Catalytic Behaviour Of Ionic Liquids And Structure-Activity Relationship Of CO/Styrene Copolymerization

The polyketones are a fascinating polymeric material with excellent properties, including mechanical property, pressure tight, high temperature resistance and bio/photo-degradation. Aliphatic polyketones are prepared by a perfectly alternating copolymerization of carbon monoxide (CO) with olefins in the presence of palladium-based catalysts. However, these catalysts are too expensive to be afforded by most chemical industries. Here, the objective of our work is to improve the catalytic activity of palladium system, and to analyze catalytic mechanism and optimal reaction conditions.The copolymerization between CO and styrene is implemented in the [bmim]+PF6? ionic liquid in the presence of the novel palladium/rare-earth catalytic system. The catalyst in the ionic liquid was repeatedly used four times with virtually no loss in its activity and selectivity. The product was characterized by means of NMR, IR, XPS and TEM, indicating that poly(1-oxo-2-phenyltrimethylene) is a high-crystallized linear alternated copolymer. We also investigate the influence of several reaction conditions such as rare earth type, ionic liquid volume, reaction time, benzoquinone content and system pressure, on the catalytic activity. In chain termination of the copolymerization carried out by dodecanol, It is found that only ketone-type group is in the terminus of polyketone backbone under ionic liquid solvent.Various ionic liquids are synthesized and used as solvent of the CO/styrene copolymerization. The affect of electrostatic environment of cation (or anion) and length of alkyl chain on the catalyst system was studied by comparison of structures from different ionic liquids. The results show that [bmim]+PF6? is good for the copolymerization in which the catalytic activity reaches 464 gSTCO/(gPd·h).On the other hand, a series of 2,2'-bipyridine homologues available to catalyzed polyketones were synthesized. We use Gaussian 98 software to predict the catalytic activity according to relationship between 4,4-groups and electron-cloud density of N,N-spaces, suggesting that, as the electronic donor of 4,4-groups are increased, the catalytic activity and the relative molecule weight increased steadily. In top catalytic activity system in the presence of 4,4'-dimethyl-2,2'-bipyridines, the optimal condition is that the ratio of methanol/styrene (V/V) is 0.75, the ratio of BQ/Pd2+ (mol/mol) is 100, and the ratio of 4,4'-dimethyl-2,2'-bipyridine/Pd2+ (mol/mol) is 2. The copolymerization easily occurs at 80℃under atmosphere of 2 MPa.In addition, polystyrene-supported and polyacrylonitrile-supported palladium acetate catalysts are prepared, respectively. These microspheres are characterized by IR and SEM and also employed in the copolymerization of CO with styrene. By analyzing influence of resin dosage, loadability of palladium and reaction time on the yield, polystyrene-supported palladium catalyst is better than polyacrylonitrile -supported one, although the two catalysts are available in five copolymerization cycles. The correlation between influencing factors is determined by SPSS statistics, showing that dosage of benzoquinone is significant.