Synthesis and ethylene polymerization of 8‐(fluorenylarylimino)‐5,6,7‐trihydroquinolylnickel chlorides: Tailoring polyethylenes by adjusting fluorenyl position and adduct Et2Zn

A series of 8‐(arylimino)‐5,6,7‐trihydroquinolines ligand pendant fluorenyl group at N‐aryl ring, and their nickel complexes ( Ni1 ? Ni5 ) have been prepared and characterized. Once activated with Et₂AlCl, the complexes Ni1 , Ni2 , and Ni3 bearing ligands from para‐fluorenylaniline produced unimodal polyethylenes; on the contrary complexes Ni4 and Ni5 gave bimodal polyethylenes due to steric influence of ligands from ortho‐fluorenyl anilines. With a increment of Et₂Zn/ Ni4 ratio from 0 to 400, the distinct bimodel polyethylenes were obtained with molecular weights shifted from 14.3 to 57.6 kg·mol^?1; apart shiftment to higher molecular weights, the portion of low molecular weight decreased along with higher portion of high molecular weight. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1910–1919     

Pd(II) complexes bearing di‐ and monochelate fluorinated β‐ketonaphthyliminato ligand and their catalytic properties towards vinyl‐addition polymerization and copolymerization of norbornene and ester‐functionalized norbornene derivative

Fluorinated β‐ketonaphthyliminate ligand CF₃C(O)CHC[HN(naphthyl)]CH₃ ( L1 ) and Pd(II) complexes with dichelate fluorinated β‐ketonaphthyliminato ligand, {CF₃C(O)CHC[N(naphthyl)]CH₃}₂Pd ( C1 ), as well as with monochelate fluorinated β‐ketonaphthyliminato ligand, {CF₃C(O)CHC[N(naphthyl)]CH₃}Pd(CH₃)(PPh₃) ( C2 ), were synthesized and their solid‐state structures were confirmed using X‐ray crystallographic analysis. The Pd(II) complexes were employed as precursors to catalyze norbornene (NB) homo‐ and copolymerization with ester‐functionalized NB derivative using B(C₆F₅)₃ as a co‐catalyst. High activity up to 2.3 × 10⁵ g_polymer mol_Pd^?1 h^?1 for the C1 /B(C₆F₅)₃ system and 3.4 × 10⁶ g_polymer mol_Pd^?1 h^?1 for the C2 /B(C₆F₅)₃ system was exhibited in NB homopolymerization. Moreover, the Pd(II) complexes exhibited a high level of tolerance towards the ester‐functionalized MB monomer. In comparison with the C1 /B(C₆F₅)₃ system, the C2 /B(C₆F₅)₃ system exhibited better catalytic property towards the copolymerization of NB with 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH₃), and soluble vinyl‐addition‐type copolymers were obtained with relatively high molecular weights (3.6 × 10⁴–7.5 × 10⁴ g mol^?1) as well as narrow molecular weight distributions (1.49–2.15) depending on the variation of monomer feed ratios. The NB‐COOCH₃ insertion ratio in all copolymers could be controlled in the range 2.8–21.0 mol% by tuning a content of 10–50 mol% NB‐COOCH₃ in the monomer feed ratios. Copolymerization kinetics were expressed by the NB and NB‐COOCH₃ monomer reactivity ratios: r_NB‐COOCH3 = 0.18, r_NB = 1.28 were determined for the C1 /B(C₆F₅)₃ system and r_NB‐COOCH3 = 0.19, r_NB = 3.57 for the C2 /B(C₆F₅)₃ system using the Kelen–Tüdõs method. Copyright © 2014 John Wiley & Sons, Ltd.     

Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n‐butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free‐radical process. Although the polyester‐core‐based RAFT agent mediated polymerization of n‐butyl acrylate displayed a linear evolution of the number‐average molecular weight (M_n) up to high monomer conversions (>70%) and molecular weights [M_n > 140,000 g mol^?1, linear poly(methyl methacrylate) equivalents)], the corresponding styrene‐based system reached a maximum molecular weight at low conversions (≈30%, M_n = 45,500 g mol^?1, linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n‐butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene‐based star polymers were successfully cast into highly regular honeycomb‐structured microarrays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3847–3861, 2003     

Ni(II) and Pd(II) complexes bearing benzocyclohexane–ketoarylimine for copolymerization of norbornene with 5‐norbornene‐2‐carboxylic ester

A serial of late transition metal complexes, which bearing Benzocyclohexane–ketoarylimine ligand and named as Mt(benzocyclohexane–ketoarylimino)₂ {Mt(bchkai)₂: Mt=Ni or Pd; bchkai=C₁₀H₈(O)CN(Ar)CH₃; Ar=naphthyl or fluoryl}, have been synthesized and characterized. The molecular structures of the ligands and nickel complex have been confirmed by X‐ray single‐crystal analyses. The nickel complexes exhibited very high activity up to 2.7 × 10⁵ g_polymer/mol_Ni·h and palladium complexes showed high activity up to 2.3 × 10⁵ g_polymer/mol_Pd·h for norbornene (NB) homo‐polymerization with tris(pentafluorophenyl)borane as cocatalyst. The four complexes were effective for copolymerization of NB and 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH₃) in relatively high activities (0.1–2.4 × 10⁵ g_polymer/mol_Mt·h) and produced the addition‐type copolymers with relatively high molecular weights (0.5 × 10⁵–1.2 × 10⁵ g/mol) as well as narrow molecular weight distributions (PDI < 2 for all polymers). Influences of the metals and comonomer feed content on the polymerization activity as well as on the incorporation rates (20.9–42.6%) were investigated. The achieved NB/NB‐COOCH₃ copolymers were confirmed to be noncrystalline, exhibited good thermal stability (T_d > 400°C) and showed good solubility in common organic solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Highly branched and high‐molecular‐weight polyethylenes produced by 1‐[2,6‐bis(bis(4‐fluorophenyl)methyl)‐4‐MeOC6H2N]‐2‐aryliminoacenaphthylnickel(II) halides

A series of unsymmetrical 1‐[2,6‐bis(bis(4‐fluorophenyl)methyl)‐4‐MeOC₆H₂N]‐2‐aryliminoacenaphthene‐nickel(II) halides has been synthesized and fully characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (¹H NMR), ¹³C NMR, and ¹⁹F NMR spectroscopy as well as elemental analysis. The structures of Ni1 and Ni6 have been confirmed by the single‐crystal X‐ray diffraction. On activation with cocatalysts either ethylaluminum sesquichloride or methylaluminoxane, all the title nickel complexes display high activities toward ethylene polymerization up to 16.14 × 10⁶ g polyethylene (PE) mol^?1(Ni) h^?1 at 30 °C, affording PEs with both high branches (up to 103 branches/1000 carbons) and molecular weight (1.12 × 10⁶ g mol^?1) as well as narrow molecular weight distribution. High branching content of PE can be confirmed by high temperature ¹³C NMR spectroscopy and differential scanning calorimetry. In addition, the PE exhibited remarkable property of thermoplastic elastomers (TPEs) with high tensile strength (σ_b = 21.7 MPa) and elongation at break (ε_b = 937%) as well as elastic recovery (up to 85%), indicating a better alternative to commercial TPEs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 130–145     

Free‐radical copolymerization of styrene and m‐isopropenyl‐α,α′‐dimethylbenzyl isocyanate studied by 1H NMR kinetic experiments

The free‐radical copolymerization of m‐isopropenyl‐α,α′‐dimethylbenzyl isocyanate (TMI) and styrene was studied with ¹H NMR kinetic experiments at 70 °C. Monomer conversion vs time data were used to determine the ratio k_p × k_t^?0.5 for various comonomer mixture compositions (where k_p is the propagation rate coefficient and k_t is the termination rate coefficient). The ratio k_p × k_t^?0.5 varied from 25.9 × 10^?3 L^0.5 mol^?0.5 s^?0.5 for pure styrene to 2.03 × 10^?3 L^0.5 mol^?0.5 s^?0.5 for 73 mol % TMI, indicating a significant decrease in the rate of polymerization with increasing TMI content in the reaction mixture. Traces of the individual monomer conversion versus time were used to map out the comonomer mixture composition drift up to overall monomer conversions of 35%. Within this conversion range, a slight but significant depletion of styrene in the monomer feed was observed. This depletion became more pronounced at higher levels of TMI in the initial comonomer mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1064–1074, 2002     

Solvent and Substituent Effects in the Solvolysis of 9‐Aryl‐9‐bromofluorenes

The solvolysis of eight 9‐aryl‐9‐bromofluorenes ( 6b～6i ) in a variety of solvents were studied. Correlation analysis using single‐parameter Grunwald‐Winstein equation (Eqn. 1) with different Y scales showed good linearity (R ≥ 0.98) for most cases if Y_xBnBr was employed. Linear relationships were observed from Hammett‐type analysis of logarithm of rate constants using Brown‐Okamoto σ⁺ constants (Eqn. 3), although inverse order of k(p‐CF₃)/k(m‐ CF₃) was realized in a number of cases. The ρ values were found to vary slightly with different solvent systems. Calculated atomic charge reveals the similarity between 9‐phenyl‐9‐fluorenyl cation ( 7 ) and triphenylmethyl cation ( 8 ). An extended charge delocalization throughout the fluorenyl ring led to the conclusion of the insignificance of antiaromaticity, which was in harmony with that obtained in previous studies. The variation of relative k_Br/k_Cl rate ratios was attributed to the electrophilic pull by solvents in solvolysis.     

Initiator efficiency of 2,2′‐azobis(isobutyronitrile) in bulk dodecyl acrylate free‐radical polymerizations over a wide conversion and molecular weight range

An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(21) 5559 . The initiator efficiency, f, of 2,2′‐azobis(isobutyronitrile) (AIBN) in dodecyl acrylate (DA) bulk free‐radical polymerizations has been determined over a wide range of monomer conversion in high‐molecular‐weight regimes (M_n ? 10⁶ g mol^?1 [? 4160 units of DA)] with time‐dependent conversion data obtained via online Fourier transform near infrared spectroscopy (FTNIR) at 60 °C. In addition, the required initiator decomposition rate coefficient, k_d, was determined via online UV spectrometry and was found to be 8.4 · 10^?6 s^?1 (±0.5 · 10^?6 s^?1) in dodecane, n‐butyl acetate, and n‐dodecyl acetate at 60 °C. The initiator efficiency at low monomer conversions is relatively low (f = 0.13) and decreases with increasing monomer to polymer conversions. The evolution of f with monomer conversion (in high‐molecular‐weight regimes), x, at 60 °C can be summarized by the following functionality: f^{60 °C} (x) = 0.13–0.22 · x + 0.25 · x² (for x ≤ 0.45). The reported efficiency data are believed to have an error of >50%. The ratio of the initiator efficiency and the average termination rate coefficient, 〈k_t±, (f/〈k_t〉) has been determined at various molecular weights for the generated polydodecyl acrylate (M_n = 1900 g mol^?1 (? 8 units of DA) up to M_n = 36,500 g mol^?1 (? 152 units of DA). The (f/〈k_t〉) data may be indicative of a chain length‐dependent termination rate coefficient decreasing with (average) chain length. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5170–5179, 2004     

Synthesis and characterization of Ni(II) complexes bearing of 2‐(1H–benzimidazol‐2‐yl)‐phenol derivatives as highly active catalysts for ethylene oligomerization

Novel Ni(II) complexes of 2‐(1H–benzimidazol‐2‐yl)‐phenol derivatives (HL_x: x  =  1–5; C1–C5 ) have been synthesized and characterized. In the mononuclear complexes, the ligands were coordinated as bidentate, via one imine nitrogen and the phenolate oxygen atoms. The structures of the compounds were confirmed on the basis of FT‐IR, UV–Vis, ¹H‐, ¹³C–NMR, inductively coupled plasma and elemental analyses (C, H and N). The purity of these compounds was ascertained by melting point (m.p.) and thin‐layer chromatography. The geometry optimization and vibrational frequency calculations of the compounds were performed using Gaussian 09 program with B3LYP/TZVP level of theory. All Ni(II) complexes were activated with diethylaluminum chloride (Et₂AlCl), so that C2 showed the highest activity [6600 kg mol^?1 (Ni) h^?1], where the ligand contains a chlorine substituent. Oligomers obtained from the complexes consist mainly of dimer and trimer, and also exhibit high selectivity for linear 1‐butene and 1‐hexene. Both the steric and electronic effects of coordinative ligands affect the catalytic activity and the properties of the catalytic products.     

1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐2‐aryliminoacenaphthylylnickel halides highly polymerizing ethylene for the polyethylenes with high branches and molecular weights

A series of 1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐ 2‐aryliminoacenaphthylene derivatives ( L1–L5 ) and their halonickel complexes LNiX₂ (X = Br, Ni1–Ni5 ; X = Cl, Ni6–Ni10 ) are synthesized and well characterized. The molecular structures of representative complexes Ni2 and Ni4 are confirmed as the distorted tetrahedron geometry around nickel atom by the single crystal X‐ray diffraction. Upon activation with methylaluminoxane, all nickel complexes show high activities up to 1.49 × 10⁷ g of PE (mol of Ni)^?1 h^?1 toward ethylene polymerization, producing polyethylenes with high branches and molecular weights up to 1.62 × 10⁶ g mol^?1 as well as narrow polydispersity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1369–1378     

Synthesis and kinetic study on the thermal degradation of triblock copolymer of polycaprolactone‐poly (glycidyl nitrate)‐polycaprolactone (PCL‐PGN‐PCL) as an energetic binder

In this study, an energetic binder is synthesized via ring opening copolymerization of ε‐caprolactone with poly (glycidyl nitrate) (PGN) of low molecular weight (M_n = 1350 g mol^?1) as a macroinitiator to form triblock copolymer polycaprolactone‐PGN‐polycaprolactone (PCL‐PGN‐PCL) (M_n = 4128 g mol^?1). The effects of catalyst type and its concentration, reaction time, and solvent are investigated in this polymerization reaction. The resulting triblock copolymer is characterized by Fourier transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The DSC result shows that the glass transition temperature of triblock copolymer (T_g = ?50°C) is lower than PGN (T_g = ?35°C). Also, the decomposition kinetics of this energetic binder is studied by DSC, TGA, and its derivative (DTG). An advanced isoconversional method is applied for kinetic analysis. Activation energy is calculated by Flynn‐Wall‐Ozawa (FWO) and Kissinger methods. The resulting activation energy from Kissinger method for the first and the second steps are 42.98 and 74.56 kJ mol^?1, respectively. Also, it is found from FWO results that the activation energy for the copolymer increases with degradation degree (α).     

Bimetallic Ni–Co‐based metal–organic framework: An open metal site adsorbent for enhancing CO2 capture

An open metal site framework named UTSA‐16 was synthesized and modified as a high‐capacity adsorbent for reversible CO₂ capture. Partial substitution of intrinsic Co²⁺ sites of UTSA‐16 with Ni²⁺ centres was realized in the molar composition range 0–75% Ni with the aim of increasing CO₂ uptake. Synthesized bimetallic Nix‐UTSA‐16 (x = 0, 20, 50, 75) materials were characterized using various techniques to assess the influence of chemical composition on CO₂ binding affinity and any subsequent physical change in morphology, crystal size and porosity on the total uptake. Experimental isotherm adsorption studies showed the following trend for CO₂ adsorption capacity employing the Nix‐UTSA‐16 series: Ni20‐UTSA‐16 > UTSA‐16 > Ni50‐UTSA‐16 > Ni75‐UTSA‐16. According to the dynamic breakthrough CO₂ profiles measured for a mixture of CO₂ and CH₄ (15/85 molar ratio), Ni20‐UTSA‐16 exhibited 2 times the breakthrough time with 1.5 times the loading capacity at 75 Nml min^?1 feed flow rate, compared to the parent UTSA‐16. In addition, the Ni20‐UTSA‐16 bimetallic metal–organic framework exhibited lower isosteric heat of adsorption compared to UTSA‐16 (ΔH_ave = 28.54 versus 46.85 kJ mol^?1). As a result, more than 95% of its capacity was restored by applying a partial vacuum for only 1 h at room temperature without involving any other time‐ and energy‐consuming regenerative step.     

Impact of the anion and chalcogen on the crystal structure and properties of 4,6‐dimethyl‐2‐pyrimido(thio)nium halides

By the reaction of urea or thiourea, acetylacetone and hydrogen halide (HF, HBr or HI), we have obtained seven new 4,6‐dimethyl‐2‐pyrimido(thio)nium salts, which were characterized by single‐crystal X‐ray diffraction, namely, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium bifluoride, C₆H₉N₂O⁺·HF₂^? or (dmpH)F₂H, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium bromide, C₆H₉N₂O⁺·Br^? or (dmpH)Br, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium iodide, C₆H₉N₂O⁺·I^? or (dmpH)I, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium iodide–urea (1/1), C₆H₉N₂O⁺·I^?·CH₄N₂O or (dmpH)I·ur, 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium bifluoride–thiourea (1/1), C₆H₉N₂S⁺·HF₂^?·CH₄N₂S or (dmptH)F₂H·tu, 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium bromide, C₆H₉N₂S⁺·Br^? or (dmptH)Br, and 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium iodide, C₆H₉N₂S⁺·I^? or (dmptH)I. Three HCl derivatives were described previously in the literature, namely, 4,6‐dimethyl‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium chloride, (dmpH)Cl, 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium chloride monohydrate, (dmptH)Cl·H₂O, and 4,6‐dimethyl‐2‐sulfanylidene‐2,3‐dihydropyrimidin‐1‐ium chloride–thiourea (1/1), (dmptH)Cl·tu. Structural analysis shows that in 9 out of 10 of these compounds, the ions form one‐dimensional chains or ribbons stabilized by hydrogen bonds. Only in one compound are parallel planes present. In all the structures, there are charge‐assisted N⁺—H…X^? hydrogen bonds, as well as weaker C_Ar⁺—H…X^? and π⁺…X^? interactions. The structures can be divided into five types according to their hydrogen‐bond patterns. All the compounds undergo thermal decomposition at relatively high temperatures (150–300 °C) without melting. Four oxopyrimidinium salts containing a π⁺…X^?…π⁺ sandwich‐like structural motif exhibit luminescent properties.     

The elimination kinetics and mechanisms of ethyl piperidine‐3‐carboxylate,ethyl 1‐methylpiperidine‐3‐carboxylate,and ethyl 3‐(piperidin‐1‐yl)propionate in the gas phase

The gas‐phase elimination kinetics of the above‐mentioned compounds were determined in a static reaction system over the temperature range of 369–450.3°C and pressure range of 29–103.5 Torr. The reactions are homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius expressions: ethyl 3‐(piperidin‐1‐yl) propionate, log k₁(s^?1) = (12.79 ± 0.16) ? (199.7 ± 2.0) kJ mol^?1 (2.303 RT)^?1; ethyl 1‐methylpiperidine‐3‐carboxylate, log k₁(s^?1) = (13.07 ± 0.12)–(212.8 ± 1.6) kJ mol^?1 (2.303 RT)^?1; ethyl piperidine‐3‐carboxylate, log k₁(s^?1) = (13.12 ± 0.13) ? (210.4 ± 1.7) kJ mol^?1 (2.303 RT)^?1; and 3‐piperidine carboxylic acid, log k₁(s^?1) = (14.24 ± 0.17) ? (234.4 ± 2.2) kJ mol^?1 (2.303 RT)^?1. The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene through a concerted six‐membered cyclic transition state type of mechanism. The intermediate β‐amino acids decarboxylate as the α‐amino acids but in terms of a semipolar six‐membered cyclic transition state mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 106–114, 2006     

Ni(II) and Pd(II) complexes bearing novel bis(β‐ketoamino) ligand and their catalytic activity toward copolymerization of norbornene and 5‐norbornene‐2‐yl acetate combined with B(C6F5)3

Two complexes Mt{C₁₀H₈(O)C[N(C₆H₅)]CH₃}₂ [Mt = Ni(II); Mt = Pd(II)] were synthesized, and the solid‐state structures of the complexes have been determined by single‐crystal X‐ray diffractions. Homopolymerization of norbornene (NB) and copolymerization of NB and 5‐norbornene‐2‐yl acetate (NB‐OCOCH₃) were carried out in toluene with both the two complexes mentioned above in combination with B(C₆F₅)₃. Both the catalytic systems exhibited high activity toward the homopolymerization of NB (as high as 2.7 × 10⁵ g_polymer/mol_Ni h, for Ni(II)/B(C₆F₅)₃ and 2.1 × 10⁵ g_polymer/mol_Pd h for Pd(II)/B(C₆F₅)₃, respectively.). Although the Pd(II)/B(C₆F₅)₃ shows very lower activity toward the copolymerization of NB with NB‐OCOCH₃, Ni(II)/B(C₆F₅)₃ shows a high activity and produces the addition‐type copolymer with relatively high molecular weights (MWs; 1.80–2.79 × 10⁵ g/mol) as well as narrow MW distribution (1.89–2.30). The NB‐OCOCH₃ content in the copolymers can be controlled up to 5.8–12.0% by varying the comonomer feed ratios from 10 to 50%. The copolymers exhibited high transparency, high glass transition temperature (T_g > 263.9 °C), better solubility, and mechanical properties compared with the homopolymer of NB. The reactivity ratios of the two monomers were determined to be r_NB‐OCOMe = 0.08, r_NB = 7.94 for Ni(II)/B(C₆F₅)₃ system, and r_NB‐OCOMe = 0.07, r_NB = 6.49, for Pd(II)/B(C₆F₅)₃ system by the Kelen‐Tüdõs method. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Moderately branched ultra‐high molecular weight polyethylene by using N,N′‐nickel catalysts adorned with sterically hindered dibenzocycloheptyl groups

Five examples of unsymmetrical 1,2‐bis (arylimino) acenaphthene ( L1 – L5 ), each containing one N‐2,4‐bis (dibenzocycloheptyl)‐6‐methylphenyl group and one sterically and electronically variable N‐aryl group, have been used to prepare the N,N′‐nickel (II) halide complexes, [1‐[2,4‐{(C₁₅H₁₃}₂–6‐MeC₆H₂N]‐2‐(ArN)C₂C₁₀H₆]NiX₂ (X = Br: Ar = 2,6‐Me₂C₆H₃ Ni1 , 2,6‐Et₂C₆H₃ Ni2 , 2,6‐i‐Pr₂C₆H₃ Ni3 , 2,4,6‐Me₃C₆H₂ Ni4 , 2,6‐Et₂–4‐MeC₆H₂ Ni5 ) and (X = Cl: Ar = 2,6‐Me₂C₆H₃ Ni6 , 2,6‐Et₂C₆H₃ Ni7 , 2,6‐i‐Pr₂C₆H₃ Ni8 , 2,4,6‐Me₃C₆H₂ Ni9 , 2,6‐Et₂–4‐MeC₆H₂ Ni10 ), in high yield. The molecular structures Ni3 and Ni7 highlight the extensive steric protection imparted by the ortho‐dibenzocycloheptyl group and the distorted tetrahedral geometry conferred to the nickel center. On activation with either Et₂AlCl or MAO, Ni1 – Ni10 exhibited very high activities for ethylene polymerization with the least bulky Ni1 the most active (up to 1.06  ×  10⁷ g PE mol^?1(Ni) h^?1 with MAO). Notably, these sterically bulky catalysts have a propensity towards generating very high molecular weight polyethylene with moderate levels of branching and narrow dispersities with the most hindered Ni3 and Ni8 affording ultra‐high molecular weight material (up to 1.5  ×  10⁶ g mol^?1). Indeed, both the activity and molecular weights of the resulting polyethylene are among the highest to be reported for this class of unsymmetrical 1,2‐bis (imino)acenaphthene‐nickel catalyst.     

Diels–Alder reaction of 2,7‐dichloroquinoline‐5,8‐dione with a thiazole o‐quinodimethane. Assignment of the regiochemistry by 1H–13C HMBC correlations

The Diels–Alder reaction between a thiazole o‐quinodimethane and 4,6‐dichloroquinoline‐5,8‐dione gave 6‐chloro‐9‐azaanthra[2,3‐b]thiazole‐5,10‐dione as a single regioisomer. Its structure was assigned by 2D ¹H–¹³C HMBC short‐ and long‐range correlations. Measuring the spectra in CF₃CO₂D indicated that both nitrogen atoms of pyridine and thiazole rings are deuterated. Copyright © 2001 John Wiley & Sons, Ltd.     

齐聚噻吩衍生物电致变色性质

合成了四种齐聚噻吩衍生物：5,5"-二氰基-2,2’:5’,2"-三噻吩 (DCN3T), 5,5"’-二氰基-2,2’:5’,2":5",2"’-四噻吩 (DCN4T), 5,5"’-甲氧基-2,2’:5’,2":5",2"’-四噻吩(DMO4T) 和 4,4"-二羧基-5,5"-二丙基-2,2’:5’,2"-三噻吩 (BP3T-DCOOH),研究了它们的电致变色性质,研究结果发现,这四种齐聚噻吩衍生物膜在电场作用下,可以发生可逆的颜色变化。     

Encapsulation of AGE‐Breaker Alagebrium by Cucurbit[7]uril Improved the Stability of Both Its Carbonyl α‐Hydrogen and Thiazolium C2‐Hydrogen

As determined by both ¹H NMR and UV/Vis spectroscopic titration, ESI‐MS, isothermal titration calorimetry, and DFT molecular modeling, advanced glycation end products (AGE) breaker alagebrium (ALA) formed 1:1 guest–host inclusion complexes with cucurbit[7]uril (CB[7]), with a binding affinity, K_a, in the order of magnitude of 10⁵ m ^?1, thermodynamically driven by both enthalpy (ΔH=?6.79 kcal mol^?1) and entropy (TΔS=1.21 kcal mol^?1). For the first time, a dramatic inhibition of keto–enol tautomerism of the carbonyl α‐hydrogen of ALA has been observed, as evidenced by over an order of magnitude decrease of both the first step rate constant, k₁, and the second step rate constant, k₂, during hydrogen/deuterium exchange in D₂O. Meanwhile, as expected, the reactivity of C2‐hydrogen was also inhibited significantly, with an upshift of 2.09 pK_a units. This discovery will not only provide an emerging host molecule to modulate keto–enol tautomerism, but also potentially lead to a novel supramolecular formulation of AGE‐breaker ALA for improved stability and therapeutic efficacy.     

Depolymerization kinetics of di(4‐tert‐butyl cyclohexyl) itaconate and Mark‐Houwink‐Kuhn‐Sakurada parameters of di(4‐tert‐butyl cyclohexyl) itaconate and di‐n‐butyl itaconate

Multipulse pulsed laser polymerization coupled with size exclusion chromatography (MP‐PLP‐SEC) has been employed to study the depropagation kinetics of the sterically demanding 1,1‐disubstituted monomer di(4‐tert‐butylcyclohexyl) itaconate (DBCHI). The effective rate coefficient of propagation, k, was determined for a solution of monomer in anisole at concentrations, c, 0.72 and 0.88 mol L^?1 in the temperature range 0 ≤ T ≤ 70 °C. The resulting Arrhenius plot (i.e., ln k vs. 1/RT) displayed a subtle curvature in the higher temperature regime and was analyzed in the linear part to yield the activation parameters of the forward reaction. In the temperature region where no depropagation was observed (0 ≤ T ≤ 50 °C), the following Arrhenius parameters for k_p were obtained (DBCHI, E_p = 35.5 ± 1.2 kJ mol^?1, ln A_p = 14.8 ± 0.5 L mol^?1 s^?1). In addition, the k data was analyzed in the depropagatation regime for DBCHI, resulting in estimates for the associated entropy (?ΔS = 150 J mol^?1 K^?1) of polymerization. With decreasing monomer concentration and increasing temperature, it is increasingly more difficult to obtain well structured molecular weight distributions. The Mark Houwink Kuhn Sakurada (MHKS) parameters for di‐n‐butyl itaconate (DBI) and DBCHI were determined using a triple detection GPC system incorporating online viscometry and multi‐angle laser light scattering in THF at 40 °C. The MHKS for poly‐DBI and poly‐DBCHI in the molecular weight range 35–256 kDa and 36.5–250 kDa, respectively, were determined to be K_DBI = 24.9 (10³ mL g^?1), α_DBI = 0.58, K_DBCHI = 12.8 (10³ mL g^?1), and α_DBCHI = 0.63. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1931–1943, 2007