Membranes comprising functional polyarylether having structural units of formula I are useful for hemodialysis and hemofiltration: ##STR00001## wherein X is selected from Br, NR.sup.4R.sup.5, OOCR.sup.6, OR.sup.7, NR.sup.4CONR.sup.5R.sup.6, NR.sup.4COOR.sup.5R.sup.6 and combinations thereof; R.sup.1, R.sup.2 and R.sup.3 are independently at each occurrence CH.sub.2X, H, halo, cyano, nitro, a C.sub.1-C.sub.12aliphatic radical, a C.sub.3-C.sub.12cycloaliphatic radical, a C.sub.3-C.sub.12aromatic radical or a combination thereof; R.sup.4 and R.sup.5 are independently H, a C.sub.1-10 aliphatic radical, a C.sub.3-C.sub.12cycloaliphatic radical, a C.sub.3-C.sub.12 aromatic radical, or a combination thereof; R.sup.6 is H, a C.sub.2-10 aliphatic radical, a C.sub.3-C.sub.12 cycloaliphatic radical, a C.sub.3-C.sub.12 aromatic radical or a combination thereof; R.sup.7 is OCH.sub.2CH.sub.2(OCH.sub.2CH.sub.2).sub.nOH or OOCCH.sub.2(OCH.sub.2CH.sub.2).sub.nCH.sub.3; Z is a direct bond, O, S, SO, SO.sub.2, CO, phenylphospinyl oxide, alkenyl, alkynyl, a C.sub.1-C.sub.12aliphatic radical, a C.sub.3-C.sub.12cycloaliphatic radical, a C.sub.3-C.sub.12 aromatic radical or a combination thereof; a, b, and c are independently 1 or 2; and m, n and p are independently 0 or 1.