The interaction between poly(vinylpyrrolidone) and reversed micelles of water\AOT\ n-Theptane

The interactions between poly(vinylpyrrolidone) (PVP) and the reversed micelles composed of water, AOT, and n-heptane are investigated with the aid of phase diagram, measurements of conductivity and viscosity, Fourier transform infrared (FTIR) spectrum, and dynamic light scattering (DLS). The phase diagrams of water\AOT\heptane in the presence of and absence of PVP are given. The conductivity of the water\AOT\heptane reversed micelle without PVP initially increases and then decreases with the increase of water content, omega 0 (the molar ratio of water to OT), while the plots of conductivity (kappa) versus omega 0 of the reversed micelle in the presence of PVP depend on the PVP concentrations. The plot of omega versus omega 0 with 2.0%wt PVP is similar to that without PVP. Only the omega 0,max (the water content that the maximum conductivity corresponds to) is larger than that without PVP. Nevertheless, the conductivity of the reversed micelle containing more than 4%wt PVP always rises with the increase of the water content in the measured range. The DLS results indicate that the hydrodynamic radius (R h) in the presence and absence of PVP rises with the increase of omega 0. The plots with PVP and without PVP have almost the same value when omega 0<17; and after that, it quickly increases with the increase of omega 0. It is interesting to find that there is almost no effect of the PVP concentration on the viscosity and R h of the reversed micelle at omega 0=15. The FTIR results suggest that the contents of SO 3 bound water and Na +-bound water both decrease with PVP added, while the content of the bulkylike water increases. However, the trapped water in the hydrophobic chain of the Asurfactant is nearly unaffected by PVP. It is also found from the FTIR that the carbonyl group stretching vibration of AOT is fitted into two sub-peaks, which center at 1740 and 1729 cm^-1, corresponding to the trans and cis conformations of AOT, respectively.