Disclosed is a block copolymer of the formula: A-B-A (I) or A-B (II), wherein block A is: (i) a polymer of allyl glycidyl ether or (ii) a polymer of allyl glycidyl ether wherein one more of the allyl groups have been replaced with 1,2-dihydroxypropyl group or a group of the formula: —(CH2)a—S—(CH2)b—X, wherein a, b, and X are defined herein. The block copolymers find use as wetting agents in the preparation of porous membranes from aromatic hydrophobic polymers such as polyethersulfone. Also disclosed are methods of preparing such block copolymers and porous membranes therefrom.