Syndiospecific Polymerization of Styrene Using Half-Titanocene Catalyst Covalently Supported on MgCl<Subscript>2</Subscript>/AlEt<Subscript>n</Subscript>(OEt)<Subscript>3-n</Subscript>

The novel half-titanocene catalyst bearing reactive functional amino group, η⁵-pentamethylcyclopentadienyltri(p-amino-phenoxyl) titanium [Cp^∗Ti(p-OC₆H₄NH₂)₃], was easily synthesized by the reaction of η⁵-pentamethylcyclopentadienyltrichloride titanium (Cp^∗TiCl₃) with p-amino phenol in the presence of triethyl amine (NEt₃). Cp^∗Ti(p-OC₆H₄NH₂)₃ covalently anchored on MgCl₂/AlEt_n(OEt)_3-n support obtained from the reaction of triethylaluminium (AlEt₃) with the adduct of magnesium chloride (MgCl₂) and ethanol (EtOH), has been investigated and used to catalyze syndiospecific polymerization of styrene. Influences of the support structure, cocatalyst, and the molar ratio of Al in methylaluminoxane (MAO) and Ti (Al_MAO/Ti) on catalytic activity, syndiotacticity and molecular weight of the resultant polystyrene were investigated. Compared with the corresponding Cp^∗Ti(p-OC₆H₄NH₂)₃ homogeneous catalyst, a considerable increase in activity and molecular weight of syndiotactic polystyrene (sPS) was observed for the Cp^∗Ti(p-OC₆H₄NH₂)₃-MgCl₂/AlEt_n(OEt)_3-n supported catalyst even at a relatively low Al_MAO/Ti ratio of 50, and the kinetics of polymerization was stable during the reaction process.     

Synthesis of high molecular weight copolymer of styrene and butadiene bearing high 1,4‐cis butadiene unit from copolymerization with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with CpTiCl₃/methylaluminoxane (MAO) catalyst in the presence or absence of chloranil (CA) was investigated. The CpTiCl₃/MAO catalyst showed a high activity for the copolymerization of St with Bd. The 1,4‐cis contents in the Bd units for the copolymerization of St and Bd with the CpTiCl₃/MAO catalyst was observed, and the 1,4‐cis content was optimum at a MAO/Ti mole ratio of around 225. The effect of the polymerization temperature on the copolymerization was noted, as was the effect of the 1,4‐cis microstructure in the Bd units for the copolymerization of St and Bd. The addition of CA to the CpTiCl₃/MAO catalyst was found to influence the molecular weight of the copolymer. The high weight‐average molecular weight copolymer (M_w = ca. 50 × 10⁴) consisting of mainly a 1,4‐cis microstructure of Bd units (1,4‐cis = 80.0%) was obtained from the copolymerization with the CpTiCl₃/MAO catalyst in the presence of CA (CA/Ti mole ratio = 1) at 0°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2942–2946, 2003     

Bulk polymerization of vinyl chloride with half-titanocene/MAO catalyst

Bulk polymerization of vinyl chloride (VC) with Cp^∗Ti(OPh)₃/MAO catalyst was investigated. The bulk polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst proceeded to give poly(vinyl chloride) (PVC) with high molecular weight in good yields. The M_n of the polymer increased in direct proportion to polymer yields and the line passed through the origin. The M_w/M_n of the polymer decreased with an increase of polymer yield. The GPC elution curves were unimodal and the whole curves shifted clearly to the higher molecular weight as a function of reaction time. This indicates that the control of molecular weight can be achieved in the polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst even in bulk. The structure of PVC obtained from the bulk polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst consists of a regular structure. The thermal stability of the polymer obtained with Cp^∗Ti(OPh)/MAO catalyst was higher than that of PVC obtained from radical polymerization and depended on the molecular weight of the polymer. In contrast to that, the initial decomposition temperature of the polymer obtained from a radical polymerization did not depend on the molecular weight. We presumed that the decomposition of the polymer obtained with Cp^∗Ti(OPh)₃/MAO catalyst initiated at the chain end.     

A pre-metallocene single-site catalyst for olefin polymerization: the V(acac)<Subscript>3</Subscript> – Ali-Bu<Subscript>2</Subscript>Cl system

A combination of GPC, DSC, and ¹³C NMR data for an ethylene/1-hexene copolymer prepared with the V(acac)₃ - Ali-Bu₂Cl system at 5 °C shows that this catalyst system was one of the earliest pre-metallocene catalysts for olefin polymerization.     

Synthesis and characterization of a novel bipolar Alq<Subscript>3</Subscript>-based copolymer containing carbazole and phenothiazine groups

A novel bipolar copolymer combining hole-transporting units, electron-transporting units and light-emitting units (Alq₃) had been synthesized via free radical copolymerization of N-vinylcarbazole and Alq₃ monomer containing phenothiazine group. The chemical structure and composition of the copolymer were characterized by ¹H NMR, ¹³C NMR, FT-IR spectroscopy, and elemental analysis as well as gel permeation chromatography (GPC). The number-average molecular weight (M _n) and polydispersity of these copolymers with different Alq₃ contents were around 20000 and 1.4, respectively. The DSC and TGA measurements indicated that the copolymer has excellent thermal stability and high glass transition temperatures (T _g). The optical properties of the copolymer in solution and solid state were investigated by UV-vis and photoluminescence (PL) spectra. Additionally, the effects of Alq₃ content, concentration, excitation wavelength and solvent on PL spectra were studied and the results indicated that there exists efficient energy transfer in the process of photoluminescence. The introduction of carbazole and phenothiazine, as hole-transporting groups and energy transfer stages, provides an effective way to improve carries transporting property and energy transfer efficiency, consequently improving luminescence properties of Alq₃-based copolymer.     

Preparation of ethylene/1‐octene copolymers from ethylene stock with tandem catalytic system

Tandem catalysis offers a novel synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐octene copolymers from ethylene stock as the sole monomer. The reported catalytic systems involving a highly selective, bis(diphenylphosphino)cyclohexylamine/Cr(acac)₃/methylaluminoxane (MAO) catalytic systems for the synthesis of 1‐hexene and 1‐octene, and a copolymerization metallocene catalyst, rac‐Et(Ind)₂ZrCl₂/MAO for the synthesis of ethylene/1‐octene copolymer. Analysis by means of DSC, GPC, and ¹³C‐NMR suggests that copolymers of 1‐hexene and ethylene and copolymers of 1‐octene and ethylene are produced with significant selectivity towards 1‐hexene and 1‐octene as comonomers incorporated into the polymer backbone respectively. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 101.1–134.1°C and density of 0.922–0.950 g cm^?3 can be efficiently produced. © 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.     

The copolymerization of carbon dioxide and propylene oxide with Y(CCl<Subscript>3</Subscript>COO)<Subscript>3</Subscript>-diphenylzinc-glycerol catalyst

Summary  Various organometallic compounds (diphenylzinc, dibenzylzinc, dicyclohexylzinc, bis(pentafluorophenyl)zinc, diethylzinc, di(n-butyl)zinc, triethylaluminum) were used to form Y(CCl₃COO)₃-organometallic compound-glycerol catalyst for the copolymerization of carbon dioxide and propylene oxide. It was found that Y(CCl₃COO)₃-diphenylzinc-glycerol catalyst showed the highest catalytic activity, at optimum conditions the yield could be as high as 478.8 (g polymer/mol Zn h). The catalytic activity sequence of these catalysts decreased as follows: Y(CCl₃COO)₃-diphenylzinc-glycerol>Y(CCl₃COO)₃-diethylzinc-glycerol>Y(CCl₃COO)₃-di-(n-butyl)zinc-glycerol>Y(CCl₃COO)₃-dibenzylzinc-glycerol>Y(CCl₃COO)₃-dicyclohexylzinc-glycerol>Y(CCl₃COO)₃-bis(pentafluorophenyl)zinc-glycerol. ¹H NMR, ¹³C NMR, TGA, DMA, tensile tests results indicated that microstructure and properties of the polymers varied with catalyst used. Copolymer from Y(CCl₃COO)₃-diphenylzinc-glycerol catalyst displayed the highest thermal properties and mechanical properties: the glass transition temperature (T_g) was 50.2 ^oC, the 5% weight loss temperature (T_-5%) was 222 C, the tensile strength was 34.7 MPa, the Young’s modulus was 298 MPa. The difference between the properties of the polymers was explained relating to the different polycarbonate content in the polymers.     

Polymerization of vinyl chloride with butyllithiums and metallocene catalysts

Polymerizations of vinyl chloride (VC) with butyllithium (BuLi) and metallocene catalysts were investigated. In the polymerization of VC with BuLi, the activity for polymerization decreased in the following order; t‐BuLi > n‐BuLi > s‐BuLi. A polymer controlled structurally in the main chain was found to be synthesized from the polymerization of VC with BuLi. The molecular weights of polymers obtained in bulk polymerization were higher than those of polymers obtained in solution. A linear relationship of the M_n of the polymer and the polymer yields was observed. The M_w/M_n of the polymer did not change significantly during polymerization, although the M_w/M_n was around 2. Thermal stability of the polymer obtained with BuLi was higher than that of polymer obtained with radical initiators, as determined by TGA measurements. In the polymerization of VC with Cp*TiX₃/MAO (X: Cl and OCH₃) catalysts, polymers were obtained with both catalysts, although the rate of polymerization was slow. The Cp*Ti(OCH₃)₃//MAO catalyst in CH₂Cl₂ gave higher‐molecular‐weight polymers in a better yield than in toluene. From elemental analysis and the NMR spectra of the polymers, the Cp*Ti(OCH₃)₃/MAO catalyst gave polymers consisting of repeating regular head‐to‐tail units, in contrast to the Cp*TiCl₃/MAO catalyst, which gave polymers having anomalous units.     

Synthesis and functionalization of poly(ethylene‐co‐dicyclopentadiene)

Copolymerizations of ethylene with endo‐dicyclopentadiene (DCP) were performed by using Cp₂ZrCl₂ (Cp = Cyclopentadienyl), Et(Ind)₂ZrCl₂ (Ind = Indenyl), and Ph₂C(Cp)(Flu)ZrCl₂ (Flu = Fluorenyl) combined with MAO as cocatalyst. Among these three metallocenes, Et(Ind)₂ZrCl₂ showed the highest catalyst performance for the copolymerization. From ¹H‐NMR analysis, it was found that DCP was copolymerized through enchainment of norbornene rings. The copolymer was then epoxidated by reacting with m‐chloroperbenzoic acid. ¹³C‐NMR spectrum of the resulting copolymer indicated the quantitative conversion of olefinic to epoxy groups. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 103–108, 1999     

Catalytic performance of CuCl<Subscript>2</Subscript>-modified V<Subscript>2</Subscript>O<Subscript>5</Subscript>-WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> catalyst for Hg<Superscript>0</Superscript> oxidation in simulated flue gas

CuCl₂-SCR catalysts prepared by an improved impregnation method were studied to evaluate the catalytic performance for gaseous elemental mercury (Hg⁰) oxidation in simulated flue gas. Hg⁰ oxidation activity of commercial SCR catalyst was significantly improved by the introduction of CuCl₂. Nitrogen adsorption, XRD, XRF and XPS were used to characterize the catalysts. The results indicated that CuCl₂ was well loaded and highly dispersed on the catalyst surface, and that CuCl₂ played an important role for Hg⁰ catalytic oxidation. The effects of individual flue gas components on Hg⁰ oxidation were also investigated over CuCl₂-SCR catalyst at 350 oC. The co-presence of NO and NH₃ remarkably inhibited Hg⁰ oxidation, while this inhibiting effect was gradually scavenged with the decrease of GHSV. Further study revealed the possibility of simultaneous removal of Hg⁰ and NO over CuCl₂-SCR catalyst in simulated flue gas. The mechanism of Hg⁰ oxidation was also investigated.     

Synthesis and characterization of elastoplastic poly(styrene‐co‐ethylene) using novel mono(η5‐cyclopentadienyl) titanium and modified methylaluminoxane catalysts

Elastoplastic poly(styrene‐co‐ethylene) with high molecular weight was synthesized using novel mono(η⁵‐pentamethylcyclopentadienyl)tribenzyloxy titanium [Cp*Ti(OBz)₃] complex activated with four types of modified methylaluminoxanes (mMAO) containing different amounts of residual trimethylaluminum (TMA). The ideal mMAO, used as a cocatalyst for the copolymerization of styrene with ethylene, contains TMA approaching to 17.8 wt %. The oxidation states of the titanium‐active species in different Cp*Ti(OBz)₃/mMAO catalytic systems were determined by the redox titration method. The results show that both active species may exist in the current system, where one [Ti(IV)] gives a copolymer of styrene and ethylene, and the second one [Ti(III)] only produces syndiotactic polystyrene (sPS). Catalytic activity, compositions of copolymerization products, styrene incorporation, and copolymer microstructure depend on copolymerization conditions, including polymerization temperature, Al/Ti, molar ratio, and comonomers feed ratio. The copolymerization products were fractionated by successive solvent extractions with boiling butanone and tetrahydrofuran (THF). The copolymer, chiefly existing in THF‐soluble fractions, was confirmed by ¹³C‐NMR, GPC, DSC, and WAXD to be an elastoplastic copolymer with a single glass transition temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1851–1857, 1999     

Effect of Ga modification on different pore size silicas in synthesis of LLDPE by copolymerization of ethylene and 1-hexene with [<Emphasis Type="Italic">t</Emphasis>-BuNSiMe<Subscript>2</Subscript>Flu]TiMe<Subscript>2</Subscript>/MMAO catalyst

Copolymerization of ethylene and 1-hexene for obtaining the linear low-density polyethylene was conducted along with silicas as supports for [t-BuNSiMe₂Flu]TiMe₂/MMAO catalyst. Two silicas with different pore sizes were used to investigate the effect of pore sizes on copolymerization. In addition, gallium was also introduced into both silicas to improve their properties and enhance the catalytic activities of the system. It was found that before modification, the larger pore silica exhibited higher catalytic activity than the smaller one due to low internal diffusion resistance. After modification, both silicas exhibited higher catalytic activity comparing to their pristine condition. However, 1-hexene incorporation in the obtained copolymers was lower. The reduced surface area of silica after modification was the main reason for the decrease in 1-hexene incorporation. The properties of the copolymers by means of differential scanning calorimetry, gel permeation chromatography, and ¹³C NMR spectroscopy were further discussed in more detail.     

Atom transfer radical polymerizations of styrene and butadiene as well as their copolymerization initiated by benzyl chloride / 1-octanol-substituted MoCl<Subscript>5</Subscript> / PPh<Subscript>3</Subscript>

A novel initiator system, benzyl chloride / 1-octanol-substituted MoCl₅ / triphenyl phosphine (PPh₃), was applied to the atom transfer radical polymerizations (ATRP) of both butadiene and styrene as well as their copolymerization. Characterization revealed a linear increase in the number average molecular weight with monomer conversion and rather wide molecular weight distributions of the polymerization products. Increasing the polymerization temperature promoted the reaction rate and narrowed the polydispersity index of polystyrene proportionally. The polymerization rule for butadiene catalyzed by the above Mo-based system catalyst is similar to that of styrene. The microstructure of the butadiene was investigated by IR and ¹H NMR. IR, ¹³C NMR and DSC measurements showed that the butadiene and styrene copolymer was a random copolymer. The chlorine atom at the ω end group of the polymer and the change in the valence state of molybdenum, as explored by UV-Vis spectroscopy, revealed that the polymerization proceeded in a manner closest to the mechanism of ATRP.     

Investigation of styrene/1‐hexene copolymerization by homogeneous and heterogeneous bisindenyl ethane zirconium dichloride catalyst system

Homogeneous copolymerization of styrene and 1‐hexene was carried out in toluene at room temperature using bisindenyl ethane zirconium dichloride/methylaluminoxane (MAO). The supported catalyst was prepared with immobilization of Et(Ind)₂ZrCl₂/MAO on silica (calcinated at 500°C) with premixed method. Heterogeneous copolymerization of styrene/1‐hexene with different mole ratios was carried out in the presence of supported catalyst system. The copolymers obtained from homogeneous and heterogeneous catalyst system were characterized by ¹H NMR and ¹³C NMR. Composition of the resulting copolymers was determined by ¹H NMR data. Analysis of ¹³C NMR spectra of obtained copolymers by homogeneous and heterogeneous catalyst systems present isotactic olefin‐enriched copolymers. Molecular weight and thermal behavior of resulting copolymers was investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4008–4014, 2007     

Effects of adding B<Subscript>2</Subscript>O<Subscript>3</Subscript> as a flux on phosphorescent properties in synthesis of SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>: (Eu<Superscript>2+</Superscript>, DY<Superscript>3+</Superscript> phosphor

SrAl₂O₄: (Eu²⁺, Dy³⁺) phosphor was prepared by solid state reaction. B₂O₅ as a flux was added in SrAl₂O₄:(Eu ²⁺, Dy³⁺) in order to accelerate a solid state reaction. In this paper, the effects of B₂O₃ on the crystal structure and the phosphorescent properties of the material have been evaluated. The synthesized phosphor exhibited a broad band emission spectrum peaking at 520 nm, and the spectrum peak showed little effect by the B₂O₃ contents. The maximum afterglow intensity of the SrAl₂O₄: (Eu²⁺, Dy³⁺) phosphor was obtained at the B₂O₃ content of 5%. Adding the B₂O₃ caused uniform distortion to the crystal structure of the phosphor and resulted in reducing the lengths of a and c axes and Β angle of the SrAl₂O₄ crystal. The uniform distortion was accompanied with crystal defects which can trap the holes generated by the excitation of Eu²⁺ ions. The afterglow characteristic of the SrAl₂O₄: (Eu²⁺, Dy³⁺) phosphor was thus enhanced.     

Copolymerization of ethylene and norbornene by zirconium complexes containing symmetrically tuned trianionic ligands

Homo and copolymerization of ethylene and cyclic olefins were carried out using C ₃ symmetric N[CH₂CH(Ph)O]₃ZrCl (1-ZrCl) and also pseudo-C _s symmetric N[CH₂CH(Ph)O]₃ZrCl (2-ZrCl) catalyst systems upon activation with MAO. Incorporation of comonomer into the polyethylene back bone was mainly governed by catalyst symmetry. Norbornene (NB) incorporation was as high as 40% in the ethylene–norbornene copolymer (ENC) using C ₃ symmetric 1-ZrCl/MAO catalyst system and 25% in the case of the pseudo-C _s symmetric analogue 2-ZrCl. Unlike the more efficient titanium analogues, the copolymerization of ethylene and NB showed a marginal decrease in catalyst activity and NB incorporation on switching over to the Zr analogues. The aluminum to metal ratio required for catalyst activation was higher for the Zr catalysts compared to that of its Ti analogues. ¹³C NMR spectral studies on the copolymer clearly indicated the incorporation of NB in an alternating manner.     

Copolymerization of ethylene with styrene using the catalyst system composed of Solvay-type TiCl3 and Cp2Ti(CH3)2

Summary Copolymerization of ethene and styrene was conducted at 40°C using the catalyst system composed of Solvay type TiCl₃ and Cp₂Ti(CH₃)₂. The crude polymer was fractionated with boiling chloroform to obtain 96.4 wt% of insoluble part, which was found to be a random copolymer of ethene and styrene. The copolymer was characterized in detail by DSC, ¹³C NMR, etc.     

Functionalization of polyethylene using borane reagents and metallocene catalysts

A new method to prepare functionalized polyethylene involving borane intermediates and transition metal catalysts is described. Two processes, direct and post polymerizations, were employed to prepare borane-containing polyethylene (PE-B), which can be transformed to functionalized polyethylene (LLDPE-f) with various functional groups, such as ? BR₂, ? OH, ? NH₂, ? OSi(CH₃)₃. In the direct process, the PE-B copolymers were prepared in one step by copolymerization of ethylene with a borane monomer (ω-borane-α-olefin). The post polymerization process requires two steps: copolymerization of ethylene and 1,4-hexadiene, and subsequential hydroboration reaction of unsaturated PE. Three transition metal catalysts, including two homogeneous metallocene (Cp₂ZrCl₂ [bis(cyclopentadienyl) zirconium dichloride] and Et(Ind)₂ZrCl₂ [1,1′-ethylenedi-η⁵-indenyl-zirconium dichloride] with MAO (methylaluminoxane)) and one heterogeneous (TiCl₃·AA/Et₂AlCl) ones, were studied in the copolymerization reactions. The single site Et(Ind)₂ZrCl₂/MAO homogeneous catalyst, with a strained ligand geometry and opened active site, is by far the most effective system in the incorporation of high olefins into polyethylene structures.     

Visible up-conversion luminescence of CaWO<Subscript>4</Subscript>: Er<Superscript>3+</Superscript>,Yb<Superscript>3+</Superscript> and emission enhancement by tri-doping of Li<Superscript>+</Superscript> ions

Er³⁺,Yb³⁺ co-doped CaWO₄ polycrystalline powders were prepared by a solid-state reaction and their up-conversion (UC) luminescence properties were investigated in detail. Under 980 nm laser excitation, CaWO₄: Er³⁺,Yb³⁺ powder exhibited green UC emission peaks at 530 and 550 nm, which were due to the transitions of Er³⁺ (²H_11/2)→Er³⁺ (⁴I_15/2) and Er³⁺ (⁴S_3/2)→Er³⁺ (⁴I_15/2), respectively. Effects of Li+ tri-doping into CaWO₄: Er³⁺,Yb³⁺ were investigated. The introduction of Li⁺ ions reduced the optimum calcinations temperature about 100 °C by a liquid-phase sintering process and the UC emission intensity was remarkably enhanced by Li⁺ ions, which could be attributed to the lowering of the symmetry of the crystal field around Er³⁺ ions.