with PVP. The results obtained from the oscillating barrier at low dilational frequencies (0.01–0.1 Hz) reveal that the dilational modulus passes through a maximum value with increasing C17H33COONa concentration. Addition of PVP to C17H33COONa solutions makes the maximum value occur at much lower concentration while addition of NaX to C17H33COONa/PVP mixed systems further enhances this effect.