Polyethersulfone was sulfonated by heterogeneous method with chlorosulfonic acid. Ion exchange capacity was controlled to 0.68 meq/g to reduce fouling. Sulfonation was confirmed by Fourier transform infrared spectroscopy and 1 H-nuclear magnetic resonance. Polyethersulfone and sulfonated polyethersulfone ultrafiltration membranes were prepared successively by the typical phase inversion method. Membrane performance of sulfonated polyethersulfone was compared with that of polyethersulfone. In the preparation of ultrafiltration membranes, the effect of the addition of dichloromethane and poly(vinyl pyrrolidone) in a casting solution was investigated on the membrane performance. It was observed that the addition of dichloromethane increased the solute rejection rate. By changing the ratio between polymer and poly-(vinyl pyrrolidone), membrane performance could be controlled. Negatively charged sulfonated polyethersulfone could reduce fouling at higher or lower pH than isoelectric point of protein bovine serum albumin.

ABSTRACT:The sulfonation of polymers and the pervaporation behavior of asymmetric polymeric membranes are described in this study. We confirmed that the sulfonic acid group was successively introduced into the polymer chain by FTIR and 1 H-NMR characterization. The phase diagram indicated that the modified polymer could have water tolerance, implying that the polymer-solvent miscibility was lower. The hyperthin skin layer, suitable for pervaporation, depended on the NMP-DGDE composition, which was important for the fabrication of an asymmetric membrane with high water permeance. The asymmetric membrane exhibited water selectivities equal to or slightly lower than those determined for the dense film. The hyperthin skin layer, which had hardly any defects, was possibly formed by the phase-inversion method. It is obvious that these membranes can be used for the industrial pervaporation process. The permeability and the selectivity of the water-butanol mixture for the asymmetric membranes at 50°C were measured. The permeation rates for water-butanol in the asymmetric membrane were about 80 times greater than those of film, and the separation factor was slightly lower. The NMP-DGDE solvent system might be suitable for a high permeation rate.

Polyethersulfone was sulfonated by heterogeneous method with chlorosulfonic acid. Ion exchange capacity was controlled to 0.68 meq/g to reduce fouling. Sulfonation was confirmed by Fourier transform infrared spectroscopy and 1 H-nuclear magnetic resonance. Polyethersulfone and sulfonated polyethersulfone ultrafiltration membranes were prepared successively by the typical phase inversion method. Membrane performance of sulfonated polyethersulfone was compared with that of polyethersulfone. In the preparation of ultrafiltration membranes, the effect of the addition of dichloromethane and poly(vinyl pyrrolidone) in a casting solution was investigated on the membrane performance. It was observed that the addition of dichloromethane increased the solute rejection rate. By changing the ratio between polymer and poly-(vinyl pyrrolidone), membrane performance could be controlled. Negatively charged sulfonated polyethersulfone could reduce fouling at higher or lower pH than isoelectric point of protein bovine serum albumin.

Novel soluble anion-exchange copolyimides were synthesized by the two-step method.Copolyimides had inherent viscosities between 0.35 and 0.42 dL/g. Ion exchange capacity (IEC) of the polyimides was 0.18-0.33 mequiv/g. These IEC values were well explained with the degree of substitution. All polyimides were soluble in polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide and showed amorphous patterns in X-ray diffraction studies. Soluble copolyimides synthesized in this study had glass transition temperatures between 220 and 265 °C. All unmodified polyimides were thermally stable below 560 °C. 10% weight loss temperatures were recorded in the range 560-600 °C in nitrogen. However, the 2-hydroxypropyl group of anion-exchange copolyimides was degraded at around 260 °C. The anion-exchange copolyimide nanofiltration membranes prepared from a cosolvent of diethylene glycol dimethyl ether and N-methyl-2-pyrrolidone showed better salt removal behavior than that of neutral copolyimides nanofiltration membranes.

ABSTRACT:Random copolyimides with different proportions of a diamine component were prepared by polymerizing different compositions of diamines with various dianhydrides and imidized thermally to 260°C. The imidization percent of poly(amic acid) was characterized at various temperatures by infrared spectroscopy. The homopolyimide based on bis[4-(3-aminophenoxy)phenyl]sulfone and pyromellitic dianhydride was the only one soluble. By changing the compositions of bis[4-(3-aminophenoxy)phenyl]-sulfone and other diamines with pyromellitic dianhydride in N-methyl-2-pyrrolidone, soluble random copolyimides could be prepared. By random copolymerization, the thermal properties and viscosities of homopolyimide could be controlled. All the soluble polyimides prepared in this work were amorphous because of the lack of stereoregularity.