| abstract |
A semipermeable membrane of a polyaryl ether sulfone having repeating units of the formula, ##STR1## wherein Ar 1 and Ar 2 independently represent ##STR2## wherein X, Y and Z independently represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a chlorine atom or a bromine atom; and l, m and n independently represent zero or an integer of 1 to 4, and n having a contact angle of its surface to water of at most 65°. |