Polymerization of styrene with nickel complex/methylaluminoxane catalytic systems

Polymerization of styrene using catalytic systems based on nickel derivatives and methylaluminoxane (MAO) was studied. Among tested catalysts, nickel bis(acetylacetonate) and nickel dichloride show the maximum activity. Bis(phosphine)nickel dichlorides exhibit lower activity, depending on the nature of the phosphine ligand. Polymer yields decrease by lowering the catalyst concentration, by increasing the reaction temperature, or by carrying out the polymerization in a polar donor solvent. Weight average molecular weight of most of the prepared polystyrenes ranges from 9000 to 25,000, with polydispersity indexes of 1.6–3.8. However, polystyrene prepared in dioxane solvent exhibits a small fraction of very high molecular weight (about 140,000). From NMR analysis, the products seem generally to be constituted of two polymers with different steric microstructure: atactic polystyrene and partially isotactic polystyrene (ca. 75–85% meso diads). Catalytic site specificity is correlated with the type of nickel ligand, while the effect of reaction temperature is less defined. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2119–2126, 1998     

Densely grafted polyisocyanides synthesized by two types of polymerization techniques

A series of novel polyisocyanide‐graft‐polystyrenes and polyisocyanide‐graft‐[polystyrene‐block‐poly(butyl acrylate)]s were synthesized through the grafting‐through and grafting‐from routes with two types of living polymerization techniques: polymerization with the Pd–Pt μ‐ethynediyl dinuclear complex as the initiator and catalyst for the polyisocyanide backbone and atom transfer radical polymerization for the grafted side chain. Through the introduction of a chiral center at the side chain of the polyisocyanide backbone, helical grafted and graft block polyisocyanides were prepared through the grafting‐from method. All of the obtained polymers exhibited polydispersities in the range of 1.07–1.41. This might have been the first time grafted polyisocyanides were prepared, especially helical grafted polyisocyanides, through the operation of two living polymerization techniques. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1871–1880, 2003     

Vinyl polymerization of norbornene by mono‐ and trinuclear nickel complexes with indanimine ligands

A series of new indanimine ligands [ArN?CC₂H₃(CH₃)C₆H₂(R)OH] (Ar = Ph, R = Me ( 1 ), R = H ( 2 ), and R = Cl ( 3 ); Ar = 2,6‐i‐Pr₂C₆H₃, R = Me ( 4 ), R = H ( 5 ), and R = Cl ( 6 )) were synthesized and characterized. Reaction of indanimines with Ni(OAc)₂·4H₂O results in the formation of the trinuclear hexa(indaniminato)tri (nickel(II)) complexes Ni₃[ArN = CC₂H₃(CH₃)C₆H₂(R)O]₆ (Ar = Ph, R = Me ( 7 ), R = H ( 8 ), and R = Cl ( 9 )) and the mononuclear bis(indaniminato)nickel (II) complexes Ni[ArN?CC₂H₃(CH₃)C₆H₂(R)O]₂ (Ar = 2,6‐i‐Pr₂C₆H₃, R = Me ( 10 ), R = H ( 11 ), and R = Cl ( 12 )). All nickel complexes were characterized by their IR, NMR spectra, and elemental analyses. In addition, X‐ray structure analyses were performed for complexes 7 , 10 , 11 , and 12 . After being activated with methylaluminoxane (MAO), these nickel(II) complexes can polymerize norbornene to produce addition‐type polynorbornene (PNB) with high molecular weight M_v (10⁶ g mol^?1), highly catalytic activities up to 2.18 × 10⁷ gPNB mol^?1 Ni h^?1. Catalytic activities and the molecular weight of PNB have been investigated for various reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 489–500, 2008     

Polymerization of 1,3‐cyclohexadiene with nickel/MAO catalytic systems

The polymerization of 1,3‐cyclohexadiene with nickel bis(acetylacetonate) activated by methylaluminoxane affords poly(1,3‐cyclohexadiene) in high yields; the same catalyst is unable to polymerize larger conjugated cyclic diolefins or copolymerize 1,3‐cyclohexadiene with styrene. In the latter case, the homopolymer of the diolefin is obtained. The catalyst activity increases with increasing reaction temperature, nickel concentration, and aluminum/nickel ratio or with the addition of triisobutylaluminum to the reaction medium. The obtained poly(1,3‐cyclohexadiene) samples are high‐melting crystalline polymers (melting temperature ∼ 320 °C) that are insoluble in all common organic solvents. With bis(cyclopentadienyl)nickel in place of nickel bis(acetylacetonate), the activity is much lower, but the polymer is more stereoregular, as indicated by the slightly higher value of the melting temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3004–3009, 2000     

A rigid, chiral, dendronized polymer with a thermally stable, right-handed helical conformation

First- and second-generation dendronized polymethacrylates PG1 and PG2 carrying chiral 4-aminoproline-based dendrons were obtained on the half-gram scale in high molar masses (PG1: M(n)=5 x 10(6) g mol(-1), PG2: M(n)=1x10(6) g mol(-1)) by spontaneous (radical) polymerization of the corresponding vinyl macromonomers. NMR spectroscopic studies on PG2 together with its unprecedented high glass transition temperature (T(g)>200 degrees C, decomp) and structural parameters provided by atomistic MD simulations show this polymer to be rather rigid. Optical rotation and CD measurements revealed that PG2 adopts a helical conformation that remains unchanged over wide ranges of temperature and solvent polarity. It is also retained when the polymer is deprotected (and thus positively charged, de-PG2) at its terminal amino groups, by which the mass and steric demand of the dendrons is reduced by roughly 50 %. Molecular dynamics simulations on models of PG2 reveal its helical conformation to be right-handed, irrespective of backbone tacticity, and initial results also indicate that de-PG2 retains the right-handedness.     

Facile synthesis of sterically demanding SHOP‐type nickel catalysts for ethylene polymerization

The P,O‐chelated shell higher olefin process (SHOP) type nickel complexes are practical homogeneous catalysts for the industrial preparation of linear low‐carbon α‐olefins from ethylene. We describes that a facile synthetic route enables the modulation of steric hindrance and electronic nature of SHOP‐type nickel complexes. A series of sterically bulky SHOP‐type nickel complexes with variable electronic nature, {[4‐R‐C₆H₄C(O) = C‐PArPh]NiPh (PPh₃); Ar = 2‐[2′,6′‐(OMe)₂C₆H₃]C₆H₄; R = H ( Ni1 ); R = OMe ( Ni2 ); R = CF₃ ( Ni3 )}, were prepared and used as single component catalysts toward ethylene polymerization without using any phosphine scavenger. These nickel catalysts exhibit high thermal stability during ethylene polymerization and result in highly crystalline linear α‐olefinic solid polymer. The catalytic performance of the SHOP‐type nickel complexes was significantly improved by introducing a bulky ortho‐biphenyl group on the phosphorous atom or an electron‐withdrawing trifluoromethyl on the backbone of the ligand, indicating steric and electronic effects play critical roles in SHOP‐type nickel complexes catalyzed ethylene polymerization.     

Interfacial impregnation chemistry in the synthesis of nickel catalysts supported on titania

The interfacial chemistry of the impregnation step involved in the preparation of nickel catalysts supported on titania is presented. Several methodologies based on deposition data, pH measurements, potentiometric mass titrations, and microelectrophoresis have been used in conjunction with diffuse reflectance UV/Vis/NIR spectroscopy, simulations, and semiempirical quantum chemical calculations. Three mononuclear inner-sphere complexes were formed at the compact layer of the "titania/electrolyte solution" interface: A monosubstituted, dihydrolyzed complex above a terminal oxo group, a disubstituted, dihydrolyzed complex above two terminal adjacent oxo groups, and a disubstituted, nonhydrolyzed complex above one terminal and one bridging adjacent oxo groups. The monosubstituted, dihydrolyzed complex predominates. The contribution of the disubstituted configurations is also important at very low Ni(II) surface concentration, but it decreases as the Ni(II) surface concentration increases. In addition, bi- and trinuclear inner-sphere complexes were formed. The receptor site involves one bridging and two terminal oxo groups in the first case and two bridging and three terminal oxo groups in the second case. The relative surface concentrations of these configurations increase initially with Ni(II) surface concentration and then remain practically constant. The understanding of these interfacial processes at a molecular level is very important to shift the catalytic synthesis from an art to a science as well as to obtain strict control of the impregnation step and, to some extent, of the whole preparative sequence. This study is very relevant to the synthesis of submonolayer/monolayer nickel catalysts supported on TiO(2) following equilibrium deposition filtration (otherwise called equilibrium adsorption).     

Helix-sense-selective radical polymerization of bulky styrenic monomers: chiral induction and liquid crystallinity

Eight chiral vinylterphenyl monomers,(+)-2,5-bis{4′-[(S)-1″-methylpropyloxy]phenyl}styrene(Ia),(+)-2,5-bis{4′-[(S)-2″-methylbutyloxy]phenyl}styrene(Ib),(+)-2,5-bis{4′-[(S)-3″-methylpentyloxy]phenyl}styrene(Ic),(+)-2,5-bis{4′-[(S)-4″-methylhexyloxy]phenyl}styrene(Id),(?)-2,5-bis{4′-[(R)-1″-methylpropyloxy]phenyl}styrene(Ie),(+)-2-{4′-[(S)-1″-methylpropyloxy]phenyl}-5-{4′-[(R)-1″-methylpropyloxy]phenyl}styrene(IIa),(?)-2-{4′-[(R)-1″-methylpropyloxy]phenyl}-5-{4′-[(S)-1″-methylpropyloxy]phenyl}styrene(IIb),and(+)-2-{4′-[(S)-2′′-methylbutyloxy]phenyl}-5-{4′-[(S)-1″-methylpropyloxy]phenyl}styrene(III),were synthesized and radically polymerized.These molecules were designed to further understand long-range chirality transfer in radical polymerization and to possibly tune the chiroptical properties of the polymers by varying the spatial configuration,position,and various combination of the stereogenic centers at the ends of p-terphenyl pendants.The resultant polymers adopted helical conformations with a predominant screw sense.When the stereogenic centers ran away from the terphenyl group as in Ib?d,the corresponding polymers changed the direction of optical rotation in an alternative way and showed no obvious stereomutation upon annealing in tetrahydrofuran.The two stereogenic centers of IIa,IIb,and III acted concertedly in chiral induction,whereas those of Ia and Ie played a counteractive role.The five polymers derived from Ia,Ie,IIa,IIb,and III underwent stereomutation when annealed in tetrahydrofuran.The polymers PIa?e had good thermal stability and high glass transition temperatures(Tgs).They generated liquid crystalline phases at above Tgs that could be kept upon cooling,with the exception of PIe.This result was consistent with the extended helical structures.     

Controllable synthesis of nickel hydroxide and porous nickel oxide nanostructures with different morphologies

Alpha-Ni(OH)(2) nanobelts, nanowires, short nanowires, and beta-Ni(OH)(2) nanoplates have been successfully prepared in high yields and purities by a convenient hydrothermal method under mild conditions from very simple systems composed only of NaOH, NiSO(4), and water. It has been found that the ratio of NaOH to NiSO(4) not only affects the morphology of the Ni(OH)(2) nanostructures, but also determines whether the product is of the alpha- or beta-crystal phase. A notable finding is that porous NiO nanobelts were produced after exposure of the Ni(OH)(2) products to an electron beam for several minutes during transmission electron microscopy (TEM) observations. Another unusual feature is that rectangular nanoplates with many gaps were obtained. Furthermore, porous NiO nanobelts, nanowires, and nanoplates could also be obtained by annealing the as-prepared Ni(OH)(2) products. A sequence of dissolution, recrystallization, and oriented attachment-assisted self-assembly of nanowires into nanobelts is proposed as a plausible mechanistic interpretation for the formation of the observed structures. The method presented here possesses several advantages, including high yields, high purities, low cost, and environmental benignity. It might feasibly be scaled-up for industrial mass production.     

水对镍系催化丁二烯聚合的影响

比较了正辛醇-三氟化硼乙醚络合物（n－C8H17OH─B）预混和稀三氟、化硼乙醚络合物（B）单加两种体系的丁二烯聚合中微量水的作用规律，测定了这些体系的动力学参数。研究发理,水加在丁二烯中比直接加在溶剂油中好；二种聚合体系都存在含水量的临界值范围，H2O与三异丁基铝的摩尔比约在0.3～2．3之间，在此范围内调节含水量．体系较稳定：丁二烯中有水时，稀B单加比陈化液和B组分同时加入体系中，前者聚合速度较快。     

Ethylene oligomerisation and polymerisation with nickel phosphanylenolates bearing electron-withdrawing substituents: Structure-reactivity relationships

Three SHOP-type catalysts, in which the C=C(O) double bond was substituted by electron-withdrawing substituents, [Ni{Ph2PC(R1)=C(R2)O}Ph(PPh3)] (2: R1,R2 = -C(Me)=NN(Ph)-; 3: R1 = CO2Et, R2 = Ph; 4: R1 = CO2Et, R2 = CF3), were assessed as ethylene-oligomerisation and -polymerisation catalysts and compared to Keim's complex, [Ni{Ph2PCH=C(Ph)O}Ph(PPh3)] (1). A rationale for the influence of the double-bond substituents of the P,O-chelate unit on the catalytic properties is proposed, on the basis of X-ray diffraction studies, spectroscopic data and DFT-B3 LYP calculations. Whatever their relative electron-withdrawing strength, the R1 and R2 substituents induce an increase in activity with respect to catalyst 1. For those systems in which the basicity of the oxygen atom is decreased relative to that of the phosphorus atom, the chain-propagation rate increases with respect to that for catalyst 1. Reduction of the basicity of the P relative to that of the O, however, induces higher chain-termination rates.     

Vinyl‐type polymerization of norbornene by nickel(II) bisbenzimidazole catalysts

Novel nickel(II) bisbenzimidazole complexes were prepared via a three‐step synthetic procedure consisting of aniline/diacid condensation, ligand N‐alkylation, and metal complexation. The complexes were characterized by X‐ray crystallography and found to possess a pseudotetrahedral geometry. Upon activation with methylaluminoxane, these nickel bisbenzimidazoles did not polymerize simple olefins (e.g., ethylene, propylene, and 1‐butene) but were found to carry out the rapid and efficient polymerization of norbornene. The polynorbornene products were characterized by gel permeation chromatography/light scattering, ¹³C NMR, and IR, and their Mark–Houwink and dn/dc parameters were determined. The molecular weights of the polynorbornenes were very high (weight‐average molecular weight = 587,000–797,000 g/mol). ¹³C NMR suggested that the polymerization occurred via vinyl addition (i.e., a 2,3‐linked polymer); no ring‐opened product was observed. Thermogravimetric analysis indicated that the polynorbornenes were stable up to 400 °C under nitrogen. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2095–2106, 2003     

2-phosphanylphenolate nickel catalysts for the polymerization of ethylene

The previously unknown methallylnickel 2-diorganophosphanylphenolates (R=Ph, cHex) were synthesized and found to catalyze the polymerization of ethylene. To explore the potential for ligand-tuning, a variety of P-alkyl- and P-phenyl-2-phosphanylphenols was synthesized and allowed to react with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) or with NiBr(2).DME and NaH. The complexes formed in situ with [Ni(cod)(2)] are generally active as ethylene polymerization catalysts with all the ligands tested, whereas the latter systems are inactive when 2-dialkylphosphanylphenols are applied. M(w) values, ranging from about 1000 to about 100000 g mol(-1), increase for various R(2)P groups in the order R=Ph相似文献   

Vinyl polymerizations of norbornene catalyzed by nickel complexes with acetoacetamide ligands

On the basis of a remote effect, a series of acetoacetamide ligands and corresponding nickel complexes N‐(R‐phenyl) acetoacetamide Ni(CH₂Ph) (PMe₃) (R = H, 1 ; R = 2‐methyl, 2 ; R = 2,6‐dimethyl, 3 ; R = 2,6‐diisopropyl, 4 ; R = 4‐NO₂, 5 ) were synthesized and characterized. The solid structure of complex 3 was confirmed by X‐ray single‐crystal analysis to be of cis form. ¹H and ³¹P NMR spectroscopy confirmed that cis and trans isomers of nickel complexes were present in solution. Norbornene polymerizations with acetoacetamide nickel complexes activated with modified methylaluminoxane (MMAO) were investigated in detail. Remote steric and electronic effects of acetoacetamide ligand on catalytic activity and molecular weight of polynorbornenes (PNBs) were observed. Characterizations of the obtained PNBs show that the obtained polymer products are non‐crystalline vinylic‐addition polynorbornenes. Copyright © 2013 John Wiley & Sons, Ltd.     

The synthesis of chiral periodic organosilica materials with ultrasmall mesopores

Helical organosilica materials were synthesized for the first time using a novel binaphthyl-based chiral co-monomer in less than 1?hour. The incorporation of a chiral co-monomer in the wall was shown to influence the curvature of the helical materials. As the amount of the chiral co-monomer was increased, the degree of curvature increased, illustrating the importance of this monomer to the overall morphology.     

Density functional study for the polymerization of ethylene monomer using a new nickel catalyst

The present computational study was designed to study the polymerization of ethylene catalyzed by a new Ni‐based PymNox organometallic compound. Recently, we have synthesized and tested the behavior of this type of catalyst in olefin polymerization. It has been experimentally observed that the unsubstituted catalyst Ni2 (aldimino PymNox catalyst ) is less active than the methyl substituted Ni1 (acetaldimino PymNox catalyst ) analogue. The reactivity of both catalysts was examined using density functional theory (DFT) models. Our results indicate that the methyl substituted Ni1 introduces some additional steric hindrance that probably renders a more suitable catalyst conformation for the monomer incorporation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1160–1165, 2010     

Copolymerization of Ethene and Carbon Monoxide with (Diphosphine)nickel Catalysts

This work presents the results of the ethene–CO copolymerization with in situ generated catalysts based on atropisomeric 1,4‐diphosphines and nickel(II). The influence of the reaction conditions and the NMR characterization of the copolymers are described.     

Synthesis of norbornene/divinylbenzene copolymers catalyzed by anilinonaphthoquinone-ligated nickel complexes and their applications for the synthesis of graft polymers

The copolymerization of norbornene (NB) and divinylbenzene (DVB) was carried out using anilinonaphthoquinone-ligated nickel complexes of the type [Ni(C₁₀H₅O₂NAr)(Ph)(PPh₃)] ( 1a : Ar = C₆H₃-2,6- ⁱPr; 1b : Ar = C₆H₂-2,4,6-Me; 1c: Ar = C₆H₅) with modified methylaluminoxane (MMAO) as a cocatalyst. The DVB content was varied (5–25 mol%) and the resulting copolymers exhibited number-average molecular weights (M_n) of 40,000–69,000 g/mol with polydispersities (PDI = 1.5–1.8). The styryl group of the NB/DVB copolymer was used for grafting poly(methyl methacrylate) by reverse atom transfer radical polymerization using azobisisobutyronitrile in the presence of copper chloride and bipyridine.