Disclosed are crosslinked porous membranes comprising a cellulosic material and an aromatic hydrophobic moiety or a copolymer of the formula A-B-A (I) or A-B (II), wherein block A, for example, polyglycerol, a polymer of allylglycidyl ether, or a copolymer of glycidol and allyl glycidyl ether, or a polymer of allyl glycidyl ether or a copolymer of glycidol and allyl glycidyl ether wherein one or more allyl groups having been replaced by hydrophilic groups. Block B is an aromatic hydrophobic moiety. An example of the aromatic hydrophobic moiety is polyethersulfone. Also disclosed is a method for preparing such membranes.