A method of making a composite membrane comprising the steps of forming a discriminating layer upon a surface of a porous support by sequentially applying immiscible coating solutions upon the support, wherein one coating solution comprises a crosslinking agent and another coating solution comprises a block copolymer, and the block copolymer comprises sacrificial segments and durable segments including reactive pendent groups which react with the crosslinking agent and form a crosslinked matrix comprising micro-domains of the sacrificial segments, and removing at least a portion of the sacrificial segments to yield pores.