Copolymerization of tetracyclododecene or norbornene with styrene in the presence of Ni(II) complex/MAO catalytic system: First example for transition metal catalyzed copolymerization of tetracyclododecene with styrene

The first example for transition metal catalyzed copolymerization of tetracyclododecene (TD) with styrene as well as of norbornene (NB) with styrene was achieved by the use of nickel(II) complex in the presence of MAO. High cyclic olefin contents of these copolymers were showed by ¹H NMR measurements. Their GPC curves are all unimodal and M_w/M_n ratio of both homo‐ and copolymer samples are rather narrow value. These results show that these homo‐ and copolymerization take place at a single active site. The cyclic olefin content in these copolymers could be changed by changing the comonomer feed ratio. TD/styrene copolymers showed higher T_g value than that for NB/styrene copolymers and the T_g value were increases with an increase of TD content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Vinyl polymerization of norbornene with dinuclear diimine nickel dichloride/MAO

Vinyl‐addition polymerization of norbornene was accomplished by two novel dinuclear diimine nickel dichloride complexes in combination with methylaluminoxane (MAO). The activities were moderate. The catalyst structure, Al/Ni molar ratio, solvents, and polymerization temperature all affected the catalytic activities. The obtained polynorbornenes were characterized by ¹H‐NMR, ¹³C‐NMR, FTIR, DSC, WAXD, and intrinsic viscosity measurements. The vinyl‐addition polymers were amorphous but with a short‐range order and high packing density. The polynorbornenes showed glass transition temperatures (T_g) above 240°C and decomposed above 400°C. The catalyst structure and polymerization conditions have effects on the molecular weight and the microstructure of the polymers. The nickel complex with bulkier substituents in the ligand produced polynorbornene with a higher packing density and higher regularity and, therefore, with higher T_g. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3273–3278, 2003     

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

To synthesis ethylene (E) and norbornene (NB) copolymer with high glass transition temperature and transparency, three metallocene catalysts with different symmetric structure were evaluated, respectively. The catalyst activity, NB fraction in copolymer and the transparency of copolymers produced under various conditions were investigated. It has been found that C₂ symmetric catalyst such as rac‐[En(Ind)₂]ZrCl₂ was the best choice to produce copolymer with high NB fraction while keeping high catalyst activity. Furthermore, the effects of reaction conditions on activity of rac‐[En(Ind)₂]ZrCl₂ and the resultant copolymer structure have also been thoroughly studied. The results indicate that increasing the NB/E ratio is the effective way to increase NB content of copolymer when NB/E ratio is less than 20. However, when NB/E ratio is over 20, further increase in NB/E ratio will lead to significant lower catalyst activity and very limited increase in NB content of copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Copolymerization of ethylene and 1-octadecene with the Cp2ZrCl2/MAO and Cp2HfCl2/MAO catalyst systems

Summary The comparison of the copolymers obtained with the Cp₂ZrCl₂/MAO and Cp₂HfCl₂/MAO catalyst systems showed that the catalyst having hafnocene was much more reactive towards 1-octadecene than zirconocene. The comonomer concentration had to be three times higher in the zirconocene copolymerization than in the hafnocene copolymerization when the level of 6 mol-% was reached. Although the hafnocene catalyst was more reactive towards 1-octadecene, the molecular weights were higher than in the copolymers obtained with the zirconocene catalyst.The total activity of the zirconocene was 10 times higher than with the hafnocene catalyst. With the zirconocene catalyst the activity towards ethylene was constantly increasing by increasing the comonomer concentration but stayed nearly constant with the hafnocene catalyst. It seemed that there is no rate enhancement effect upon comonomer addition with the hafnocene catalyst.     

Thermal and dynamic mechanical behavior of ethylene/norbornene copolymers with medium norbornene contents

A range of ethylene/norbornene copolymers were synthesized using the commercially available rac‐Et(Ind)₂ZrCl₂ metallocene catalyst. A large window of norbornene contents, between 30 and 55 mol % was used to facilitate the interpretation of the results. The polymers were characterized by means of wide‐angle X‐ray scattering, differential scanning calorimetry, and dynamic mechanical thermal analysis. The X‐ray diffractograms showed two amorphous halos, the low‐angle one increasing in the intensity with norbornene content. Calorimetric and dynamic mechanical results led to a linear relation between the glass transition temperature and the norbornene content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2159–2165, 2001     

Highly effective catalysts for the addition polymerization of norbornene: zerovalent-nickel complex/H2O/BF3·OEt2

A series of nickel(0)/BF₃·OEt₂ catalyst systems have been tested in the addition polymerization of norbornene. Experimental evidence for Ni(II) hydride formation as a result of interaction between Ni(PPh₃)₄ and BF₃·OEt₂ in the presence of controlled amounts of H₂O was obtained.     

乙炔氢氯化制备氯乙烯的非汞催化技术研究

介绍了非汞催化乙炔氢氯化制备氯乙烯的研究状况、催化剂性能、反应技术等,并指出了今后非汞催化乙炔氢氯化制备氯乙烯的研究重点和研究方向。     

Novel bis(acetylacetonate)palladium/boron trifluoride etherate catalyst system for the polymerization of norbornene

The boron trifluoride etherate, BF₃OEt₂, was used as an activator towards bis(acetylacetonate)palladium precursor in the polymerization of norbornene. The catalyst system Pd(Acac)₂/BF₃OEt₂ was highly active in the polymerization of norbornene. Catalytic activity up to 20,220 kg/(mol Pd · h) and intrinsic viscosities up to 2.64 dL/g were observed, respectively. Catalytic activity, polymer yield and polymer molecular weight could be controlled by varying the reaction parameters. The molar mass distribution indicates a single-site, highly homogeneous character of the active catalyst species. NMR spectroscopy study of the polymer showed exclusively 2,7-enchained repeating units of polymer backbone.     

Synthesis and utilization of mesoporous alumina as a supporting material of Ce-promoted Ni-based catalysts in the methane reforming process

Due to the large applications of hydrogen as a feedstock of chemical industries and as an energy carrier, its production on large scales with low costs has attracted researchers. Steam reforming of methane (SRM) is the most common process for producing H₂-rich syngas over Ni/Al₂O₃ catalysts, which suffer from coke deposition and Ni particles agglomeration. For overcoming these issues, we have synthesized mesoporous alumina (MA) as a supporting material of Ni particles, structure, and activity, which were compared with the bulk alumina (BA) supported catalysts in the SRM process for the first time. Besides, cerium as an appropriate promoter for lowering deposited coke was added to all prepared catalysts. The reaction temperature (600–700°C), Ni loading (10–25 wt.%), and Ce loading (1–5 wt.%) were the parameters that were optimized for maximizing H₂ yield and CH₄ conversion. Prepared samples were characterized by various techniques before and/or after reaction. The results of TEM and XRD depicted the formation of nanocrystalline and mesoporous structure for Ni-MA catalysts compare to Ni-BA samples. The observations indicated that 20Ni-3Ce/MA had the highest catalytic performance, achieving a CH₄ conversion of 91.0% and H₂ yield of 92.8% at 700°C.     

Copolymerization of ethylene/α‐olefins over (2‐MeInd)2ZrCl2/MAO and (2‐BzInd)2ZrCl2/MAO systems

Ethylene homopolymerization and ethylene/α‐olefin copolymerization were carried out using unbridged and 2‐alkyl substituted bis(indenyl)zirconium dichloride complexes such as (2‐MeInd)₂ZrCl₂ and (2‐BzInd)₂ZrCl₂. Various concentrations of 1‐hexene, 1‐dodecene, and 1‐octadecene were used in order to find the effect of chain length of α‐olefins on the copolymerization behavior. In ethylene homopolymerization, catalytic activity increased at higher polymerization temperature, and (2‐MeInd)₂ZrCl₂ showed higher activity than (2‐BzInd)₂ZrCl₂. The increase of catalytic activity with addition of comonomer (the synergistic effect) was not observed except in the case of ethylene/1‐hexene copolymerization at 40°C. The monomer reactivity ratios of ethylene increased with the decrease of polymerization temperature, while those of α‐olefin showed the reverse trend. The two catalysts showed similar copolymerization reactivity ratios. (2‐MeInd)₂ZrCl₂ produced the copolymer with higher M_w than (2‐BzInd)₂ZrCl₂. The melting temperature and the crystallinity decreased drastically with the increase of the α‐olefin content but T_m as a function of weight fraction of the α‐olefins showed similar decreasing behavior. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 928–937, 2000     

The effect of TIBA on metallocene/MAO catalyzed synthesis of propylene oxazoline copolymers and their use in reactive blending

Oxazoline‐functionalized polypropylenes were synthesized by using the rac‐Et[1‐Ind]₂ZrCl₂/MAO catalyst system. The used comonomers were 2‐(9‐decene‐1‐yl)‐1,3‐oxazoline (R‐Ox1), 2‐(9‐decene‐1‐yl)‐4,4‐dimethyl‐1,3‐oxazoline (R‐Ox2), and 2‐(4‐(10‐undecene‐1‐oxy)phenyl)‐1,3‐oxazoline (R‐Ox3). The oxazolines reduce the catalyst activity in the order R‐Ox3 > R‐Ox1 > R‐Ox2. By the addition of triisobutylaluminum (TIBA), the catalyst poisoning is reduced and is most pronounced in the R‐Ox1‐ and R‐Ox2‐containing systems. The oxazoline‐containing copolymers were melt blended with carboxylic acid end‐functionalized polystyrene (PS‐COOH) at 200°C. Strong changes in the morphology of the reactive blends compared to the nonreactive blends, especially the cocontinuous morphology in a poly(propylene‐co‐R‐Ox3)/PS‐COOH blend, indicate the usefulness of the modified copolymers in the reactive blending processes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2174–2181, 2002     

Microstructural evolution and mechanical property of a SiCf/SiC composite/Ni-based superalloy joint brazed with an Au-Cu-Ti filler

A new Au-Cu-Ti filler featuring superior mechanical properties was developed to enable the brazing of a SiC_f/SiC composite (CMCs) to itself and a Ni-based superalloy (GH536). The progression of the interfacial reactions was studied using a combination of thermodynamic calculations and experimental observations. It was found that the interfacial reaction was Ti-dominant at the early brazing stage and then gradually transformed to Ni-dominant with the continuous dissolution of the GH536 substrate. Thus, the typical microstructure of GH536/Ti-Ni-Cr-Fe+(Au, Cu)ss + MoNiSi/Ni-Cr-Fe-Si-C (Ni₂Si + Fe₂Si + Cr₃C₂)+(Au, Cu)ss/Ni₂Si + TiC+(Au, Cu)ss/ Cr₃C₂+Ni₂Si + TiC + Fe₂Si/CMCs could be described by the following three stages: a Ti-dominated stage, full interdiffusion stage, and Ni-dominated stage. A maximum shear strength of 36 MPa was obtained for joints brazed at 1050℃ for 10 min, at which a failure occurred at the CMCs/brazing seam interface. The control of the interfacial reactions and the stress relaxation of (Au, Cu)ss contributed to the superior mechanical performance of the composite.     

Effects of tris(pentafluorophenyl)borane on the activation of zerovalent-nickel complex in the addition polymerization of norbornene

The effects of B(C₆F₅)₃ on the activation of the Ni(0) and Ni(II) complexes were studied in the polymerization of norbornene. The Ni(0) complex, such as bis(1,5-cyclooctadiene)nickel (Ni(COD)₂ (1), biacetylbis(2,6-diisopropylphenylimmine)(1,3-butadiene)nickel (2), or tetrakis(triphenylphosphine)nickel (5), in combination with B(C₆F₅)₃, was determined to have high activity in the polymerization of norbornene. On the other hand, the Ni(II) complex with B(C₆F₅)₃ did not provide any activity at all under analogous conditions regardless of the structure of the Ni(II) complex. The use of other borane compounds, such as B(C₆H₅)₃, BEt₃, and BF₃ etherate, with Ni(COD)₂ (1) in place of B(C₆F₅)₃ clearly showed the main functions of B(C₆F₅)₃. The high Lewis acidity of B(C₆F₅)₃ enabled it to activate catalytic complexes, thus inducing polymerization. The study of the ¹H, ¹³C, and ¹⁹F NMR spectra of the polynorbornene produced with Ni(COD)₂ (1) and B(C₆F₅)₃, in the presence or absence of ethylene, showed that the initiation of addition polymerization occurred through the insertion of the exo face of the norbornene into the Ni-C bond of the C₆F₅ ligand. A new polymerization mechanism was proposed in norbornene polymerization, wherein the active complex formed from Ni(COD)₂ (1) and B(C₆F₅)₃ acts as a catalyst.     

Polymerization of norbornene using bis(β‐ketoamino)nickel(II)/MAO catalytic systems

The polymerizations of norbornene were investigated using a series of bis(β‐ketoamino)nickel(II) complexes( 1–6 ) in combination with methylaluminoxane (MAO) in toluene solution. The effects of catalyst structure, Al/Ni molar ratio, reaction temperature, and reaction time on catalytic activity and molecular weight of the polynorbornene were examined in detail. The electronic effect of the substituent around the imino group in the ligand is stronger than the steric bulk one on the polymerization activities, and the activities are in the order of 1 > 2 > 4 > 5 > 6 > 3 . The obtained polynorbornenes were characterized by means of ¹H‐NMR, ¹³C‐NMR, FTIR, TG, and WAXD techniques. The analyses results of polymers' structures and properties indicate that the polymerization reaction of norbornene runs in vinyl‐addition polymerization mode. The obtained polynorbornene was confirmed to be vinyl‐type and atactic polymers and showed good thermostability (T_dec > 458°C) and were noncrystalline but had short‐range order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4172–4180, 2006     

Aliphatic ketones/water/alcohol as a new photoinitiating system for the photografting of methacrylic acid onto high-density polyethylene

The photografting of methacrylic acid (MAA) onto high-density polyethylene (HDPE) initiated by aliphatic ketones, butanone, pentanone, heptanone, etc. has been reported. When these ketones were used alone or just with ethanol, grafting did not occur. However, grafting took place when a proper butanone/water/ethanol mixed solvent was used. When the volume ratio of butanone was fixed, the grafting of MAA onto HDPE became easier with an increase in the volume ratio of water. The grafting of MAA onto HDPE became easier and faster with a decrease in the volume ratio of butanone. The grafting rate increased with the increase of monomer concentration. The nature of the alcohol also affected the self-initiation by aliphatic ketone; ethanol was found to be better than methanol. Possibly, hydrogen bond formed between aliphatic ketone and water increases the energy and lifetime of the excited state of the ketone, permitting it to act as a grafting and polymerisation initiator. FTIR characterization of the grafted samples proves the successful grafting of MAA onto HDPE. The water absorbency of the grafted samples increased almost linearly with the extent of grafting both in air and in water. The PE films grafted in the butanone/water/ethanol solvent adsorbed approximately 30-40 mass% water per p-MAA.     

Copolymerization of norbornene with ethylene: A high-resolution liquid NMR, DSC and solid state NMR study

In this paper, we report the monomer reactivity on the copolymerization of norbornene and ethylene. The reactivity ratios for ethylene (M₁) and norbornene (M₂) are 18.5 and 0.035, respectively. Different copolymerization conditions can produce COC with different microstructures. A ¹³C NMR shift assignment in pentad sequences in copolymers has been obtained. More isolated polynorbornene or a micro-block length can be obtained using a low Zr/Al catalyst/co-catalyst ratio and at a lower NB/ethylene feed ratio. The T_1p ^C decay curve shows two component decays in all resonance peaks. These two component decays come from different norbornene microstructures, while the block and alternative have similar T_1p ^C values.     

Bound-state Ni species — a superior form in Ni-based catalyst for CH4/CO2 reforming

The effects of nickel loading, calcination temperature, support, and basic additives on Ni-based catalyst structure and reactivity for CH₄ reforming with CO₂ were investigated. The results show that the structure of the nickel active phase strongly depends on the interactions of the metal and the support, which are related to the support properties, the additives and the preparation conditions. “Free” Ni species can be formed when the interaction is weak and their mobility makes them easily deactivated by coking and sintering. The effect of strong metal-support interaction (SMSI effect) is different for various supports. The formation of solid solution of Ni–Mg–O₂ and the blocking of TiO_x by the partially reduced TiO₂ can both decrease the availability of Ni active sites in Ni/MgO and Ni/TiO₂. The spinel NiAl₂O₄ formed in Ni/γ-Al₂O₃ might be responsible for its high activity and resistance to coking and sintering because it can produce a highly dispersed active phase and a large active surface area as bound-state Ni species when the catalyst is prepared at high calcined temperatures or with low nickel loading. The addition of La₂O₃ or MgO as alumina modifiers can also be beneficial for the performance of the Ni/γ-Al₂O₃ catalyst.     

LDPE接枝MMA及与高岭土共混

本文研究在水介质中，以过氧化苯甲酰为引发剂，ＬＤＰＥ与ＭＭＡ的技枝共聚反应，并用它制备了与高岭土的共混物。探讨了单体用量，反应时间对接枝度的影响规律，用红外光谱验证了接枝物的存在，还探讨了接枝度及高岭土填充量对拉伸强度的影响。结果表明在接枝度为１５％，高岭土填充量为１０％时，体系具有较高的拉伸强度。     

Preparation and characterization of core‐shell polystyrene/polyaniline/Pd composites and their catalytic properties for the reduction of 4‐nitrophenol

Herein, polystyrene/polyaniline/Pd (PS/PANI/Pd) core‐shell composite catalysts were prepared by a facile swelling‐diffusion‐interfacial polymerization method. PS microparticles were firstly prepared by dispersion polymerization and were swollen by aniline monomer without any surface modification. H₂PdCl₄ acid was used as palladium precursor. The was adsorbed on the surface of aniline‐swollen PS microparticles because of the electrostatic attraction between and anilinium positive ions protonated by H⁺, which was diffused from the aniline‐swollen PS microparticles. Then HCl solution was added to control the diffusion rate of anilinium positive ions and ammonium persulfate (APS) was used to polymerize the anilinium ions to get PANI shell. Due to the redox activity between PANI and Pd ions, Pd nanoparticles can be in situ formed on the surfaces of PS. Therefore, the core‐shell PS/PANI/Pd composite catalysts were obtained. The morphology and structure of the obtained composites was characterized by TEM, FT‐IR and EDX. Results showed that the products presented excellent catalytic properties for the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) in the presence of NaBH₄ by virtue of the interaction between Pd nanoparticles and conducive PANI shell. The catalytic reaction obeyed the pseudo‐first‐order reaction equations and the reaction rate constants were also calculated in this article. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44812.     

Butadiene polymerization in the presence of VOCl3–dialkylmagnesium catalytic system

The butadiene polymerization in toluene at 25°C on VOCl₃? (n‐C₄H₉)Mg(iso‐C₈H₁₇) catalytic system was investigated. The kinetic parameters of polymerization and molecular characteristics of polybutadiene were determined. It was shown that substitution of traditional organoaluminum cocatalysts in trans‐regulating vanadium systems does not have an effect on its stereospecificity, but significantly influences on the active centers reaction ability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 596–600, 2003