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 n BuLi in tetrahydrofuran (THF), giving [(EDBP-H)Li(THF) 3 ] ( 1 ) in high yield. However, the reaction of EDBP-H 2 with n 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.