Preparation of POM-ILs and their application in synthesis of polyglycol mixed dibasic acid ester
Mono-substituted polyoxometalate ionic liquids(POM-ILs)catalysts of Keggin-type with Sn,Fe,Ti and Zn as coordination metals were prepared,characterized and analyzed by FTIR,XRD,SEM,EDS and TGA.The POM-ILs were then applied to catalyze the synthesis of polyglycol mixed dibasic acid ester(PDBE)from dimethyl dibasic acid(DBE)and ethylene carbonate(EC),with the influence of different coordination metals on their catalytic activity evaluated.Product PDBE was further characterized by FTIR,GPC,TGA,DSC and microcomputer control electronic universal testing machine,and assessed for its enzymatic degradation performance.The results showed that Sn mono-substituted zinc tungstate ionic liquid[Bmim]6ZnW11SnO39(H2O)exhibited the best catalytic performance.Under the optimum conditions of n(EC)∶n(DBE)=1.5∶1,reaction time 5 h,reaction temperature 215℃,catalyst dosage being 1.1%of the total mass of raw materials,the selectivity and yield of PDBE prepolymer were 57.85%and 54.76%.Under the optimum polycondensation conditions of reaction time 3.5 h,reaction temperature 220℃,the PDBE obtained showed an intrinsic viscosity of 0.591 dL/g,a tensile strength of 33.4 MPa,an elongation at break of 17.9%,a relative number-average molecular mass of 14433,a relative weight-average molecular mass of 33429,an average relative molecular mass of 70859,and a polydispersity index(PDI)of 2.3161.When the phosphate buffer solution of Novozymes immobilized lipase 435 with a mass concentration of 1.2 g/L was added to degrade to a mass residual rate of 2%～3%,PDBE took 28 d,while poly(ethylene succinate)(PES)took 30 d.
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