Synthesis Of Innovative Rare Earth Complexes And Their Catalytic Activity Toward The The Ring-Opening Polymerization

A new tertrahydrosalen-stabilized yttrium complex was prepared by simple in-situ method through metathesis reactions. The lanthanide complex was characterized by FT-IR and element analysis (EA) and employed as a precursor for the polymerization ofε-caprolactone(ε-CL) in the presence of NaBH4. Based on the results, we further explored its reactivity in the polymerization of 2,2-dimethyltrimethylene carbonate (DTC), L-lactone(LLA) and the copolymerization of DTC and CL. On the other hand, discrete iron-pair lanthanide complex Sm(EDBP)2(DME)Na(DME)3 was prepared, characterized and used as an initiator in the polymerization of LLA.The effect of [monomer]/[initiator] ([M]/[I]), temperature and reaction time on the polymerization ofε-CL, DTC and copolymerization ofε-CL and DTC initiated by lanthanide borohydride complex and Sm(EDBP)2(DME)Na(DME)3 was systematically investigated. It was found that under the condition:[CL]/[I]=1200,55℃, toluene:0.5mL,ε-CL:0.5mL, PCL with Mw=32600 and PDI=1.47 was obtained by the polymerization ofε-CL initiated by yttrium borohydride complex. The poly (2, 2-dimethyltrimethylene carbonate) (PDTC) with one hydroxyl and one formate terminal functions was also synthesized by the yttrium borohydride complex. Moreover, the random copolymerization of DTC and CL initiated by rare-earth borohydride compound was studied. The microstructure of PDTC-co-PCL includes four diads:DTC-CL, CL-CL, DTC-DTC and CL-DTC, which occupy 12.9%,23.0%, 51.5% and 12.6% of the copolymer determined by the intergration of the specific signals in 1H NMR spectroscopy.Furthermore, the polymerization of LLA initiated by salen ligand stabilized lanthanide borohydride complex and Sm(EDBP)2(DME)Na(DME)3 was studied at the first time. The results showed that the reactivity of lanthanide borohydride complex was much lower than the bridged bisphenolate stabilized lanthanide compound. As an efficient initiator, the latter could initiate the polymerization of LLA under the condition of [LLA]/[I]=300, T=70℃,0.5mL of toluene, and PCL with Mn=1.67*104 g/mol and PDI=1.47 was obtained. The 1H NMR indicated that the resulting polymer pocess the main chain structure of [-CH(CH3)-C(O)-O-]n. Further investigation of the mechanism of the polymerization of LLA was on the progress.