[Infrared spectral studies of separation of QAPVA/PMPVA complex membrane for dehydrating water of 95% ethanol].

Quaternized polyvinyl alcohol (QAPVA) and phosphate monoester polyvinyl alcohol (PMPVA) were self-assembled into polyion complex (PIC) membrane. The infrared spectra (IR) of PIC membrane dipped in 95% ethanol for 48 h were studied in the temperature range of 20-120 degrees C with an interval of 20 degrees C by analyzing the temperature dependent variations of OH stretch vibration base bands (upsilonOH) at >3000 cm(-1). Hydrogen-bond of water in 95% ethanol with PIC was studied. Since the upsilonOH strongly overlapped at >3000 cm(-1), combined with the static electric effect between water in 95% ethanol and ion-bond of PIC at 1300-1700 cm(-1), two-dimensional infrared (2DIR) correlation analysis was applied to describe the possible combined modes between PIC and water in water-alcohol. The result shows that the upsilonOH overlapped was distinguished at >3000 cm(-1), the change of water with varing tempertature was earlier than the intra-membrane OH self association and water was desorbed to separate from ethanol. The absorption peak of water and poly-electrolyte group intra-PIC membrane was identified. The water combined with ion-bond in PIC membrane by static electric effect was adsorbed with the temperature going up and separate from ethanol. The present study provides a simple method for investigating the separation performance of PIC membrane used in dehydration of organic compounds.