Synthesis, Characterization Of Trinuclear And Tetranuclear Magnesium Complexes And Applications In ROP Of Lactide

As biocompatibility and degradable synthetic polymers, aliphatic polyesters have advantages of nontoxicity to human beings, biodegradability and the degradation products which can be involved in human metabolism. Thus, their potential applications have been researched extensively in medical field as well as daily life, such as containers, thin film, costume, and automotive coatings. The raw materials of polyesters come from recycling agriculture products, which can replace petroleum-based plastics and other limited resources. These environmental friendly materials also do well to solve pollution problems. As a result of both economic and social significancy, there has been considerable interest in the synthesis of polyesters. This thesis focuses on efficient, environmental catalysts made from nontoxic metal and accessible ligands and their catalytical properties in ring opening polymerization have been researched in detail.This thesis is composed of three chapters.Chapter1:A brief review about the ROP of cyclic esters is presented in three aspects, metal center, ligands, and reaction mechanism respectively.Chapter2:A series of novel trinuclear magnesium clusters2,3,4have been synthesized from phenols, Mg"Bu2and DMEA. Their structures are well characterized and catalytic effects are discussed in details. Experimental results show that complexes2,3,4can efficiently initiate the ROP of L-LA in a controlled fashion together with merits of controllability, high load capacity and high activity. Notably, Complex2can even catalyze the ROP of4000equiv of L-LA in1min in a controlled model(Mn=100,000,PDI=1.02).Chapter3:Based on the results of Chapter2, tetranuclear complexes6and7were synthesized via reactions of phenols, MgnBu2and2-Methoxyethanol. They are fully characterized.6,7exhibit well-controlled properties in the ROP of L-LA, which is similar to complexes2,3,4. Nevertheless, the differences in structures and catalytic activity are under reasonable discussion. At last, we make an outlook about these certain structures and proper applications.