“Star-shaped PHB-PLA block copolymers: Immortal polymerization with dinuclear indium catalysts”
The first example of a one-component precursor to star-shaped polyesters, and its utilization in the syn- thesis of previously unknown star-shaped poly(hydroxybutyrate)–poly(lactic acid) block copolymers, is reported. A series of such mono- and bis-benzyl alkoxy-bridged complexes were synthesized, fully characterized, and their solvent dependent solution structures and reactivity were examined. These com- plexes were highly active catalysts for the controlled polymerization of β-butyrolactone to form poly- (hydroxybutyrate) at room temperature. Solution studies indicate that a mononuclear propagating species formed in THF and that the dimer–monomer equilibrium affects the rates of BBL polymerization. In the presence of linear and branched alcohols, these complexes catalyze well-controlled immortal polymeriz- ation and copolymerization of β-butyrolactone and lactide.