A porous composite membrane includes a porous support layer of a poly(phenylene ether) or poly(phenylene ether) copolymer; and an amphiphilic copolymer having a hydrophobic block and a hydrophilic block or graft, wherein the hydrophobic block includes a polystyrene block, a poly(phenylene ether) block, or a poly(phenylene ether) copolymer block; and an ultrathin, cross-linked, water permeable layer, which is the reaction product of an electrophilic monomer and a nucleophilic monomer, in contact with a side of the porous support layer. The reaction product can be a polyamide that is the interfacial condensation product of: an aromatic, polyfunctional acyl halide comprising of 3 to 6 acyl halide groups per aromatic ring and an aromatic polyamine comprising at least two primary amine groups and a maximum number of primary amine groups that is less than or equal to the number of acyl halide groups on the polyfunctional acyl halide.