Direct Synthesis of New Types of Phosphazene Polymers Using Alkaline Carbonates PDF Download
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Languages : en
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Author: R. H. Neilson
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Languages : en
Pages : 13
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The project involves a detailed study of the synthesis, characterization, and reactivity of silicon-nitrogen-phosphorus compounds, some of which are useful precursors to an important class of inorganic polymers known as polyphosphazenes. Our results include the successful development of a new, general, and direct method for the synthesis of such polymers including poly(dimethyl-phosphazene), (Me2PN)n. Thus, we report here the synthesis of a variety of new phosphazenes including several homopolymers, copolymers, crosslinked polymers, and transition metal containing polymers. The latter and many other new types of phosphazenes are now readily accessible by a recently discovered anion formation reaction of the polymer precursors.
Author: Roger De Jaeger
Publisher: Nova Publishers
ISBN: 9781594540257
Category : Science
Languages : en
Pages : 322
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Gleria (National Research Council, Italy) and De Jaeger (chemistry, University of Sciences and Technologies, France) present material dedicated to the use of poly(organophosphazenes) in biology, photochemistry, and high energy radiation chemistry. Their use as hybrid materials, flame and fire retardants, blend components, ionic conductors, membranes, and catalysts is also examined. Research on cyclomatrix polyphosphazene for membrane applications, sulfonated polyphosphazene membranes for direct methanol fuel cells, and synthesis and applications of phosphazene compounds is described. Annotation : 2004 Book News, Inc., Portland, OR (booknews.com).
Author: Zhicheng Tian
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Languages : en
Pages :
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The work described in this thesis is divided into three major parts, and all of which involve the exploration of the chemistry of polyphosphazenes. The first part (chapters 2 and 3) of my research is synthesis and study polyphoshazenes for biomedical applications, including polymer drug conjugates and injectable hydrogels for drug or biomolecule delivery. The second part (chapters 4 and 5) focuses on the synthesis of several organic/inorganic hybrid polymeric structures, such as diblock, star, brush and palm tree copolymers using living cationic polymerization and atom transfer radical polymerization techniques. The last part (chapters 6 and 7) is about exploratory synthesis of new polymeric structures with fluorinated side groups or cycloaliphatic side groups, and the study of new structure property relationships.Chapter 1 is an outline of the fundamental concepts for polymeric materials, as such the history, important definitions, and some introductory material for to polymer chemistry and physics. The chemistry and applications of phopshazenes is also briefly described.Chapter 2 is a description of the design, synthesis, and characterization of development of a new class of polymer drug conjugate materials based on biodegradable polyphosphazenes and antibiotics. Poly(dichlorophosphazene), synthesized by a thermal ring opening polymerization, was reacted with up to 25 mol% of ciprofloxacin or norfloxacin and three different amino acid esters (glycine, alanine, or phenylalanine) as cosubstituents via macromolecular substitutions. Nano/microfibers of several selected polymers were prepared by an electrospinning technique. The hydrolysis rate and the antibiotic release profile can be well tuned by either the polymer compositions, or the surface area monitored by a six week in vitro hydrolysis experiment. All the polymers gave a near-neutral hydrolysis environment with the pH ranging from 5.9--6.8. In an in vitro antibacterial test against E.coli, the antibacterial activity of the hydrolysis media was maintained as long as the polymer hydrolysis continued.Chapter 3 is concerned with the development of a class of injectable and biodegradable hydrogels based on water-soluble poly(organophosphazenes) containing oligo(ethylene glycol) methyl ethers and glycine ethyl esters. The hydrogels can be obtained by mixing [alpha]-cyclodextrin aqueous solution and poly(organophosphazenes) aqueous solution in various gelation rates depending on the polymer structures and the concentrations. The rheological measurements of the supramolecular hydrogels indicate a fast gelation process and flowable character under a large stain. The hydrogel system also exhibits structure-related reversible gel-sol transition properties at a certain temperature. The formation of a channel-type inclusion complex induced gelation mechanism was studied by DSC, TGA, 13C CP/MAS NMR and X-ray diffraction techniques. In vitro bovine serum albumin release of the hydrogel system was explored and the biodegradability of poly(organophosphazenes) was studied.Chapter 4 outlines the preparation of a number of amphiphilic diblock copolymers based on poly[bis(trifluoroethoxy)phosphazene] (TFE) as the hydrophobic block and poly(dimethylaminoethylmethacrylate) (PDMAEMA) as the hydrophilic block. The TFE block was synthesized first by the controlled living cationic polymerization of a phosphoranimine, followed by replacement of all the chlorine atoms using sodium trifluoroethoxide. To allow for the growth of the PDMAEMA block, 3-azidopropyl-2-bromo-2-methylpropanoate, an atom transfer radical polymerization (ATRP) initiator, was grafted onto the endcap of the TFE block via the 'click' reaction followed by the ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA). Once synthesized, micelles were formed by a standard method and their characteristics were examined using fluorescence techniques, dynamic light scattering, and transmission electron microscopy. The critical micelle concentrations of the diblock copolymers as determined by fluorescence techniques using pyrene as a hydrophobic probe were between 3.47 and 9.55mg/L, with the partition equilibrium constant of pyrene in these micelles ranging from 0.12x105-1.52x105. The diameters measured by dynamic light scattering were 100-142nm at 25oC with a narrow distribution, which were also confirmed by transmission electron microscopy. Chapter 5 is a report on the design and assembly of polyphosphazene materials based on the non-covalent "host--guest" interactions either at the terminus of the polymeric main-chains or the pendant side-chains. The supramolecular interaction at the main chain terminus was used to produce amphiphilic palm-tree like pseudo-block copolymers via host-guest interactions between an adamantane end-functionalized polyphosphazene and a 4-armed [beta]-cyclodextrin ([beta]-CD) initiated poly[poly(ethylene glycol) methyl ether methacylate] branched-star type polymer. The formation of micelles of the obtained amphiphiles was analyzed by fluorescence technique, dynamic light scattering, transmission electron microscopy, and atomic force microscopy. The supramolecular interactions involving polymer side-chains were achieved between polyphosphazenes with [beta]-CD pendant units and other polyphosphazene molecules with adamantyl moieties on the side-chains. These interactions worked as physical crosslinks which were responsible for the formation of a supramolecular hydrogel. The results of this work demonstrated the synthetic possibilities for these novel polymeric structures. These materials show potential for applications as smart drug delivery micro-vehicles, responsive hydrogels, and self-healing materials.Chapter 6 is an investigation of the influence of bulky fluoroalkoxy side groups on the properties of polyphosphazenes. A new series of mixed-substituent high polymeric poly(fluoroalkoxyphosphazenes) containing trifluoroethoxy and branched fluoroalkoxy side groups was synthesized and characterized by NMR and GPC methods. These polymers contained 19--29 mol% of di-branched hexafluoropropoxy groups or 4mol% of tri-branched tert-perfluorobutoxy groups, which serve as regio-irregularities to reduce the macromolecular microcrystallinity. The structure--property correlations of the polymers were then analyzed and interpreted by several techniques: specifically by the thermal behavior by DSC and TGA methods, the crystallinity by wide-angle X-ray diffraction, and the surface hydrophobicity/oleophobicity by contact angle measurements. Ultraviolet crosslinkable elastomers were prepared from the new polymers through the incorporation of 3mol% of 2-allylphenoxy and photo-irradiation. The mechanical properties and the elastomeric deformation--recovery behavior were then monitored by varying the time of ultraviolet irradiation. Side reactions detected during the synthesis of the high polymers, such as side group exchange reactions and alpha-carbon attack, were analyzed via use of a cyclic trimer model system.Chapter 7 is an outline of the exploratory synthesis of a new series of phosphazene model cyclic trimers and single- and mixed- substituent high polymers containing cyclic aliphatic rings, --CnH2n-1 (where n = 4--8). The cylco-aliphatic side group containing phosphazenes expand the structural and property boundaries of phosphazene chemistry, and suggest additional approaches for studying slow macromolecular substitution reactions and substituent exchange reactions. Polymer structure--property relationships are interpreted and correlated to glass transition temperatures, thermal decomposition temperatures, hydrophobicity, and membrane mechanical properties. Films prepared from these polymers are low cost, tough and non-adhesive. They can be used in variety of applications especially where transparency is important.
Author: Roger De Jaeger
Publisher: Nova Publishers
ISBN: 9781594540240
Category : Science
Languages : en
Pages : 390
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Book Description
Gleria (materials science, Padova University, Italy) and De Jaeger (chemistry, University of Sciences and Technologies, France) present the latest work in the synthesis and characterization of poly(organophosphazenes). The book opens with a general introduction on background, developments, and future perspectives, then covers the synthetic aspects of phosphazene polymers, with chapters on areas such as ambient temperature cationic condensation synthesis of polyphosphazenes and high molecular weight polyspirophosphazenes. Chapters on the characterization of phosphazene polymers in solution explore topics including thermal and mechanical properties of polyphosphazenes and electrochemical behavior of phosphazenes. Annotation : 2004 Book News, Inc., Portland, OR (booknews.com).
Author: Andrew Hess
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Category :
Languages : en
Pages :
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The work described in this dissertation involves progress toward phosphazene-based ion conducting materials with a focus on structure-property relationships and the use of the knowledge of those relationships to improve these materials. This dissertation also includes some more fundamental exploratory syntheses to probe the limits of phosphazene chemistry and discover structure-property relationships that may be useful in designing compounds to fulfill important technical requirements. Chapter 1 provides a brief introduction to polymers and polyphosphazenes as well as ion-conducting materials and the contribution of polyphosphazene chemistry to that field. Chapter 1 also provides a brief introduction to some of the analytical techniques employed in this dissertation.Chapter 2 begins with the use of organophosphates as stand-alone non-volatile and fire-retardant liquid electrolyte media for dye sensitized solar cells (DSSCs) as well as their use as plasticizer in polymer gel electrolytes intended for application in lithium batteries. These organophosphates are the smallest phosphorus containing model molecules investigated in this dissertation. A homologous series of oligoalkyleneoxy substituted phosphates was synthesized and the effect of the substituent chain length on viscosity and conductivity was investigated. Small, test-scale DSSCs were constructed and showed promising results with overall cell efficiencies of up to 3.6% under un-optimized conditions. Conductivity measurements were performed on polymer gel-electrolytes based on poly[bis(2-(2-methoxyethoxy)ethoxy)phosphazene] (MEEP) plasticized with the phosphate with the best combination of properties, using a system loaded with lithium trifluoromethanesulfonate as the charge carrier. These measurements yielded promising results with conductivities (at 30 °C) as high as 3.0x10-3 S·cm-1 at the highest plasticizer loading.In chapter 3 the effect of the cation of the charge carrier species on the anionic conductivity of DSSC type electrolytes is evaluated using hexakis(2-(2-methoxyethoxy)ethoxy)cyclotriphosphazene (MEE-trimer) as a small molecule model for MEEP. The iodides of lithium, sodium, and ammonium as well as the ionic liquid, 1-propyl-3-methylimidazolium iodide (PMII) were tested in various electrolyte concentrations. After identifying PMII as the most efficient salt additive for promoting anion conduction in the MEE-trimer systems, it was tested in MEEP-based DSSC polymer-gel electrolytes plasticized with propylene carbonate (PC). The MEEP/PMII type electrolytes were compared against and outperformed similar formulations based on poly(ethylene oxide). An overall cell efficiency of 1.88% was obtained.Chapter 4 extends the concept of poly[(oligoethyleneoxy)phosphazene] electrolytes by the synthesis of MEEP-analogues with various ammonium ions covalently bound to the polymer side chains in order to create a single-ion conducting polyelectrolyte. The motivation for this approach is that in this system the polymer serves as the conductive medium and provides the charge carriers. In this case iodide is the only ion that is free to move and carry charge since the cation is bound to the polymer. Two candidates from the series of polyelectrolytes were selected for extensive study, one in which the ammonium ion has a hexyl group, and another in which the ammonium ion has an MEE-group. The polymers were characterized by dielectric spectroscopy, X-ray scattering, and density functional theory calculations.In chapter 5 the concept of polyphosphazene based polyelectrolytes is extended further by quaternization of nitrogen atoms that are a part of the polymer backbone rather than a pendent group. The feasibility of the concept is first explored using cyclic-trimeric phosphazenes as small molecule models and is then extended to high polymeric systems. It was found that it is indeed possible to produce stable backbone-quaternized polyphosphazene electrolytes using strong methylation reagents such as methyl trifluoromethanesulfonate or trimethyloxonium fluoroborate. Unfortunately for their potential use in DSSCs, ion-exchange of the anions from the methylation reagents for iodide ion results in dealkylation or decomposition of the polyelectrolyte due to the high nucleophilicity of iodide. However, the conductivities of the unplasticized polyelectrolytes containing mobile trifluoromethanesulfonate ion are among the highest observed for unplasticized solid-state polymer electrolytes or polyelectrolytes.Chapter 6 begins a new section of exploratory synthesis meant to probe the limits of phosphazene chemistry and discover useful structure-property relationships as well as to improve on the synthetic procedures of the past. Thus, in chapter 6 a series of cyclotriphosphazenes is synthesized for evaluation as compounds with the ability to complex to metal surfaces or to form ceramic materials after pyrolysis. Several known compounds are resynthesized, many with improvements over previously published procedures either in yield or simplicity of reaction conditions. Also, two new cyclotriphosphazenes were synthesized in an attempt to produce a catechol-like side group that could mimic the metal complexation and adhesive abilities of mussel adhesive proteins which take advantage of similar catecholic moieties.Chapter 7 presents the synthesis of fluorine-bearing aryloxy phosphazenes in an attempt to overcome the deficiencies of some of the classical fluorinated organic polymers. Classical organic fluorinated polymers designed to be flexible often contain aliphatic C-H bonds which limits their thermal, chemical, and radiation stability. Poly(fluoroaryloxy)phosphazenes can offer many of the same advantages without the deficiencies of some of the more classical materials. The materials synthesized are excellent candidates for dielectric film materials in capacitors.In chapter 8 new ground is broken in phosphazene chemistry, wherein cycloalkanoxy groups, a type of side-group for phosphazenes that has been neglected in the past, are attached to the phosphazene skeleton. First, a single previous report of the synthesis of hexakis(cyclohexanoxy)cyclotriphosphazene was reproduced as a model system. Then a series of single substituent polyphosphazenes was synthesized in order to determine how large a saturated cyclic ring can be attached to the polymer backbone while still completing the replacement of the chlorine atoms attached to the backbone. Subsequently, a series of mixed substituent polymers containing both cycloalkanoxy groups (from cyclopentoxy to cyclooctanoxy) and the well-studied trifluoroethoxy group was synthesized and characterized in order to study larger saturated cyclic rings as polyphosphazene side-groups. These polymers are interesting not only from a fundamental scientific point of view, but may have applications in the field of membrane separations and are promising candidates for mechanical damping applications.Chapter 9 contains the author's recommendations for the continuation of the research presented in this dissertation.
Author: Phuong Nguyen Tri
Publisher: Elsevier
ISBN: 0128230843
Category : Technology & Engineering
Languages : en
Pages : 396
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Book Description
The gradual increase of population and the consequential rise in the energy demands in recent years have led to the widespread use of fossil fuels. CO2 transformation by various processes is considered as a promising alternative technology. This book sets out the fundaments of how nanomaterials are being used for this purpose. Nanomaterials for CO2 Capture, Storage, Conversion and Utilization summarizes the research, development and innovations in the capture, storage, transformation and utilization of CO2 into useful products and raw chemicals for industry. This is achieved by using advanced processes such as CO2 reforming, bi-reforming and tri-reforming of hydrocarbons or biomass derivatives; homogeneous and heterogeneous hydrogenation; photochemical reduction; photoelectrochemical reduction; electrochemical reduction; biochemical reduction; supercritical CO2 technology; advanced catalyst synthesis for CO2 conversion; organic carbonates for polymers synthesis from CO2, and CO2 capture and sequestration. The systematic and updated reviews on the mentioned sectors, especially on the use of nanotechnology for the transformation of CO2 is scarce in the literature. Thus, the book addresses the recent knowledge gaps and potential solutions of the storage, utilization and transformation of CO2 as well as its promising applications. This is an important reference source for materials scientists, engineers and energy scientists who want to understand how nanotechnology is helping us to solve some of the world's major energy problems. - Shows how nanomaterials are being used to create more efficient CO2 capture, storage and conversation systems - Outlines the major nanomaterials-based techniques to create such systems - Assesses the major challenges in using nanomaterials for energy capture, storage and conversion
Author: Narendra Chauhan
Publisher: CRC Press
ISBN: 1040096549
Category : Science
Languages : en
Pages : 247
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Book Description
Polymer-supported organic catalysts are largely insoluble in most reaction solvents, which allows for easy recovery and recycling of the catalysts. They are generally stable, readily available, and environmental friendly, so they have attracted the interest of many synthetic chemists in the industrial and academic fields. In this book, different types of polymer-supported catalysts based on peptides, polystyrene, polyethers, poly(acrylic acid), poly(ethylene imine), poly(2-oxazoline), poly(isobutylene), poly(norbornene), etc., as well as metals are included with their synthetic organic synthesis applications. It is believed that this work will be of interest to organic chemists, material scientists, chemical engineers, polymer scientists and technologists.
Author: John Scheirs
Publisher: John Wiley & Sons
ISBN: 0470090677
Category : Technology & Engineering
Languages : en
Pages : 784
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Book Description
Provides an overview of the family of polyester polymers which comprise an important group of plastics that span the range of commodity polymers to engineering resins. It describes the preparation, properties and applications of polyesters. Readers will also find details on polyester-based elastomers, biodegradable aliphatic polyester, liquid crystal polyesters and unsaturated polyesters for glass-reinforced composites. Presents an overview of the most recent developments. Explores synthesis, catalysts, processes, properties and applications. Looks at emerging polyester materials as well as existing ones. Written by foremost experts from both academia and industry, ensuring that both fundamentals and practical applications are covered.
Author: Tsutomu Ishikawa
Publisher: John Wiley & Sons
ISBN: 9780470740866
Category : Science
Languages : en
Pages : 336
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Book Description
Guanidines, amidines and phosphazenes have been attracting attention in organic synthesis due to their potential functionality resulting from their extremely strong basicity. They are also promising catalysts because of their potential for easy molecular modification, possible recyclability, and reduced or zero toxicity. Importantly, these molecules can be derived as natural products – valuable as scientists move towards “sustainable chemistry”, where reagents and catalysts are derived from biomaterial sources. Superbases for Organic Synthesis is an essential guide to these important molecules for preparative organic synthesis. Topics covered include the following aspects: an introduction to organosuperbases physicochemical properties of organic superbases amidines and guanidines in organic synthesis phosphazene: preparation, reaction and catalytic role polymer-supported organosuperbases application of organosuperbases to total synthesis related organocatalysts: proton sponges and urea derivatives amidines and guanidines in natural products and medicines Superbases for Organic Synthesis is a comprehensive, authoritative and up-to-date guide to these important reagents for organic chemists, drug discovery researchers and those interested in the chemistry of natural products.
