Poly(arylether-sulfone) semipermeable membrane comprising substituted halomethyl and/or quaternary nitrogen groups

A semipermeable membrane made of a modified poly (arylether-sulfone) polymer consisting essentially of repeating units of the formula ##STR5## wherein A and A', which are the same or different, are aromatic hydrocarbon groups having from 6 to 14 carbon atoms in which hydrogen atoms on said aromatic groups are substituted by halomethyl groups and/or quaternary nitrogen atom-bearing groups, the degree of substitution of the halomethyl groups and the quaternary nitrogen atom-bearing groups in said polymer being within the hatched pentagonal area of FIG. 1 of the attached drawings, said halomethyl group having the formula --CH.sub.2 X wherein X is halogen, said quanternary nitrogen atom-bearing group having the formula ##STR6## wherein R.sub.1 and R.sub.2, which can be the same or different, are alkyls having one to 4 carbon atoms, R.sub.3 is alkyl having one to 20 carbon atoms, T is alkyl having one to 4 carbon atoms, m is zero or an integer of one to 5 and X.sub.1 is hydrogen or halogen,

• and wherein S.sub.1 and S.sub.2, which are the same or different, are substituent groups which are inert to halomethylation and quaternization reactions, the suffixes i, j, k, l, which are the same or different, are zero or an integer of from one to 4, and at least one of those suffixes in less than 4, n is zero or one, and R is a valence bond, --O-- or a bivalent organic hydrocarbon group.