| Polystyrene, as one of common resins, with the good pellucidity, rigidity, water resistance, chemical stability, electroconductibility, radiotolerance and handling characteristics, could be well used in many fields. Because stereochemistry of polystyrene decided on its performance, so in order to improve the performance of polystyrene, three impoved ways could be applied:Firstly, using the design of the catalyst to directly get isotactic or syndiotactic polystyrene; secondly, by the copolymerization from styrene and other monomers; and finally, by improvement of the syndiotactic or isotactic content of atactic polystyrene. In this thesis, we focus on the third way, namely, depending on the special design of catalysts to get the syndiotactic-riched atactic polystyrene.Three series of Schiff-base Cu2+/Ni2+ catalysts were synthetized:bilateral symmetrical Schiff-base Cu2+/Ni2+ catalysts, unilateral Schiff-base Cu2+/Ni2+ catalysts and bilateral asymmetric Schiff-base Cu2+/Ni2+ catalysts. The molecular structures of the catalysts were characterized by the infrared spectra (FT-IR), the nuclear magnetic resonance spectra (NMR), the X-ray diffraction analyses (XRD), and thermogravimetric analysis (TGA). All the catalysts were used for the polymerization of styrene on the method of solution polymerization, and their molecular weights (Mw or Mn) and molecular weight distributions (PDI) were determined by gel permeation chromatography (GPC). Furthermore, the stereo-specific structures of polymers were characterized by the FT-IR,1H NMR and TGA. In order to investigate the relationship of the catalysts structures and the property of polystyrene, the type of catalysts, the molar ratio of monomer and catalyst, polymerization temperature and polymerization time were systematically considered, for the requirement of the controlled molecular weight size, the narrow molecular weight distribution and the key to the syndiotactic content of the atactic polystyrene.At the first, two catalysts containing different metal activation centers are synthesized by coordination of late transition metal ion Cu2+/Ni2+ with the designed ligand, and the polymerization of styrene is investigated. When the molar ratio of monomers and catalyst of 2000:1, the molar ratio of catalyst and cocatalyst of 1:3, the polymerization time of 18 h and the polymerization temperature of 130℃are selected, the yield of the polystyrene was the highest (56%), and on the condition of 6 h,130℃, the activity of catalysts was the highest.Secondly, six unilateral single-site Schiff-base Cu2+/Ni2+ catalysts based on two unilateral ligands are synthesized, and their polymerization behavior of styrene is studied. Stronger pull electronic group can reduce the electronic cloud density of catalysts, which is propitious to the reaction of metal active center with styrene. The higher steric hindrance effect results in the lower activity of catalysts, the probable reason is the rate of monomer insertion declines along with the higher steric hindrance of metal active center, leading to the reduction of the catalytic activity.Thirdly, five single-site catalysts containing different electronic-pulling, electronic-withdrawing and steric effects were synthesized. Through the comparison of the styrene polymerization behavior of five catalysts at the same condition, it can be discovered that the catalytic activity is strongly relative to those of the effects:the input of electronic-withdrawing groups (bromine groups) leads to the increase of the activity.Fourthly, similar to the content of chapter 3, five Ni2+ catalysts were synthesized. From the polymerization comparison with the two kinds of active centers, the higher activity of 32428.6 g·mol-1h-1 with Ni2+ -based active center is observed than that (14507.9 g·mol-h-1) of with Ni2+-based active center. So the change of catalytic active center is important.
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