Preparation of Amphiphilic Poly(ethylene glycol)- b-poly(γ-butyrolactone) Diblock Copolymer via Ring Opening Polymerization Catalyzed by a Cyclic Trimeric Phosphazene Base or Alkali Alkoxide

Preparation of Amphiphilic Poly(ethylene glycol)- b-poly(γ-butyrolactone) Diblock Copolymer via Ring Opening Polymerization Catalyzed by a Cyclic Trimeric Phosphazene Base or Alkali Alkoxide