Application Of Rare Earth Metal Phenolates In The Ring-opening Polymerization Of Cyclic Esters

Biodegradable polymers have been considered as alternative environment-friendly polymers due to their unique and excellent properties. Polylactide (PLA), a biodegradable and biocompatible aliphatic polyester, has emerged as a valuable polymer for both commercial and special applications in recent years. Polylactide becomes the most promising synthetic polymers which can be used to make polymeric devices in drug delivery and medicine. The ring-opening polymerization (ROP) of cyclic esters, which have many applications in various areas such as agriculture and medicine, has become a convenient way for the synthesis of biodegradable and biocompatible polyesters. In order to improve the property of polyesters in applications, the development of efficient catalytic systems for the preparation of Polylactide (PLA) is attracting a lot of interest from both industrial and academic research groups. Therefore, the studies on application of rare earth, rare earth and Na phenoxides in ROP of cyclic esters are presented in this article.This article consists of three chapters:Chapter 1:A brief review of ring-opening polymerization (ROP) of cyclic esters in recent years was given.Chapter 2:A C3-symmetrical yttrium complex [LY(THF)2] supported by a sterically encumbering N-anchored tris-arylphenoxide ligand was prepared by the reaction of H3L{ L= tris(4,6-di-tert-butyl-2-hydroxybenzyl)amine} and Y[N(TMS)2]3 in THE The complex acts as a good catalyst for the heteroselective ring-opening polymerization (ROP) of rac-lactide, yielding polymers with Pr up to 0.73 under melt polymerization. In addition, the complex [LY(THF)2] can also effectively catalyze the coupling reaction of carbon dioxide with cyclohexene oxide using n-Bu4NCl/n-Bu4NBr/n-Bu4NI as a co-catalyst.Chapter 3:Anhydrous alkali metal lanthanide R-binaphtholates M3[Ln(R-binol)3] (M= Na; Ln= lanthanum(5) or yttrium(6); H2binol= R-binaphthol) are prepared by reaction of Ln[N(TMS)2]3 with 3 equiv of MHbinol. The experimental results indicate that complex 5 can efficiently catalyze the ring-opening polymerization of rac-Lactide with the isotacticity of 0.60 (Pm), yielding polymers with relatively narrow molecular weight distribution, while complex 6 could achieve the syndiotacticity of 0.58 (Pr).