Synthesis, characterization, and catalytic studies of lithium complexes: Efficient initiators for ring-opening polymerization of L-lactide

The reaction of 2,2'-ethylidenebis(4,6-di-tert-butylphenol) (EDBP-H-2) with 'BuLi in tetrahydrofuran (THF), giving [(EDBP-H)Li(THF)(3)] (1) in high yield. However, the reaction of EDBP-H-2 with 'BuLi in the presence of benzyl alcohol (BnOH) in diethyl ether or tetrahydrofuran produces compounds [(EDBP-H)Li(BnOH)](2) (2) and [(EDBP-H)Li(BnOH)(THF)(2)] (3), respectively. Further reaction of 2 with excess of THF produces 3. Alternatively, 3 can also be prepared by the reaction of benzyl alcohol with 1 in toluene. Experimental results show that 2 and 3 efficiently initiate the ring-opening polymerization (ROP) Of L-lactide in a controlled fashion, yielding polymers with very narrow polydispersity indexes in a wide range of monomer-to-initiator ratios. Block copolymers, polystyrene-b-poly(L-lactide), have also been prepared from the ring-opening polymerization Of L-latide catalyzed by 3 using polystyrene as a macroinitiator.