Abstract
A series of lithium, sodium and their mixed-metal complexes have been synthesized by the reaction of 2,2’-methylene-bis(4,6-di(1-methyl-1-phenylethyl)phenol) (MMPEP-H2) with sodium bis(trimethylsilyl)amide, nBuLi, ZnEt2 and MgnBu2 in diethyl ether (Et2O) or tetrahydrofuran (THF), respectively. Experimental results show that compounds 2-4 efficiently catalyze the ring-opening polymerization (ROP) of L-lactide (L-LA) in a controlled fashion, yielding polymers with very narrow polydispersity indexes (PDI) in a wide range of monomer-to-initiator ratios. Lithium n-butylmagnesium, lithium ethylzinc, sodium n-butylmagnesium and sodium ethylzinc complexes (compounds 5-8 ) have been synthesized. Catalytic studies illustrate that complexes 5-8 are efficient catalysts for the ring-opening polymerization of L-Lactide. The activity of sodium complex is higher than its lithium analogues, and its bimetallic complexes show greater activity than homometallic magnesium and zinc compounds. In addition, complexes 5 and 6 have been used as initiators for the polymerization of methyl methacrylate. Complex 6 is highly reactive as initiators for highly selective polymerization of MMA.
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