Study On Synthesis Of Polycarbonates Catalyzed By Superbase Ionic Liquids

In this paper,the property,application and synthesis method of polycarbonate are briefly introduced.Considering the current several processes for the synthesis of polycarbonates and their development,two non-phosgene melt polycondensation polycarbonates were selected:one is the synthesis of aromatic polycarbonate(PC)by dipenyl carbonate(DPC)and bisphenol A,another is the synthesis of biobased polycarbonate(PIC)by DPC and isosorbide.The details are as follows:We designed and synthesized several basic ionic liquids(quaternary ammounium and ZHHN-based ionic liquids)and investigated their catalytic activities for the synthesis of PIC and PC via the melt polycondensation,respectively.The influence of the feed ratio,the amount of catalyst,the polycondensation time and the polycondensation temperature on the polymerization process was observed to obtain the optimum reaction conditions.The results showed that the optimum catalyst for the synthesis of PIC was TEAI,and PIC with a weight-average molecular weight(M_w)of25600 g/mol was obtained.The optimum catalyst for the synthesis of PC was ZHHN-2,and PC with M_w of 71 000g/mol was obtained.In order to modify the molecular flexibility and thermal properties of the homopolycarbonates,copolycarbonates were synthesized by introducing flexible groups(aliphatic diols)into the molecular chain of homopolycarbonates.The structures of copolycarboantes were characterized by NMR and FT-IR,and their thermal properties were characterized by thermogravimetric analysis and differential scanning calorimetry.The results show that the copolycarbonates were random copolymers.The glass transition temperature(T_g)of copolycarbonates shifted to lower temperatures with increasing methylene numbers in the linear aliphatic diol units,but the thermal stability was gradually improved.The copolycarbonates incorporated with cycloalipahtic diols showed a higher T_g than that with linear diols.