A crystalline conjugated block copolymer( PLA- b- PF- b- PLA) of poly( 9,90- didodecylfluorene) ( PF) and poly( L- lactide) ( PLA) was synthesized by a ring opening polymerization method. The oligofluorene with hydroxyl ends was prepared by the Yamamoto- type coupling of 2,7- dibromo- 9,9- didodecyl- fluorene using a Ni( COD) 2 catalyst as reductive transition metal- base coupling agent. The molecular structure of PLA- b- PF- b- PLA was characterized by H-1- NMR, GPC, DSC and PL techniques. The photoluminescence of PLA- b- PF- b- PLA was highly influenced by the crystalline PLA blocks.