The Influence of Sorbitol Impurity on the Polymerization of Isosorbide-Based Polycarbonate
Isosorbide-based polycarbonate(PIC)was an ideal bio-based polycarbonate which could replace traditional bisphenol A polycarbonate(BPA-PC)and had a wide range of application prospects.The industrial utilization of isosorbide(IS),however,was severely restricted because minute impurities in isosorbide interfered with the polymerization process,producing low molecular weight and yellow products.The effects of impurities on the PIC polymerization could provide ideas for the performance optimization.PIC was successfully prepared through melt transesterification and polycondensation based on isosorbide and diphenyl carbonate(DPC),lithium acetylacetonate was used as a catalyst.The viscosity-average molecular weight(M)ηcould reach up to 40 180 and the glass transition temperature(Tg)can be as high as 174 ℃.The effects of sorbitol on the polymerization of PIC are investigated via the reverse addition method combined with the kinetics study of the transesterification reaction,and the results reveal that the presence of sorbitol significantly decreases both the polymerization reaction rate(k')and the molecular weight of PIC.When the addition of sorbitol is 1％of the total amount of isosorbitol and impurities,the Mv is reduced by 22 042.Additionally,with the increase of the sorbitol contents,the PIC gradually changes from light yellow to brownish black.Moreover,the increase of sorbitol causes a slight decrease in the Tg and thermal stability of PIC.
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