Synthesis, Characterization And Structures Of Phenoxide Metal Complexes And Application In ROP Of Cyclic Esters

Polyesters are among the most versatile synthetic polymers, due to their biodegradability and biocompatibility and non-toxic advantages, which has great economic benefits and social benefits. In recent years, using metal complexes to the ring-opening polymerization of synthetic polyesters has made good achievements, and many polymers of well-controlled molecular weight and narrow polydispersity degrees have been obtained. It is reported that a lot of mononuclear metal complexes can catalyze the ring-opening polymerization of cyclic esters with well-controlled molecular weight and narrow polydispersity degrees but also with certain stereo selectivity. Compared to the mononuclear metal complexes, the high activity dual-core metal complexes and neutral metal complexes are reported less. So we used phenoxide ligands to synthesis dual-core metal complexes and neutral metal complexes with expected high activity which can be used for the ring-opening polymerization ofε-lactone and L-lactide to get polymers with well-controlled molecular weight and narrow polydispersity degrees. We characterized the structures of the complexes by the X-ray single crystal diffraction and NMR method. So we can provide some useful information to the research of ring-opening polymerization.This paper consists of three parts:1. The first chapter is a brief review of ring-opening polymerization and the application of cyclic esters.2. A series of sodium, aluminum and their mixed-metal complexes have been synthesized by the reaction of H3L1 with sodium, Al(Me)3 or both of them in tetrahydrofuran. We have got 5 new complexes as follows:aluminum complex [(TTBP)Al(THF)2] 1, complex [(TTBP)Na3(THF)5] 2, complex [(TTBP)AlNa(THF)2] 3, complex [(TTBP)AlNa4(THF)6] 4 and complex [(TTBP)AlNa-(BnOH)(THF)2] 5. It's worth noting that the complex 4 is composed of a large anion and a large cation which consists of four nuclear sodium. Experimental results show that the complex 5 has slight activity for catalyzing the ring-opening polymerization (ROP) of L-lactide (Z-LA) andε-lactone (CL).3. A series of Zn, Mg and Al complexes (complexes 6-8) have been synthesized by the reaction of HL2 with Zn(Et)2, Mg(nBu)2 and Al(Me)3 in tetrahydrofuran(THF), respectively. The results show that the activity of zinc complex 7 is higher than its magnesium analogues for the ring-opening polymerization of L-lactide. Complex 7 is an efficient catalyst for ring-opening polymerization ofε-lactone in controlled indexes fashion, yielding polymers with expectative molecular weight and low polydispersity indexes. Complex 6 has slight activity for ring-opening polymerization ofε-lactone.