Ring‐opening metathesis polymerization of dicyclopentadiene catalyzed by titanium tetrachloride adduct complexes with oxygen‐containing ligands

Ring‐opening metathesis polymerization of dicyclopentadiene catalyzed by TiCl₄ · 2L/CH₃Li system [where L is tetrahydropyran (1), dioxane, 2,5‐dimethylfuran, or tetrahydrofurfyl alcohol] is reported. The obtained polymer was characterized by IR and ¹H‐NMR. These catalytic systems effectively promoted the polymerization reaction. Seven influencing factors are discussed. When the aging temperature was 0°C, the aging time was 90 min, the polymerization temperature was 60°C, Li/Ti was 1.5–2, and the monomer/catalyst molar ratio ranged between 30 and 50, the polymerization reaction catalyzed by complex 1 yielded better results within a shorter period of time. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 662–666, 2001     

Polymerization of styrene using novel bispyrazolylimine dinickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with a series of bispyrazolylimine dinickel (II) complexes of bis‐2‐(C₃HN₂(R₁)₂‐3,5)(C(R₂) = N(C₆H₃(CH₃)₂‐2,6)Ni₂Br₄ (complex 1 : R₁ = CH₃, R₂ = Ph; complex 2 : R₁ = CH₃, R₂ = 2,4,6‐trimethylphenyl; complex 3 : R₁ = R₂ = Ph; complex 4 : R₁ = Ph, R₂ = 2,4,6‐trimethylphenyl) in the presence of methylaluminoxane (MAO) was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, reaction time, and catalyst concentration on catalytic activity and molecular weight of the polystyrene were investigated in detail. The influence of the bulkiness of the substituents on polymerization activity was also studied. All of the four catalytic systems exhibited high activity (up to 10.50 × 10⁵ gPS/(mol Ni h)) for styrene polymerization and provide polystyrene with moderate to low molecular weights (M_w = 4.76 × 10⁴–0.71 × 10⁴ g/mol) and narrower molecular weight distributions about 2. The obtained polystyrene was characterized by means of FTIR, ¹H‐NMR, and ¹³C‐NMR techniques. The results indicated that the polystyrene was atactic polymer. The analysis of the end groups of polystyrene indicated that styrene polymerization with bispyrazolylimine dinickel complexes/MAO catalytic systems proceeded through a coordination mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Ethylene/α‐olefin copolymerization by nonbridged (cyclopentadienyl)(aryloxy)titanium(IV) dichloride/AliBu3/Ph3CB(C6F5)4 catalyst systems

A series of nonbridged (cyclopentadienyl) (aryloxy)titanium(IV) complexes of the type, (η⁵‐Cp′)(OAr)TiCl₂ [OAr = O‐2,4,6‐^tBu₃C₆H₂ and Cp′ = Me₅C₅ ( 1 ), Me₄PhC₅ ( 2 ), and 1,2‐Ph₂‐4‐MeC₅H₂ ( 3 )], were prepared and used for the copolymerization of ethylene with α‐olefins (e.g., 1‐hexene, 1‐octene, and 1‐octadecene) in presence of AlⁱBu₃ and Ph₃CB(C₆F₅)₄ (TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was examined. The substituents on the cyclopentadienyl group of the ligand in 1 – 3 play an important role in the catalytic activity and comonomer incorporation. The 1 /TIBA/B catalyst system exhibits the highest catalytic activity, while the 3 /TIBA/B catalyst system yields copolymers with the highest comonomer incorporation under the same conditions. The reactivity ratio product values are smaller than those by ordinary metallocene type, which indicates that the copolymerization of ethylene with 1‐hexene, 1‐octene, and 1‐octadecene by the 1–3/ TIBA/B catalyst systems does not proceed in a random manner. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemical degradation of polyurethanes. II. Degradation of microporous polyurethane elastomer by phosphoric acid esters

Microporous polyurethane elastomer, based on 4,4′‐diphenylmethane diisocyanate and polyester polyol Bayflex 2003 (Bayer AG), was degraded by phosphoric acid esters  (CH₃CH₂O)₃P(O) and (ClCH₂CH₂O)₃P(O) at 180°C. Structure of degraded products was investigated by means of ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 886–893, 2000     

Expanding the chemistry of single‐ion conducting poly(ionic liquid)s with polyhedral boron anions

The synthesis of a new family of single‐ion conducting random copolymers bearing polyhedral boron anions is reported. For this purpose two novel ionic monomers, namely [B₁₂H₁₁(OCH₂CH₂)₂OC(?O)C(CH₃)?CH₂]^2?[(C₄H₉)₄N⁺]₂ and [8‐(OCH₂CH₂)₂OC(?O)C(CH₃)?CH₂‐3,3′‐Co(1,2‐C₂B₉H₁₀)(1′,2′‐C₂B₉H₁₁)]^?K⁺, having methacrylate function, diethylene glycol bridge and closo‐dodecaborate or cobalt bis(1,2‐dicarbollide) anions were designed. Such monomers differ from previously reported ones by (i) chemically attached highly delocalized boron anions, by (ii) valency of the anion (divalent anion and monovalent one) and by (iii) the presence of oxyethylene flexible spacer between the methacrylate group and bonded anion. Their free radical copolymerization with poly(ethylene glycol) methyl ether methacrylate and subsequent ion exchange provided lithium‐ion conducting polyelectrolytes showing low glass transition temperature (?53 to ?49 °C), ionic conductivity up to 9.1 × 10^?7 S cm^?1, lithium transference number up to 0.61 (70 °C) and electrochemical stability up to 4.1 V versus Li⁺/Li (70 °C). The incorporation of propylene carbonate (20–40 wt%) into the copolymers resulted in the enhancement of their ionic conductivity by one order of magnitude and significantly increased their electrochemical stability up to 4.7 V versus Li⁺/Li (70 °C). © 2019 Society of Chemical Industry     

Comparison of Gas and Liquid Propylene Polymerization Technique – Hydrogen Effect on Thermal,Rheological, and Morphological Properties of PP

Summary: A comparison of PP qualities, which are produced with two different polymerization techniques–gas phase(GP) and liquid pool (LP)–under precise control of the polymerization temperature (70 °C) and pressure (GP = 25 bar, LP < 60 bar) using identical Ziegler‐Natta catalyst (TiCl₄/phthalate/MgCl₂ + TEA/silane), is presented. A series of homopolymer PP in a wide MW range from 100 000 to 1 600 000 g · mol^?1 was polymerized. During polymerization all samples were characterized exactly by their Rp‐profil. The effect of hydrogen on the initial reaction rate and on MW and MWD was analyzed on the basis of this so‐called kinetic fingerprint. The results showed that the polymerization rate reached a maximum for LP, of about 150 kg · g_cat^?1 · h^?1, in contrast to GP with a maximum of R_p,₀ = 45 kg · g_cat^?1 · h^?1. Analysis was carried out by means of GPC, SEM, DSC, platte‐platte rheometer, and WAXS. The results first showed that the MWD of LP PP is narrower (PD ～ 6.8) than for the GP PP (PD ～ 8), polymerized in two steps. An SEM study of the powder particle shows the typical dent surface morphology of polymers using Ziegler‐Natta catalysts for polymerization. WAXS and DSC analysis demonstrated that almost only the α‐modification of crystalline structure exists and that the crystallinity becomes considerably higher after solidification from melt. Furthermore, it was found that the crystallite size distribution depends on the polymerization technique. Rheological studies indicate that GP PP behaves more elastically. To summarize, it is shown that PP produced with the LP polymerization technique is more homogenous and of high quality.

Particle geometry of gas phase and liquid pool polymerized PP powder observed by SEM (PP‐L0).     

Halogen-free polyisobutylene by in situ methylation of living polyisobutylene using dimethylzinc

Summary Halogen-free polyisobutylene (PIB) was synthesized by in situ methylation of living PIB using dimethylzinc. Quantitative methylation of living PIB was achieved within 60 min using a ratio of [(CH₃)₂Zn]/[TiCl₄]₀= 1 without any side reactions. Under similar conditions, living PIB capped with 1,1-diphenylethylene (PIB-DPE⁺) yielded close to 1:1 mixture of methoxy- and methyl-functionality. By using the ratio of [(CH₃)₂Zn]/[TiCl₄]₀≥ 3, however, quantitative methylation of PIB-DPE⁺ could be achieved in 120 min without any side reactions as confirmed by spectroscopic and chromatographic analyses. Received: 1 February 2000/Revised version: 23 April 2000/Accepted: 23 April 2000     

Synthesis,Surface and Antimicrobial Activities of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants [C_nH_2n+1–O–CH₂–CH(OH)–CH₂–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? [ 3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2‐hydroxy‐1,3‐oxypropylene group [?CH₂–CH(OH)–CH₂–O–] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C_nH_2n+1–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? (n‐4‐n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.     

New dinuclear cobalt (ΙΙ, ΙΙΙ) and tetranuclear manganese (ΙΙΙ) complexes assembled by a polydentate Schiff-base ligand: synthesis,structure and magnetic properties

The reactions of 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H₄L) and Mn(ClO₄)₂·6H₂O or Co(SCN)₂·3H₂O in the presence of triethylamine in methanol led to the formation of two new complexes [Mn^ΙΙΙ₄(HL)₂(H₂L)₂(CH₃OH)₄]·4CH₃OH·(ClO₄)₂ (1) and [Co^ΙΙCo^ΙΙΙ(H₂L)₂(CH₃OH)(SCN)]·1.5CH₃OH·1.5H₂O (2), respectively. According to structural data and magnetic properties tetranuclear complex 1 contains four homo-valence manganese (ΙΙΙ) atoms, while in the binuclear complex 2 composed of hetero-valence bi- and trivalent cobalt (ΙΙ, ΙΙΙ) atoms. Weak antiferromagnetic exchange interactions between neighboring manganese ions in 1 have place. χ_MT for 2 was fitted using a model of isolated cobalt (ΙΙ) ion with zero-field splitting parameters and the study confirms its mixed valence Co^ΙΙ/Co^ΙΙΙ nature. No slow magnetic relaxation effects were observed for both complexes in the absence of an applied dc magnetic field.     

Synthesis and Characterization of 5-Coordinate Tungsten Hydride Anions: [(tBu3SiNH)(tBu3SiN=)2HWR]M

Treatment of (^tBu₃SiNH)(^tBu₃SiN=)₂WH ( 1 -H) with small alkyl anions (RM) afforded tungsten alkyl hydride anions [(^tBu₃SiNH)(^tBu₃SiN=)₂HWR)]M ( 3 -(R)M: R=CH₃, M=Li; R=ⁿBu, M=Li; R=^neoPe, M=Li; R=CH₂Ph (Bn), M=K (two isomers); R=CCH, M=Na; R=CH=CH₂ (Vy), M=Li). The saturated alkyl anions 3 -(R)M ( 3 -(R)M: R=CH₃, M=Li; R=ⁿBu, M=Li; R=^neoPe, M=Li; R=CH₂Ph (Bn), M=K) degraded via apparent 1,2-RH-elimination to produce the known [(^tBu₃SiN=)₃WH]M ( 2 -HM), but the acetylide ( 3 -(C₂H)Na) and vinyl ( 3 -(Vy)Li) anions converted to their hydrogenated isomers, [(^tBu₃SiN=)₃WVy]Na ( 2 -VyNa) and [(^tBu₃SiN=)₃WEt]Li ( 2 -EtLi), respectively. The structure of 3 -(ⁿBu)Li is reported, and a discussion of tungsten-hydride coupling constants in ^tBu₃SiX-ligated (X=O, NH, N) systems is given.     

Solid-State NMR characterization of a superactive supported ziegler–natta catalyst

The formation of CH-type catalysts has been investigated by high-resolution and solid-state NMR. These catalysts are prepared from a soluble MgCl₂ and 2-ethyl-1-hexanol adduct (MgCl₂·3EH) by reaction with phthalic anhydride (PA) to form dioctylphthalate (DOP) and then with TiCl₄ in the presence of di-i-butylphthalate (BP). In the model systems MgCl₂·3EH/PA, MgCl₂/BP, and MgCl₂/TiCl₄/BP, the ester is complexed with MgCl₂ and /or TiCl₄ in two or more states. Only single-ester C?O and OCH₂ resonances are seen in TiCl₄/BP, probably due to exchange of ester coordinations. CH-catalysts prepared by three different procedures exhibit a single mode of bonding for the ester. The chemical shift values are consistent for ester complexed with MgCl₂. The most active and stereoselective catalyst has the most shielded chemical shift values for the C?O and —OCH₂— carbons, shortest T^H₁ and T^H_1p, and longest T_CH relaxation times. These parameters change monotonically with the decrease of activity and stereoselectivity of the catalyst preparation. © 1993 John Wiley & Sons, Inc.     

Improved synthesis of oxymethylene-linked poly(oxyethylene)

Polyethylene glycol 400 was reacted with CH₂Cl₂ in the presence of KOH to form oxymethylene-linked chains. The method gave a high yield of colourless high-molecular-weight elastomer. The ionic conductivity of a mixture of the polymer with LiCF₃SO₃ ([O]/[Li] = 25) was about 5 × 10^?5S cm^?1 at 25°C.     

Response Surface Optimization of the Critical Media Components for the Production of Surfactin

Optimization of the fermentation media for maximization of surfactin production was carried out. The carbon source (glucose), the nitrogen source (ammonium nitrate) and the mineral salts ferrous and manganous sulphates were the critical components of the medium optimized. A 2⁴ full factorial central composite experimental design followed by multi-stage Monte-Carlo optimization was used in the design of experiments and in the analysis of results. This procedure limited the number of actual experiments performed while allowing for possible interactions between the four components. The optimum values for the tested variables for the maximal production of surfactin were (in g dm⁻³): glucose = 36·5; NH₄NO₃ = 4·5; FeSO₄ = 4×10⁻³ and MnSO₄ = 27·5 ×10⁻². Relative surfactant concentrations were expressed as the reciprocal of the critical micelle concentration (CMC⁻¹) and the maximum predicted yield of surfactin in terms of CMC⁻¹ was 45·5. © 1997 SCI.     

Novel oligonuclear ZnII4, ZnII8 and ZnII2NiII2 complexes with bis(benzoylacetone)-1,3-diiminopropan-2-ol

Reactions of bis(benzoylacetone)-1,3-diiminopropan-2-ol (abbreviated as H₃L) with zinc salts in the presence of triethylamine afforded the compounds [Zn₄(HL)₄]·4CH₃CN (1·4CH₃CN) and [Zn₈L₄(OH)₄]·2CH₃CN (2·2CH₃CN). Further reaction of 1 with Ni(CH₃COO)₂·4H₂O gave the heteronuclear species [Zn₂Ni₂(L)₂(CH₃O)₂(CH₃OH)₂] (3). The crystal structures of 1·4CH₃CN, 2·2CH₃CN and 3 were determined by the X-ray diffraction method.     

Microwave synthesis of tubular zeolitic imidazolate framework ZIF-8 membranes for CO2/CH4 separation

The separation of CO₂/CH₄ is reported in detail by using zeolitic imidazolate framework (ZIF-8) membrane which was prepared on 3-aminopropyltriethoxysilane modified Al₂O₃ tube through microwave heating synthesis. Attributed to the preferential adsorption affinity of CO₂ over CH₄ and a narrow pore window of 0.34 nm, the ZIF-8 membrane shows high separation performances for the separation of CO₂/CH₄ mixtures. For the separation of equimolar CO₂/CH₄ mixture at 100°C and 2 bar feed (1 bar permeate) pressure, a CO₂ permeance of 1.02 × 10^?8 mol/m²· s· Pa and a CO₂/CH₄ selectivity of 6.8 are obtained, which is promising for CO₂ separation.     

Simultaneous oxidative conversion and CO2 or steam reforming of methane to syngas over CoO–NiO–MgO catalyst

CO₂ reforming, oxidative conversion and simultaneous oxidative conversion and CO₂ or steam reforming of methane to syngas (CO and H₂) over NiO–CoO–MgO (Co: Ni: Mg=0·5: 0·5:1·0) solid solution at 700–850°C and high space velocity (5·1×10⁵ cm³ g⁻¹ h⁻¹ for oxidative conversion and 4·5×10⁴ cm³ g⁻¹ h⁻¹ for oxy-steam or oxy-CO₂ reforming) for different CH₄/O₂ (1·8–8·0) and CH₄/CO₂ or H₂O (1·5–8·4) ratios have been thoroughly investigated. Because of the replacement of 50 mol% of the NiO by CoO in NiO–MgO (Ni/Mg=1·0), the performance of the catalyst in the methane to syngas conversion process is improved; the carbon formation on the catalyst is drastically reduced. The CoO–NiO–MgO catalyst shows high methane conversion activity (methane conversion >80%) and high selectivity for both CO and H₂ in the oxy-CO₂ reforming and oxy-steam reforming processes at ⩾800°C. The oxy-steam or CO₂ reforming process involves the coupling of the exothermic oxidative conversion and endothermic CO₂ or steam reforming reactions, making these processes highly energy efficient and also safe to operate. These processes can be made thermoneutral or mildly exothermic or mildly endothermic by manipulating the process conditions (viz. temperature and/or CH₄/O₂ ratio in the feed). © 1998 Society of Chemistry Industry     

A one-step synthesis of protected functionalised titanocene dichlorides

We report a novel, high yield one-step synthesis of water stable and soluble titanocene dichloride dihydrochloride salts from the direct reaction of the neutral amino-substituted cyclopentadienes with TiCl₄. The following novel complexes have been synthesised: C₅H₄(CH₂)₂N(CH₂)₅]₂TiCl₂ (5), [C₅H₄CH(CH₂)₄NMe]₂TiCl₂ (6), [C₅H₄(CH₂)₂N(CH₂)₅]₂TiCl₂·2HCl (7), [C₅H₄CH(CH₂)₄]₂NMeTiCl₂·2HCl (8), [C₅H₄(CH₂)₂N(CH₂)₅]₂TiMe₂ (9).     

New high permeable polysulfone/ionic liquid membrane for gas separation

In this study, the effects of 1-Ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on CO₂/CH₄ separation performance of symmetric polysulfone membranes are investigated. Pure polysulfone membrane and ionic liquid-containing membranes are characterized. Field emission scanning electron microscopy (FE-SEM) is used to analyze surface morphology and thickness of the fabricated membranes. Energy dispersive spectroscopy (EDS) and elemental mapping, Fourier transform infrared (FTIR), thermal gravimetric (TGA), X-ray diffraction (XRD) and Tensile strength analyses are also conducted to characterize the prepared membranes. CO₂/CH₄ separation performance of the membranes are measured twice at 0.3 MPa and room temperature (25 °C). Permeability measurements confirm that increasing ionic liquid content in polymer-ionic liquid membranes leads to a growth in CO₂ permeation and CO₂/CH₄ selectivity due to high affinity of the ionic liquid to carbon dioxide. CO₂ permeation significantly increases from 4.3 Barrer (1 Barrer=10^-10 cm³(STP)·cm·cm^-2·s^-1·cmHg^-1, 1cmHg=1.333kPa) for the pure polymer membrane to 601.9 Barrer for the 30 wt% ionic liquid membrane. Also, selectivity of this membrane is improved from 8.2 to 25.8. mixed gas tests are implemented to investigate gases interaction. The results showed, the disruptive effect of CH₄ molecules for CO₂ permeation lead to selectivity decrement compare to pure gas test. The fabricated membranes with high ionic liquid content in this study are promising materials for industrial CO₂/CH₄ separation membranes.     

Synthesis and characterization of linear asymmetrical poly(propylene oxide) diol

Linear asymmetrical poly(propylene oxide) was synthesized through four‐step reactions: selective benzylation, alcohol exchange reaction, propylene oxide anionic polymerization, debenzylation. One terminal of the asymmetrical polymer chains is alcohol hydroxyl and the other is phenol hydroxyl. It was characterized with infrared (IR) and ¹H Nuclear Magnetic Resonance (¹H‐NMR). Peaks at 1.11, 3.38, and 3.53 ppm were attributed to side groups (? OCH₂CH(CH₃)? ), backbone units (? OCH₂CH(CH₃)? ) and (? OCH₂CH(CH₃)? ) of poly(propylene oxide), respectively. Molecular weight and molecular weight distribution were measured with ¹H‐NMR and laser light scattering (LLS), which showed that the linear asymmetrical poly(propylene oxide) was mono‐disperse (PDI = 1.02–1.07). Then, its carbamate reaction with phenyl isocyanate was studied; the reaction rate constants for phenol hydroxyl and alcohol hydroxyl of poly(propylene oxide) were k₁ = 0.209 mol L^?1 min^?1 and k₂ = 0.051 mol L^?1 min^?1. There was a great reactivity difference for two types of hydroxyls in asymmetrical poly(propylene oxide), contrasting to the single carbamate reaction rate constant of symmetrical poly(propylene oxide) (k₃ = 0.049 mol L^?1 min^?1). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison of Alkali Metal Promoted MgO Catalysts for Their Surface Acidity/Basicity and Catalytic Activity/Selectivity in the Oxidative Coupling of Methane

Alkali metal (viz. Li, Na, K, Rb and Cs) promoted MgO catalysts (with an alkali metal/Mg ratio of 0·1) calcined at 750°C have been compared for their surface properties (viz. surface area, morphology, acidity and acid strength distribution, basicity and base strength distribution, etc.) and catalytic activity/selectivity in the oxidative coupling of methane (OCM) to C₂-hydrocarbons at different temperatures (700–750°C), CH₄/O₂ ratios (4·0 and 8·0) in feed, and space velocities (10320 cm³ g⁻¹ h⁻¹). The surface and catalytic properties of alkali metal promoted MgO catalysts are found to be strongly influenced by the alkali metal promoter and the calcination temperature of the catalysts. A close relationship between the surface density of strong basic sites and the rate of C₂-hydrocarbons formation per unit surface area of the catalysts has been observed. Among the catalysts calcined at 750°C, the best performance in the OCM is shown by Li–MgO (at 750°C). © 1997 SCI.