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Polymerisation
Kinds of Polymerisation Terms modified by Polymerisation Selected AbstractsOIL POLYMERISATION AND FLUID EXPULSION FROM LOW TEMPERATURE, LOW MATURITY, OVERPRESSURED SEDIMENTSJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2008D. D. J. Antia A mechanism for hydrocarbon expulsion from low temperature (T = <20 , 150° C), low maturity (Ro=<0.6), overpressured sediments (clays, shales and enclosed sands) with active hydrocarbon concentration and/or generation is outlined. Low temperature polymerisation of light hydrocarbons (e.g. biogenic methane) is considered to be a potential source for some oils found in association with hydrates (resulting from fluidisation discharges from overpressured zones), and some oils found in shales displaying suppression of vitrinite reflectance. It is observed that low temperature polymerisation will increase the potential pressure load retained within an overpressured zone and increase the overall volume of gas/fluids discharged on pressure release. Field observations, including measured recharge volumes and the fluid discharge volumes through a chimney from an overpressured zone, have been used to produce a triple porosity, poroelastic fluidisation expulsion model which links the discharge volume to pressure loading. The model predicts that expulsion from an active pressure mound will be cyclic and episodic. Published geochemical results from seismic chimneys in the Lower Congo Basin have been reinterpreted using the model to demonstrate that expulsion through a chimney is episodic, and to identify overpressured zones where the dominant fluid is oil and others where the overpressured zone contains both oil and gas. It is suggested that some of the oil in these overpressured zones, currently interpreted as thermogenic, may be derived from the polymerisation of biogenic gas. [source] [Bis(guanidine)]zinc Complexes and Their Application in Lactide PolymerisationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2007Janna Börner Abstract The bis(guanidine)-stabilised zinc complexes [N1,N2 -bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]dichloridozinc(II), [Zn(DMEG2e)Cl2] (C1), diacetato[N1,N2 -bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]zinc(II),[Zn(DMEG2e)(CH3COO)2] (C2), and bis[N1,N2 -bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]zinc(II) bis(trifluoromethanesulfonate), [Zn(DMEG2e)2](CF3SO3)2 (C3), have been synthesised and completely characterised by means of X-ray structure analysis, NMR spectroscopy and mass spectrometry. These [bis(guanidine)]zinc complexes were investigated regarding their activity in the bulk polymerisation of D,L -lactide. It could be shown that these compounds are able to act as initiators for lactide polymerisation, and polylactides with molecular weights (Mw) of around 18000,59000 g/mol could be obtained. Variation of the reaction temperature revealed that the molecular weights decrease with increasing temperature. Additionally, the correlation of the intrinsic viscosity with the molecular weight demonstrates that the obtained polymers are linear and structurally homogeneous.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Role of Silica Properties in the Polymerisation of Ethylene Using Supported Metallocene CatalystsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2010Virginie F. Tisse Abstract The role of certain morphological properties of different silica used as supports for metallocene catalysts was investigated in order to quantify their eventual influence on the kinetics of ethylene polymerisation in heptane slurry, as well as on the polymer properties. It was shown that there is no clear link between porosity and observed activity with some highly porous silica producing relatively inactive supported catalysts. It was further shown that within a batch of silica, the particle size had a significant impact on observed kinetics. While it appears that there is possibly some diffusion resistance encountered in the larger particles, it was also shown that prolonged contact between the support and the alkylating agent could increase reaction rates in the larger particles. [source] Synthesis of New Cellobiose-Based Glycopolysiloxanes and their Use as Polymer Stabilizers in Miniemulsion PolymerisationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2008Solenn Berson Abstract New glycopolysiloxanes were synthesized from cellobiose and commercially available reactive silicone oils or MD,M precursors. Their synthesis is based on the hydrosilylation of allyl-functionalized cellobiose onto the reactive silicone oil, after protection of the hydroxyl functions. The subsequent deprotection step leads to a redistribution of the silicon chain to yield oligomers with around 5 or 6 silicon atoms. Two water-dispersible glycosiloxanes were used for the steric stabilisation of vinyl acetate (VAc) miniemulsion polymerisation with up to 10% Miglyol® as the hydrophobic component. The best performances were obtained by using a mixture of non-ionic triblock copolymer and glycopolysiloxane. Poly(vinyl acetate) (PVAc) latex with particle sizes around 200 nm were obtained, displaying colloidal stabilisation upon long-time storage. [source] A Facile Method for Grafting Polymerisation of Acrylonitrile onto LDPE Film with High Grafting EfficiencyMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2006Jianwu Zhu Abstract Summary: A facile and effective surface grafting polymerisation method was designed and investigated to graft acrylonitrile (AN) onto low-density polyethylene (LDPE) film using benzoyl peroxide (BPO) as an initiator. This method consisted of two steps. In the first step, BPO was adsorbed on the surface of LDPE film by immersing LDPE film in BPO solution; in the second step, grafting polymerisation of AN onto LDPE film was carried out under heat. Because the grafting polymerisation was carried out with AN in vapour phase and the concentration of AN was very low, the homopolymerisation of AN could be effectively suppressed and therefore the grafting efficiency was very high (approaching 100%). Grafting percent (Gp) could be controlled from 0 to 118% by adjusting reaction conditions in the first step and/or in the second step respectively. A possible model was proposed to interpret the experimental results. Schematic procedure and chemistry for grafting polymerisation of AN on LDPE film. [source] Radical Polymerisation of 1H,1H,2H,2H-perfluoro-3,5-alkyldiynol and 1H,1H-perfluoro-2,4-alkyldiynol Acrylates and Methacrylates: A New Family of Fluorinated PolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2004Ana Robert Estelrich Abstract Summary: The preparation of a new family of acrylic esters with a perfluorinated chain directly bonded to one or two conjugated triple bonds from 1H,1H,2H,2H-perfluoro-3,5-alkyldiynol and 1H,1H-perfluoro-2,4-alkyldiynol is reported. Their solution homopolymerisation was studied in the presence of a radical initiator and it was found that the polymerisation process bore more similarity to that observed with the analogous hydrocarbonated monomers containing triple bonds rather than that observed with polyfluorinated monomers without any alkyne groups. Furthermore, under the reaction conditions used, the triple bonds remained unchanged as there was no cross-linking process. The homopolymers obtained were characterised by NMR, infrared spectroscopy and gel permeation chromatography whenever possible. Structure of new fluorinated homopolymers. [source] In Situ Polymerisation of Polyamide-6 Nanocompounds from Caprolactam and Layered SilicatesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2009Bernd Rothe Abstract An in situ process for the production of polyamide-6 nanocompounds is investigated as an alternative to melt compounding. During the in situ production, the layered silicates are dispersed in the monomer caprolactam before the polymerisation in a twin screw extruder, leading to an intercalation of the silicates. The production of a polyamide compound containing 0, 2 and 4 wt.-% nanoscale silicates was successful. An improvement of the elastic modulus of approximately 30,60% was reached. The figure shows the TEM micrograph of a nanocompound containing 2 wt.-% nanoclay at a magnification of 30,000×. [source] Electrochemical Polymerisation of N -Arylated and N -Alkylated EDOT-Substituted Pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) Derivatives: Influence of Substitution Pattern on Optical and Electronic PropertiesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2009Kai Zhang Abstract New pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) derivatives carrying 3,4-ethylenedioxy-thiophenylphenyl (EDOT-phenyl) substituent groups in the 3- and 6-position, or in the 2- and 5-position of the DPP chromophore were synthesised and electrochemically polymerised. The properties of the polymers were investigated using cyclic voltammetry and UV/Vis absorption spectroscopy. It was found that the optical and electronic properties differ greatly between the two polymers. Materials with EDOT-phenyl groups in the 3- and 6-positions represent conjugated polymers with a low oxidation potential and reversible electrochromic properties, whereas the polymer with EDOT-phenyl groups in the 2- and 5-positions is non-conjugated and possesses a high oxidation potential and irreversible redox behaviour. [source] Synthesis and Controlled Polymerisation of a Novel Gramicidin S AnalogueMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2005Lee Ayres Abstract Summary: The controlled polymerisation of a bulky, peptide-based monomer was investigated. The cyclic , -sheet forming decapeptide gramicidin S was modified with a methacrylate handle and subsequently polymerised via atom transfer radical polymerisation (ATRP), to yield a well-defined gramicidin-S-containing polymer. The secondary structure of the peptide moiety was retained within the resulting polymer, as indicated by IR spectroscopy. This is the first example of the use of ATRP to create a synthetic polymer with a cyclic peptide as a side chain. The gramicidin S based monomers synthesised here were then polymerised by ATRP. [source] Simultaneous Controllability of PSD and MWD in Emulsion PolymerisationMACROMOLECULAR REACTION ENGINEERING, Issue 5 2008Stephen J. Sweetman Abstract A sensitivity study of particle size distribution (PSD) and molecular weight distribution (MWD) responses to perturbations in initiator, surfactant, monomer and chain transfer agent in a semi-batch emulsion polymerisation is presented. The objective is to provide a systematic study on the ability to simultaneously control both PSD and MWD, towards inferential control of end-use product properties. This would lead towards identification of the practical feasible regions of operability. All inputs appeared to have an intrinsic and simultaneous influence on end-time PSD and MWD. Trends shown in experimental results have been explained in a mechanistic sense and also compared to simulation results from a combined PSD/MWD population balance model. The preliminary comparison between experiment and simulation highlights areas to be focussed on with respect to model improvement. [source] Design and Implementation of a Novel Quench Flow Reactor for the Study of Nascent Olefin PolymerisationMACROMOLECULAR REACTION ENGINEERING, Issue 2 2007Audrey Di Martino Abstract A novel stopped flow reactor system is described in the current work, along with the underlying design philosophy. While the concept of stopped flow technology is not recent, this system is the first to be designed with the objective of studying particle morphology, and to work at extremely short (40 ms) residence times. It is shown that traditional chemical engineering principles are required to properly design and operate this type of reactor, and that when correctly design, it is a very flexible tool for the study of nascent polymerisation of olefins. [source] Heat Transfer in Gas Phase Olefin PolymerisationMACROMOLECULAR SYMPOSIA, Issue 1 2009Estevan Tioni Abstract A fixed bed microreactor has been used to study heat transfer during the initial transient state of gas phase olefin polymerization on a supported catalyst. It has been shown that heat transfer during this stage of the polymerisation is critical, and under conditions found commercially problems can arise with hot spots and polymer melting. It is proven how the thermal properties of the gas mixture flowing on the catalytic bed exert great influence on heat dissipation reducing the sudden increase in temperature by as much as a factor of 5. Flow rate and especially the process gas composition are the key factors in controlling the bed temperature. [source] Polymerisation of ethylene catalysed by mono-imine-2,6-diacetylpyridine iron/methylaluminoxane (MAO) catalyst system: effect of the ligand on polymer microstructurePOLYMER INTERNATIONAL, Issue 12 2002Susete Fernandes Abstract The complex, {1-{6-[(2,6-diisopropylphenyl)-ethaneimidoyl]-2-pyridinyl}-1-ethanone}iron(II) dichloride (2), has been synthesised and characterised. Treatment of complex 2 with methylaluminoxane resulted in a very active catalytic system for the preparation of polyethylene (PE). The system shows activities in the order of magnitude 107,g (PE) mol,1(Fe) h,1 bar,1. Characterisation by 13C NMR indicated that branched PE was obtained and that experimental conditions affect polymer microstructure. PE produced contained six to eight branches per 100 carbons. © 2002 Society of Chemical Industry [source] Radikalische Polymerisation: Kann man das Unumkehrbare umkehren?,ANGEWANDTE CHEMIE, Issue 49 2009Christopher Barner-Kowollik Rückwärtsgang: Die Anlagerung primärer Radikale an sterisch nicht gehinderte vinylische Bindungen könnte nicht so unumkehrbar sein, wie immer angenommen. Eine 1H-CIDNP-NMR-spektroskopische Untersuchung an photoinitiierten Polymerisationssystemen weist nach, dass die Anlagerung von photolytisch erzeugten Mesitoyl- und Phosphinoylradikalen an (Meth)acrylat-Monomere bei Raumtemperatur reversibel sein kann (siehe Schema; I=Initiator). [source] Cathodic Deposition of Polypyrrole Enabling the One-Step Assembly of Metal,Polymer Hybrid Electrodes,ANGEWANDTE CHEMIE, Issue 44 2009Yongju Jung Dr. In,situ generierte oxidierende Agentien ermöglichen die kathodische Abscheidung von Polypyrrol (ppy) durch oxidative Polymerisation. Leitfähige Polymere mit neuen nanoskaligen Morphologien wurden hergestellt, z.,B. Nanokügelchen, die ein dreidimensionales, poröses Netzwerk bilden (siehe Bild). Hybridelektroden aus Metall und leitfähigem Polymer sind über nur eine Stufe zugänglich. [source] Corrigendum: Chain-Growth Versus Step-Growth Mechanisms for the Suzuki,Heck Polymerisation of Fluorenyldibromides with Potassium Vinyl TrifluoroborateCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2010Roberto Grisorio Dr. No abstract is available for this article. [source] Catalytic Ethylene Polymerisation in Carbon Dioxide as a Reaction Medium with Soluble Nickel(II) CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2006Amaia Bastero Dr. Abstract A series of neutral NiII,salicylaldiminato complexes substituted with perfluorooctyl- and trifluoromethyl groups, [Ni{,2 - N,O -6-C(H)NAr-2,4-R,2C6H2O}(Me)(pyridine)] (6,a: Ar=2,6-{4-(F17C8)C6H4}2C6H3, R,=I; 6,b: Ar=2,6-{4-(F3C)C6H4}2C6H3, R,=I; 6,c: Ar=2,6-{3,5-(F3C)2C6H3}2C6H3, R,=3,5-(F3C)2C6H3; 6,d: Ar=2,6-{4-(F17C8)C6H4}2C6H3, R,=3,5-(F3C)2C6H3; 6,e: Ar=2,6-{3,5-(F3C)2C6H3}2C6H3, R,=I) were studied as catalyst precursors for ethylene polymerisation in supercritical CO2. Catalyst precursors 6,a and 6,c, which are soluble in scCO2, afford the highest polymer yields, corresponding to 2×103 turnovers. Semicrystalline polyethylene (Mn typically 104 g,mol,1) is obtained with variable degrees of branching (11 to 24 branches per 1000 carbon atoms, predominantly Me branches) and crystallinities (54 to 21,%), depending on the substitution pattern of the catalyst. [source] UV Polymerisation of Surfactants Adsorbed at the Nematic Liquid Crystal,Water Interface Produces an Optical ResponseCHEMPHYSCHEM, Issue 17 2009Paul D. I. Fletcher Prof. Abstract We have investigated the changes in crossed polariser optical textures produced by adsorption and UV polymerisation of a range of polymerisable surfactants at the interface between a nematic liquid crystal and water. Similar to non-polymerisable surfactants, the adsorption of polymerisable surfactants with sufficiently long hydrophobic tail groups produces a transition from planar to homeotropic anchoring. UV polymerisation of surfactants with a polymerisable group located in the hydrophobic tail region changes the anchoring from homeotropic back to planar. Polymerisation in the hydrophilic headgroup region does not produce an optical transition. We demonstrate that these systems can be used to "write with light" in the interfaces and that they form the basis of a UV sensor device in which the optical response is visible to the naked eye. [source] Monolithic poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for simultaneous separation of low- and high-molecular-weight compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Andreas Greiderer Abstract Monolithic poly(1,2-bis(p -vinylphenyl)ethane (BVPE)) capillary columns were prepared by thermally initiated free radical polymerisation of 1,2-bis(p -vinylphenyl)ethane in the presence of inert diluents (porogens) and ,,,,-azoisobutyronitrile (AIBN) as initiator. Polymerisations were accomplished in 200 ,m ID fused silica capillaries at 65°C and for 60 min. Mercury intrusion porosimetry measurements of the polymeric RP support showed a broad bimodal pore-size-distribution of mesopores and small macropores in the range of 5,400 nm and flow-channels in the ,m range. N2 -adsorption (BET) analysis resulted in a tremendous enhancement of surface area (101 m2/g) of BVPE stationary phases compared to typical organic monoliths (,20 m2/g), indicating the presence of a considerable amount of mesopores. Consequently, the adequate proportion of both meso- and (small) macropores allowed the rapid and high-resolution separation of low-molecular-weight compounds as well as biomolecules on the same monolithic support. At the same time, the high fraction of flow-channels provided enhanced column permeability. The chromatographic performance of poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for the separation of biomolecules (proteins, oligonucleotides) and small molecules (alkyl benzenes, phenols, phenons) are demonstrated in this article. Additionally, pressure drop versus flow rate measurements of novel poly(1,2-bis(p -vinylphenyl)ethane) capillary columns confirmed high mechanical robustness, low swelling in organic solvents and high permeability. Due to the simplicity of monolith fabrication, comprehensive studies of the retention and separation behaviour of monolithic BVPE columns resulted in high run-to-run and batch-to-batch reproducibilities. All these attributes prove the excellent applicability of monolithic poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for ,-HPLC towards a huge range of analytes of different chemistries and molecular sizes. [source] Susceptibility of isolated myofibrils to in vitro glutathionylation: Potential relevance to muscle functions,CYTOSKELETON, Issue 2 2010Chiara Passarelli Abstract In this study we investigated the molecular mechanism of glutathionylation on isolated human cardiac myofibrils using several pro-glutathionylating agents. Total glutathionylated proteins appeared significantly enhanced with all the pro-oxidants used. The increase was completely reversed by the addition of a reducing agent, demonstrating that glutathione binding occurs by a disulfide and that the process is reversible. A sensitive target of glutathionylation was ,-actin, showing a different reactivity to the several pro-glutathionylating agents by ELISA. Noteworthy, myosin although highly sensitive to the in vitro glutathionylation does not represent the primary glutathionylation target in isolated myofibrils. Light scattering measurements of the glutathionylated ,-actin showed a slower polymerisation compared to the non-glutathionylated protein and force development was depressed after glutathionylation, when the myofibrils were mounted in a force recording apparatus. Interestingly, confocal laser scanning microscopy of cardiac cryosections indicated, for the first time, the constitutive glutathionylation of ,-cardiac actin in human heart. Due to the critical location of ,-actin in the contractile machinery and to its susceptibility to the oxidative modifications, glutathionylation may represent a mechanism for modulating sarcomere assembly and muscle functionality under patho-physiological conditions in vivo. © 2009 Wiley-Liss, Inc. [source] Src-dependent phosphorylation of Scar1 promotes its association with the Arp2/3 complexCYTOSKELETON, Issue 1 2006Hazel Ardern Abstract The WAVE/Scar proteins regulate actin polymerisation at the leading edge of motile cells via activation of the Arp2/3 complex in response to extracellular cues. Within cells they form part of a pentameric complex that is thought to regulate their ability to interact and activate the Arp2/3 complex. However, the exact mechanism for this is not known. We set out to assess whether phosphorylation of Scar1 by the non-receptor tyrosine kinase Src may influence the function of Scar1 and its ability to regulate Arp2/3-mediated actin polymerisation. We show that Scar1 is phosphorylated by Src in vitro and in vivo and identify tyrosine 125 as the major site in Scar1 to be phosphorylated in cells. Src-dependent phosphorylation of Scar1 on tyrosine 125 enhances its ability to bind to the Arp2/3 complex and regulates its ability to control actin polymerisation in cells. Thus, Src may act as an intermediary to regulate the activity of the Arp2/3 complex in response to external stimuli, via modulation of its interaction with WAVE/Scar proteins. Cell Motil. Cytoskeleton, 2006. © 2005 Wiley-Liss, Inc. [source] Pulp capping with adhesive resin-based composite vs. calcium hydroxide: a reviewDENTAL TRAUMATOLOGY, Issue 6 2000A. H. B. Schuurs Abstract , The results of some short-term experiments suggest that direct capping of a vital pulp with the modern resin-based composite systems may be as effective as capping with calcium hydroxide. Total cavity etching with 10% phosphoric acid seems to be safe for the exposed pulp, but unless annulled by calcium hydroxide 35% phosphoric acid may be disastrous. For hemostasis and cleaning of the pulp wound both sodium hypochlorite and saline seem suitable, whereas the effectiveness of a 2% chlorhexidine solution is questionable. Although hard-setting calcium hydroxide cements may induce the formation of dentin bridges, they appear not to provide an effective long-term seal against bacterial factors. Within a few years, the majority of mechanically exposed and capped pulps show infection and necrosis due to microleakage of such capping materials and tunnel defects in the dentin bridges. It is unknown whether newer types of resin containing calcium-hydroxide-products will act as a permanent barrier. The cytotoxicity of the resin-based composites and the temperature rise during polymerisation may not be of concern, but microleakage, sensitisation and allergic reactions may pose problems. Based on available data, pulp capping with resin-based composites may be said to be promising, but more and long-term research is mandatory before the method can be recommended. [source] Monocyclopentadienyl Phenoxido,Amino and Phenoxido,Amido Titanium Complexes: Synthesis, Characterisation, and Reactivity of Asymmetric Metal Centre DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2008Giuseppe Alesso Abstract Reduction of phenol,imine derivatives R,N=CH(3,5-R2C6H2 -2-OH) (R = tBu; R, = C6H51a, p -MeC6H41b, Cy 1c, tBu 1d, 2,6-Me2C6H31e; R = H; R, = p -MeC6H41f; Cy = cyclohexyl) with MBH4 (M = Li, Na) or AlLiH4 in ethyl ether or thf at room temperature affords the phenol,amine compounds R,NHCH2(3,5-R2C6H2 -2-OH) 2a,c and 2e,f. The N -R-[2,4-di- tert -butyl]benzo-1-oxa-3-azine species (R = tBu 2d1, 2,6-Me2C6H32e1) are obtained by Mannich reaction of 2,4-di- tert -butylphenol with RNH2 in refluxing methanol. Intermediate 2d1 is converted in ethanol at room temperature into N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylamine (2d), whereas 2e is not obtained from 2e1 by using this procedure.N -alkyl,N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylaminecompounds tBuN(R)CH2(3,5- tBu2C6H2 -2-OH) (R = Me 2g, Et 2h, nPr 2i, CH2Ph 2j) are also prepared by the appropriate synthetic method. Treatment of 2a,c with 1 equiv. of TiCpCl3 in the presence of 2.5 equiv. of NEt3 in hexane at room temperature gives the monocyclopentadienyl phenoxido,amido monochloride complexes TiCp[R,NCH2(3,5- tBu2C6H2 -2-O)]Cl (R, = C6H53a, R, = p -MeC6H43b, R, = Cy 3c). The analogous complex Ti(,5 -C5H4SiMe2Cl)[C6H5NCH2(3,5- tBu2C6H2 -2-O)]Cl (4a) results from the reaction of 2a with Ti(,5 -C5H4SiMe2Cl)Cl3. Nevertheless, 2d reacts with TiCpCl3 in hexane in the presence of NEt3 at room temperature yielding the monocyclopentadienyl phenoxido dichloride compound TiCp[tBuNHCH2(3,5- tBu2C6H2 -2-O)]Cl2 (5), whereas in ethyl ether and in the absence of NEt3 adduct 5·HCl is obtained, which is further converted into TiCp[tBuNCH2(3,5- tBu2C6H2 -2-O)]Cl (3d) by addition of a NEt3/ethyl ether solution. The reaction of TiCpCl3 with 2a in the presence of 2.5 equiv. of NEt3 in a polar solvent (thf, CH2Cl2 or toluene) at room temperature affords TiCp[Ph(H)NCH2(3,5- tBu2C6H2 -2-O)]Cl (6a) as a mixture of two stereoisomers. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2a, 2d, 2e and 3d were determined by X-ray diffraction analysis from suitable single crystals. Preliminary studies of catalytic activity for ethylene polymerisation by using solid methylaluminoxane as cocatalyst were performed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] [Bis(guanidine)]zinc Complexes and Their Application in Lactide PolymerisationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2007Janna Börner Abstract The bis(guanidine)-stabilised zinc complexes [N1,N2 -bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]dichloridozinc(II), [Zn(DMEG2e)Cl2] (C1), diacetato[N1,N2 -bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]zinc(II),[Zn(DMEG2e)(CH3COO)2] (C2), and bis[N1,N2 -bis(1,3-dimethylimidazolidin-2-ylidene)ethane-1,2-diamine]zinc(II) bis(trifluoromethanesulfonate), [Zn(DMEG2e)2](CF3SO3)2 (C3), have been synthesised and completely characterised by means of X-ray structure analysis, NMR spectroscopy and mass spectrometry. These [bis(guanidine)]zinc complexes were investigated regarding their activity in the bulk polymerisation of D,L -lactide. It could be shown that these compounds are able to act as initiators for lactide polymerisation, and polylactides with molecular weights (Mw) of around 18000,59000 g/mol could be obtained. Variation of the reaction temperature revealed that the molecular weights decrease with increasing temperature. Additionally, the correlation of the intrinsic viscosity with the molecular weight demonstrates that the obtained polymers are linear and structurally homogeneous.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Studies of the Nature of the Catalytic Species in the ,-Olefin Polymerisation Processes Generated by the Reaction of Diamido(cyclopentadienyl)titanium Complexes with Aluminium Reagents as CocatalystsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2005Vanessa Tabernero Abstract The reaction of the diamido(chloro)cyclopentadienyltitanium compounds TiCpRx[1,2-C6H4(NR,)2]Cl [CpRx = ,5 -C5H5, ,5 -C5(CH3)5, ,5 -C5H4(SiMe3); R, = CH2tBu, Pr] with the Grignard reagent MgClR (R = Me, CH2Ph) affords the monomethyl and monobenzyl derivatives TiCpRx[1,2-C6H4(NR,)2]R. Upon addition of methylaluminoxane (MAO), the chloro- and alkyltitanium complexes show low activity towards the polymerisation of ethylene and styrene. However, no methylation was observed during the treatment of trimethylaluminium with the chloro compounds TiCpRx[1,2-C6H4(NR,)2]Cl. Instead, these reactions give the dinuclear aluminium complexes Al2[1,2-C6H4(NR,)2]Me4 (R, = CH2tBu, Pr) through transmetallation of the diamido ligand, suggesting a deactivation process of the catalysts in the olefin polymerisation reactions. In an additional effort to model the catalytic species, stoichiometric reactions between the methyl derivatives TiCpRx[1,2-C6H4(NR,)2]Me and solid methylaluminoxane (MAO) were studied by NMR spectroscopy. Monitoring of these reactions revealed the formation of zwitterionic species depending on the nature of the solvent. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Neutral and Cationic Methylaluminium Complexes of 2-Anilinotropone Ligands: Synthesis, Characterization, and Reactivity toward EthyleneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004Daniela Pappalardo Abstract Some new aluminium complexes bearing bidentate monoanionic 2-anilinotroponate ligands have been synthesized and characterized. Reaction of 2-(2,6-diisopropylanilino)tropone or 2-(perfluoroanilino)tropone with AlMe3 (1 equiv.) gave, by methane elimination, compounds [2-(2,6-diisopropylanilino)tropone]AlMe2 (1) and [2-(perfluoroanilino)tropone]AlMe2 (2), respectively, as yellow solids. Reaction of 1 with 1 equiv. of the ligand furnished, by protodealumination of a second Al,CH3 bond, the [2-(2,6-diisopropylanilino)tropone]2AlMe derivative 3. The structure of 3 has been determined by single-crystal X-ray diffraction, showing a five-coordinate aluminium atom with a distorted trigonal-bipyramidal geometry. Compounds 1 and 3 underwent methyl abstraction reactions with B(C6F5)3; the resulting cationic species was trapped in the presence of THF in dichloromethane solution. The reactivity of the synthesized compounds in ethylene polymerisation has also been explored. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Dimensional accuracy of upper complete denture bases: the effect of metallic flask closure methodsGERODONTOLOGY, Issue 1 2009Rafael Leonardo Xediek Consani Objectives:, To verify the dimensional accuracy of upper complete denture bases under the effect of different methods of metallic flask closure. Materials and methods:, Wax record bases were assigned to six groups: 1,2: traditional clamp; 3,4: RS system; and 5,6: flask with screws. Flasks were immediately polymerised or bench stored for 6 h prior to polymerisation. Resin base-cast sets were sectioned at regions corresponding to the canines, first molars and posterior palatal zone. Gap discrepancies were measured at five points: right and left ridge crests, palatal midline, and right and left marginal limits of the flanges. An optical micrometer was used for measurement purposes. Results:, Data were submitted to anova, and the means compared by Tukey's test (, = 0.05). Results revealed significant differences in the flask closure technique, polymerisation time, section, and their interactions. Discrepancy values for the RS system and flask with screws were significantly lower than those related to the traditional clamp, regardless of whether resin polymerisation was immediate or delayed for 6 h. Conclusions:, Flask closure methods should be considered when the denture base stability and comfort of the patient are being assessed during clinical use of the dentures. [source] The occurrence of porosity in reline acrylic resins.GERODONTOLOGY, Issue 1 2009Effect of microwave disinfection Background:, Microwave energy has proved to be an effective method for disinfecting acrylic dentures. However, the effect of microwave heating on the porosity of autopolymerising denture reline resins has not been investigated. Objective:, The purpose of the study was to determine the effect of microwave disinfection on the porosity of autopolymerised denture reline materials (Kooliner-K, New Truliner-NT, Tokuso Rebase Fast-TR and Ufi Gel Hard-UGH) and a conventional heat-polymerised denture base resin (Lucitone 550-L). Material and methods:, Specimens (10 mm × 20 mm × 1 mm) were obtained from the impression surface of the palatal mucosa in a single person and divided into four groups (n = 5). The porosity was evaluated after polymerisation (C1), after two cycles of microwave disinfection (MW2), after seven cycles of microwave disinfection (MW7) and after 7 days storage in water at 37°C (C2). Specimens from group MW7 were exposed to microwave disinfection daily being stored in water at 37°C between exposures. All the replicas were sputter coated with gold and micrographs/digital images were taken of each replica using scanning electron microscopy at magnification × 100. The SEM micrographs were then examined using an image analyser to determine the number of pores. Comparison between materials and groups were made using Kruskal,Wallis tests. Results:, MW7 resulted in a significant increase in the number from the pores of material K, but decreased in number in reline material TR and UGH reline resin. The number of pores in materials NT and L remained unaffected following microwave disinfection. Conclusion:, Differences in the porosity amongst the materials and for different experimental conditions were observed following microwave disinfection. [source] Insoluble Perfluoroalkylated Polymers: New Solid Supports for Supported Fluorous Phase CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Nicolas Audic Abstract New perfluoroalkylated polystyrene resins have been prepared by the suspension polymerisation of 4-(perfluoro- n -octyl)styrene. The evaluation of these highly fluorinated insoluble materials as catalyst supports for rhodium-catalysed hydrogenation of styrene and palladium-mediated Suzuki,Miyaura carbon-carbon bond forming reactions with 4-bromoacetophenone and 4-bromoanisole revealed improvements in the recycling of the perfluoroalkylated catalysts as compared to that achieved using fluorous reverse-phase silica gel. [source] OIL POLYMERISATION AND FLUID EXPULSION FROM LOW TEMPERATURE, LOW MATURITY, OVERPRESSURED SEDIMENTSJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2008D. D. J. Antia A mechanism for hydrocarbon expulsion from low temperature (T = <20 , 150° C), low maturity (Ro=<0.6), overpressured sediments (clays, shales and enclosed sands) with active hydrocarbon concentration and/or generation is outlined. Low temperature polymerisation of light hydrocarbons (e.g. biogenic methane) is considered to be a potential source for some oils found in association with hydrates (resulting from fluidisation discharges from overpressured zones), and some oils found in shales displaying suppression of vitrinite reflectance. It is observed that low temperature polymerisation will increase the potential pressure load retained within an overpressured zone and increase the overall volume of gas/fluids discharged on pressure release. Field observations, including measured recharge volumes and the fluid discharge volumes through a chimney from an overpressured zone, have been used to produce a triple porosity, poroelastic fluidisation expulsion model which links the discharge volume to pressure loading. The model predicts that expulsion from an active pressure mound will be cyclic and episodic. Published geochemical results from seismic chimneys in the Lower Congo Basin have been reinterpreted using the model to demonstrate that expulsion through a chimney is episodic, and to identify overpressured zones where the dominant fluid is oil and others where the overpressured zone contains both oil and gas. It is suggested that some of the oil in these overpressured zones, currently interpreted as thermogenic, may be derived from the polymerisation of biogenic gas. [source] | |||||||||||||||||||