Disclosed are block copolymers of the formula A-B-A (I) or A-B (II), comprising blocks A and B, wherein block A is a hydrophilic polymeric segment comprising polyglycerol and block B is an aromatic hydrophobic polymeric segment. The block copolymers find use as wetting agents in the preparation of porous membranes from aromatic hydrophobic polymers such as polyethersulfone.