AbstractHydrophobic‐hydrophilic poly(2‐vinlypyridine)/poly(ethylene oxide) block copolymers were synthesized by anionic polymerization in tetrahydrofuran in vacuum with diphenylmethylpotassium as initiator. The resulting polymers were fractionated from benzene solution by progressive precipitation with 2,2,4‐trimethylpentane at 35°C. Gel permeation chromatography, light scattering, osmometry, and1H NMR were used to characterize the fractions. The copolymers, thus prepared, were found to have a well defined structure and a low polydispersity in both molecular weight and chemical compo