| Carbon dioxide(CO2) is the cheapest and most abundant raw material source of carbon. Utilization of CO2 to produce biodegradable aliphatic polycarbonate represents a promising green polymerization process to fix CO2. Among many catalytic systems, (salen)MX, which is developed in recent years, is a macrocyclic ligand metal complex. The homogeneous (salen)MX catalyst has the advantages of low sensitivity to water and air, mild reaction conditions. However, the most of homogeneous (salen)MX catalyst systems suffer from the problems associated with catalyst/polymer separation and catalyst residues. Therefore, the organic metal complex supported on a polymer compound is a good idea to convert homogeneous catalyst into heterogeneous catalyst. Polypyrrole (PPy) which is a conducting polymer has been widely investigated due to its easy preparation, environmental stability and high electrical conductivity. This paper describes the synthetic and structural characterization of the PPy-Cr(Ⅲ)(salen)Cl. The catalyst was prepared for alternating copolymerization of cyclohexene oxide (CHO) and carbon dioxide (CO2). And the effect of copolymerization conditions were studied.1. A variety of polypyrrole nanofibers were synthesized through the centrifugation. As a catalyst carrier, polypyrrole supported Cr(Ⅲ)(salen)Cl have been reported in this paper. The supported catalysts were characterized by FTIR, XRD, XPS, ICP-MS, SEM and TEM. After the study, we concluded that the homogeneous Cr(Ⅲ)(salen)Cl is successfully supported on the PPy.2. The reaction of PPy-Cr(Ⅲ)(salen)Cl for alternating copolymerization of CHO with CO2 have been studied. The copolymerization products were characterized by FTIR, UV and NMR. The reaction conditions of the mass of catalyst, the reaction temperature, the reaction pressure, the reaction time and the doping different acids for the catalytic activity and the molecular weight of the copolymerization have been analyzed. The optimum condations are: CHO 5ml, m(PPy-Cr(Ⅲ)(salen)Cl)=0.0564 g, m(PPNCl)=0.0286 g, T=80 ℃, t=10 h, P=5 MPa。TON=4812, Mn= 9.8×103g·mol-1, PDI=1.19.3. The thermal stability of the products were characterized by Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). We concluded that with the increase of the mass of catalyst, the catalytic activity can reach the maximum, the molecular weight will become large and the thermal stability can be improved. If we continue to increase the amount of the mass of catalyst, the molecular weight and the thermal stability of the products will decline. Futher, the thermi-decomposing temperature and maximum weight-loss temperatures of copolymer using PPy(nanowire shape)-Cr(Ⅲ)(salen)Cl are 275 ℃ and 320 ℃, other copolymer using PPy(particle morphology)-Cr(Ⅲ)(salen)Cl catalyst are 275 ℃and 291 ℃, copolymer using PPy(rod-shaped)-Cr(Ⅲ)(salen)Cl catalyst are 262 ℃and 275 ℃.4. The polymer selectivity, product selectivity and carbonate bond unit content of the copolymer have been analyzed by ~1HNMR and 13C NMR. And the conditions of doping different acids and cocatalyst for the three-dimensional structure of the copolymerization have been studied. The results of the product for four doping acids(HCl, H2SO4, HNO4 chiral camphor sulfonic acid) have shown that the polymer selectivity were 97.1%,96.5%, 96.6% and 98.7% respectively and the product selectivity almost reach 99% except the HNO4(97.8%). Moreover, with the introduction of the HC1 or H2SO4, the carbonate bond unit content of the copolymer were 99.6% and 99.1%. In addition, the ratio of isotactic and syndiotactic were 1:0.43,1:0.7,1:0.86 and 1:0.56 respectively in products catalyzed by by PPy-Cr(Ⅲ)(salen)Cl doped with HC1, H2SO4, HNO4 and chiral camphor sulfonic acid.5. The effect of cocatalysts for the copolymerizations sterepregularity of CO2 with CHO have been studied. Without the presence of cocatalyst, the product selectivity was 94.31%, the carbonate bond unit content was 80.33% and the ratio of isotactic and syndiotactic was 1:0.97. When adding the cocatalyst N-Melm or DMAP, the product selectivity was improved from 94.31% to 98.20% and 99.25% respectively, the carbonate bond unit content was improved from 80.33% and 92.72% or 95.04% respectively, the ratio of isotactic and syndiotactic increase gradually. When adding the cocatalyst PPNC1, the product selectivity reached 99.64%. the carbonate bond unit content was higher than 99% and the copolymerizations sterepregularity was more better than the product without cocatalyst.
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