Microporous membranes prepared from blends of polysulfone and sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)

Membranes were prepared from solutions containing Udel-type polysulfone (PS f) and sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO). Polymer s olutions in 1-methyl-2-pyrrolidone were cast on a nonwoven textile and prec ipitated in a water bath. The permeabilities and selectivities of the prepa red membranes depended on the concentrations of both polymers in the castin g solution. The higher the concentration of PSf, the lower were the permeab ilities to water and average pore sizes of the membranes. On the other hand , a very small amount of SPPO in the casting solution (about 1-4 wt % relat ive to the casting solution weight:) brought about a considerable increase in water permeabilities and had a small influence on the average pore sizes . The effects were most pronounced if SPPO with a degree of sulfonation of 20-40% was used. The considerable increase in water permeabilities was expl ained by separation of the PSf and SPPO phases during precipitation in wate r and by the concentration of hydrophilic SPPO on the surface of the membra ne and its pores. The determinations of the oriented concentration potentia ls proved the presence of a negative surface charge in the membranes. (C) 2 001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 133-142, 2001.