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Poly(Alpha-olefins)

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https://www.readbyqxmd.com/read/28968059/organic-modified-silver-nanoparticles-as-lubricant-additives
#1
Chanaka Kumara, Huimin Luo, Donovan N Leonard, Harry M Meyer, Jun Qu
Advanced lubrication is essential in human life for improving mobility, durability, and efficiency. Here we report the synthesis, characterization, and evaluation of two groups of oil-suspendable silver nanoparticles (NPs) as candidate lubricant additives. Two types of thiolated ligands, 4-(tert-butyl)benzylthiol (TBBT) and dodecanethiol (C12), were used to modify Ag NPs in two size ranges, 1-3 and 3-6 nm. The organic surface layer successfully suspended the Ag NPs in a poly-alpha-olefin (PAO) base oil with concentrations up to 0...
October 25, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27425829/impact-resistance-of-oil-immersed-lignum-vitae
#2
Wei Yin, Lei Shan, Hongyu Lu, Yelong Zheng, Zhiwu Han, Yu Tian
Biological materials immersed in vegetable and mineral oil, such as rattan armor and wooden sleepers, have been extensively used since ancient times because of their excellent mechanical properties. This study quantitatively investigated the viscoelasticity and tribological performance of lignum vitae immersed in poly-alpha-olefin (PAO) and tung oils (Aleuritesfordii Hemsl.) to reveal the mechanism of impact resistance. The acceleration of samples immersed in tung oil was higher than that of dry and PAO-immersed samples in the first impact...
July 18, 2016: Scientific Reports
https://www.readbyqxmd.com/read/23427568/-investigation-of-the-chain-structure-and-thermal-property-of-xylene-solubles-of-impact-polypropylene-copolymers
#3
Hua-Lin Luo, Ying Zhao, Jin-Guang Wu, Du-Jin Wang
Impact polypropylene copolymers (IPC) are in-situ blends of polypropylene homopolymer and ethylene-alpha-olefin copolymers formed in the reactor, which is a multiphasic complex material with isotactic polypropylene (iPP) as a matrix in which poly(ethylene-alpha-olefin) elastomeric copolymer is finely dispersed, and ethylene-alpha-olefin random copolymer (EPR) acts as an elastomer to improve the impact resistance properties of iPP at room temperature and low temperature. In the present, the content of xylene soluble is used to evaluate the content of EPR rubber phase in IPC...
December 2012: Guang Pu Xue Yu Guang Pu Fen Xi, Guang Pu
https://www.readbyqxmd.com/read/20704394/development-of-a-high-sensitivity-rapid-sandwich-elisa-procedure-and-its-comparison-with-the-conventional-approach
#4
COMPARATIVE STUDY
Chandra Kumar Dixit, Sandeep Kumar Vashist, Feidhlim T O'Neill, Brian O'Reilly, Brian D MacCraith, Richard O'Kennedy
A highly sensitive and rapid sandwich enzyme-linked immunosorbent assay (ELISA) procedure was developed for the detection of human fetuin A/AHSG (alpha2-HS-glycoprotein), a specific biomarker for hepatocellular carcinoma and atherosclerosis. Anti-human fetuin A antibody was immobilized on aminopropyltriethoxysilane-mediated amine-functionalized microtiter plates using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride and N-hydroxysulfosuccinimide-based heterobifunctional cross-linking. The analytical sensitivity of the developed assay was 39 pg/mL, compared to 625 pg/mL for the conventional assay...
August 15, 2010: Analytical Chemistry
https://www.readbyqxmd.com/read/20527779/enhancing-heat-capacity-of-colloidal-suspension-using-nanoscale-encapsulated-phase-change-materials-for-heat-transfer
#5
Yan Hong, Shujiang Ding, Wei Wu, Jianjun Hu, Andrey A Voevodin, Lois Gschwender, Ed Snyder, Louis Chow, Ming Su
This paper describes a new method to enhance the heat-transfer property of a single-phase liquid by adding encapsulated phase-change nanoparticles (nano-PCMs), which absorb thermal energy during solid-liquid phase changes. Silica-encapsulated indium nanoparticles and polymer-encapsulated paraffin (wax) nanoparticles have been made using colloid method, and suspended into poly-alpha-olefin (PAO) and water for potential high- and low-temperature applications, respectively. The shells prevent leakage and agglomeration of molten phase-change materials, and enhance the dielectric properties of indium nanoparticles...
June 2010: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/20496357/olefin-epoxidation-by-h2o2-mecn-catalysed-by-cyclopentadienyloxidotungsten-vi-and-molybdenum-vi-complexes-experiments-and-computations
#6
Chiara Dinoi, Marco Ciclosi, Eric Manoury, Laurent Maron, Lionel Perrin, Rinaldo Poli
Compounds [Cp*(2)M(2)O(5)] (M = Mo, 1; W, 2) are efficient pre-catalysts for cyclooctene (COE) epoxidation by aqueous H(2)O(2) in acetonitrile/toluene. The reaction is quantitative, selective and takes place approximately 50 times faster for the W system (k(obs) = 4.32(9)x10(-4) s(-1) at 55 degrees C and 3x10(-3) M concentration for the dinuclear complex, vs. 1.06(7)x10(-5) s(-1) for the Mo system). The rate law is first order in catalyst and COE substrate (k = 0.138(7) M(-1) s(-1) for the W system at 55 degrees C), whereas increasing the concentration of H(2)O(2) slows down the reaction because of an inhibiting effect of the greater amount of water...
August 16, 2010: Chemistry: a European Journal
https://www.readbyqxmd.com/read/20058281/a-computational-study-of-the-olefin-epoxidation-mechanism-catalyzed-by-cyclopentadienyloxidomolybdenum-vi-complexes
#7
Aleix Comas-Vives, Agustí Lledós, Rinaldo Poli
A DFT analysis of the epoxidation of C(2)H(4) by H(2)O(2) and MeOOH (as models of tert-butylhydroperoxide, TBHP) catalyzed by [Cp*MoO(2)Cl] (1) in CHCl(3) and by [Cp*MoO(2)(H(2)O)](+) in water is presented (Cp*=pentamethylcyclopentadienyl). The calculations were performed both in the gas phase and in solution with the use of the conductor-like polarizable continuum model (CPCM). A low-energy pathway has been identified, which starts with the activation of ROOH (R=H or Me) to form a hydro/alkylperoxido derivative, [Cp*MoO(OH)(OOR)Cl] or [Cp*MoO(OH)(OOR)](+) with barriers of 24...
February 15, 2010: Chemistry: a European Journal
https://www.readbyqxmd.com/read/19778147/application-of-the-entropy-theory-of-glass-formation-to-poly-alpha-olefins
#8
Evgeny B Stukalin, Jack F Douglas, Karl F Freed
The entropy theory of glass formation, which has previously been developed to describe general classes of polymeric glass-forming liquids, is extended here to model the thermodynamic and dynamic properties of poly(alpha-olefins). By combining this thermodynamic theory with the Adam-Gibbs model (which relates the configurational entropy to the rate of structural relaxation), we provide systematic computations for all four characteristic temperatures (T(A), T(c), T(g), T(0)), governing the position and breadth of the glass transition, and the fragility parameters (D,m) describing the strength of the temperature dependence of the structural relaxation time, where T(A) is the temperature below which the relaxation is non-Arrhenius, T(c) is the crossover or empirical mode-coupling temperature, T(g) is the glass transition temperature, and T(0) is the temperature at which the extrapolated relaxation time diverges...
September 21, 2009: Journal of Chemical Physics
https://www.readbyqxmd.com/read/19655906/smart-materials-behavior-in-phosphates-role-of-hydroxyl-groups-and-relevance-to-antiwear-films
#9
Dmitry Shakhvorostov, Martin H Müser, Yang Song, Peter R Norton
The elastic properties of materials under high pressure are relevant to the understanding and performance of many systems of current interest, for example, in geology and tribology. Of particular interest is the origin of the dramatic increase in modulus with increasing pressure, a response which is also called "smart materials behavior." In this context, simple phosphate-containing materials have been studied experimentally and theoretically, and the origins of this behavior have been associated with factors such as coordination of the cations and changes in the degree of polymerization and hydrogenation of the phosphate units...
July 28, 2009: Journal of Chemical Physics
https://www.readbyqxmd.com/read/19588950/development-and-application-of-fi-catalysts-for-olefin-polymerization-unique-catalysis-and-distinctive-polymer-formation
#10
Haruyuki Makio, Terunori Fujita
Catalysts contribute to the efficient production of chemicals and materials in almost all processes in the chemical industry. The polyolefin industry is one prominent example of the importance of catalysts. The discovery of Ziegler-Natta catalysts in the 1950s resulted in the production of high-density polyethylenes (PEs) and isotactic polypropylenes (iPPs). Since then, further catalyst development has led to the production of a new series of polyolefins, including linear low-density PEs, amorphous ethylene/1-butene copolymers, ethylene/propylene/diene elastomers, and syndiotactic PPs (sPPs)...
October 20, 2009: Accounts of Chemical Research
https://www.readbyqxmd.com/read/19225630/alumina-nanowire-forests-via-unconventional-anodization-and-super-repellency-plus-low-adhesion-to-diverse-liquids
#11
Weici Wu, Xiaolong Wang, Daoai Wang, Miao Chen, Feng Zhou, Weimin Liu, Qunji Xue
Multiple facet supported alumina nanowires are produced very efficiently in a very short time via high field anodization; upon modification with perfluorosilane, the surface becomes super-repellent towards a broad range of liquids, which includes (salted) water, water emulsion, common organic liquids like glycerol and alkanes, and a variety of lubrication oils including ionic liquids, poly(alpha-olefin), polydimethylsiloxane oils etc.
March 7, 2009: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/17321675/the-effect-of-additives-on-the-treatment-of-oil-in-water-emulsions-by-vacuum-evaporation
#12
Gemma Gutiérrez, Angel Cambiella, José M Benito, Carmen Pazos, José Coca
A simple batch vacuum evaporation process for the treatment of several oil-in-water (O/W) emulsions is reported. The experiments were carried out with waste emulsions from an industrial copper rolling process and with model emulsions prepared in the laboratory. No detailed information on the formulation of the industrial waste O/W emulsions was available. Several model emulsions were formulated using the same base oil (an 85-15% (w/w) mixture of a synthetic poly-alpha-olefin and a trimethylol propane trioleate ester, respectively) and one of the three following surfactants: Brij-76 (polyethylene glycol octadecyl ether, non-ionic), CTAB (hexadecyltrimethyl ammonium bromide, cationic), and Oleth-10 (glycolic acid ethoxylate oleyl ether, anionic)...
June 18, 2007: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/17096515/synthesis-of-functional-poly-1-4-ketone-s-bearing-bioactive-moieties-by-pd-catalyzed-insertion-polymerization
#13
Violeta Malinova, Bernhard Rieger
The synthesis of novel alternating polyketones bearing pendent bioactive moieties is presented. These materials were prepared by palladium catalyzed coordination polymerization of carbon monoxide and alpha-olefins substituted with protected tyrosine or with dipeptide sequences such as tyrosine-glycine, tyrosine-alanine, and tyrosine-valine. Copolymerization experiments of CO with monomers containing vitamin E or testosterone were also successfully performed under mild reaction conditions. The dicationic Pd (II) bis(phoshine) complex [Pd(dppp)(NCCH(3))(2)](BF(4))(2) was used as catalyst precursor giving rise to macromolecules with well-defined structures...
November 2006: Biomacromolecules
https://www.readbyqxmd.com/read/16967949/copolymerization-of-silyl-vinyl-ethers-with-olefins-by-alpha-diimine-pdr
#14
Shuji Luo, Richard F Jordan
This paper reports that (alpha-diimine)PdMe+ catalyzes the copolymerization of olefins and silyl vinyl ethers. The reactions of (alpha-diimine)PdMe+ (alpha-diimine = (2,6-iPr2-C6H3)N=CMe-CMe=N(2,6-iPr2-C6H3)) with excess vinyl ethers CH2=CHOR (1a-d: R = tBu (a), SiMe3 (b), SiPh3 (c), Ph (d)) in CH2Cl2 at 20 degrees C afford polymers for 1a (rapidly) and 1b (slowly) but not for 1c or 1d. The structures of poly(1a,b) indicate a cationic polymerization mechanism. The reaction of (alpha-diimine)PdMe+ with 1-2 equiv of 1a-d proceeds by sequential C=C pi-complexation to form (alpha-diimine)PdMe(CH2=CHOR)+ (2a-d), 1,2 insertion to form (alpha-diimine)Pd(CH2CHMeOR)+ (3a-d), reversible isomerization to (alpha-diimine)Pd(CMe2OR)+ (4a-d), beta-OR elimination to generate (alpha-diimine)Pd(OR)(CH2=CHMe)+ (not observed), and allylic C-H activation to yield (alpha-diimine)Pd(eta3-C3H5)+ (5) and ROH...
September 20, 2006: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/16839123/1-o-vinyl-glycosides-via-tebbe-olefination-their-use-as-chiral-auxiliaries-and-monomers
#15
Jialong Yuan, Kristof Lindner, Holger Frauenrath
A series of anomerically pure 1-O-formyl glycosides 1 was prepared and converted into the corresponding 1-O-vinyl glycosides 2 by Tebbe olefination. The unsubstituted vinyl glycosides were obtained as anomerically pure compounds in good yields, and the method of preparation was compatible with the presence of a variety of functional groups. Remarkably, the anomeric formate group was regioselectively converted into the corresponding olefin in the presence of acetate and benzoate protecting groups. With the perspective to use the 1-O-vinyl glycosides as monomers for the preparation of glycosylated poly(vinyl alcohol) derivatives with controlled tacticity, their scope as chiral auxiliaries for a stereodifferentiation in addition reactions to the olefin function was investigated by using the [2+2] cycloaddition to dichloroketene as a model reaction...
July 21, 2006: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/16681209/water-based-condensation-particle-counters-for-environmental-monitoring-of-ultrafine-particles
#16
Wei Liu, Stanley L Kaufman, Brian L Osmondson, Gilmore J Sem, Frederick R Quant, Derek R Oberreit
TSI Inc. (Shoreview, MN) has introduced three new water-based condensation particle counters (WCPCS) that were designed to detect airborne particles larger than 2.5 nm (model 3786), 5 nm (model 3785), and either 10 or 20 nm (model 3782). These WCPCs are well suited for real-time, environmental monitoring of number concentration of airborne ultrafine particles. Their unique design incorporates the use of water as the working fluid instead of alcohol. Water is odor free, readily available, and eliminates the problem of water condensation and absorption into alcohol working fluids during operation in humid environments...
April 2006: Journal of the Air & Waste Management Association
https://www.readbyqxmd.com/read/16290745/elongational-flow-of-solutions-of-poly-ethylene-oxide-and-sulfonated-surfactants
#17
L M Smitter, J C Ruiz, M E Torres, A J Müller, A E Sáez
In this work, the elongational flow behavior of aqueous solutions of poly(ethylene oxide) (PEO) was studied in the presence of sulfonated surfactants. The technique of opposed-jets flow was used to generate an elongational flow field in which pressure drops were measured as a function of strain rates. The surfactants used were sodium dodecyl benzene sulfonate (SDBS) and an alpha-olefin sulfonate (AOS). Solutions of PEO and other flexible polymers exhibit extension thickening in opposed-jets flow due to the formation of transient networks of entangled molecules...
July 15, 2002: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/16018691/synthesis-of-pipecolic-acid-based-spiro-bicyclic-lactam-scaffolds-as-beta-turn-mimics
#18
Ravindranadh V Somu, Rodney L Johnson
A series of 6.5.5 spiro bicyclic lactam scaffolds were synthesized from pipecolic acid in a sequence of reactions that was initiated with the alpha-allylation of tert-butoxycarbonyl pipecolic acid. Oxidative cleavage of the olefin to give an aldehyde followed by condensation with D-cysteine methyl ester gave a mixture of pipecolyl thiazolidines. Cyclization of the pipecolyl thiazolidines with Mukaiyama's reagent yielded the spiro bicyclic lactams 4a-d. Epimerization of the 7'a bridgehead carbon under acidic conditions was observed for those spiro bicyclic lactam scaffolds with an S stereochemistry at this position...
July 22, 2005: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/16011340/unprecedented-syndioselectivity-and-syndiotactic-polyolefin-melting-temperature-polypropylene-and-poly-4-methyl-1-pentene-from-a-highly-active-sterically-expanded-eta1-fluorenyl-eta1-amido-zirconium-complex
#19
Levi J Irwin, Stephen A Miller
The structurally unique, sterically expanded eta1-fluorenyl-eta1-amido single-site precatalyst, Me2Si(eta1-N-tBu)(eta1-C29H36)ZrCl2.OEt2 (3), upon activation with methylaluminoxane (MAO), is remarkably active and constitutes the most syndioselective alpha-olefin polymerization catalyst system yet reported. 3/MAO affords as-prepared syndiotactic polypropylene with [rrrr] > 99% and unprecedented melting temperatures for the unannealed (165 degrees C) and annealed (174 degrees C) polymers. The activity of this system is 4 times that of the prototypical syndioselective catalyst Me2C(eta5-C5H4)(eta5-C13H8)ZrCl2/MAO...
July 20, 2005: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/15877397/asymmetric-epoxidation-of-alpha-olefins-having-neighboring-sugar-chiral-templates-and-alternating-copolymerization-with-dicarboxylic-anhydrides
#20
Akinori Takasu, Takashi Bando, Yusuke Morimoto, Yosuke Shibata, Tadamichi Hirabayashi
Sugar-substituted epoxides 5-8 were synthesized by asymmetric epoxidation (in CH(2)Cl(2)/water) of alpha-olefins having neighboring sugars (1-4) by use of an achiral oxidant (MCPBA), in which the sugar moiety acted as a chiral template. The diastereoselectivities depend on the methylene spacer between vinyl group and carbohydrate derivatives. The methylene spacer between sugar and vinyl groups influenced the diastereoselectvity. In the case of epoxidation of 4 at 27 degrees C for 24 h, the diastereoselectivity was the highest (99/1)...
May 2005: Biomacromolecules
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