Binuclear complexes have attracted extensive attention in fields such as catalysis because of their likely bimetallic synergistic effect;however,the mechanism and factors influencing this synergism remain unclear.In t...Binuclear complexes have attracted extensive attention in fields such as catalysis because of their likely bimetallic synergistic effect;however,the mechanism and factors influencing this synergism remain unclear.In this work,six bis-β-ketoimine binuclear titanium complexes4a-4f containing different alkylthio sidearms and configurations were synthesized and characterized by nuclear magnetic resonance hydrogen spectrum(~1H-NMR),nuclear magnetic resonance carbon spectrum(^(13)C-NMR),Fourier transform infrared spectrum(FTIR),and elemental analysis.The intermetallic distances of isomeric complexes 4a,4d,4e and 4f determined through density functional theory(DFT)optimization were in the order 4a<4d<4e<4f and were found to significantly influence the catalytic performance for ethylene(co)polymerization.These complexes could efficiently catalyze ethylene polymerization and ethylene/1-hexene or ethylene/1-octene copolymerization with high activity to produce highmolecular-weight ethylene homo-and co-polymers.Among the three binuclear titanium complexes 4a-4c with similar structures but different lengths of alkylthio sidearms,complex 4a,which contained the shortest methylthio sidearm,exhibited the highest activity for ethylene polymerization and copolymerization with 1-hexene or 1-octene.Additionally,for ethylene/1-hexene or ethylene/1-octene copolymerization,it showed the highest comonomer incorporation compared with propylthio(4b)and octylthio(4c)derivatives because of the smaller steric hindrance of the methyl group in 4a and the more open coordination space for vinyl monomers.Furthermore,among the isomeric complexes 4a,4d,4e and4f,complex 4a with the shortest bimetallic distance also exhibited the highest activity towards ethylene(co)polymerization,and the highest 1-hexene or 1-octene incorporation in comparison with its regioisomeric counterparts 4d,4e and p-phenyl-bridged analog 4f,owing to a more appropriate bimetallic distance that is conducive to a synergistic effect.展开更多
A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were ...A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were investigated. The activity with a Al/Ti molar ratio of 500 exhibited a maximum of 2.8×10~5 g/(mol.h) at 30℃. The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2/MAO system at different Al/Ti molar ratios were studied. For the QCpTiMeCl/MAO system and the CpTiMe_2Cl/MAO system, binding energies of the examined intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorinebridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCpTiMeCl/MAO system, olefin-separated ion pair (OSIP) mechanism is much favorable than ion-pair dissociation (IPD) mechanism. The experimental result on the CpTiMe_2Cl/MAO system showed lower activity for ethylene polymerization than that on the QCpTiMeCl/MAO system, which revealed that the CpTiMe_2Cl/MAO system is unfavorable to form active species with ethylene.展开更多
The condensation of acetylacetone （CH3COCH2COCH3） with benzdine （H2N-C6H4-C6H4-NH2） yielded diimine ligand 1 [HOC（Me）C（H）（Me）C=N（p-C6H4）（C6H4-p）N= C（Me）C（H）C（Me）OH）], which was converted into sodi...The condensation of acetylacetone （CH3COCH2COCH3） with benzdine （H2N-C6H4-C6H4-NH2） yielded diimine ligand 1 [HOC（Me）C（H）（Me）C=N（p-C6H4）（C6H4-p）N= C（Me）C（H）C（Me）OH）], which was converted into sodium salts. And then the sodium salts reacted with monosalicylaldiminato titanium complex 2{[3,5-di-But′2-（O）C6H2CHN（PH）]TiCl3（THF）} in dried dichloromethane to give a new benzdine-bridged binuclear complex 3{[3,5-di-Bu′-2-（O）C6H2CHN（PH）]2 [OC（Me）C（H）（Me）C=N（p-C6H4）-（C6H4-p）N=C（Me）C（H） C（Me）]Ti2Cl4}. The complex 3 was characterized by ^1HNMR and elemental analysis. In the presence of MAO（methylaluminoxane）, the complex 3 in toluene was effective to catalyze polymerization, affording moderately high catalytic activity 1.93 × 10^5 g PE/（mol.Ti.h）]and high molecular weight polyethylene [5.63× 10^5 g/moll. The high temperature gel permeation chromatography （GPC） curve of polyethylene obtained revealed a single peak, but the molecular weight distribution （MWD = 3.21） is obviously broader than that of the similar mononuclear titanium complex. The melting points of the obtained polyethylene reaches 138 ℃, indicating that the polyethylene is of high crystallinity.展开更多
Titanium complex greases were prepared by using naphthenic mineral oil and polydimethylsiloxane as the mixed base oil. The effect of polydimethylsiloxane molecular weight and polydimethylsiloxane content in mixed base...Titanium complex greases were prepared by using naphthenic mineral oil and polydimethylsiloxane as the mixed base oil. The effect of polydimethylsiloxane molecular weight and polydimethylsiloxane content in mixed base oil on the physicochemical and tribological properties of titanium complex greases was investigated.As compared to the sole mineral oil-based titanium complex grease, the use of polydimethylsiloxane(H201-350)as a co-base oil increased the dropping point from 310 to 329℃, decreased the oil separation from 3.7% to 2.3%,reduced the corrosion extent, and obviously improved the tribological properties. When the mixed oil-based titanium complex grease was used as a lubricant, lubricating films of polydimethylsiloxane were probably formed on the surfaces of friction pairs, giving good lubricating property.展开更多
The titanium trichloride complex 1-TiCl_(3)((C_(6)H_(5)-NH-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-O)TiCl_(3))with the phenoxy-imine-amine(O,N,N)ligand containing an N-H group was synthesized and used as a pre-catalyst f...The titanium trichloride complex 1-TiCl_(3)((C_(6)H_(5)-NH-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-O)TiCl_(3))with the phenoxy-imine-amine(O,N,N)ligand containing an N-H group was synthesized and used as a pre-catalyst for olefin polymerization.Its structure,activation mechanism,and catalytic properties were compared with those of the titanium dichloride analogue 1-TiCl_(2)((C_(6)H_(5)-N-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-^(t)Bu-2-O)TiCl_(2))bearing the same ligand but devoid of N-H groups.Under optimum conditions,1-TiCl_(3) showed unprecedented activity of up to 5.10×10^(8) g(PE)mol^(-1)(Ti)h^(-1) leading to polyethylenes with unimodal or bimodal distributions(2.9≤D(dispersity)≤6.1),while 1-TiCl_(2) afforded polyethylene with narrow and unimodal distribution(D=1.8).In situ NMR and single-crystal X-ray diffraction experiments revealed that the activation of 1-TiCl_(3) with 5 equiv.of d-MAO(dried methylaluminoxane)was slow,probably resulting in the production of polyethylene with a bimodal/broad distribution.When pre-activated with 200 equiv.of d-MAO,1-TiCl_(3) and 1-TiCl_(2) showed very similar catalytic properties,including their activity and the molecular weights and mass distributions of the polymers formed,which is fully consistent with the results of in situ NMR studies.For comparison,a methyl group was introduced on the amine-N and the corresponding ligand 2-L(C_(6)H_(5)-NMe-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-OH)afforded 2-TiCl_(3)((C_(6)H_(5)-NMe-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-O)TiCl_(3)).Its catalytic properties were similar whether pre-activation with excess d-MAO was performed or not,further establishing the strong influence of the amine-N substituent on catalysis.Remarkably,2-TiCl_(3) exhibited high activity(8.10×10^(7) g(polymer)mol^(-1)(Ti)h^(-1))in ethylene/1-octene copolymerization and produced a poly(ethylene-co-1-octene)copolymer with an ultra-high-molecular-weight and narrow distribution(Mw=362×10^(4) g mol^(-1),D=1.4).展开更多
Three kinds of bimetallic Schiff base titanium complexes with different substituent moieties on organic ligands were synthesized.Ring-opening polymerizations （ROP） of lactides were carried out by using these titaniu...Three kinds of bimetallic Schiff base titanium complexes with different substituent moieties on organic ligands were synthesized.Ring-opening polymerizations （ROP） of lactides were carried out by using these titanium complexes as catalysts.The polymerization data and kinetic studies showed that complex 1a had the highest activity and complex 2a had the lowest activity for ROP of lactides.Moreover,all these three newly synthesized bimetallic titanium complexes showed higher polymerization activity and better molecular weight control than their monometallic counterparts reported in our previous work.展开更多
An unexpected carbon-oxygen bond cleavage of THF (THF = tetrahydrofuran) promoted by guanidinate titanium complex was described. Guanidinate lithium [Pr2iNC(NCy)2]Li (Cy = cyclohexyl) formed in situ reacted with TiCl4...An unexpected carbon-oxygen bond cleavage of THF (THF = tetrahydrofuran) promoted by guanidinate titanium complex was described. Guanidinate lithium [Pr2iNC(NCy)2]Li (Cy = cyclohexyl) formed in situ reacted with TiCl4(THF)2 in a 2:1 molar ratio to produce the gua- nidinate titanium chloride [Pr2iNC(NCy)2]2TiCl2 (1) in good yield. The reaction of [Pr2iNC(NCy)2]2TiCl2 with lithium diisopropylamide in THF afforded an unexpected [Pr2iNC(NCy)2]2Ti(OBun)2 (2), which was formed by the cleavage of carbon-oxygen bond of THF. Complexes 1 and 2 were fully characterized by elemental analysis, NMR and IR spectroscopies, and X-ray crystal structure determination for complex 2.展开更多
The reaction of C3H6(N=CH-Ar-OH)2 (Ar = 5-tert-butyl-C6H3 (2a), 3-tert-butyl-C6H3 (2b), 3-methyl-C6H3 (2c)) with 2 equiv. of BuLi followed by 1 equiv TiCl4 yields the dichloride complexes [C3H6(N=CH-Ar-O)2]TiCl2[Ar = ...The reaction of C3H6(N=CH-Ar-OH)2 (Ar = 5-tert-butyl-C6H3 (2a), 3-tert-butyl-C6H3 (2b), 3-methyl-C6H3 (2c)) with 2 equiv. of BuLi followed by 1 equiv TiCl4 yields the dichloride complexes [C3H6(N=CH-Ar-O)2]TiCl2[Ar = 5-tert-butyl-C6H3 (3a), 3-tert-butyl-C6H3 (3b), 3-methyl-C6H3 (3c)]. The structure of compound 3a has been confirmed by X-ray crystallographic analysis. These Ti (IV) dichloride complexes are active catalysts for the polymerization of eth- ylene with methylaluminoxane (MAO) as a cocatalyst. Ac- tivities up to 4.14×105 g (mol Ti h)?1 were obtained in dried toluene. And the molecular weights of polyethylene are in the range 1.53×104—16.4×104. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by changing the ligand structure and variation of reac- tion parameters such as Al-Ti ratio and polymerization reac- tion temperature.展开更多
AIM: To evaluate the effectiveness and safety of complex orbital fracture reconstruction with titanium implants. METHODS: A retrospective review of 46 patients treated with complex orbital fractures reconstruction usi...AIM: To evaluate the effectiveness and safety of complex orbital fracture reconstruction with titanium implants. METHODS: A retrospective review of 46 patients treated with complex orbital fractures reconstruction using titanium implants from January 2005 to December 2008 was conducted. The following data were recorded: age, gender, mechanism of injury, preoperative and postoperative orbital CT, visual acuity, diplopia, ocular motility and Hertel exophthalmometer. RESULTS: The most common cause was motor vehicle accident (47.8%), followed by industrial injury (30.4%). All patients had improved appearance after operation and CT scan at one week after operation showed the fracture defects of orbit and neighboring areas had been reconstructed. Forty-six cases had various degrees of enophthalmos before operation. Among them, 32 cases were completely corrected, 11 cases improved obviously and 3 cases had no improvement after operation. Thirty-six patients with visual acuity =20/60 revealed diplopia of various degrees, including 26 patients had diplopia in right ahead and/or reading positions. At the sixth month after operation, diplopia disappeared in five patients, 7 patients still had diplopia in right ahead and/or reading positions, 14 patients had diplopia in positions rather than right ahead and reading positions (<20 degrees) and ten patients had diplopia only at peripheral gazing (>20 degrees). All patients had various degrees of ocular motility disorders before operation. At the sixth month after operation, eyeball movement disorder disappeared in 9 patients, 31 patients showed improvement and 6 patients had no improvement. Complications of implant infection, rejection and displacement were not reported after operation. CONCLUSION: The application of titanium implants in the repair of complex orbital fractures greatly improves the appearance and functional results, which is a favorable material for plastic surgery of complex orbital fracture.展开更多
The aim of this study was to investigate the inhibitory effect of heparin/fibronectin （Hep/Fn） complexes on neointimal hyperplasia following endovascular intervention. Hep/Fn complexes were immobilized onto titanium...The aim of this study was to investigate the inhibitory effect of heparin/fibronectin （Hep/Fn） complexes on neointimal hyperplasia following endovascular intervention. Hep/Fn complexes were immobilized onto titanium （Ti） surfaces, with subsequent X-ray photoelectron spectroscopy （XPS）, Toluidine Blue 0 （TBO） and immunohistochemistry methods were used to characterize surface properties. Smooth muscle cell （SMC） cultures were used to evaluate the effect of Hep/Fn complexes on SMC proliferation. Results showed that Hep/Fn complexes successfully immobilized onto Ti surfaces and resulted in an inhibition of SMC proliferation. This study suggests that Hep/Fn surface-immobilized biomaterials develop as a new generation of biomaterials to prevent neointimal hyperplasia, particularly for use in cardiovascular implants.展开更多
A new complexes of Cp2Ti[S2P(OR)2]2 (where R = Et, Pr-n, Pr-i, Bu-i and Ph) and Cp2Ti[S2POGO]2 (where G = -CH2CMe2CH2-, -CH2CEt2CH2- and -CMe2CMe2-) were prepared by the dropwise addition of the appropriate O,O’-dial...A new complexes of Cp2Ti[S2P(OR)2]2 (where R = Et, Pr-n, Pr-i, Bu-i and Ph) and Cp2Ti[S2POGO]2 (where G = -CH2CMe2CH2-, -CH2CEt2CH2- and -CMe2CMe2-) were prepared by the dropwise addition of the appropriate O,O’-dialkyl or -alkylenedithiophosphoric acid to biscyclopentadienyl titanium dichloride in 1:2 molar ratio and refluxed in benzene solution. These novel deep red colored complexes were characterized by elemental analyses, molecular weight measurements and spectroscopic techniques (IR., NMR 1H, 13C and 31P NMR). These titanium (IV) dithio complexes have also been screened for their antibacterial activities.展开更多
-The i. r. spectra of Na4 [UO2 (CO3)3], Na [UO2 (OH)3] and the surface species of uranium on HTO underthe condition of flowing natural seawater and concentrated seawater (NaCl-NaHCO3-U) were recorded, with the bands o...-The i. r. spectra of Na4 [UO2 (CO3)3], Na [UO2 (OH)3] and the surface species of uranium on HTO underthe condition of flowing natural seawater and concentrated seawater (NaCl-NaHCO3-U) were recorded, with the bands of urany! of surface species obtained and the finding that iigands of surface species besides HTO are mainly water and OH, and there are some CO32- groups under the condition of natural seawater. Some relations between the complex properties and the j. r. spectroscopic characters for uranyl complexes were studied, and the transferred change quantity of surface complex was calculated.Structure models for surface species of adsorption are herein presented and the mechanism for uranium adsorption is deduced.展开更多
Three mono-cyclopentadienyl metal complexes, [C_6H_4O_2]CpTiCl (Ⅰ),[C_(12)H_8O_2]CpTiCl (Ⅱ), and [C_(20)H_(12)O_2] CpTiCl (Ⅲ), were prepared via the reactions ofcyclopentadienyl titanium trichloride with catechol, ...Three mono-cyclopentadienyl metal complexes, [C_6H_4O_2]CpTiCl (Ⅰ),[C_(12)H_8O_2]CpTiCl (Ⅱ), and [C_(20)H_(12)O_2] CpTiCl (Ⅲ), were prepared via the reactions ofcyclopentadienyl titanium trichloride with catechol, 2,2i-bisphenol, and 2,2'-bisnaphthol,respectively. In the presence of a moderate amount of methylaluminoxane (MAO), the complexesexhibited catalytic activities for ethylene polymerization. Complex Ⅰ showed the highest activityat Al/Ti molar ratio of 500 at the temperature of 30℃. With increasing of polymerizationtemperature, catalytic activities and molecular weight of the obtained polyethylene tended todecrease, and molecular weight distribution of polyethylene became narrower. With the molecularsimulation method, the charges on titanium atoms of complexes Ⅰ, Ⅱ, and Ⅲ, and the bond anglesformed by Ti and bisphenoxy ligands were calculated. It was concluded that the smaller the netcharge on Ti and the smaller the angle of O1―Ti―O2, the higher the activity of the complex.展开更多
The activation of dinitrogen by a titanium hydride complex with two bridging hydrides located between metal Ti and Li was investigated.Exposing cyclic bis-alkylidene titanium complex 1 to H2 in THF solution yielded ti...The activation of dinitrogen by a titanium hydride complex with two bridging hydrides located between metal Ti and Li was investigated.Exposing cyclic bis-alkylidene titanium complex 1 to H2 in THF solution yielded titanium hydride 2,{[(2-butene)(C_(5)H_(5))Ti](μ-H)_(2)Li(THF)_(3)}.2 aggregated into dimer 3 in hexane,accompanied by the release of LiH.展开更多
The purpose of this study was to prepare nano-titanium tannate complex (TTC) and to investigate its adsorption capacity for removal of cationic dyes such as crystal violet (CV) dye. The morphology and the main element...The purpose of this study was to prepare nano-titanium tannate complex (TTC) and to investigate its adsorption capacity for removal of cationic dyes such as crystal violet (CV) dye. The morphology and the main elements of TTC adsorbent were characterized by scanning electron microscopy (SEM-EDS), while its crystal structure was characterized by X-ray diffraction (XRD). Also, FT-IR spectroscopy study structural aspects of TTC. A “cotton-ball”-like and porous surface structure of titanium tannate complex (TTC) with nanoparticle size of 16.18 nm show high capability for absorbing crystal violet dye. The effect of several parameters such as contact time, initial concentrations of CV, solution pH and the amount of TTC was investigated. Three different kinetic equations such as pseudo-first order, pseudo-second order and intraparticle diffusion were used to study the order and the mechanism of the adsorption process. The adsorption of CV dye followed pseudo- second order equation. Moreover, equilibrium data were tested with four adsorption isotherm models namely, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R). Langmuir was the best fit for the data with maximum capacity as 58.8 mg/g. The results of Separation factor, Surface coverage and standard free energy (ΔG°) indicated that adsorption of CV onto TTC was favorable with fast rate and spontaneous physical adsorption process.展开更多
基金financially supported by the National Natural Science Foundation of China(No.21172269)the Fundamental Research Funds for the Central Universities,SouthCentral Minzu University(No.CZH24005)。
文摘Binuclear complexes have attracted extensive attention in fields such as catalysis because of their likely bimetallic synergistic effect;however,the mechanism and factors influencing this synergism remain unclear.In this work,six bis-β-ketoimine binuclear titanium complexes4a-4f containing different alkylthio sidearms and configurations were synthesized and characterized by nuclear magnetic resonance hydrogen spectrum(~1H-NMR),nuclear magnetic resonance carbon spectrum(^(13)C-NMR),Fourier transform infrared spectrum(FTIR),and elemental analysis.The intermetallic distances of isomeric complexes 4a,4d,4e and 4f determined through density functional theory(DFT)optimization were in the order 4a<4d<4e<4f and were found to significantly influence the catalytic performance for ethylene(co)polymerization.These complexes could efficiently catalyze ethylene polymerization and ethylene/1-hexene or ethylene/1-octene copolymerization with high activity to produce highmolecular-weight ethylene homo-and co-polymers.Among the three binuclear titanium complexes 4a-4c with similar structures but different lengths of alkylthio sidearms,complex 4a,which contained the shortest methylthio sidearm,exhibited the highest activity for ethylene polymerization and copolymerization with 1-hexene or 1-octene.Additionally,for ethylene/1-hexene or ethylene/1-octene copolymerization,it showed the highest comonomer incorporation compared with propylthio(4b)and octylthio(4c)derivatives because of the smaller steric hindrance of the methyl group in 4a and the more open coordination space for vinyl monomers.Furthermore,among the isomeric complexes 4a,4d,4e and4f,complex 4a with the shortest bimetallic distance also exhibited the highest activity towards ethylene(co)polymerization,and the highest 1-hexene or 1-octene incorporation in comparison with its regioisomeric counterparts 4d,4e and p-phenyl-bridged analog 4f,owing to a more appropriate bimetallic distance that is conducive to a synergistic effect.
基金The work is sub sidized by Special Funds for Major State Basis Research Projects of China(No.G1999064801)
文摘A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were investigated. The activity with a Al/Ti molar ratio of 500 exhibited a maximum of 2.8×10~5 g/(mol.h) at 30℃. The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2/MAO system at different Al/Ti molar ratios were studied. For the QCpTiMeCl/MAO system and the CpTiMe_2Cl/MAO system, binding energies of the examined intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorinebridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCpTiMeCl/MAO system, olefin-separated ion pair (OSIP) mechanism is much favorable than ion-pair dissociation (IPD) mechanism. The experimental result on the CpTiMe_2Cl/MAO system showed lower activity for ethylene polymerization than that on the QCpTiMeCl/MAO system, which revealed that the CpTiMe_2Cl/MAO system is unfavorable to form active species with ethylene.
基金Fund by the National Natural Science Foundation of China (20374043)
文摘The condensation of acetylacetone （CH3COCH2COCH3） with benzdine （H2N-C6H4-C6H4-NH2） yielded diimine ligand 1 [HOC（Me）C（H）（Me）C=N（p-C6H4）（C6H4-p）N= C（Me）C（H）C（Me）OH）], which was converted into sodium salts. And then the sodium salts reacted with monosalicylaldiminato titanium complex 2{[3,5-di-But′2-（O）C6H2CHN（PH）]TiCl3（THF）} in dried dichloromethane to give a new benzdine-bridged binuclear complex 3{[3,5-di-Bu′-2-（O）C6H2CHN（PH）]2 [OC（Me）C（H）（Me）C=N（p-C6H4）-（C6H4-p）N=C（Me）C（H） C（Me）]Ti2Cl4}. The complex 3 was characterized by ^1HNMR and elemental analysis. In the presence of MAO（methylaluminoxane）, the complex 3 in toluene was effective to catalyze polymerization, affording moderately high catalytic activity 1.93 × 10^5 g PE/（mol.Ti.h）]and high molecular weight polyethylene [5.63× 10^5 g/moll. The high temperature gel permeation chromatography （GPC） curve of polyethylene obtained revealed a single peak, but the molecular weight distribution （MWD = 3.21） is obviously broader than that of the similar mononuclear titanium complex. The melting points of the obtained polyethylene reaches 138 ℃, indicating that the polyethylene is of high crystallinity.
基金Supported by the National Natural Science Foundation of China(21506078,21506082)China Postdoctoral Science Foundation(2016M591786,2016M601739)
文摘Titanium complex greases were prepared by using naphthenic mineral oil and polydimethylsiloxane as the mixed base oil. The effect of polydimethylsiloxane molecular weight and polydimethylsiloxane content in mixed base oil on the physicochemical and tribological properties of titanium complex greases was investigated.As compared to the sole mineral oil-based titanium complex grease, the use of polydimethylsiloxane(H201-350)as a co-base oil increased the dropping point from 310 to 329℃, decreased the oil separation from 3.7% to 2.3%,reduced the corrosion extent, and obviously improved the tribological properties. When the mixed oil-based titanium complex grease was used as a lubricant, lubricating films of polydimethylsiloxane were probably formed on the surfaces of friction pairs, giving good lubricating property.
基金the National Natural Science Foundation of China(No.52073152)the Ministry of Education of the People’s Republic of China,the 111 Project(No.D17004)the Department of Science and Technology of Shandong Province(No.2021CXGC010902)is gratefully acknowledged.
文摘The titanium trichloride complex 1-TiCl_(3)((C_(6)H_(5)-NH-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-O)TiCl_(3))with the phenoxy-imine-amine(O,N,N)ligand containing an N-H group was synthesized and used as a pre-catalyst for olefin polymerization.Its structure,activation mechanism,and catalytic properties were compared with those of the titanium dichloride analogue 1-TiCl_(2)((C_(6)H_(5)-N-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-^(t)Bu-2-O)TiCl_(2))bearing the same ligand but devoid of N-H groups.Under optimum conditions,1-TiCl_(3) showed unprecedented activity of up to 5.10×10^(8) g(PE)mol^(-1)(Ti)h^(-1) leading to polyethylenes with unimodal or bimodal distributions(2.9≤D(dispersity)≤6.1),while 1-TiCl_(2) afforded polyethylene with narrow and unimodal distribution(D=1.8).In situ NMR and single-crystal X-ray diffraction experiments revealed that the activation of 1-TiCl_(3) with 5 equiv.of d-MAO(dried methylaluminoxane)was slow,probably resulting in the production of polyethylene with a bimodal/broad distribution.When pre-activated with 200 equiv.of d-MAO,1-TiCl_(3) and 1-TiCl_(2) showed very similar catalytic properties,including their activity and the molecular weights and mass distributions of the polymers formed,which is fully consistent with the results of in situ NMR studies.For comparison,a methyl group was introduced on the amine-N and the corresponding ligand 2-L(C_(6)H_(5)-NMe-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-OH)afforded 2-TiCl_(3)((C_(6)H_(5)-NMe-C_(6)H_(4)-NvCH-C_(6)H_(2)-3,5-tBu-2-O)TiCl_(3)).Its catalytic properties were similar whether pre-activation with excess d-MAO was performed or not,further establishing the strong influence of the amine-N substituent on catalysis.Remarkably,2-TiCl_(3) exhibited high activity(8.10×10^(7) g(polymer)mol^(-1)(Ti)h^(-1))in ethylene/1-octene copolymerization and produced a poly(ethylene-co-1-octene)copolymer with an ultra-high-molecular-weight and narrow distribution(Mw=362×10^(4) g mol^(-1),D=1.4).
文摘Three kinds of bimetallic Schiff base titanium complexes with different substituent moieties on organic ligands were synthesized.Ring-opening polymerizations （ROP） of lactides were carried out by using these titanium complexes as catalysts.The polymerization data and kinetic studies showed that complex 1a had the highest activity and complex 2a had the lowest activity for ROP of lactides.Moreover,all these three newly synthesized bimetallic titanium complexes showed higher polymerization activity and better molecular weight control than their monometallic counterparts reported in our previous work.
基金supported by the National Natural Science Foundation of China(Grant No.20472063).
文摘An unexpected carbon-oxygen bond cleavage of THF (THF = tetrahydrofuran) promoted by guanidinate titanium complex was described. Guanidinate lithium [Pr2iNC(NCy)2]Li (Cy = cyclohexyl) formed in situ reacted with TiCl4(THF)2 in a 2:1 molar ratio to produce the gua- nidinate titanium chloride [Pr2iNC(NCy)2]2TiCl2 (1) in good yield. The reaction of [Pr2iNC(NCy)2]2TiCl2 with lithium diisopropylamide in THF afforded an unexpected [Pr2iNC(NCy)2]2Ti(OBun)2 (2), which was formed by the cleavage of carbon-oxygen bond of THF. Complexes 1 and 2 were fully characterized by elemental analysis, NMR and IR spectroscopies, and X-ray crystal structure determination for complex 2.
文摘The reaction of C3H6(N=CH-Ar-OH)2 (Ar = 5-tert-butyl-C6H3 (2a), 3-tert-butyl-C6H3 (2b), 3-methyl-C6H3 (2c)) with 2 equiv. of BuLi followed by 1 equiv TiCl4 yields the dichloride complexes [C3H6(N=CH-Ar-O)2]TiCl2[Ar = 5-tert-butyl-C6H3 (3a), 3-tert-butyl-C6H3 (3b), 3-methyl-C6H3 (3c)]. The structure of compound 3a has been confirmed by X-ray crystallographic analysis. These Ti (IV) dichloride complexes are active catalysts for the polymerization of eth- ylene with methylaluminoxane (MAO) as a cocatalyst. Ac- tivities up to 4.14×105 g (mol Ti h)?1 were obtained in dried toluene. And the molecular weights of polyethylene are in the range 1.53×104—16.4×104. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by changing the ligand structure and variation of reac- tion parameters such as Al-Ti ratio and polymerization reac- tion temperature.
文摘AIM: To evaluate the effectiveness and safety of complex orbital fracture reconstruction with titanium implants. METHODS: A retrospective review of 46 patients treated with complex orbital fractures reconstruction using titanium implants from January 2005 to December 2008 was conducted. The following data were recorded: age, gender, mechanism of injury, preoperative and postoperative orbital CT, visual acuity, diplopia, ocular motility and Hertel exophthalmometer. RESULTS: The most common cause was motor vehicle accident (47.8%), followed by industrial injury (30.4%). All patients had improved appearance after operation and CT scan at one week after operation showed the fracture defects of orbit and neighboring areas had been reconstructed. Forty-six cases had various degrees of enophthalmos before operation. Among them, 32 cases were completely corrected, 11 cases improved obviously and 3 cases had no improvement after operation. Thirty-six patients with visual acuity =20/60 revealed diplopia of various degrees, including 26 patients had diplopia in right ahead and/or reading positions. At the sixth month after operation, diplopia disappeared in five patients, 7 patients still had diplopia in right ahead and/or reading positions, 14 patients had diplopia in positions rather than right ahead and reading positions (<20 degrees) and ten patients had diplopia only at peripheral gazing (>20 degrees). All patients had various degrees of ocular motility disorders before operation. At the sixth month after operation, eyeball movement disorder disappeared in 9 patients, 31 patients showed improvement and 6 patients had no improvement. Complications of implant infection, rejection and displacement were not reported after operation. CONCLUSION: The application of titanium implants in the repair of complex orbital fractures greatly improves the appearance and functional results, which is a favorable material for plastic surgery of complex orbital fracture.
基金supported by the financial support of Natural Science Research Program of Jiangsu Education Department(No.13KJB310014)Natural Science Foundation of Jiangsu Province(BK20140429)the Natural Science Foundation of Nantong University(No.14ZY015,No.13R23)
文摘The aim of this study was to investigate the inhibitory effect of heparin/fibronectin （Hep/Fn） complexes on neointimal hyperplasia following endovascular intervention. Hep/Fn complexes were immobilized onto titanium （Ti） surfaces, with subsequent X-ray photoelectron spectroscopy （XPS）, Toluidine Blue 0 （TBO） and immunohistochemistry methods were used to characterize surface properties. Smooth muscle cell （SMC） cultures were used to evaluate the effect of Hep/Fn complexes on SMC proliferation. Results showed that Hep/Fn complexes successfully immobilized onto Ti surfaces and resulted in an inhibition of SMC proliferation. This study suggests that Hep/Fn surface-immobilized biomaterials develop as a new generation of biomaterials to prevent neointimal hyperplasia, particularly for use in cardiovascular implants.
文摘A new complexes of Cp2Ti[S2P(OR)2]2 (where R = Et, Pr-n, Pr-i, Bu-i and Ph) and Cp2Ti[S2POGO]2 (where G = -CH2CMe2CH2-, -CH2CEt2CH2- and -CMe2CMe2-) were prepared by the dropwise addition of the appropriate O,O’-dialkyl or -alkylenedithiophosphoric acid to biscyclopentadienyl titanium dichloride in 1:2 molar ratio and refluxed in benzene solution. These novel deep red colored complexes were characterized by elemental analyses, molecular weight measurements and spectroscopic techniques (IR., NMR 1H, 13C and 31P NMR). These titanium (IV) dithio complexes have also been screened for their antibacterial activities.
文摘-The i. r. spectra of Na4 [UO2 (CO3)3], Na [UO2 (OH)3] and the surface species of uranium on HTO underthe condition of flowing natural seawater and concentrated seawater (NaCl-NaHCO3-U) were recorded, with the bands of urany! of surface species obtained and the finding that iigands of surface species besides HTO are mainly water and OH, and there are some CO32- groups under the condition of natural seawater. Some relations between the complex properties and the j. r. spectroscopic characters for uranyl complexes were studied, and the transferred change quantity of surface complex was calculated.Structure models for surface species of adsorption are herein presented and the mechanism for uranium adsorption is deduced.
基金The work is supported by Special Funds for State Major Basic Research Projects of China(No.G1999064801)
文摘Three mono-cyclopentadienyl metal complexes, [C_6H_4O_2]CpTiCl (Ⅰ),[C_(12)H_8O_2]CpTiCl (Ⅱ), and [C_(20)H_(12)O_2] CpTiCl (Ⅲ), were prepared via the reactions ofcyclopentadienyl titanium trichloride with catechol, 2,2i-bisphenol, and 2,2'-bisnaphthol,respectively. In the presence of a moderate amount of methylaluminoxane (MAO), the complexesexhibited catalytic activities for ethylene polymerization. Complex Ⅰ showed the highest activityat Al/Ti molar ratio of 500 at the temperature of 30℃. With increasing of polymerizationtemperature, catalytic activities and molecular weight of the obtained polyethylene tended todecrease, and molecular weight distribution of polyethylene became narrower. With the molecularsimulation method, the charges on titanium atoms of complexes Ⅰ, Ⅱ, and Ⅲ, and the bond anglesformed by Ti and bisphenoxy ligands were calculated. It was concluded that the smaller the netcharge on Ti and the smaller the angle of O1―Ti―O2, the higher the activity of the complex.
基金supported by the National Natural Science Foundation of China(No.21988101 and 22201013)the Beijing Natural Science Foundation(No.2222008).
文摘The activation of dinitrogen by a titanium hydride complex with two bridging hydrides located between metal Ti and Li was investigated.Exposing cyclic bis-alkylidene titanium complex 1 to H2 in THF solution yielded titanium hydride 2,{[(2-butene)(C_(5)H_(5))Ti](μ-H)_(2)Li(THF)_(3)}.2 aggregated into dimer 3 in hexane,accompanied by the release of LiH.
文摘The purpose of this study was to prepare nano-titanium tannate complex (TTC) and to investigate its adsorption capacity for removal of cationic dyes such as crystal violet (CV) dye. The morphology and the main elements of TTC adsorbent were characterized by scanning electron microscopy (SEM-EDS), while its crystal structure was characterized by X-ray diffraction (XRD). Also, FT-IR spectroscopy study structural aspects of TTC. A “cotton-ball”-like and porous surface structure of titanium tannate complex (TTC) with nanoparticle size of 16.18 nm show high capability for absorbing crystal violet dye. The effect of several parameters such as contact time, initial concentrations of CV, solution pH and the amount of TTC was investigated. Three different kinetic equations such as pseudo-first order, pseudo-second order and intraparticle diffusion were used to study the order and the mechanism of the adsorption process. The adsorption of CV dye followed pseudo- second order equation. Moreover, equilibrium data were tested with four adsorption isotherm models namely, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R). Langmuir was the best fit for the data with maximum capacity as 58.8 mg/g. The results of Separation factor, Surface coverage and standard free energy (ΔG°) indicated that adsorption of CV onto TTC was favorable with fast rate and spontaneous physical adsorption process.
