Poly(vinyl acetate)-TEMPO (PVAc-TEMPO) macroinitiators were synthesized by bulk polymerization of vinyl acetate in the presence of benzoyl peroxide (BPO) followed by termination with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). Radicals were mainly transferred to the acetoxy methyl groups in PVAc during the polymerization. The PVAc-TEMPO macroinitiators had several TEMPO-dormant sites and styrene bulk polymerization with the macroinitiators produced poly(vinyl acetate)-graft-polystyrene (PVAc-g-PS). All the TEMPO-dormant sites of PVAc-TEMPO macroinitiators participated in the styrene polymerization with almost equal reactivity. Methanolysis of PVAc-g-PS broke the PS branches apart from the PVAc backbone chains. Hydrophobic or hydrophilic porous membranes with controlled pore size could be prepared by removing the PVAc domains or the PS domains from the graft copolymer.