Poly(L-lactide-b-gamma-benzyl glutamate) copolymers with various block lengths were synthesized by sequential ring-opening polymerization of L-lactide and N-carboxyanhydride of gamma-benzyl glutamate. The copolymers were characterized by SEC and NMR spectrometry. DSC and SAXS data suggested that the copolymers were phase-separated in domains containing either crystalline PLLA or liquid-crystalline columnar hexagonal morphology of PBLG. When varying the temperature, reversible local order-order transition could be observed on these diblock copolymers.