The present disclosure provides a porous membrane made of pentablock copolymer. The porous membrane includes an ABCBA block copolymer and has a number of pores. The A block is immiscible with each of the B block and the C block, the B block has a glass transition temperature (Tg) of 90 degrees Celsius or greater, and the C block has a Tg of 25 degrees Celsius or less. The A block comprises a poly(alkylene oxide), a substituted epoxide, a polylactam, or a substituted carbonate; B block comprises a vinyl aromatic monomer or a polyalkylmethacrylate and C block comprises a polyacrylate, a polysiloxane or a polyisoprene. A method of making a porous membrane is also provided. The method includes forming a film or a hollow fiber from a solution including a solvent and solids containing an ABCBA block copolymer. The method further includes removing at least a portion of the solvent from the film or the hollow fiber and contacting the film or the hollow fiber with a nonsolvent.