Highly efficient CO2 and propylene oxide co-polymerization using Zn glutarate/Zn-Cr double metal cyanide composite catalyst

A highly active zinc glutarate-double metal cyanide (DMC) composite catalyst (ZnGA/Zn-CrDMC) was designed for the carbon dioxide (CO2) and propylene oxide (PO) copolymerization reaction. The composite catalyst was synthesized in a rheological phase reaction and characterized using Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The synthesized composite catalysed the solvent free reactions of PO and CO2 to afford biodegradable polypropylene carbonate (PPC) copolymer. 1H NMR,13C NMR, FT-IR and ESI-TOF mass spectrometry measurements were employed to confirm the characteristics of the PPC produced. Under optimal reaction conditions (50 bar CO2, 70 °C, 24 h), the ZnGA-Zn3[Cr(CN)6]2 composite displayed higher catalytic activities in the copolymerization reactions than the individual catalysts. The ZnGA:Zn3[Cr(CN)6]2 ratio of 15:1 gave PPC yield of 47.9 g polymer/g cat compared to ZnGA that produced 42.6 g polymer/ g cat in 24 h. In addition, the PPC produced from the composite catalyst displayed higher carbonate linkage content (Fc = 85.4 %) compared to the value of Fc = 33.9 %. obtained using the Zn3[Cr(CN)6]2 catalyst. Similaly, the composite catalsyt produced PPC with molecular weight of 4200 g/mol and narrow polydispersity index of 2.2. The resultant PPC copolymer displayed good thermal stability, exhibiting a high degradation temperatures (TGA-10%) of 229 °C and complete decomposition at 350 °C.