Various hydrophilic modification approaches for solid polymer articles have been proposed. However, most methods scarcely ensure the long-term stability of the hydrophilicity due to the surface reorganization. The direct surface modification of polymer fibers and films by surface-initiated atom transfer radical polymerization (SI-ATRP) of charged monomers was investigated to achieve the stable surface modification of polymer articles. 2-(Methacryloyloxy)ethyl phosphorylcholine (MPC) was polymerized in the presence of compression molded sheets of bromo-functionalized polyethylene or polypropylene macroinitiators under mild conditions to provide a superhydrophilic PMPC-grafted surface layer. The PMPC-grafted polyolefin sheets showed excellent wettability and oil-detachment behavior in water. The PMPC-grafted PP sheets retained a water contact angle of less than 10° for over three years in air. A facile surface modification procedure for electrospun poly(butylene terephthalate) (PBT) fibers by SI-ATRP was proposed. ATRP initiators were introduced on the surface of the PBT fibers through aminolysis and subsequent chemical vapor adsorption. Poly[3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate)] (PMAPS) was grafted to the PBT fibers via SI-ATRP without altering the fiber geometry. After modification with zwitterionic poly(sulfobetaine) brushes, the surface became superhydrophilic. The surface properties were thermally stable due to the high melting temperature of the PBT crystallites, and were maintained for a prolonged period.