Poly [(R, S)-3-hydroxybutyratel oligomers containing dihyroxyl (PHB-diol), dicarboxylic acid (PHB-diacid) and hydroxyl-carboxylic acid (a-PHB) end functionalities were obtained by the anionic polymerization of beta-butyrolacton (beta-BL). Ring opening anionic polymerization of beta-BL was initiated by a complex of 18-Crown-6 with gamma-bydroxybutyric acid sodium salts (for PHB-diol and a-PHB) or succinic acid disodium salt (for PHB-diacid). Dihydroxyl functionalization was formed by the termination of polymerization with bromo-ethanol or bromo-decanol while the others were done by protonation. Hydroxyl and/or carboxylic acid functionalized PHB oligomers with eerie salts were used to initiate the polymerization of methylmethacrylate (MXIA). PHB-b-PMMA block copolymers obtained by this way were purified by fractional precipitation and characterized using H-1-NMR and C-13-NMR, gel permeation chromatography (GPC), and thermal analysis (DSC and TGA) techniques.