Preparation of block copolymers with polymeric azocarbamate as an initiator

Block copolymers containing polystyrene and poly(ethylene oxide) or poly(propylene oxide) segments were prepared via chemical reactions. A stepwise procedure was first employed to prepare macroazocarbamates by capping poly(ethylene oxide) glycols or poly(propylene oxide) glycols and an aliphatic diisocyanate and subsequently by reacting this intermediate with an azobisalcohol. This macroazocarbamate was later used to initiate free radical polymerization at elevated temperatures. Styrene contents, molecular weights, and elastic modulus‐temperature relationships were determined.