Isoporous ultrafiltration (UF) membranes derived from block copolymer self-assembly and non-solvent induced phase separation (SNIPS) are highly tunable and industrially scalable. By combining high pore density with narrow pore size distributions in the separation layer, SNIPS membranes overcome the permeability-selectivity trade-off faced by conventional UF membranes. To improve selectivity beyond simple size-exclusion effects, membranes with well controlled pore chemistries at the nanoscale are highly desirable for applications, e.g., in the biopharmaceutical industry or for component recovery in industrial effluents. To that end, this thesis will focus on SNIPS derived UF membrane systems blended from two chemically distinct block copolymers in the polymer solution (dope) submitted to standard membrane fabrication. It will be demonstrated that this blending approach provides advanced pathways to the tailoring of membrane pore surface chemistries and functionalities that could enable novel capabilities in selectivity and complex separations in ways consistent with existing traditional membrane fabrication equipment.