Polyvinyl alcohol membranes modified by low-hydroxylated fullerenol C60(OH)12

Hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated fullerenol C60(OH)12 have been assembled. In this study, two different procedures for PVA membrane cross-linking were applied including a thermal treatment, with elevated temperatures (140 °C 100 min) and chemical treatment with the addition of 35% maleic acid to the polymer matrix and thermal treatment (110 °C 120 min). The structure of the membranes was examined by wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). Thermal properties and stability were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that fullerenol, being an effective cross-linker for PVA, prevented the crystallization of the polymer during annealing, resulting in the increase of membrane permeability for chemically cross-linked membranes. Transport properties of hybrid membranes containing up to 5 wt% fullerenol were studied by the pervaporation of (1) chemical-equilibrium quaternary mixtures of n-propyl acetate, acetic acid, n-propanol and water in order to identify the properties of the membranes used in the hybrid process of esterification+pervaporation, and (2) ternary azeotropic n-propyl acetate-n-propanol-water mixtures. All the membranes were selective with respect to water and the optimal transport properties were obtained for the PVA-5% fullerenol membranes containing maleic acid.