Synthesis and Characterization of Group 1 and 4 Metal Complexes : Efficient Catalysts for Ring-Opening Polymerization of Lactides

• Main Authors: Hsiu-Wei Ou, 歐修瑋
• Other Authors: 林助傑
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/61220951879487528267

博士 === 國立中興大學 === 化學系所 === 105 === Abstract The background of biodegradable polymer and ring-opening polymerization of polylactide (PLA) was introduced. The motivation of choosing ONO-tridentate Schiff base bisphenolate ligands to associate with titanium (Ti) and zirconium (Zr), and NNO-tridentate Schiff base ligands to associate with sodium (Na) or potassium (K) are described. A series of Ti and Zr complexes bearing ONO-tridentate Schiff base ligands were synthesized and used as catalysts for the ring opening polymerization of L-lactide (L-LA). The Ti and Zr complexes with electron-donating groups show greater catalytic reactivity than that of electron-withdrawing groups in ligand. Among these Ti and Zr complexes [L5-NEt2Zr(OiPr)2]2 shows the highest catalytic reactivity in ring-opening polymerization of L-LA with conversion up to 93% within 1 hr at 30 oC. Furthermore, single-crystal X-ray analyses show that Ti and Zr complexes are all dinuclear structure. In addition, a series of lithium (Li), sodium (Na), and potassium (K) complexes bearing NNO-tridentate Schiff base ligands with a N-pendant arm were synthesized. The catalytic activity for the ring opening polymerization of L-LA was also investigated. Experimental results indicate that ligands with electron-donating groups increase the catalytic activity of the metall complexes in L-LA polymerization. Among sodium complexes, [L4-OMeNa]2 shows the highest activity with conversion up to 95% within 30 second at 0 oC and producing polylactide with narrow polydispersity index (PDI) of 1.13 in the presence of benzyl alcohol (BnOH) proves its great controll ability. Furthermore, [L5-OMeK]4 has the highest activity among potassium complexes with conversion up to 99% within 10 second at 0 oC (PDI = 1.13). Single-crystal X-ray analyses show that sodium complex [LHNa(THF)]2 is a dinuclear species and potassium complex [L6-MeK]4 froms tetrameric structure.