Block copolymers containing poly(ethylene oxide) or poly(propylene oxide) prepolymer segments and methyl methacrylate were prepared. A stepwise procedure was first employed to prepare macro-azocarbamates by capping hydroxy-terminated poly(ethylene oxide) or poly(propylene oxide) with 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and subsequently reacting this intermediate with 4,4'-azobis(4-cyano-n-pentanol)**. The resulting polymeric azocarbamates were used as free-radical initiators for the polymerization of methyl methacrylate. Various modes of preparation and the properties of the copolymers are described. Formation of block copolymers is illustrated by several analyses and measurements of elastic modulus versus temperature.