Air-stable copper derivatives as efficient catalysts for controlled lactide polymerization: Facile synthesis and characterization of well-defined benzotriazole phenoxide copper complexes

作者：Li Chen Yu; Hsu Shi Jie; Lin Chin lung; Tsai Chen Yen; Wang Jun Han; Ko Bao Tsan^*; Lin Chia Her; Huang Hsi Ya

来源：Journal of Polymer Science Part A: Polymer Chemistry , 2013, 51(18): 3840-3849.

DOI：10.1002/pola.26780

• benzotriazole phenoxide
• biodegradable
• catalysis
• copper
• lactide
• polyesters
• ring-opening polymerization (ROP)

Air-stable copper catalysts supported by bis-BTP ligands (BTP 5 N, O-bidentate benzotriazole phenoxide) were synthesized and structurally characterized. The reactions of Cu(OAc)(2)center dot H2O with 2.0 molar equivalents of sterically bulky 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl) phenol ((BTP)-B-CMe2Ph-H) and 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol (t-BuBTP-H) in refluxing ethanol solution afforded monomeric copper complexes [((BTP)-B-CMe2Ph)(2)Cu] (1) and [(t-BuBTP)(2)Cu] (2), respectively. The four-coordinated copper analogue [((BTP)-B-TMCl)(2)Cu] (3) resulted from treatment of 2-tert-butyl-6-(5chloro- 2H-benzotriazol-2-yl)-4-methylphenol (TMCl BTP-H) as the ligand under the same synthetic method with ligand to metal precursor ratio of 2: 1, but treatment of complex 3 in acetone gave five-coordinated monomeric complex [((BTP)-B-TMCl)(2)Cu (Me2CO)] (4). X-ray diffraction of single crystals indicates that Cu complex 4 assumes a distorted square pyramidal geometry, penta-coordinated by two BTP ligands, and one Me2CO molecule. Catalysis for lactide (LA) polymerization of BTP-containing Cu complexes in the presence of various alcohol initiators was investigated. Complex 3 initiated by 9-anthracenemethanol catalyzes the ring-opening polymerization effectively not only in a %26quot;living%26quot; fashion but also in an %26quot;immortal%26quot; manner, yielding polymers with the predictable molecular weights and narrow molecular weight distributions. Initiations from multifunctional alcohols were able to produce PLLAs with two-arm linear and three-arm star-shaped molecular architectures. The controlled character of Cu complex 3 also enabled us to synthesize the PEG-b-PLLA copolymer.

• 出版日期2013-9-15