Synthesis of novel functional polyolefin containing carboxylic acid via Friedel-Crafts acylation reaction

The strong polar group, carboxylic acid, has triumphantly been introduced into ethylene and allylbenzene copolymers without obvious degradation or crosslinking via Friedel-Crafts (F-C) acylation reaction with glutaric anhydride (GA), succinic anhydride (SA) and phthalic anhydride (PA) in the presence of anhydrous aluminum chloride in carbon disulfide. Some important reaction parameters were examined in order to optimize the acylation process. In the optimum reaction conditions, almost all of the phenyls can be acylated with any anhydride. The microstructure of acylated copolymer was characterized by Fr-IR, H-1 NMR and H-1-H-1 COSY. All the peaks of acylated copolymers can be accurately attributed, which indicates that all the acylation reactions occur only at the para-positions of the substituent of the aromatic rings. The thermal behavior was studied by differential scanning calorimetry (DSC), showing that the melting temperatures (T(m)s) of acylated copolymers with GA firstly decrease slowly and then increase significantly with the increase of the amount of carboxyl acid groups.

Synthesis, molecular structures, and norbornene addition polymerization activity of the neutral nickel catalysts supported by beta-diketiminato [N, N], ketiminato [N, O], and Schiff-Base [N, O] ligands

A series of neutral nickel complexes [Ni(Ph)(PPh3)(N, O)] with Schiff-base ligands (N, O) [N, O = 5-Me-3-tert-Bu-(Ar-N=CH)C6H2O (1, Ar = 2,6-Me2C6H3; 2, Ar = 2,6-i-Pr2C6H3)], [Ni(Ph)(PPh3)(N,O)1, with beta-ketiminato ligands (N, O) [N, O = CH3COCHC=(CH3)N-Ar (3, Ar = 2,6-Me2C6H3; 4, Ar = 2,6-i-Pr2C6H3)] and [Ni(N, N)(PPh3)], and with beta-diketiminato ligands (N, N) [5, N, N = [2,6-i-Pr-2(C6H3)N=C(CH3)](2)CH] have been synthesized and characterized. The molecular structures of complexes 1, 4, and 5 have been confirmed by X-ray single-crystal analyses. Although their ligands have similar structures, complex 4 possesses a structure similar to that of four-coordination nickel with complex 1, while complex 5 reveals a rare three-coordination nickel geometry. These compounds show high catalytic activities of up to 3.16 x 10(7) g PNB mol(-1) Ni h(-1) for the addition polymerization of norbornene in the presence of modified methylaluminoxane (MMAO) as cocatalyst. Catalytic activities, polymer yield, molecular weights, and molecular weight distributions of polyborbornene have been investigated under various reaction conditions.

Electron effect of p-substituent on iron(II) and cobalt(II) pyridinebisimine catalyst for ethylene polymerization

A series of 2,6-bis(imino)pyridyl iron and cobalt complexes bearing p-substituent [2,6-(ArN=CMe)(2)C5H3N]-MCl2 (Ar=2,6-Me2C6H3, 2,4,6-Me3C6H2, 2,6-Me-2-4-BrC6H2, 2,6-Me-2-4-ClC6H2, 2,4-Me-2-6-BrC6H2, 2,4-Me-(2)-6-ClC6H2, while M=Fe, Co) have been synthesized and investigated as catalysts for ethylene polymerization in the presence of modified methylaluminoxane as a cocatalyst. The electron effect and positions of the substitueni of pyridinebisimine ligands were observed to affect considerably catalyst activity and polymer property.

Ethylene polymerization by self-immobilized neutral nickel catalysts bearing allyl groups

[Ni(Ph)(PPh3)(N,O)] complexes containing phenyliminophenolato ligands (N,O) (1: N,O = A; 2: N,O = B; 3: N,O = Q 4: N,O = D; 5: N,O = E) have been synthesized and characterized. The molecular structure of 4 was determined by single-crystal X-ray analysis. Complexes 2-5 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization without the use of co-catalysts. The high ethylene polymerization activities of ca. 10(5) g.PE mol(-1) Ni.h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene could be accomplished by changing the ligand structures and reaction conditions. The self-immobilization of catalysts brings about a dramatic increase in the catalytic activities of ethylene polymerization.

Self-immobilized catalysts for ethylene polymerization: neutral, single-component salicylaldiminato phenyl nickel(II) complexes bearing allyl substituents

A new family of self-immobilized ethylene polymerization catalysts, derived from neutral, single-component salicylaldiminato phenyl nickel complexes, is described.

UNSTEADY DIFFUSION KINETICS OF ZIEGLER-NATTA HETEROGENEOUS CATALYST POLYMERIZATION .4. PREDICTION OF EXPERIMENTAL RESULTS OF PROPYLENE ETHYLENE 1-HEXADECENE TERPOLYMERIZATION

The prediction, based on unsteady diffusion kinetics, of the enhancement of reactivity and incorporation of 1-hexadecene in its copolymerization with propylene on adding a small amount of ethylene (increase from 5,2 mol-% to 10,8 mol-% when 2% of ethylene was added, and to 16,1 mol-% when 5% was added) was verified in the terpolymerization of propylene/1-hexadecene/ethylene on a commercial Solvay-type delta-TiCl3 catalyst. The catalyst efficiency was thus also increased. These augmentations originate from the increase in diffusion coefficient of 1-hexadecene at the catalyst surface when the PP crystallinity decreases on introduction of ethylene. Calculation based on unsteady diffusion kinetics showed that the order of diffusion coefficients ethylene > propylene > 1-hexadecene is reversed as the monomer concentration increases when the monomers are not at their equilibrium concentration. Sequence distribution as determined by means of C-13 NMR revealed a tendency of blocky structure rather than a Bernoullian one. The terpolymer compositions obtained by means of an IR method developed in this work conform rather well with the NMR results. Results in this work not only support the unsteady diffusion kinetics but also provide a new route to prepare olefinic copolymer rubbers with heterogeneous titanium catalysts.

FACTORS AFFECTING THE ROLE OF SIO2 IN MGCL2-SUPPORTED ZIEGLER-NATTA COPOLYMERIZATION CATALYSTS

This paper describes the roles of silica (SiO2), the butoxy ligand (-OBu) and ethyl benzoate (EB) on ethylene/1-butene copolymerization with MgCl2/SiO2-supported titanium catalysts. The distribution of SiO2 and of the elements Mg and Ti was observed by means of an energy-dispersed X-ray microanalyzer on a scanning electron microscope (SEM). An inversed Si/Mg ratio results, at invariant Ti/Mg ratio and -OBu content, in higher catalyst efficiency and higher comonomer incorporation, with a correspondingly decreased crystallinity of the copolymers. Thus, the inert carrier SiO2 favors copolymerizability, as seen from the values of the reactivity ratios. The copolymer compositional distribution is also affected by the SiO2 content, as seen from the DSC curves of the copolymers. As to the copolymer morphology, addition of SiO2 makes the copolymer particles larger and more uniform.

A density functional theory study of the a-olefin selectivity in Fischer-Tropsch synthesis

We studied the alpha-olefin selectivity in Fischer-Tropsch (FT) synthesis using density functional theory (131717) calculations. We calculated the relevant elementary steps from C-2 to C-6 species. Our results showed that the barriers of hydrogenation and dehydrogenation reactions were constant with different chain lengths, and the chemisorption energies of alpha-olefins from DFT calculations also were very similar, except for C-2 species. A simple expression of the paraffin/olefin ratio was obtained based on a kinetic model. Combining the expression of the paraffin/olefin ratio and our calculation results, experimental findings are satisfactorily explained. We found that the physical origin of the chain length dependence of paraffin/olefin ratio is the chain length dependence of both the van der Waals interaction between adsorbed alpha-olefins and metal surfaces and the entropy difference between adsorbed and gaseous alpha-olefins, and that the greater chemisorption energy of ethylene is the main reason for the abnormal ethane/ethylene ratio. (c) 2008 Elsevier Inc. All rights reserved.

Eumenitin, a novel antimicrobial peptide from the venom of the solitary eumenine wasp Eumenes rubronotatus

A novel antimicrobial peptide, eumenitin, was isolated from the venom of the solitary eumenine wasp Eumenes rubronotatus. The sequence of eumenitin, Leu-Asn-Leu-Lys-Gly-Ile-Phe-Lys-Lys-Val-Ala-Ser-Leu-Leu-Thr, was mostly analyzed by mass spectrometry together with Edman degradation, and corroborated by solid-phase synthesis. This peptide has characteristic features of cationic linear a-helical antimicrobial peptides, and therefore, can be predicted to adopt an amphipathic a-helix secondary structure. In fact, the CD spectra of eumenitin in the presence of TFE or SDS showed a high content of alpha-helical conformation. Eumenitin exhibited inhibitory activity against both Gram-positive and Gram-negative bacteria, and moderately stimulated degranulation from the rat peritoneal mast cells and the RBL-2H3 cells, but showed no hemolytic activity against human erythrocytes. This antimicrobial peptide in the eumenine wasp venom may play a role in preventing potential infection by microorganisms during prey consumption by their larvae. (c) 2006 Elsevier B.V. All rights reserved.

Anoplin, a novel antimicrobial peptide from the venom of the solitary wasp Anoplius samariensis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis of Macrocyclic Polymers Formed via Intramolecular Radical Trap-Assisted Atom Transfer Radical Coupling

The synthesis of cyclic polystyrene (Pst) with an alkoxyamine functionality has been accomplished by intramolecular radical coupling in the presence of a nitroso radical trap Linear alpha,omega-dibrominated polystyrene, produced by the atom transfer radical polymerization (ATRP) of styrene using a dibrominated initiator, was subjected to chain-end activation via the atom transfer radical coupling (ATRC) process under pseudodilute conditions in the presence of 2-methyl-2-nitrosopropane (MNP). This radical trap-assisted, intramolecular ATRC (RTA-ATRC) produced cyclic polymers in greater than 90% yields possessing < G > values in the 0.8-0.9 range as determined by gel permeation chromatography (GPC). Thermal-induced opening of the cycles, made possible by the incorporated alkoxyamine, resulted in a return to the original apparent molecular weight, further supporting the formation of cyclic polymers in the RTA-ATRC reaction. Liquid chromatography-mass spectrometry (LC-MS) provided direct confirmation of the cyclic architecture and the incorporation of the nitroso group into the macrocycle RTA-ATRC cyclizations carried out with faster rates of polymer addition into the redox active solution and/or in the presence of a much larger excess of MNP (up to a 250:1 ratio of MNP:C-Br chain end) still yielded cyclic polymers that contained alkoxyamine functionality.

Oligomerisation process

This invention relates to base oils for lubricating compositions. In particular, the present invention provides a process for the selective oligomerisation of C5 to C 20 alpha-olefins to produce polyalphaolefin oligomers with a molecular weight distribution that is suitable for use in lubricant base oils.

Oligomerisation process

This invention relates to base oils for lubricating compositions. In particular, the present invention provides a process for the selective oligomerisation of C5 to C20 alpha-olefins to produce polyalphaolefin oligomers with a molecular weight distribution that is suitable for use in lubricant base oils.

Photochemistry of .alpha.,.beta.-unsaturated thiones: addition to electron-rich olefins from T1

1,1,3-Trimethyl-2-thioxo-1,2-dihydronaphthale(1n)e adds to electron-rich olefins upon excitation to either Sz (PP*) or Sl (ns*) states. Excitation to S2 level resulted in the same mixture of products, namely thietane and 1,4-dithiane, as on excitation to S1 level. Addition occurs to the thiocarbonyl function and not to the carbon-carbon double bond. The addition is site-specific, and the formation of thietane is regiospecific. The ratio of thietane to 1,4-dithiane in the product mixture is dependent on the concentration of the thioenone. The addition is suggested to originate from the lowest triplet state (Tl) and involves diradical intermediates.

Photochemistry of .alpha.,.beta.-unsaturated thiones. Cycloaddition to electron-deficient olefins from higher excited states

Electron-deficient olefins add to thioenone 1 upon m* excitation. Cycloaddition occurs to the thiocarbonyl chromophore preferentially from the less-hindered side to yield thietanes. Thietane formation is stereospecific and regioselective. This addition has been inferred to originate from the second excited singlet, S2(?rx*), state. The exciplex intermediacy has been inferred from the dependence of the fluorescence quenching rate constant on the electron-acceptor properties of the olefin. The observed site specificity and regioselectivity are rationalized on the basis of PMO theory. The observed photochemical behavior of thioenone is different from that of enones.