Synthesis, Characterization Of Alkali-metal Calix[4]arene Complexes And Application In The Ring-opening Polymerization Of Lactide

PLA is a polymer plastic which possesses biodegradability and biocompatibility, the raw materials to synthesize PLA can be obtained from corn, beets and other natural crops, and eventually degrades into carbon dioxide and water. The raw materials of PLA is renewable resources while the traditional plastic was from petroleum, so it can reach the environmental protection, and it have been agreed by industry as the most promising of the new “eco material”. Now the method of “Ring-opening Polymerization” is an operative way to synthsize PLA. Currently, it has become a research highlight that how to improve the mechanical properties of PLA by developing the advanced catalyst systems and the synthesis of the novel copolymers. This thesis focus on building advanced catalyst systems, and study the effect of calixarene complexes to the stereoregularity of PLA and catalytic activity deeply.This paper consists of three chapters.Chapter 1: A brief review of ROP of the cyclic esters in recent years.Chapter 2: A series of sodium and potassium complexes with novel structures supported by 1, 3-dipropoxy-p-tert-butyl-calix[4]arene(L1H2) ligand and it have been fully characterized. In this chapter, we disscussed the influence of the different metal centers with additional auxiliary ligands on the stuctures, and we also explored the ring-opening polymerization for LA of the complexes 1-3. The results indicate that the complexes 1-3 are highly active for the ROP of rac-lactide, at the room temperature it can catalize 100 times LA in 3 minutes. Especially, the complex 2 poesses a sandwich structure with an auxiliary ligand of 18-crown-6. It leads the steric hindrance of the actived potassium atom increased, as a result it does not affect the catalytic activity and controllability for the ROP but also it can improve the regularity of PLA. At-60 oC the obtained isotactic PLA with a Pm = 0.67.Chapter 3: On the basic of chapter 2 we study the effect of the differnent coordinated crown of the complexes to ROP of rac-lactide futher. We synthesized complexes 4-5 by using 1,3-dihydroxy-p-tert-butyl-calix[4]arene-crown-5(L2H2) and 1,2-dihydroxy-p-tert-butyl-calix[4]arene-crown-5(L3H2) as ligands respectively, all the complexes have been characterized. The results indicate that the conformation of complex 4 is a partial cone, it has some advantages of highly active and a better controllability for the ROP of rac-lactide. At-60 OC the obtained isotactic PLA has a high Pm value of 0.73. Complex 5 has only one potassium atom and its catalytic activity is lower than the complexes 1-4, its catalytic activity is very low due to the exsit of intramolecular hydrogen bond.