A novel approach to RE-OR bond from in situ reaction of rare earth triflates and sodium alkoxides: A versatile catalyst for living ring-opening polymerization of ε-caprolactone

作者：You, Lixin; Shen, Zhiquan; Kong, Jie; Ling, Jun^*

来源：Polymer, 2014, 55(10): 2404-2410.

DOI：10.1016/j.polymer.2014.03.032

• Living ring-opening polymerization
• Catalysis
• Rare earth triflates

A series of rare earth triflates (RE(OTf)(3), RE = Sc, Y and Lu) were used for the first time as moisture-stable precursors to generate rare earth alkoxide complexes through an in situ reaction with sodium alkoxides (NaOR) in tetrahydrofuran. H-1 NMR and C-13 NMR results confirmed the fast ligands exchange process and the formation of rare earth oxygen (RE OR) bond. The in situ formed catalysts displayed high reactivity toward living ring-opening polymerization (ROP) of epsilon-caprolactone (CL). For instance, Lu(OTf)(3)/sodium isopropoxide ((NaOPr)-Pr-i)-catalyzed ROP of CL with the [CL](0)/[(NaOPr)-Pr-i](0)/(Lu(OTf)(3)](0) feeding ratio of 300/3/1 produced poly(e-caprolactone) (PCL) with controlled molecular weight (M-n,M-exp = 11.9 kDa vs M.,theo = 11.8 kDa) and narrow polydispersity (PDI) of 1.08 within 3 mm at 25 C. The kinetic studies and chain extension confirmed the controlled/living nature for the Lu(OTf)(3)/(NaOPr)-Pr-i-catalyzed ROP of CL. In addition, end-functionalized PCLs bearing vinyl or allcynyl group with narrow PDIs were obtained by using funCtional sodium alkoxides in the presence of Lu(OTf)(3). H-1 NMR and MALDI-ToF MS analyses of the obtained PCLs clearly indicated the presence of the residue of OR groups at the chain ends. A coordination insertion polymerization mechanism was proposed including a fast ligand exchange between Lu(OTf)(3) and NaOR giving the respective lutetium alkoxide complexes, and a CL insertion into RE OR bond via acyl-oxygen cleavage.

• 出版日期2014-5-13
• 单位浙江大学; 西北工业大学