Hypothesis: Developing separation membranes functionalized by polymer brushes with high separation efficiency and good cycling stability is of great importance for oil/water separation, yet is still challenged. Experiments: In this work, the covalently embedded polyzwitterionic brush-functionalized nanofibrous membrane was developed for efficient and durable oil/water separation. The nanofibrous membrane was prepared by the electrospinning method using initiator-embedded polyacrylonitrile (PAN) resin, followed by novel subsurface-initiated atom transfer radical polymerization (SSI-ATRP) to graft embedded poly(sulfobetaine methacrylate) brushes (PSBMA). The hydration ability, underwater oil adhesion, oil/water separation performance as well as self-cleaning properties of the as prepared membrane (PAN-sg-PSBMA) were systematically studied. Findings: The PAN-sg-PSBMA membrane exhibited extraordinary hydration ability and underwater superoleophobicity with extremely low oil adhesion, which outperformed conventional polymer brush-modified membrane (PAN-g-PSBMA). The PAN-sg-PSBMA membrane was able to separate both oil/water mixture and surfactant-stabilized emulsions with ultrahigh permeation flux and separation efficiency. Moreover, compared with PAN-g-PSBMA, PAN-sg-PSBMA membrane exhibited unprecedented recycling stability in both permeation flux and separation efficiency, which is attributed to mechanical robustness of embedded polymer brushes and outstanding antifouling ability. The current findings revealed that embedded polymer brushes from SSI-ATRP could offer a promising design of functionalized nanofibrous membrane for highly efficient and durable oil/water separation. (C) 2020 Elsevier Inc. All rights reserved.