Ningzhang Liu,Chuanhai Gu,Qinghe Wang,Linhua Zhu,Huiqiong Yan,Qiang Lin
To achieve the poly(propylene carbonate trimellitic anhydride) (PPCTMA) with excellent performance, high molecular weight, enhanced yield and good thermal stability, the ternary composite catalyst system of zinc glutarate/rare earth ternary complex/double metal cyanide (ZnGA/RET/DMC) was proposed to perform the terpolymerization of CO2, propylene oxide and trimellitic anhydride. Since the crystallinity and surface activity point of Zn–Co DMC could significantly influence the catalytic ability, mechanical ball milling was applied to increase the surface area of the Zn–Co DMC catalyst with better surface activity point. Moreover, the ZnGA/RET/DMC composite catalytic system and polycarbonate products were comparatively evaluated by XRD, SEM, FT-IR, TGA, NMR, XPS and TEM. Experimental results showed that the ZnGA/RET/DMC composite catalyst system displayed outstanding synergistic effect on the terpolymerization of CO2, PO and TMA with better selectivity, activity, and higher molecular weight (Mw) tercopolymer than those of the individual catalyst. According to optimum reaction conditions, the Mw of PPCTMA could be up to 8.29 × 104 g mol−1, and the yield could be up to 66 gpolym/gcat. The alternating tercopolymer, PPCTMA, showed wonderful thermal stability and high decomposition temperature (TGA10% = 313 °C). A possible synergistic catalytic mechanism of the ZnGA/RET/DMC ternary composite catalyst system was also conjectured.
In order to improve the catalytic efficiency of zinc glutarate (ZnGA) used in the CO 2 /propylene oxide (PO) copolymerization, silica-supported zinc glutarate catalysts (ZnGA/SiO 2 ) are prepared via a rheological phase reaction with a little toluene as a reaction medium. Wide-angle X-ray diffraction (WAXD) tests of the catalysts illustrate that the crystal quality increases and the overall crystallinity declines after supporting. The scanning electron microscope (SEM) images show that the proportion of supported ZnGA increases with increasing the SiO 2 proportion. Accordingly, the polymer yields increase from 12.7 Kg polymer/mol Zn of ZnGA to 25.6 of ZnGA/SiO 2 . And the almost alternating poly(propylene carbonasstes) (PPCs) with the carbonate content of above 97 % and the M
n s of above 10, 000 g/mol are obtained. This work illustrates that the catalytic efficiency does not increase sharply like the supported catalysts used in olefin polymerization because of the decline in overall crystallinity of ZnGA. The catalytic efficiency is expected to be enhanced significantly if it can be improved for ZnGA/SiO 2 .
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