The block copolymer poly(ethylene oxide)-b-poly(4-vinylpyridine) was synthesized by a combination of living anionic ring-opening polymerization and a controllable radical mechanism. The poly(ethylene oxide) prepolymer with the 2,2,6,6-tetramethylpiperidinyl-1-oxy end group (PEOT) was first obtained by anionic ring-opening polymerization of ethylene oxide with sodium 4-oxy-2,2,6,6-tetramethylpiperidiny-1-oxy as the initiator in a homogeneous process. In the polymerization UV and electron spin resonance spectroscopy determined the 2,2,6,6-tetramethylpiperidinyl-1-oxy moiety was left intact. The copolymers were then obtained by radical polymerization of 4-vinylpyridine in the presence of PEOT. The polymerization showed a controllable radical mechanism. The desired block copolymers were characterized by gel permeation chromatography, Fourier transform infrared, and NMR spectroscopy in detail.