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

As one of the environment-friendly materials, polyester polymer has prominent advantages in energy recycling and environmental protection. For example, polylactide (PLA) is a biodegradable polyester material with good biocompatibility, its final degradation product is CO2 and H2O, and the intermediate product in PLA’s degradation is lactic acid, which is also a product of normal metabolism of glucose in vivo. Non-toxic, no stimulation, controllable biodegradation, good biocompability, and cycle crops (such as corn, sucrose) as the the raw material, all these advantages of PLA not only significantly curb the growing problem of "white pollution", but also effectively mitigate the energy crisis which is brought from dwindling of oil resources. Up to now, the polylactide and its copolymers have become emerging biodegradable materials which are concerned by more and more people, while having a broad field in industrial and medical appillcations. However, the catalytic synthesis of polyester are mostly under the protection of inert gas, which has greatly increased the consumption in production of polyester, then reducing the synthetic steps of catalyst/initiator or synthesizing a robust catalyst/initiator which is less sensitive to water and other acidic impurities has become one of the effective ways to reduce the costs in the production of polyester, referring to these measures above, this paper is mainly focused on the studying of the synthesis of bulky metal complexes and their catalytic application in ring-opening polymerization of lactide.This paper consists of four chapters1. A brief review of ring-opening polymerization about cyclic esters was given.2. Both of adamantyl substituted and benzenesulfonate substituted phenol that are simple and easy to get were used as ligand, after reacting with different metal reagent, a series of metal complexes were synthesized. Applying these complexes to ring-opening polymerization of lactide, expecting that by reducing the costs of consumption of the synthesis of polyester with the means of making the ligand easier to be synthesized, and a controlled catalyst/initiator which is easy to get with high catalytic activity to the monomer will be obtained. The results showed complexes 3,5 have excellent catalytic activity.3. Based on the reports that the steric effects can reduce the destruction which is caused by water and acidic impurities to metal center of complex in a certain extent, thereby increasing the whole stability of the complex, we used t-butyl substituted bisphenol TBBP-H2 as ligand, after reacting with different metal reagent, a series of bulky metal complexes were synthesized, and then applying them to ring-opening polymerization of lactide. Hoping that the catalyst will be stable and controlled in the polymeric system after the introduction of water vapor. The experimental results showed that complex 10 still had high catalytic activity to monomer after the water which is 50 equiv. compared to catalyst added in the catalytic system, and molecular weight of the obtained polyester is still controlled.4. Synthesis, charaterization of bulky hetero-bimetallic complexes with t-butyl substituted linear phenol as ligand are descripted. Based on the work in the third chapter, the studying has been focused on these complexes’ catalytic application in polymerization of lactide after the introduction of trace amounts of water. It is found that under the conditions of the introduction of 1 equiv. water compared to catalyst in polymerization system, complexes 14,15 almost keep their catalytic activity.