NaOH AND TEAH CATALYZED POLYCARBONATE SYNTHESES THROUGH MELT TRANSESTERIFICATION AND THE REARRANGMENT PRODUCTS IN BOTH PROCESSES

The synthesis of polycarbonate(PC) was carried out by using the melt transesterification of bisphenol A(BPA) and diphenyl carbonate(DPC) catalyzed respectively by NaOH and tetraethylammonium hydroxide(TEAH).When the molar ratio of DPC to BPA was 1.05∶ 1 and that of catalysts to BPA was 5 × 10-4∶ 1,under the process conditions selected,polycarbonates with Mn of 1.69 × 104,Mw/Mn of 1.97(catalyzed by NaOH) and M n of 1.23 × 104,M w/M n of 1.44(catalyzed by TEAH) were produced.The variation of intrinsic viscosity of the PC samples and the liquidity of relevant melt flow in different stages of the reaction process were determined.The 1H-NMR spectroscopy,UV spectroscopy and HPLC were employed to analyze the Fries,Kolbe-Schmitt and isopropyl radical combination rearrangement.In different catalytic processes,all these rearrangements have different forming and varying conditions.It is observed that the Fries rearrangement is the one most prone to appear among the three kinds of rearrangement reactions,which exists in the entire NaOH-catalyzed process.Kolbe-Schmitt rearrangement is impacted significantly by the high-temperature and melt viscosity of the reaction system.Compared with NaOH,in the TEAH-catalyzed system,the molecular weight of polycarbonate is lower,the molecular weight distribution is narrower and the degree of Fries and Kolbe-Schmitt rearrangements is much lower.In both catalytic processes,no rearrangement products caused by the combination of isopropyl radicals were found.