Relevant bibliographies by topics / Vinylidenes / Dissertations / Theses

Dissertations / Theses on the topic 'Vinylidenes'

To see the other types of publications on this topic, follow the link: Vinylidenes.
Author: Grafiati
Published: 10 December 2022
Last updated: 29 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 dissertations / theses for your research on the topic 'Vinylidenes.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.

1

Baati, Rachid. "Etude de la reactivite de vinylidenes carbenoides de chrome(iii) et mise au point de nouveaux procedes de synthese." Université Louis Pasteur (Strasbourg) (1971-2008), 2000. http://www.theses.fr/2000STR13177.

Full text
Abstract:
Nous avons etudie la reactivite des trichloroalcanes geminaux primaires, secondaires et tertiaires avec crcl 2. Nous avons montre que cette reaction permet de generer des vinylidenes carbenoides de chrome(iii) de facon hautement stereospecifique a temperature ambiante. Une etude mecanistique nous a permis de mettre en evidence le mecanisme de formation de ces nouveaux organometalliques de stereochimie e ou z. La remarquable stabilite des vinylidenes carbenoides de chrome(iii) nous a permis d'etudier leurs reactivites. Nous avons montre que ces reactifs presentent un caractere nucleophile, un caractere electrophile et donnent lieu au rearrangement de fritsch-buttenberg-wiechel ainsi qu'a la reaction de cyclopropanation, typique des carbenes. Nous avons egalement observe le phenomene de reprotonation interne lors de reactions de deuteration des vinylidenes carbenoides, et le phenomene de transfert d'hydrogene lors de l'etude de leur stabilite thermique. La remarquable chimioselectivite de ses organometalliques avec les aldehydes nous a a permis de mettre au point de nouvelles methodologies pour la synthese stereoselective d'alcools allyliques chlores de stereochimie z, d'aldehydes ,-insatures -chlores z, d'ethers d'enol chlores e, d'esters d'enol e et de 1-chloro olefines de stereochimie z. Nous avons egalement etendu le champs d'application de la reaction de nozaki-hiyama a des substrats polyhalogenes, pour la synthese totale de l'halomon. Dans la seconde partie, realisee en collaboration avec les laboratoires pierre fabre nous avons etudie la mise au point de nouveaux procedes de synthese. L'etude portant sur la mequitazine, nous a permis de mettre au point une nouvelle voie d'acces a la 3-carboxymethyl quinuclidine optiquement pure. Ce compose peut etre deracemise avec un exces enantiomerique de 100% en utilisant une 1,2-disulfonamide chirale ditriflee. Cette strategie appliquee au 2,3,5,-trimethyl-4-hydroxy--dodecylthiophenylacetanilide permet d'obtenir un ee de 60% de l'enantiomere (s). Nous avons mis au point de nouvelles conditions pour realiser le rearrangement de fries permettant de preparer des intermediaires avances de la synthese totale de la rhein. Nous avons egalement mis au point une methode generale pour la preparation de sels d'amidinium, basee sur la reaction de pinner.
APA, Harvard, Vancouver, ISO, and other styles
2

Ji, Jing. "Poly(vinylidene fluoride) membranes." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/43532.

Full text
Abstract:
Poly(vinylidene fluoride) (PVDF) membranes have been intensively investigated and commercialised with broad applications in water purification and wastewater treatment for decades due to its outstanding properties. Currently, PVDF membranes are mainly produced by the phase inversion technique, which is predominant in both laboratory research and industrial manufacturing. Various modification methods based on the phase inversion technique have also been developed to improve the membrane performances, but these improvements are incremental and there have been no important breakthroughs during the past decade. This thesis first explores the preparation of reinforced PVDF flat sheet membranes by blending nanoclay followed by the phase inversion process. Although the membranes showed improved water permeation flux and enhanced abrasion resistance, further improvements are limited by the phase inversion technique itself. Consequently, a new concept of membrane manufacturing procedure has been proposed by combining unidirectional crystallisation of green solvent and polymer diffusion. The new method uses crystallites of a solvent dimethyl sulfoxide with controlled sizes as pore templates to create enormous nanosized flow passages. It follows a completely different pore formation mechanism and therefore overcomes the drawbacks of the phase inversion technique. The resultant PVDF membranes have an asymmetric structure composed of a highly porous separation layer and gradually opened micro-channels. Due to the unique structure, the prepared membranes showed excellent permeation performances and mechanical properties overwhelming commercial PVDF membranes prepared by the phase inversion technique. The filtration performance of the PVDF membranes can be further improved by modification of the membrane material, for example, by blending polyethylene glycol in the dope solution. The obtained membrane with pore size of 36 nm showed extraordinary high flux of 1711 L/m2h and could withstand 35 bar in the test. Moreover, the new manufacturing process is of much fewer influencing factors compared to the phase inversion approach and thus highly reliable and repeatable. In principle, it is also applicable to other common polymeric membrane materials such as polyethersulfone and cellulose acetate.
APA, Harvard, Vancouver, ISO, and other styles
3

James, M. I. "Emulsion polymerisation of vinylidene chloride copolymers." Thesis, Lancaster University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235213.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Shamsuddin, Siti Rosminah. "Carbon fibre reinforced poly(vinylidene fluoride)." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9803.

Full text
Abstract:
The demand for oil in the world is expected to rise by 1.7% in the fourth quarter of 2012 compared to fourth quarter of 2011. In order to cater for this increasing demand, the oil and gas industry continues to explore and develop deep-sea oilfields where oil and gas risers and pipelines encounter extreme conditions. The combination of high pressure and temperature with aggressive media which contains of hydrocarbon, alkanes, acids, sour gas (H2S), and CO2, etc., requires superior material performance and durability. Conventional engineering materials, such as steel are heavy and require corrosion protection, which are currently used as risers, flowlines and choke and kill lines have reached their limits. This is because of the poor chemical resistance and damage tolerance and the high costs involved in supporting their own weight. This has motivated the industry to explore non-corroding and lighter alternative materials if deeper sea reservoirs are to be explored. One such material that has the potential to overcome such limitations thus enabling new design strategies for cost effective, weight and energy saving materials is fibre reinforced composites. The remarkable properties and the tailorability of fibre reinforcement along load paths to achieve excellent performance of the composites is an attribute not found in any other material. The aim of this research was to manufacture novel carbon fibre reinforced polyvinylidene fluoride (PVDF) composites by incorporating atmospheric plasma fluorination of the carbon fibres. Powder impregnation method was adapted for the manufacturing of continuous unidirectional (UD) carbon fibre reinforced PVDF composite prepregs. The resulting composite laminates were characterised through various macro-mechanical tests. The impact of atmospheric plasma fluorination of the carbon fibre on the tensile, flexural, short beam shear and tearing properties of the UD composites were investigated to determine whether the improvements observed in the single fibre model composite can be translated to macro-level composite laminates. Apart from this, the impact of combining both fibre and matrix modifications on the composite were studied and the preliminary results on micro-mechanical scale are presented. Finally, composite pipe structures, made by filament winding technique using unidirectional carbon fibre reinforced PVDF composite prepregs onto a pure PVDF liner were fabricated, and characterised with respect to its mechanical properties.
APA, Harvard, Vancouver, ISO, and other styles
5

Hashim, Nur Awanis Binti. "Fabrication of poly(vinylidene fluoride) (PVDF) membranes." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6366.

Full text
Abstract:
In water filtration processes, the employment of polymeric membranes has become increasingly popular over the past few decades. However, the application of membrane processes is often limited due to the low fluxes and membrane failures caused by fouling and low membrane durability, which eventually leads to high operating costs in comparison with conventional processes. These limitations could be overcome by the development of high performance membranes with enhanced properties through a cost effective method. This thesis explores the preparation of high performance poly(vinylidene fluoride) (PVDF) membranes with the use of inorganic silica particles via a conventional immersion precipitation method and from an amphiphilic graft copolymer. A technique to improve the performance of PVDF membranes fabricated via immersion precipitation has been developed, which involves using inorganic silica (SiO2) particles during the preparation of the dope solution, followed by subsequent acid or alkaline treatments of the resultant membranes. By removing the SiO2 particles from the membrane substrates using either an acid or alkaline treatment, the resultant membranes exhibit an interconnected porous structure accompanied by a significant improvement in the water permeability. Due to the poor mechanical strength demonstrated by the NaOH treated membranes, detailed investigations of the stability of PVDF membranes in NaOH solutions are carried out on hollow fibre membranes prepared from different raw materials. Hollow fibre membranes exhibit different degrees of chemical degradation upon exposure to a sodium hydroxide solution under various conditions. Also, a simplified method has been developed as a cost effective way for the preparation of PVDF membranes with improved hydrophilicity, fouling resistance and water permeability from the amphiphilic graft copolymer, PVDF-g-PEGMA, which has a PVDF backbone and poly(ethylene glycol) methyl ether methacrylate (PEGMA) side chains. By eliminating three common steps involved during the conventional preparation method, the use of chemicals and energy can be substantially reduced.
APA, Harvard, Vancouver, ISO, and other styles
6

Doverspike, Montee A. "A nuclear magnetic resonance study of deuterated poly(vinylidene fluoride) and a copolymer of deuterated vinylidene fluoride and tetrafluoroethylene." W&M ScholarWorks, 1986. https://scholarworks.wm.edu/etd/1539623766.

Full text
Abstract:
Pulsed deuterium NMR experiments have been performed on deuterated samples of poly(vinylidene fluoride), PVF(,2), repeat unit CH(,2)CF(,2) and the copolymer poly(vinylidene fluoride)-tetrafluoroethylene (80-20), (PVF(,2)-F(,4)E). A deuterium line shape study has been employed to characterize the orientational distribution of the dipole moments in both poled and unpoled samples. In addition, the orientational distributions of chain axis alignment has been measured in stretched samples.;PVF(,2) and PVF(,2)-F(,4)E exhibit unique piezoelectric and pyroelectric properties which are due to their crystalline components (approximately 50% in typical material). Four crystalline phases exist in the homopolymer PVF(,2), the (alpha), (beta), (gamma), and the (delta). The relatively electrically inactive, melt solidified (alpha) phase can be transformed into the ferroelectric (beta) phase by mechanical deformation (stretching) or by application of large electric fields (poling- 200 Mv/meter). The copolymer melt solidifies directly into the (beta) phase. The (beta) phase is characterized by a net dipole moment per unit cell due to the parallel alignment of the CF(,2) dipole moments in the unit cell. The orthorhombic unit cell dimensions of the (beta) phase render a nearly pseudohexagonal packing structure of the molecular chains and is thought to allow for dipole reorientations via 60(DEGREES) steps during the poling process.;The orientationally dependent quadrupole interaction has been used to characterize the orientational distributions of the molecular dipole moments about the poling direction in both poled and unpoled samples of PVF(,2) and PVF(,2)-F(,4)E. No orientational dependence was found in either the poled or unpoled samples. This is in contrast to recent x-ray results which report substantial orientational anisotropy in rolled, poled protonated films. We have also measured the degree of chain axis alignment in stretched samples of both PVF(,2) and PVF(,2)-F(,4)E. Alignment in both samples is characterized by a gaussian distribution function about the stretch direction with a half width 1/e maximum of 22(DEGREES) and 18(DEGREES) respectively.;The characterization of the experimental results was done by comparing computer simulated line shapes with the experimental line shapes.
APA, Harvard, Vancouver, ISO, and other styles
7

Andrews, G. W. "Piezoelectric properties and microstructure of poly(vinylidene fluoride)." Thesis, University of Brighton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233373.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Abdelsayed, Ihab Maher. "CHARACTERIZATION OF ELECTROSPRAYED POLY(VINYLIDENE FLUORIDE)/CNT NANOCOMPOSITE." VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/1443.

Full text
Abstract:
PVDF, Poly(vinylidene fluoride), is a polymer that has been studied for over four decades due to its good electromechanical properties, stability, and durability in various environments. Currently, PVDF is the only commercially available piezoelectric polymer. PVDF is a polymorph, which indicates the presence of several crystalline phases such as α, β, γ, and δ-phase. Oriented β-phase PVDF exhibits ferroelectric properties and displays the largest piezoelectricity amongst the four phases, which makes it the most desirable phase. Preparing oriented β-phase PVDF is a multi-step process, which is cost intensive, due to the time, labor and energy utilized. The main goal of this work is to prepare oriented β-phase PVDF using the electrospraying technique in a one step process. During the electrospraying process a polymer jet is ejected. This jet disintegrates into droplets due to overwhelming surface tension, resulting in a sprayed coating on the collector substrate. Because of the combination of jet ejection and the high voltage applied between the needle tip and the substrate, the droplets can be stretched and the polymer chains can be oriented. Both the stretching and the high electric field are required for the transformation of α-phase to the oriented β-phase. This study proposes that by using the electrospraying technique it is possible to transform the α-phase to the β-phase in a one step process starting from solution. This research focuses on the processing and characterization of electrosprayed PVDF as well as electrosprayed PVDF/carbon nanotubes (PVDF/CNT) nanocomposites. The specific tasks are to determine the changes to the PVDF phases due to the electrospraying technique, and to determine the changes in the PVDF morphology due to the addition of carbon nanotubes to the polymer matrix.PVDF with two different molecular weights were electrosprayed using different solvents and parameters. Initial observations after electrospraying were that, high boiling point solvents resulted in the spraying of the solution and forming films, whereas a low boiling point volatile solvent such as acetone resulted in the spinning of the solution thus forming non-woven fiber mats. The thermal and electrical properties of the electrosprayed PVDF and PVDF/CNT composites are measured using several characterization techniques, including Modulated Differential Scanning Calorimetry (MDSC), Dielectric spectroscopy, Thermally Stimulated Current (TSC), Fourier Transform Infrared Spectroscopy (FT-IR), and X-Ray Diffraction (XRD). MDSC results show that electrosprayed PVDF has a lower melting point temperature than that of PVDF commercially available pellets. In addition, electrosprayed PVDF/CNT nanocomposites show a linear increase in the percentage of crystallinity with the increase of CNT concentration in the composite. Dielectric spectroscopy results indicate that by increasing the CNT concentration in the composite, the dielectric constant and the polymer conductivity increase.From the four characterizing techniques used, two of them, FT-IR and XRD, show that it is possible to transform α-phase to β-phase PVDF in a one-step process using electrospraying. The other two techniques, TSC and dielectric spectroscopy, show α-phase for the electrosprayed samples without CNT, and some β-phase formation with samples electrosprayed with CNT. These last two techniques; TSC and dielectric spectroscopy have results that differ from the FT-IR and XRD techniques. This contradiction may be a result of the small amounts of β-phase in the sample, which cannot be detected using these techniques. Another reason may be due to the difference in the probing levels between these techniques. XRD and FT-IR probe at the molecular level, whereas TSC and dielectric probe at a much larger scale, which may make it hard to detect small amounts of β-phase.
APA, Harvard, Vancouver, ISO, and other styles
9

Mendez, Ecoscia Ana Carolina. "Experimental Study of Emulsion Polymerization of Vinylidene Fluoride." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1203.

Full text
Abstract:
Le développement d’un procédé de polymérisation en émulsion est complexe de par la nature hétérogène de ce type de réaction. En outre, dans le cas de la polymérisation en émulsion du fluorure de vinylidène, la difficulté est d’autant plus accrue que le monomère est habituellement en phase gazeuse ou supercritique dans les conditions d’intérêt. Or la littérature manque d’informations concernant ce type de procédé de synthèse du PVDF sous une pression comprise entre 30 bar et 90 bar.Ainsi cette thèse a pour objectif de contribuer à une meilleure compréhension des mécanismes cinétiques et de stabilisation intervenants dans la polymérisation radicalaire en émulsion du VDF dans des conditions supercritiques et, plus particulièrement, de fournir des données expérimentales nécessaires à l’élaboration de futurs modèles.Avant même d’entreprendre les études expérimentales, cette thèse s’intéresse d’abord aux aspects d’installation et d’automatisation de l’unité de polymérisation ainsi qu’au démarrage et à l’optimisation du réacteur. Ensuite, plusieurs tests sont réalisés afin de comprendre certaines caractéristiques du latex produit ainsi que certaines propriétés du tensioactif fluoré. Une nouvelle méthode a spécialement été développée afin de suivre le phénomène de coagulation des particules de polymère.Finalement des réactions sont réalisées par lot et en semi-continu et une étude paramétrique des conditions opératoires et de la composition des réactifs est effectuée afin d’évaluer leur impact sur l’évolution de la polymérisation en émulsion. Notamment, le profil de vitesse de polymérisation est obtenu par calorimétrie, à partir d’une approche pratique fondée sur un estimateur d’état en cascade, ainsi que sur la mesure de la consommation de monomère, et sur l’analyse gravimétrique réalisée par prélèvement
The heterogeneous nature of the conventional emulsion polymerization can render the process quite complex. In the case of the emulsion polymerisation of vinylidene fluoride (VDF), the situation is more complicated than for the majority of industrial processes because the monomer is typically either a gas or a supercritical fluid under the polymerization conditions of interest. Given the relatively high pressure required for this process (30bar
APA, Harvard, Vancouver, ISO, and other styles
10

Yeow, May Ling. "Fabrication of poly(vinylidene fluoride) hollow fibre membranes." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426179.

Full text
APA, Harvard, Vancouver, ISO, and other styles
11

Milner, Lucy. "Mechanistic investigations of ruthenium-mediated reactions via vinylidene intermediates." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15529/.

Full text
Abstract:
Experimental and computational mechanistic studies are reported for several ruthenium-promoted processes, including the anti-Markovnikov hydration of terminal alkynes, the alkenylation of pyridine and electrophilic fluorination. The synergy between experimental and theoretical results revealed new insights into the previously reported hydration and alkenylation processes of alkynes and allowed the elucidation of a novel outer-sphere electrophilic fluorination mechanism, ‘OSEF’. The mechanism of the anti-Markovnikov hydration of phenylacetylene by [Ru(ƞ5-C5H5)(NCMe)(6-DPPAP)(3-DPICon)]+ (where 3-DPICon = 3-diphenylphosphinoisoquinolone and 6-DPPAP = 6-(diphenylphosphino)-N-pivaloyl-2-aminopyridine) was investigated using density functional theory. The proposed mechanism involves three ligand-assisted processes; alkyne-to-vinylidene tautomerism, attack of water at the vinylidene electrophilic α-carbon and tautomerisation from a hydroxyvinyl to acyl species. A catalyst deactivation product was identified experimentally and a potential mechanism of formation has been explored. The reactivity of [Ru(ƞ5-C5H5)(PR3)(L)2]PF6 (where PR3 = triphenylphosphine, 2-(1,1-dimethylpropyl)-6-(diphenylphosphino)pyridine or diphenyl-2-pyridylphosphine, L = pyridine) in pyridine alkenylation was trialed in order to optimise a previously reported catalytic procedure and eliminate the solvent dependence of the reaction. The synthesis and reactivity of these complexes in both stoichiometric and catalytic reactions have been investigated. A new electrophilic fluorination methodology is reported for the formation of carbon-fluorine bonds in the coordination sphere of ruthenium. A ruthenium-pyridylidene complex, synthesised from non-activated substrates, was observed to undergo rapid and selective monofluorination or deprotio-difluorination under mild reaction conditions. The procedure was then extended to allow the facile preparation of the first mononuclear fluorovinylidene complexes. Retention of the ligands allowed for subsequent investigation of metal-mediated reactivity and revealed unusual carbon-fluorine bond cleavage and migration processes. Experimental and computational mechanistic data suggested that fluorination was taking place via an unprecedented mechanism without metal-fluoride intermediates.
APA, Harvard, Vancouver, ISO, and other styles
12

Damour, Dominique. "Propargyltriméthylsilanes ...-fonctionnels précurseurs d'hétérocycles à groupe vinylidène." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37604185t.

Full text
APA, Harvard, Vancouver, ISO, and other styles
13

Ross, Gillian J. "The surface modification of poly(vinylidene fluoride) by alkaline media." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301346.

Full text
APA, Harvard, Vancouver, ISO, and other styles
14

MAZEAUD, BRIGITTE. "Modification chimique de polyisobutenes porteurs d'extremite vinylidene par des thiols." Paris 6, 1992. http://www.theses.fr/1992PA066246.

Full text
Abstract:
La modification de polyisobutenes a terminaisons vinylidene par des thiols est effectuee en presence de generateurs de radicaux libres qui sont soit des amorceurs de type percarbonates ou aibn, soit l'irradiation ultraviolette. La reaction est une addition de type anti-markovnikov de la fonction thiol sur la double liaison. Les pib modifies obtenus sont caracterises essentiellement par spectrometrie ir et rmn du proton. Dans un premier temps, une etude realisee avec le mercaptoethanol a mis en evidence l'influence de divers facteurs tels que la temperature, la presence de solvant ou le rapport fonctions thiol sur extremites vinylidene. La modification du pib par le mercaptoethanol ne s'effectue qu'en presence d'un apport minimal d'oxygene (oxygene de l'air), en solution et avec un exces de thiol. L'influence de la nature du thiol est examinee dans la deuxieme partie et permet de generaliser le procede. La comparaison des resultats obtenus avec differents thiols montre que des conditions optimales doivent etre recherchees pour chaque cas. La derniere partie decrit d'une part la synthese d'elastomeres realisee a partir de pib modifies par des mercaptopropyltrimethoxy et triethoxysilanes par hydrolyse et condensation des fonctions si-(or)#3 et, d'autre part la synthese de copolymere en peigne obtenus par greffage des pib sur des polysiloxanes porteurs de fonctions thiol
APA, Harvard, Vancouver, ISO, and other styles
15

Saraf, Manish Kumar. "Polymerization of Vinylidene Fluoride in Supercritical Carbon Dioxide: Molecualr Weight Distribution." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011119-185032.

Full text
Abstract:

SARAF, Manish Kumar. Polymerization of Vinylidene Fluoride in Supercritical Carbon Dioxide: Molecular Weight Distribution (Under the direction of Drs. George W. Roberts and Joseph M. DeSimone)Conventional vinylidene fluoride polymerizations require the use of large amounts of water. Therefore, energy and cost-intensive drying and separation steps are required to isolate the polymer. Additionally, some conventional polymerizations use fluorosurfactants that belong to 3M?s ?Scotchgard? family of surfactants, which are being phased out due to environmental concerns. In this research, we investigate a "green" process for the continuous polymerization of vinylidene fluoride by free-radical precipitation polymerization in supercritical carbon dioxide (scCO2). Significant technological and environmental improvements can be achieved by this technology, such as: 1) elimination of waste streams generated by conventional suspension, and emulsion processes; and 2) achievement of major energy savings, as the polymer is isolated in a dry form with no water or solvent to evaporate. The experimental system used in this research consisted of a continuous stirred tank reactor (CSTR) for polymerization, and a polymer withdrawal system where polymer was collected, and continuously ejected to ambient conditions. The polymer was collected as a dry "free-flowing" powder, and was characterized by GPC (gel permeation chromatography), DSC (differential scanning calorimetry), and Fluorine-19 NMR (nuclear magnetic resonance spectroscopy). Experiments were carried out to study the effect of different parameters such as inlet monomer concentration ([M]in= 0.78 to 3.5 M), pressure (P=3050 to 4400 psig) , temperature (T=65 to 85 oC) , and average residence time (t = 12 to 50 mins.), on the polymerization rate and the average molecular weights. A homogeneous model based on classical free radical kinetics predicted the polymerization rate very well at the lower rates. However, this could not predict an inhibition in the rate that was observed at higher monomer concentrations. A bimodal molecular weight distribution was obtained at inlet monomer concentrations greater than around 1.9 M. The second (high molecular weight) mode was more prominent at higher monomer concentrations, higher residence times, and lower temperatures. Two hypothesis, poor mixing and long chain branching, were investigated to explain these broad and bimodal molecular weight distributions (MWDs). Agitation studies showed that poor mixing can account for the slower rate of polymerization at high monomer concentrations, but does not to bimodal MWDs. End group analysis using NMR showed that chain transfer occurs, probably to polymer. A homogeneous kinetic model was developed to investigate the effect of chain branching arising from chain transfer to polymer. This model showed that broad MWDs with large polydispersity indices (PDIs) are obtained at high monomer concentrations and at high residence times. These predictions matched very well with experimental data. However, the model predicted a unimodal MWD even at very high values of the rate constant for chain transfer to polymer.Batch polymerization studies were carried out to develop alternate low temperature initiators, which could reduce operating and equipment costs and potentially produce high molecular weight polymer with reasonable yields. A fluorinated initiator obtained from hexafluoropropynl oxide dimer produced PVDF with very high molecular weights (~90 K) at reasonable yields.

APA, Harvard, Vancouver, ISO, and other styles
16

Tai, Hongyun. "Free radical heterogeneous polymerisation of vinylidene fluoride in supercritical carbon dioxide." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428931.

Full text
APA, Harvard, Vancouver, ISO, and other styles
17

Day, John Anthony. "Piezoelectric and pyroelectric properties of an oriented vinylidene fluoride/trifluoroethylene copolymer." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277365.

Full text
APA, Harvard, Vancouver, ISO, and other styles
18

Esterly, Daniel Mason. "Manufacturing of Poly(vinylidene fluoride) and Evaluation of its Mechanical Properties." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34677.

Full text
Abstract:
Poly(vinylidene fluoride) (PVDF) receives an increasing amount of attention because it exhibits the strongest piezoelectric response of any commercially available polymer. These piezoelectric properties have proved useful as actuators and sensors. Current manufacturing processes limit PVDF to thin films and restricting their uses largely to sensors. Further applications utilizing the changes in mechanical properties of piezoelectric polymers are being realized. Evaluating to what extent the mechanical properties will change with applied electric field and finding new ways to manufacture PVDF will lead to new applications of piezoelectric polymers. In-situ mechanical testing of biased piezoelectric PVDF films successfully measured changes in loss and storage modulus. In-situ creep testing measured an increase in stiffness while in-situ dynamic mechanical analysis (DMA) measured and overall decrease in loss and storage modulus. Differences in results between the two experiments are attributed to orientation of the polymer and piezoelectric forces acting on the equipment. DMA results are accepted as being the most accurate and measured changes of over 20% in elastic modulus. Results were believed to be greatly influence by attached electrodes and actuation forces. Cryogenic mechanical milling successfully converted a phase PVDF powder to b phase as measured with wide-angle x-ray diffraction. This is the first recorded instance of b phase powders forming from the a phase through ball milling. These b phase powders maintained their crystal structure during compression molding at 70°C.
Master of Science
APA, Harvard, Vancouver, ISO, and other styles
19

Clark, Kelly L. "Synthesis of maleated poly(vinylidene fluoride) in supercritical carbon dioxide medium /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3137685.

Full text
APA, Harvard, Vancouver, ISO, and other styles
20

Hashim, Kamaruddin. "Compatibilization of poly(vinylidene fluoride)/nylon 6 blends by intermolecular association." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/25382.

Full text
Abstract:
Blends of poly(vinylidene fluoride) (PVDF) and polyamide 6 (N6) are interesting for both scientific studies and commercial exploitation. PVDF is known to be miscible with polymers produced from monomers containing carbonyl side groups, eg. polyethyl acrylate, polyacrylamide etc., but is not miscible with polymers containing carbonyl groups in the main chain, ego polyamides, polyester, etc. Although complete miscibility of the blend components is not always necessary, strong physical interactions between the two components are needed in order to obtain a compatible blend, i.e. one which exhibits good mechanical properties. An investigation was carried out to explore the possibility to compatibilise blends of PVDF and N6 using y-radiation to graft acid groups on either polymer and subsequently ionomerizing these with zinc cations. Graft copolymer type of compatibilizer was produced when the acid functionalized PVDF (grafted PVDF) was blended with N6 or acid functionalized N6 (grafted N6). Fourier transform infrared analysis has confirmed the occurance of reactions between acid groups in the grafted PVDFand amine groups in the N6. The compatibility of the PVDF/N6 blends was found to increase with increasing amount of carboxylic acid groups in the two polymers. This was accompanied by an increase in Tg of the N6 phase in blend, which became more pronounced when both components were grafted. Tensile test and solvent resistance experiments were carried out to relate the compatibization of the blend to the improvement in mechanical properties. Ionomerization of the functionalized polymers with zinc cations was performed in order to study the effect on compatibility of the blend. The neutralization of the acid groups in either polymer in the blend by addition of zinc acetyl acetonate was found to suppress the chemical reaction with the amine end groups in the N6 phase, and to cause a reduction in the T g and a reduction in crosslinking of the N 6 phase. However when both polymers were grafted, the crystallinity of the N6 phase was restored, which was accompanied by an increase in Tg.
APA, Harvard, Vancouver, ISO, and other styles
21

Clare, Philip M. "Aspects of the chemistry of dimolybdenum acetylide, vinylidene and allenylidene complexes." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387420.

Full text
APA, Harvard, Vancouver, ISO, and other styles
22

Bartlett, Ian Mark. "The redox activiation of alkyne ligands in group 6 transition metal complexes." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390376.

Full text
APA, Harvard, Vancouver, ISO, and other styles
23

Minton, Mary Amanda. "Reactions of Halogenated Ethylenes on the alpha-Cr2O3 (1012) Surface." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29014.

Full text
Abstract:
The thermally induced reaction of halogenated ethylenes on the α-Cr2O3 (10 2) single crystal surface results in the formation of gas phase hydrocarbons including acetylene, ethylene, butadiene, and dihydrogen, and deposition of surface chlorine adatoms. No surface carbon or combustion products are observed in any reactions indicating no thermally induced C-C bond cleavage occurs and surface lattice oxygen is not incorporated into surface intermediates. Thermal desorption spectroscopy indicates that in all halogenated ethylene reactions acetylene is the major product, regardless of the reaction scheme. The surface reactions of halogenated ethylenes are proposed to proceed through C-X (X=halogen) bond cleavage to form surface halogen adatoms and surface C2 hydrocarbon fragments. Halogen adatom deposition affects reaction barriers to hydrocarbon formation, and eventually shuts down surface chemistry. Photoemission and near edge x-ray absorption fine structure spectra show that all studied reactants undergo some C-X bond cleavage upon low temperature adsorption forming adsorbed C2 fragments and halogen adatoms. Photoemission for each reaction system shows at least two C1s features (283.0-286.0 eV) and two Cl2p features (2p3/2=198.0-201.0 eV) with higher binding energy features associated with molecularly intact halogenated ethylenes and lower binding energy features associated with dissociated surface species. Near edge x-ray absorption fine structure spectra taken, corresponding to photoemission spectra, indicate the occurrence of C1sâ Ï * transitions, indicating intact p-systems are present. Heating the surface results in a reduction in intensity of higher energy photoemission and near edge x-ray absorption fine structure indicative of a decrease in surface C-X bonds.
Ph. D.
APA, Harvard, Vancouver, ISO, and other styles
24

Dawson, Noel Mayur. "The Processing and Polarization Reversal Dynamics of Thin Film Poly(vinylidene) Fluoride." Thesis, The University of New Mexico, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10641207.

Full text
Abstract:

Many ferroelectric devices benefit from the ability to deposit thin ferroelectric layers. Poly(vinylidene) fluoride (PVDF) is the prototypical ferroelectric polymer, but processing of thin film ferroelectric PVDF remains a challenge due to the formation of large voids in the film during traditional thin film processing. The research described in this dissertation starts by investigating the origin of these voids. The cause of these voids is found to be caused by vapor induced phase separation (VIPS). Guided by the thermodynamics of VIPS, a process is then designed to produce void-free ferroelectric PVDF thin films on polar and non-polar substrates. The films are shown to have a high remnant polarization (~6.5 C m–2). The later part of this dissertation is focused on understanding the temperature and structural phase dependent kinetics of polarization switching in PVDF films. A polarization switching model is developed with considerations of Avrami nucleation and growth, local electric fields, temperature and structural phase. The kinetics of polarization switching are shown to follow a universal behavior when correctly accounting for temperature and structural phase.

APA, Harvard, Vancouver, ISO, and other styles
25

Johnson, Tony Richard. "Vinylidene and cyclic carbene chemistry of iron and manganese half-sandwich complexes." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340247.

Full text
APA, Harvard, Vancouver, ISO, and other styles
26

RUNDQVIST, KARIN. "Piezoelectric behaviour of woven constructions based on poly(vinylidene fluoride) bicomponent fibres." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17386.

Full text
Abstract:
During this project it was investigated how the newly developed piezoelectric PVDF bicomponent fibre behaved when integrated in different weave constructions. The possibility to integrate conductive yarns as outer electrode was studied in order to see if it was possible to create a fully textile piezoelectric sensors. The piezoelectric properties of the bicomponent fibre is given by the sheath material, which is a polymeric material known as poly(vinylidene fluoride) (PVDF). Today only piezoelectric film made by PVDF is commercially available, but with a flexible PVDF bicomponent fibre it improves the possibility to integrate piezoelectric material into a textile construction. In this study the PVDF bicomponent fibre was integrated in the warp direction into weave constructions, such as plain weave, twill and weft rib. All the woven bands included 60 PVDF bicomponent yarns, with 24 filaments in each bundle and the average width of the bands produced was 30 mm. Different conductive materials and fibres, acting as outer electrode, were coated or integrated together with the PVDF fibre and the behaviour of the PVDF fibres was analysed. All the woven samples went through corona poling with a voltage of 7 kV in 70 ⁰C for 3 min. The weave construction that gave highest piezoelectric output signal was twill with weft that has low tex. The twill construction gave a range amplitude of 1.5- 3.3 V when subjected to a dynamic strain of about 0.25% at 4 Hz. It was shown that different conductive materials influenced the PVDF fibre in different ways, due to the resistance of the material. It was also shown that it was possible to integrate piezoelectric bicomponent fibre into a textile construction and that a fully textile piezoelectric sensor could be produced by using conductive yarns as outer electrode.
Program: Masterutbildning i textilteknik,
APA, Harvard, Vancouver, ISO, and other styles
27

Yang, Lianyun. "Novel Ferroelectric Behavior in Poly(vinylidene fluoride-co-trifluoroethylene)-Based Random Copolymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1431686125.

Full text
APA, Harvard, Vancouver, ISO, and other styles
28

Johnson, David. "A computational study of ruthenium metal vinylidene complexes : novel mechanisms and catalysis." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/6170/.

Full text
Abstract:
A theoretical investigation into several reactions is reported, centred around the chemistry, formation, and reactivity of ruthenium vinylidene complexes. The first reaction discussed involves the formation of a vinylidene ligand through non-innocent ligand-mediated alkyne-vinylidene tautomerization (via the LAPS mechanism), where the coordinated acetate group acts as a proton shuttle allowing rapid formation of vinylidene under mild conditions. The reaction of hydroxy-vinylidene complexes is also studied, where formation of a carbonyl complex and free ethene was shown to involve nucleophilic attack of the vinylidene Cα by an acetate ligand, which then fragments to form the coordinated carbonyl ligand. Several mechanisms are compared for this reaction, such as transesterification, and through allenylidene and cationic intermediates. The CO-LAPS mechanism is also examined, where differing reactivity is observed with the LAPS mechanism upon coordination of a carbonyl ligand to the metal centre. The system is investigated in terms of not only the differing outcomes to the LAPS-type mechanism, but also with respect to observed experimental Markovnikov and anti-Markovnikov selectivity, showing a good agreement with experiment. Finally pyridine-alkenylation to form 2-styrylpyridine through a half-sandwich ruthenium complex is also investigated. The mechanism for this process is elucidated, along with a description of the formation of the unexpected experimental deactivation product. Additionally the chemistry and bonding of pyridylidene complexes is also studied.
APA, Harvard, Vancouver, ISO, and other styles
29

Jee, Tae Kwon. "Nanoscale characterization of solution-cast poly(vinylidene fluoride) thinfilms using atomic force microscopy." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4790.

Full text
Abstract:
This thesis research focuses on the characterization of thinfilms made of poly(vinylidene fluoride) (PVDF) using an atomic force microscope. Thinfilms of PVDF were fabricated by a spin coating method with different conditions and characterized using the Atomic Force Microscopy (AFM) for morphological changes. Phase and conformational changes of PVDF were investigated using both wide angle X-ray diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR). From this analysis, in-situ corona poling with annealing of spin-cast PVDF enabled a phase change from α to the mixture of β and γ phases. This process can decrease the complexity of the conventional method which requires mechanical stretching before poling PVDF in addition to thermal annealing for β phase transformation. This thesis describes some materials and surface properties of solution-cast PVDF thinfilms with various conditions such as topography and phase image, adhesion force, friction force, and roughness. Through the AFM topography and phase images, polymeric behavior and spherulites are discussed in the later part of the thesis.
APA, Harvard, Vancouver, ISO, and other styles
30

Walters, Stephen John. "Acyl(oxy) carbene and vinylidene chemistry of iron and ruthenium half-sandwich complexes." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245691.

Full text
APA, Harvard, Vancouver, ISO, and other styles
31

Carbeck, Jeffrey Davis. "Temperature dependent structure and properties of crystalline poly(vinylidene fluoride) from molecular simulation." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11247.

Full text
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.
Includes bibliographical references (leaves 129-134).
by Jeffrey Davis Carbeck.
Ph.D.
APA, Harvard, Vancouver, ISO, and other styles
32

Faulkner, Charlotte Waveney. "A study of some ruthenium(II) and manganese(I) acetylide and vinylidene complexes." Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/272793.

Full text
APA, Harvard, Vancouver, ISO, and other styles
33

Moghareh, Abed Mohammad Reza. "Poly(vinylidene fluoride) (PVDF) based hydrophilic hollow fibre membranes : prospects for wastewater treatment." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9830.

Full text
Abstract:
The growing need for suitable water resources has attracted attention to new water and wastewater treatment processes, such as membrane filtration. Due to the excellent properties of poly(vinylidene fluoride) (PVDF) polymer and membranes, such as excellent chemical and thermal resistance along with great mechanical strength, the PVDF membrane is a suitable candidate for the water and wastewater industry. As a result, there have been many attempts to improve the performance of PVDF membranes, particularly in terms of water flux and fouling resistance, in order to increase the membrane’s lifespan and reduce operating costs. This thesis explores such PVDF membrane performance improvements through hydrophilic modification of the bulk membrane. In this study, the recently developed process of atom transfer radical polymerisation (ATRP) was used to graft hydrophilic chains of poly(ethylene glycol) methyl ether methacrylate (POEM) onto the backbone of the PVDF polymer to synthesise an amphiphilic copolymer (PVDF-g-POEM). A new, environmentally-friendly and cost-effective method was introduced to purify the synthesised amphiphilic copolymer by using water instead of volatile solvents. The amphiphilic copolymer was used as a blend in the spinning dope and the effect of blending this amphiphilic copolymer on the prepared hollow fibres was studied in detail. A wide range of hydrophilic PVDF based hollow fibres was achieved by changing the spinning parameters and dope compositions. Moreover, nano-sized γ-Al2O3 particles were used as an additive to improve PVDF flat sheet membranes. By using alumina particles, the filtration performance, surface hydrophilicity and fouling resistance of membranes improved significantly. In addition, by using triethyl phosphate (TEP) as the solvent, PVDF hollow fibre membranes with interconnected pore structures were produced via a single step immersion precipitation technique. The resultant PVDF hollow fibre membranes displayed excellent mechanical properties because of their macro-void free structures. Polyethylene glycol (PEG) was used as an additive to improve the water flux of the produced membranes and PVDF hollow-fibre membranes suitable for water and wastewater treatments in the range of ultrafiltration were obtained.
APA, Harvard, Vancouver, ISO, and other styles
34

Yang, Jing. "Phosphonium ionic liquids : Versatile nanostructuration and interfacial agents for poly(vinylidene fluoride-chlorotrifluoroethylene)." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI072/document.

Full text
Abstract:
Ce travail de thèse porte sur la compréhension du rôle polyvalent des liquides ioniques (LIs) phosphonium comme agents de nanostructuration et interfaciaux pour la matrice polymère fluorée poly(fluorure de vinylidène-chlorotrifluoroéthylène) (P(VDF-CTFE)). Dans un premier temps, deux LIs phosphonium avec des fonctionnalités différentes générant un encombrement stérique et des fonctions dipolaire additionnelles sont tout d'abord incorporés dans la matrice P(VDF-CTFE) pour préparer des films de polymère additives. La structure de la phase cristalline, la morphologie issue de la dispersion et le comportement de cristallisation sont finement caractérisés dans le but de fournir une compréhension fuie et complète du rôle joué par le LI sur la nanostructuration. Dans un second temps, le rôle d’agent interfacial du LI est étudié avec un LI phosphonium fluoré comprenant un cation combinant trois phényles et une chaîne fluorée courte.Ce LI est utilise pour modifier la surface de l'oxyde de graphène (GO) et de l'oxyde de graphène réduit (rGO) afin de rendre ces nanocharges fonctionnelles et les incorporer dans la matrice P(VDF-CTFE). Ainsi, des films composites de P(VDF-CTFE)/graphène avec différentes teneurs en nanocharges sont préparés et une caractérisation fuie de la structure et des propriétés est entreprise afin de mieux comprendre les mécanisme d’interaction interfaciale et leurs influences sur les films composites, tels que la structure de la phase cristalline, le comportement de cristallisation, la relaxation des chaînes, la morphologie et les propriétés diélectriques finales
This thesis work deals with an understanding of the versatile roles of phosphonium ionic liquids (ILs) as nanostructuration and interfacial agents for the fluorinated polymer matrix, i.e.,poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)). In this context, two phosphonium ILs with different functionalities in steric hindrance and extra dipolar groups are firstly incorporated in P(VDF-CTFE) matrix to prepare polymer films. The crystalline phase structure, dispersion morphology and crystallization behavior are finely characterized with the goal of providing a full and deep understanding of the versatile and tunable nanostructuration effect of phosphonium ILs. Subsequently, in order to elucidate the mechanism of interfacial influence of IL, a fluorinated phosphonium IL with a cation structure combining three phenyls and a short fluorinated chain is added on the surface of graphene oxide (GO) and reduced graphene oxide (rGO), making them as functional nanofillers to be incorporated into P(VDF-CTFE) matrix. Thus,P(VDF-CTFE)/graphene composite films with different filler contents are prepared in order to investigate the mechanism of interfacial interaction and its influence on the composite films, such as crystalline phase structure, crystallization behavior, chain segmental relaxation behavior, dispersion morphology and the final dielectric properties
APA, Harvard, Vancouver, ISO, and other styles
35

Zhou, Xin Zhang Qiming. "High energy/capacitance density poly(vinylidene fluoride) based polymers for energy storage capacitor applications." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4578/index.html.

Full text
APA, Harvard, Vancouver, ISO, and other styles
36

Chavan, Harshad S. "Investigation of ß-phase poly (vinylidene fluoride) films using small-angle x-ray scattering." Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1145990710.

Full text
APA, Harvard, Vancouver, ISO, and other styles
37

El, Mohajir Badr-Eddine. "Effets de l'histoire thermomécanique sur le comportement structural et mécanique du polyfluorure de vinylidene." Doctoral thesis, Universite Libre de Bruxelles, 2001. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211646.

Full text
APA, Harvard, Vancouver, ISO, and other styles
38

Riosbaas, Miranda Tiffany. "Phase Change Activation and Characterization of Spray-Deposited Poly(vinylidene) Fluoride Piezoelectric Thin Films." Thesis, University of California, Davis, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1585118.

Full text
Abstract:

Structural safety and integrity continues to be an issue of utmost concern in our world today. Existing infrastructures in civil, commercial, and military applications are beginning to see issues associated with age and environmental conditions. In addition, new materials are being put to service that are not yet fully characterized and understood when it comes to long term behavior. In order to assess the structural health of both old and new materials, it is necessary to implement a technique for monitoring wear and tear. Current methods that are being used today typically depend on visual inspection techniques or handheld instruments. These methods are not always ideal for large structures as they become very tedious leading to a substantial amount of both time and money spent. More recently, composite materials have been introduced into applications that can benefit from high strength-to-weight ratio materials. However, the use of more complex materials (such as composites) leads to a high demand of structural health monitoring techniques, since the damage is often internal and not visible to the naked eye. The work performed in this thesis examines the methods that can be used for phase change activation and characterization of sprayable poly(vinylidene) fluoride (PVDF) thin films in order to exploit their piezoelectric characteristics for sensing applications. PVDF is widely accepted to exist in four phases: alpha, beta, gamma, and delta. Alpha phase PVDF is produced directly from the melt and exhibits no piezoelectric properties. The activation or transition from α phase to some combination of beta and/or gamma phase PVDF leads to a polarizable piezoelectric thin film to be used in sensing applications. The work herein presents the methods used to activate phase change in PVDF, such as mechanical stretching, annealing, and chemical composition, to be able to implement PVDF as an impact detection sensor. The results and analysis provided in this thesis will present the possibilities of spray-deposited PVDF thin films in both small-scale and large-scale sensing applications that can be applied to both simple and complex geometries.

APA, Harvard, Vancouver, ISO, and other styles
39

Ke, Kai. "Piezoresistive Behavior of Carbon Nanotube based Poly(vinylidene fluoride) Nanocomposites towards Strain Sensing Applications." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-201959.

Full text
Abstract:
With the development of modern industrial engineering technology, increasing demands of multifunctional materials drive the exploration of new applications of electrical conductive polymer nanocomposites (CPNCs). Toward applications of smart materials, sensing performance of CPNCs has gained immense attention in the last decade. Among them, strain sensors, based on piezoresistive behavior of CPNCs, are of high potential to carry out structural health monitoring (SHM) tasks. Poly(vinylidene fluoride) (PVDF) is highly thought to be potential for SHM applications in civil infrastructures like bridges and railway systems, mechanical systems, automobiles, windgenetors and airplanes, etc. because of its combination of flexibility, low weight, low thermal conductivity, high chemical corrosion resistance, and heat resistance, etc. This work aimed to achieve high piezoresistive sensitivity and wide measurable strain ranges in carbon nanotube based poly(vinylidene fluoride) (PVDF) nanocomposites. Four strategies were introduced to tune the sensitivity of the relative electrical resistance change (ΔR/R0) versus the applied tensile strain for such nanocomposites. Issues like the influence of dispersion of multi-walled carbon nanotubes (MWCNTs) on initial resistivity of PVDF nanocomposites and conductive network structure of MWCNTs, as well as piezoresistive properties of the nanocomposites, were addressed when using differently functionalized MWCNTs (strategy 1). In addition, the effects of crystalline phases of PVDF, mechanical ductility of its nanocomposites and interfacial interactions between PVDF and fillers on piezoresistive properties of PVDF nanocomposites were studied. Using hybrid fillers, to combine MWCNTs with conductive carbon black (strategy 2) or isolating organoclay (strategy 3), piezoresistive sensitivity and sensing strain ranges of PVDF nanocomposites could be tuned. Besides, both higher sensitivity and larger measurable strain ranges are achieved simultaneously in PVDF/MWCNT nanocomposites when using the ionic liquid (IL) BMIM+PF6- as interface linker/modifier (strategy 4). The detailed results and highlights are summarized as following: 1. The surface functionalization of MWCNTs influences their dispersion in the PVDF matrix, the PVDF-nanotube interactions and crystalline phases of PVDF, which finally results in different ΔR/R0 and the strain at the yield point (possibly the upper limit of sensing strain ranges). As a whole, regarding to the fabrication of strain sensors based on PVDF/MWCNT nanocomposite, in contrast to pristine CNTs, CNTs-COOH and CNTs-OH, CNT-NH2 filled PVDF nanocomposites possess not only high piezoresistive sensitivity but also wide measurable strain ranges. Gauge factor, i.e. GF, is ca.14 at 10% strain (strain at the yield point) for the nanocomposites containing 0.75% CNTs-NH2. 2. Using hybrid fillers of CNTs and CB to construct strain-susceptible network structure (conductive pathway consisting of string-like array of CNTs and CB particles) enhances the piezoresistive sensitivity of PVDF nanocomposites, which is tightly associated with the CNT content in hybrid fillers and mCNTs/mCB. The best piezoresistive effect is achieved in PVDF nanocomposites with fixed CNT content lower than the ΦC (0.53 wt. %) of PVDF/CNT nanocomposites. 3. ΔR/R0 and possible sensing strain ranges of PVDF nanocomposites were tailored by changing crystalline phases of PVDF and PVDF-MWCNT interactions. Besides, the increase of the strain at yield point in PVDF nanocomposites filled by CNTs-OH is more obvious than that in the nanocomposites containing the same amount of clay and CNTs. The nanocomposite consisting of 0.25% clay and 0.75% CNTs-OH have ca. 70% increase of the strain at the yield point (17%) and the GF at this strain is ca. 14, while GF for the nanocomposite filled by only 0.75% CNTs-OH is ca. 5 at 10% strain. 4. IL BMIM+PF6- served as interface linker for PVDF and MWCNTs, which significantly increased the values of ΔR/R0 and strain at the yield point of PVDF nanocomposites simultaneously. Besides, this increases with increasing IL content. With the aid of IL, the dispersion of nanotube and toughness of the nanocomposites are greatly improved, but the electrical conductivity of the nanocomposites is decreased with the incorporation of IL, which is related to the IL modified PVDF-MWCNT interface connection or bonding. GF reaches ca. 60 at 21% strain (the strain at the yield point) for PVDF nanocomposites filled by 10% IL premixed 2%CNTs-COOH.
APA, Harvard, Vancouver, ISO, and other styles
40

Marturano, Raffaella. "The kinetics and mechanism of the ene reaction of vinylidene alkenes with maleic anhydride." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843936/.

Full text
Abstract:
The 'ene' reaction is a pericyclic reaction related to the Diels-Alder reaction. It can be used to synthesise products of commercial importance. An example is its use to attach a 'succinic acid functionality' (via maleic anhydride -MA-), to the ene-terminated polyisobutylene (PIB) to yield PIBSA. While there have been a limited number of studies of the ene reaction, none have concentrated on the reactivity of the vinylidene fragment (CH2-C(=CH2)-CH3) which is found in PIB. In addition there are difficulties in the determination of the kinetics of the PIBSA reaction, because of several competitive processes, which may occur. Therefore the overall aim of the project is to investigate the kinetics and mechanism of the ene reaction between a range of simple vinylidene alkenes (including PIB) and maleic anhydride. A small range of alkenes, 2-methyl-4-phenylbut-1-ene, 2-methyl-4-phenylpent-1-ene, 2.4-dimethyl-4-phenylpent-1-ene and 2,4-dimethyl-4-(-4-fluorophenyl)pent-1-ene, were synthesised, in overall yields of 10 to 35 %. Syntheses were achieved using 1,4-conjugate addition, Friedel-Crafts and Wittig methodologies, and purification involved column chromatography and distillation. Product identification was by 1H NMR and 13C NMR spectroscopy. NMR monitoring of the reaction of 4-phenylbut-1-ene under conditions of equimolar MA in 1,2,4-trichlorobenzene solvent allowed the identification of the adduct 3-(4- phenyl-2-butenyl)dihydro-2,5-furandione as a 9:1 mixture of E and Z isomers. No evidence for further reaction to yield a di-adduct. Similar monitoring of the reactions of the other enes yielded no clear evidence of the adduct. However, under conditions of excess MA, 2,4-dimethyl-4-phenylpent-1-ene, 2.4-dimethyl-4-(-4-fluorophenyl)pent-l-ene yielded the expected adduct. PIB showed evidence of the adduct. A comparison of the 1H-NMR spectra for 2,4-dimethyl-4-phenylpent-1-ene, 2,4-dimethyl-4-(-4-fluorophenyl)pent-1-ene, PIB showed that, in all cases, only product derived from migration of the 1° H was found. Furthermore, no di-adduct was formed even for 2,4-dimethyl-4-phenylpent-1-ene, 2,4-dimethyl-4-(-4-fluorophenyl)pent-1-ene, with large excess of MA. The rate constants in the range 160 °C to 190 °C were determined for all alkenes mostly under conditions of excess MA, but some under conditions of excess alkene. Second order rate constants at 180°C varied from 4*10-5 to 100*10-5 with 4-phenylbut-1-ene being significantly slower than the others. A small medium effect of ca. 2 was identified as resulting from the change from excess ene to excess maleic anhydride. The activation parameters were in the range DeltaH+ 48 to 120 kJ mol-1 and DeltaS+ -53 to -229 J mol K-1. A computational calculation using Hartree-Fock and Semi-Empirical methods of the FMO, HOMOene-LUMOenophile gap allowed ranking of the alkenes. In general the gross trend in reactivity found experimentally was reflected in the computational work. The findings are compared to others and rationalised in terms of a pericyclic, exo Transition State, with the incipient C=C preferring an E configuration.
APA, Harvard, Vancouver, ISO, and other styles
41

Pirio, Nadine. "Activation d'alcynes par les derives du ruthenium : preparation de complexes vinylidene, acetylure et allenylidene." Rennes 1, 1992. http://www.theses.fr/1992REN10063.

Full text
Abstract:
Le precurseur cis-rucl#2(dppm)#2 (dppm:ph#2pch#2pph#2) s'est revele etre un bon modele pour activer les alcynes vrais et des alcools propargyliques. Il a permis de preparer facilement les complexes vinylidene- et allenylidene-ruthenium(ii) trans-((dppm)#2(cl)ru=(c=)#ncrr)pf#6 (n=1, 2) pour lesquels quelques regles de stabilite et de reactivite ont ete precisees. L'acces a des acetylures du ruthenium(ii) difficiles a obtenir par des methodes directes a ete ainsi rendu possible. L'utilisation de diynes fonctionnalises a permis de synthetiser des complexes a chaine polyinsaturee. Il est envisageable de generer le metallacumulene ((dppm)#2(cl)ru=c=c=c=c=cph#2)#+ soit par complexation directe, soit par transformation d'un complexe diynyl-ruthenium. Cet intermediaire tres reactif conduit dans le methanol a un alcenylallenylidene, et dans le dichloromethane a un allenylidene inattendu possedant un groupement indenylidene. Le developpement de cette methode a tout particulierement permis d'obtenir des systemes insatures originaux bis(allenylidene)- et bis(diynyl)-ruthenium(ii)
APA, Harvard, Vancouver, ISO, and other styles
42

CHAVAN, HARSHAD S. "INVESTIGATION OF β-PHASE POLY (VINYLIDENE FLUORIDE) FILMS USING SMALL- ANGLE X-RAY SCATTERING." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145990710.

Full text
APA, Harvard, Vancouver, ISO, and other styles
43

Hanlon, David James. "u-vinylidene and n-1-cyclopropenyliron complexes : chemistry and synthesis via 1, 1-dichlorocyclopropanes /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1985.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
44

Schulenburg, Wilhelm-Karl von der. "Thermische Cyclopropen-Isomerisierungen: Mechanistische Untersuchungen von thermisch erzeugten Vinyliden-Intermediaten." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=957236492.

Full text
APA, Harvard, Vancouver, ISO, and other styles
45

Kopf, Henning. "Carben-, Vinyliden- und Allenyliden-Komplexe des Rutheniums mit Heteroskorpionat-Liganden." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-69370.

Full text
APA, Harvard, Vancouver, ISO, and other styles
46

Li, Chia-Ling. "Preparation of poly(vinylidene fluoride) (PVDF) membrane by nonsolvent-induced phase separation and investigation into its formation mechanism." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20155.

Full text
Abstract:
Cette thèse décrit comment la morphologie et le polymorphisme de membranes en fluorure de poly(vinylidène) (PVDF) préparées par séparation de phase induite par la vapeur d'eau (VIPS) et par un non-solvant liquide peuvent être ajustés par la température à laquelle le PVDF est dissous (Tdis) pour former la solution de coulée. Les résultats montrent que Tdis présente une transition, notée comme la température de dissolution critique (Tcri), à partir de laquelle la morphologie et le polymorphisme des membranes changent radicalement. Ce phénomène observé pour les trois solvants, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,M-dimethylformamide (DMF), et les non-solvants (eau et une série d'alcools) utilisés dans cette étude peut être considéré comme général. La cristallisation a lieu avant la démixtion L-L quelle que soit Tdis. Pour une Tdis supérieure à Tcri, les membranes se présentent sous forme de nodules (cristallite forme beta) dont la taille décroît lorsque Tdis diminue. Ce domaine a été dénommé "à grossissement libre" car les chaînes de polymère peuvent cristalliser librement pendant la séparation de phase. Pour une Tdis inférieure à Tcri, des membranes avec une structure bi-continue (cristallite forme alpha) sont obtenues. Ce domaine a été appelé "à grossissement empêché" dans la mesure où la séparation de phase s'accompagne d'une gélification. Nous avons démontré que la morphologie et le polymorphisme cristallin des membranes de PVDF peuvent ainsi être contrôlés par la Tdis et la vitesse d'échange avec le non-solvant. Ces résultats sont interprétés en termes d'auto germination et de compétition entre gélification, cristallisation et démixtion L-L
This dissertation shows how the morphology and polymorphism of poly(vinylidene fluoride) (PVDF) membranes prepared by using vapor-induced phase separation (VIPS) and liquid-induced phase separation (LIPS) were tuned by varying the dissolution temperature at which PVDF was dissolved (Tdis) to form the casting solution. We observed a transition temperature denoted by critical dissolution temperature, Tcri, across which the morphology and polymorphism of membranes (obtained by VIPS) drastically changed. The phenomenon was considered as general, as a Tcri was observed for all the three solvents N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF) and the non-solvents, water and a series of alcohols, used in the present study. No matter which Tdis we used, polymer crystallization occurred prior to the L-L demixing. With Tdis above Tcri, the prepared membranes were composed of nodules (mainly in beta crystalline form) and the size of polymer domains decreased as the Tdis decreased. Because the polymer chains could freely coarsen to a large domain during the phase separation, we called the system free coarsening. With Tdis below Tcri, membranes with lacy (bi-continuous) structure (mainly in alpha crystalline form) were obtained. Because the polymer solution gelled during the phase separation, we called the system hindered coarsening. It was proven that PVDF membrane morphology and crystalline polymorphs can be monitored by Tdis and the solvent-nonsolvent exchange rate. These results were discussed in terms of self-seeding effect and competition between the gelation, crystallisation and L-L demixing
APA, Harvard, Vancouver, ISO, and other styles
47

Cowgill, Andrew William. "The viability of poly (chlorotrifluoroethylene-co-vinylidene fluoride) as an oxidiser in extrudable pyrotechnic compositions." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/62771.

Full text
Abstract:
In a push towards more environmentally friendly pyrotechnics, new greener pyrotechnic compositions need to be developed. A primary goal is to replace components such as lead, barium, and chromium in pyrotechnic compositions. Fused Deposition Modelling (FDM) is a 3D printing/additive manufacturing method whereby a thin filament is passed through a heated nozzle, and extruded onto a substrate in successive layers. This method of manufacturing could be used to produce pyrotechnic time delays based on suitable “green” polymer/fuel mixtures. Fluoropolymers are an attractive oxidising system for pyrotechnic use as fluorine is highly reactive and reacts relatively easily with common metallic fuels such as aluminium and magnesium to release a large amount of energy. Fluoropolymers are already in use as oxidisers and binders, especially in infrared decoy flares. PTFE has found wide use in the pyrotechnics industry, but is not melt-processible. A similar fluoropolymer, poly(chloro-trifluoroethylene) (PCTFE) was considered instead. PCTFE differs from PTFE in that one of the fluorine atoms in the TFE monomer has been replaced by a chlorine atom. The larger chlorine atom interferes with the packing of the polymer chains during polymerisation and, as such, may make it easier to process than PTFE. It was found that pure PCTFE degraded heavily during processing and was therefore precluded from any further study. Melt-processible copolymers containing PCTFE are available from industry. These copolymers contain vinylidene fluoride (VDF) in addition to the CTFE i.e. poly(CTFE-co-VDF). Two grades of copolymer were obtained from 3M: FK-800® resin and Dyneon® 31508 resin. These two polymers contain different ratios of CTFE to VDF. FK-800® resin was successfully extruded and showed minimal signs of degradation. Pyrotechnic films, containing aluminium powder as the fuel, were cast with both polymers using solvent techniques. Differential thermal analysis (DTA) was used to determine the ignition points of the compositions. All of the FK-800®-based compositions ignited at approximately 450 °C whilst all the Dyneon® 31508-based compositions ignited at approximately 400 °C. The energy output of the compositions was determined using bomb calorimetry. The experimental energy outputs of the FK-800®-based compositions correlated well with the predictions from the thermodynamic simulations. The maximum energy output, ~7.0 MJ∙kg1, occurred at a fuel loading between 30 – 35 wt.%. Except for one composition, the Dyneon® 31508-based compositions did not ignite in the bomb calorimeter. FK-800® was successfully extruded into a filament and showed minimal signs of degradation. In order to assess the impact of adding a solid filler on the mechanical properties and extrudability of the polymer, magnesium hydroxide was used as inactive model compound in place of aluminium. A filament of FK-800® and Mg(OH)2 was successfully compounded and produced using a filler loading of 30 wt.%. Compounding of the Dyneon 31508® with the magnesium hydroxide was unsuccessful. Addition of LFC-1® liquid fluoroelastomer improved the processibility of the Dyneon 31508® by lowering the melt viscosity.
Dissertation (MEng)--University of Pretoria, 2017.
Chemical Engineering
MEng
Unrestricted
APA, Harvard, Vancouver, ISO, and other styles
48

Tsai, Wen-Ru. "Preparation of Multinuclear Ruthenium Vinylidene Complexes and The Diels-Alder Reaction of Ruthenium Vinylidene Complexes." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1407200814382900.

Full text
APA, Harvard, Vancouver, ISO, and other styles
49

Yeh, Cheng-Wei, and 葉正緯. "Synthesis and Characterization of Dimetallic Vinylidene Complexes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/75457276492448107712.

Full text
Abstract:
碩士
國立臺灣大學
化學研究所
95
Ferrocenyl ferrocenyl-substituted allenylidene complexes [(η5-C5H5)(L)2Ru=C=C=C (Ph)(Fc)][PF6] (L = PPh3, 1a; 1/2 dppe, 1b) was prepared by treatment of a methanol solution of (η5-C5H5)(L)2RuCl (L = PPh3, 1/2 dppe) with the propargylic alcohol 1-ferrocenyl-1-phenylprop-2-yn-1-ol in the presence of NH4PF6. Reaction of 1a-b with Grignard reagent RMgBr or MeLi in THF yielded the neutral acetylide complexes 2a-3d (η5-C5H5)(L)2Ru-C≡CCPh(Fc)R (Fc = (η5-C5H4)Fe(η5-C5H5), L = PPh3, R = CH2CH=CH2, 2a; R = CH2C≡CH, 2b; R = CH2C(CH3)=CH2, 2c; L = 1/2 dppe, R = CH2CH=CH2, 3a; R = CH2C≡CH, 3b; R = CH2C(CH3)=CH2, 3c; R = Me, 3d). Complexes 2a-3d undergo protonation reactions affording the corresponding vinylidene complexes 4a-5d [(η5-C5H5)(L)2Ru=C=CHCPh(Fc)R]+ (L = PPh3 ,R = CH2CH=CH2, 4a; R = CH2C≡CH, 4b; R = CH2C(CH3)=CH2, 4c; L = 1/2 dppe, R = CH2CH=CH2, 4a; R = CH2C≡CH, 4b; R = CH2C(CH3)=CH2, 4c; R = Me, 4d). The cationic complex 4a in methanol solution for 12h followed by subsequent addition of NaOMe to give the new neutral acetylide complex (η5-C5H5)(PPh3)2Ru-C≡C-CH2C (Ph)([Fc])CH=CH2 (6). This transformation was proposed that a metathesis process of the terminal vinyl group with the C=C of the vinylidene group as mechanism. The presence of a gem-ferrocenylphenylmethylene moiety at the vinylidene ligand with the appropriate terminal vinyl or alkynyl group along with the correct steric environment implements such a specific reactivity in the ruthenium vinylidene complexes. The bisvinylidene complex [Ru]=C=C(Ph)CH2CH=C=[Ru]2+ (8) ([Ru] = (η5-C5H5) (dppe)Ru) can be obtained from the reaction of {[Ru]=C=CPhCH2C≡CH}+ with [Ru]Cl in the presence of NH4PF6 and methanol. Deprotonation of the bisvinylidene complex 8 formed the alkylnyl vinylidene complex [Ru]=C=C(Ph)CH2C≡C-[Ru]+ (9), which was alkylated by primary alkyl halide to give the ruthenium bisvinylidene complex [Ru]=C=C(Ph)CH2C(CH2R)=C=[Ru]2+ (R = CN, 10a; R = COOMe, 10b; R = C≡CH, 10c). Deprotonation of 10a by NaOMe is followed by a cyclization process yielding the stable complex 11, containing a three-membered carbocyclic ring ligand, which is characterized by NMR spectroscopy. No deprotonation reactions of 10c was observed under various basic conditions. Deprotonation reaction of the cationic isocyanide complexes of molybdenum {[Mo]-C≡NCH2C6F5}Br ([Mo] = (η7-C7H7)(dppe)Mo), with NaOMe in the presence of acetone leads to the synthesis of oxazolinyl complexes 13. This reaction proceeds via an azirinyl intermediate detected by NMR spectra followed by insertion of a carbonyl group into the C-C single bond of the three-membered ring. Regiochemistry of the C-C bond formation is different from that in the photolytically induced insertion of carbonyl compound to organic azirine. Methyl substituted isocyanide complex 14 containing a stereogenic carbon center was obtained by treatment of iodomethane with oxazolinyl complex 13. Complex 14 are determined by X-ray diffraction studies.
APA, Harvard, Vancouver, ISO, and other styles
50

Yeh, Cheng-Wei. "Synthesis and Characterization of Dimetallic Vinylidene Complexes." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2407200711371300.

Full text
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the bibliographies on the topic 'Vinylidenes' for other source types:
Journal articles Books
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography