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Synthesis of Novel Molybdenum-based ROMP Catalysts and Study on Pdcpd with Molybdenum Catalyst System

Author: HaoYinGe
Tutor: ZhangYuQing;YaoJingCai
School: Henan University of Science and Technology
Course: Polymer Chemistry and Physics
Keywords: molybdenum(Ⅵ)catalysts DCPD ROMP MMT nano-composites Dissertation
CLC: O643.36
Type: Master's thesis
Year: 2009
Downloads: 37
Quote: 0
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Abstract


Polydicyclopentadiene （PDCPD） is a kind of engineering plastic which possesses excellent mechanical properties, which becomes a focus of the engineering and technological field. There are many kinds of catalysts for DCPD’s polymerization reaction. The most effective catalysts proved to be tungstenic or molybdenic compounds as primary catalyst and alkylaluminium as cocatalyst. In this thesis molybdenic compounds were mainly studied. Low-cost molybdic acid was used as raw material, and new molybdenic catalysts were prepared which can catalyze DCPD’s polymerization reaction and prepare PDCPD materials.The catalyst MoO2Cl2（OPPh3）2 was synthesized according to the published literature, the method of which was refined and improved. For the first time MoO2Cl2（OPPh3）2 was used as primary catalyst, Et2AlCl as cocatalyst to catalyze DCPD’s polymeraztion reaction. MoO2Cl2（OPPh3）2 was very active for the polymerization, besides, this catalyst possesses other advantages, such as low cost of material, simple synthetic method and it is stable to air and moisture. Reactions of PPh3 with MoO2Cl2 yielded new MoO2Cl2-PPh3 coordination compound, the structure of which was charactered by FT-IR and 1H NMR. MoO2Cl2-PPh3 was active for DCPD’s polymerization reaction. As for MoO2Cl2（OPPh3）2 catalyst, the parameters for gel time, such as the amount of monomer, primary catalyst, cocatalyst and reaction temperature were all studied. The conversion and cross-linking rates of polymers were determined. Results showed that, this catalyst was more active than WCl6, the best reaction ratio was 2000:1:20, suitable reaction temperature was 70℃. In this catalytic system, monomer conversion rate was 80% above, and cross-linking grade determination indicated that cross-linking polymers were prepared. MoO2Cl2（OPPh3）2 was loaded on MMT and support catalyst was prepared. This support catalyst was used to catalyze DCPD’s polymerization reaction, and PDCPD-MMT nano-composites were prepared. XRD indicated that real nano-composites were prepared and MMT’s addition amount was 1.5% for the best.During experiment MoO2Cl2（OPPh3）2 was found to be suspended in DCPD liquid, which resulted in DCPD’s heterogeneous polymerization. In the end the catalytic efficiency of the system was low. So its structure needed to improve. It was devised to increase alkyls of benzene ring of OPPh3, thus increase the solubility of primary catalyst in monomer, hoping that the polymerization turned to be homogeneous. For these reasons above a new ligand tri-（4-tert-butylphenyl）phosphine was firstly synthesized. Tri-（4-tert-butyl phenyl）phosphine oxide was obtained through H2O2 oxidation reaction. They were both charactered by FT-IR, 1H NMR, MS and XRD. These two new ligands reacted with MoO2Cl2, and two new compositions MoO2Cl2-P（t-BuPh）3 and MoO2Cl2（OP（t-BuPh）3）2 were obtained. Results showed that these two kinds of catalysts were active for DCPD’polymerization reaction. Otherwise, MoO2Cl2（OP（t-BuPh）3）2 was blended with DCPD, then the mixture was heated at 60℃. In the end the system turned to be homogeneous.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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