The preparation of ultrafiltration membranes from a moderately sulfonated poly(Oxy(2,6-Dimethyl-1,4-Phenylene))

The preparation of microporous membranes from blends of poly(2,6-dimethyl-1,4-phenylene oxide) and sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)

“…13,16 Generally, the sulfur content of the modified polymer does not exceed to 2.5 wt %. Contrary to this powder modifiing technique, the precipitation of the PPO solution with concentrated sulfuric acid generated a highly swollen PPO gel with very small particle sizes and, therefore, a high surface that can be more readily modified with sulfonic groups.…”

“…Permeabilities of resulting membranes are (as it is always the case with the phase inversion membranes) strongly dependent on the polymer and the nonsolvent concentrations in the casting solution: Low concentrations of the membrane-forming polymer solution and/or a high content of a nonsolvent in the casting solution generate high water permeabilities. However, it was not possible to increase substantially 1-butanol concentration in the casting system: higher 1-butanol concentrations caused polymer precipitation in the casting solution, 13 and second, it was not possible to use casting solution with substantially lower polymer concentrations: Mechanical strength of resulting membranes is then too low for membrane applications. 13 Finally, it is also necessary to stress that all results concerning heterogeneously sulfonated PPO given in Rejection and porosity characteristics of the blend membranes exhibiting high hydraulic permeabilities are given in Table I.…”

“…However, it was not possible to increase substantially 1-butanol concentration in the casting system: higher 1-butanol concentrations caused polymer precipitation in the casting solution, 13 and second, it was not possible to use casting solution with substantially lower polymer concentrations: Mechanical strength of resulting membranes is then too low for membrane applications. 13 Finally, it is also necessary to stress that all results concerning heterogeneously sulfonated PPO given in Rejection and porosity characteristics of the blend membranes exhibiting high hydraulic permeabilities are given in Table I. However, it should be emphasized that all calculations of pore sizes 14 have been based on permeabilities and rejections of water solutions, and therefore, the values express the effective pore sizes with respect to aqueous medium.…”

“…By sulfonation the polymer becomes more hydrophilic. 13 It is evident that increased hydrophilicity at the surface of pores makes the membrane more wettable to the aqueous solutions and, thereby, more permeable but, on the other hand, increased swelling in water resulting from increased hydrophilicity of the bulk of the polymer decreases pore sizes and, therefore, the permeabilities.…”

“…These membranes, when used for the purification of aqueous solutions in an ultrafiltration process, had, however, very low permeabilities to water. In a former work, Schauer et al 13 prepared membranes from a moderately sulfonated PPO (sulfur content: 1.2 wt %) by immersion precipitation method. Chloroform/1-butanol were used as solvent/nonsolvent binary mixtures.…”