A new biocompatible triblock copolymer, poly(e-caprolactone-b-ethylene oxide-b-y-benzyl L-glutamate) (PCL-b-PEO-b-PBLG), has been prepared through sequential ring-opening polymerizations, with two degrees of polymerization for the PBLG block segment when using an amino terminated PCL-b-PEO diblock copolymer as the macro initiator. The hydrogen bonding strengths (interassociation equilibrium constants) followed the order of phenolic/PEO (K-A = 264.8) > phenolic/PCL (K-C = 116.8) > phenolic/PBLG (K-D = 9.0), indicating that the phenolic OH groups preferred to interact with the C-O-C units of PEO block, then the C=O units of PCL block, and finally with the C=O units of PBLG block. The hydrogen bonding behavior of these four competing functional units could be predicted accurately using the Painter-Coleman association model. These competitive hydrogen bonding interactions induced various miscibility behaviors and self-assembled hierarchical structures, ranging from the hexagonally packed cylinder structure of a-helical conformation of PBLG block segment in the crystalline lamellar structure of the PCL block segment to a miscible ordered structure upon increasing phenolic concentrations in the phenolic/PCL-b-PEO-b-PBLG blend system.