A novel graft copolymer was synthesized via graft copolymerization of an inimer, 2-(2-bromoisobutyryloxy)ethyl acrylate (BIEA), with ozone-pretreated poly(vinylidene fluoride) (PVDF) (the PVDF-g-PBIEA copolymer). Porous membranes could be fabricated from the copolymer solution by phase inversion. The BIEA polymer (PBIEA) side chains allowed the initiation of atom transfer radical polymerization (ATRP) of functional monomers on the copolymer and the membrane surface. An arborescent copolymer was prepared via ATRP of sodium 4-styrenesulfonate (NaSS) initiated from the PVDF-g-PBIEA copolymer side chains (PVDF-g-PBIEA-ar-NaPSS copolymer). In comparison with the PVDF-g-PBIEA-ar-NaPSS copolymer membrane cast in water by phase inversion, the copolymer membrane cast in 1 M aqueous NaCl solution had enriched NaPSS side chains on the surface and larger pore size. The PVDF-g-PBIEA-ar-PPEGMA membrane was prepared via the surface-initiated ATRP of poly(ethylene glycol) methacrylate (PEGMA) on the porous PVDF-g-PBIEA membrane. Protein adsorption studies indicated that the PVDF-g-PBIEA-ar-PPEGMA membrane exhibited substantially improved antifouling properties. Thus, the PVDF-g-PBIEA membranes with the active ATRP inimer repeat units on the surface offers opportunities for the functionalization of membranes via surface molecular design.