Search

Poly(vinylidene fluoride) (PVDF) membranes were fabricated using two different methods: the electro-spinning technique and the phase inversion process. The effect of a DMF/acetone solvent composition on the quality of the electrospun fibers of the PVDF membrane was investigated. The prepared PVDF membranes have been characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and contact angle. Uniform fibrous membranes with fiber diameters ranging mainly from 6 μm to 1.5 μm were formed from 16% (w/w) PVDF solutions in 50/50 (w/w) DMF/acetone at 30 kV voltage and 0.3 mL/h flow rate. The effect of surface morphology and hydrophilicity on anti-fouling potential was also studied and compared with flat-sheet membranes. It was found that the spun fibrous membranes exhibited the best hydrophilicity and antifouling properties with an average pure water permeability up to 400 L/m2/h, higher than that of the flat-sheet membranes, which exhibited 200 L/m2/h. Performance evaluation of the prepared PVDF membranes (water flux and organic matter retention) has been done through the use of a dead-end apparatus, where the results demonstrated the efficiency of electrospun membrane over the conventionally prepared flat-sheet membrane for utilization as a pretreatment stage of ultrafiltration and microfiltration (MF/UF), before reverse osmosis (RO) in the desalination plant.

Three binary systems were prepared by mixing of two different mesogenic derivatives, homologues, the first is azo/ester, namely 4-alkoxyphenylazo-4&prime, phenyl-4&Prime, alkoxybenzoates (IIn+m) and the second is Schiff base/ester, namely 4-(arylideneamino)phenyl-4&Prime, alkoxy benzoates (In+m). The two corresponding analogues from both series in the binary mixtures investigated are of the same terminal alkoxy chain length. Mesomorphic properties were investigated by differential scanning calorimetry (DSC) and phases identified by polarized optical microscope (POM). Photophysical studies were investigated by UV spectroscopy connected to a hot stage. Results were discussed based on constructed binary phase diagrams. All mixtures were found to exhibit eutectic compositions, with linear or slightly linear nematic and smectic A stability/composition dependences. Geometrical parameters were predicted applying density functional theory (DFT) calculations. Twist angle (&theta, ), aspect ratio, dipole moment and the polarizability of the individual compounds were discussed and correlated with the experimental results to illustrate the enhanced the mesophase stability and the mesophase range of the mixture at the eutectic composition compared with those of their individual components.