Ni(Ⅱ) Or Pd(Ⅱ) Bearing Benzocyclohexan-Keto(4-hydroxyethylphenyl)Imine And Their Covalently Immobilized Supported Catalyts:Preparation And Catalytic Copolymerization For Norbornene

Addition-type polynorbornene(PNB) is a kind of potential polymer material with high stability, excellent optical and electrical properties. However, these polymers suffer some insufficients in brittleness, solubility and adhesion, which limits applications of the polymers for the poor formability. By restructuring molecular structure of catalysts and comonomers, controllable polymer microstructure and morphology could be achieved to improve comprehensive performance of PNB. Supported catalysts, which possess benefits of both homogeneous and heterogeneous ones, become a focus of study due to their outstanding designability characteristic, high catalytic activity and controllable molecular weight distribution. Therefore, the immobilizition of catalysts on nanometer support is a desirable, easy and versatile method to improve the catalyst stability and prepare functional nanocomposites.In this paper, nano-silica(Si O2) and multiwalled carbon nanotubes(MWNTs) covalently immobilized supported nickel(II), palladium(II) catalysts were successfully prepared by corresponding nickel(II), palladium(II) catalysts bearing hydroxylfunctionalized ligand{C10H8(O)C[4-C6H4(C2H4OH)NH]CH3} and Si O2 or MWNTs activated by trimethylaluminum(Me3Al). The molecular structures of the ligand and catalysts were confirmed by X-ray single-crystal analyses, NMR and X-ray photoelectron spectroscopy. The unsupported and covalently immobilized supported catalysts were used in homopolymerizations of norbornene to afford highly productive norbornene addition polymerization systemes in combination with B(C6F5)3 as cocatalyst. The effect of amount of cocatalyst, polymerization temperature and time on catalytic activity were studied. Compared with nickel(II), palladium(II) catalysts without loading and physical mixing of nickel(II), palladium(II) catalysts with Si O2 or MWNTs, the nano-particles immobilized supported nickel(II), palladium(II) catalysts exhibited improved activity and productivity with lower feed ratio of cocatalyst and better stability at continuous high temperature.The unsupported and covalently immobilized supported nickel(II) catalysts were selected to investigate the copolymerization behaviors of norbornene(NB) with 5-norbornene-2-carboxylic ester(NB-COOCH3) and showed high activities(104 gpolymer/mol Ni·h), large molecular weights[Mw=(2.38-6.10)×104 g/mol] as well as narrow molecular weight distributions(PDI≈1.4). The NB-COOCH3 contents in copolymers could be adjusted to be 7.76-40.82 mol% by varying NB-COOCH3 feed ratios from 10 to 80 mol%. On account of the large specific surface area as well as good heat and mass transfer of nano-particles, covalently immobilized supported nickel(II) catalysts showed better activities, larger molar incorporations of polar monomer, higher molecular weights and narrower molecular weight distributions of copolymers. The reactivity ratios of the NB and NB-COOCH3 monomers for Ni(II)/B(C6F5)3 system estimated by the Kelen-Tüd?s method were determined to be r NB-COOCH3 = 0.05 and r NB = 6.72, respectively, which indicated the random copolymerization of NB/NB-COOCH3. The addition-type amorphous nanocomposites grown in-situ were demonstrated to be with good solubility in common organic solvents and high thermal stability. Copolymers were processed into films and fibers by solution casting method and electrospinning owing to improved film-forming property. The films showed good transparency and the average diameters of the fibers were about 1 μm. The morphology of the resulting nanocomposites obtained from Si O2 covalently immobilized supported nickel(II) catalyst revealed that the nano-particles were dispersed uniformly in polymers and wrapped by polymers to squeeze out of spherical particles, leading to the enhanced mechanical properties.