The Synthesis and Characterization of Polyphosphazene Copolymers PDF Download
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Author: Michael L. White
Publisher:
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Category :
Languages : en
Pages : 0
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Author: Michael L. White
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Category :
Languages : en
Pages : 0
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Author: Roger De Jaeger
Publisher: Nova Publishers
ISBN: 9781594540240
Category : Science
Languages : en
Pages : 390
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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: Zhicheng Tian
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Category :
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.
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Languages : en
Pages : 9
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It was observed that competitive nucleophilic addition processes may be observed by 31P NMR spectroscopy. Methoxyethoxyethanol (MEE) and p-methoxyphenol readily substitute for chlorineonto phosphorus and the relative rates are generally comparable to each other. Sterically, the phenol presents is slightly larger than MEE but this does not appear to effect substitution judging by the observed PN(OAr)2 NMR signal. These processes are still being studied.
Author: Joseph Jagur-Grodzinski
Publisher: Nova Publishers
ISBN: 9781594543302
Category : Science
Languages : en
Pages : 398
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The living/controlled polymerisation techniques opened new vistas in polymer chemistry. The leading authorities in this field and its pioneers contributed chapters to this collective volume. The controlled polymerisation techniques have enabled preparation of polymers, copolymers, and block copolymers with predetermined molecular weights and narrow polydispersity, in which functional groups or biologically active molecules could be placed at well defined locations. They have also enabled preparation of advanced polymeric structures with precisely determined architectures and improved properties. Moreover, they have provided opportunities for preparation of novel polymeric materials from monomers, which before have not been suitable or accessible for such purposes. Properties of some of these polymeric materials may be significantly different from those of the existing ones. They provide opportunities for new applications. Several patents have already been approved for such speciality applications as, drug delivery, biocompatible surfaces, thermoplastic elastomers, moisture curable sealants, and so on. Many more products, based on polymers fabricated by the living/ controlled polymerisation techniques, will certainly emerge in such specialised areas as, nanotechnology, medical devices, "smart polymers", sensors , smart separation technologies, optical fibres and other optical applications, various biomaterials, etc.
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Languages : en
Pages : 0
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Polyphosphazenes are a new polymers with unique properties which include a combination of high temperature stability, low temperature flexibility, low surface energy, biofriendliness, and inflammability. We focused our research on polymerization of phosphoranimines catalyzed by Lewis acids and Lewis bases and synthesis of poly(diarylphosphazenes) by silyl azide intermediates and characterized the new polymers and copolymers using various techniques. The catalyzed polymerization of phosphoranimineshas been successfully used for the synthesis of random copolymers and the first block copolymers between two different polyphosphazenes. Additonally, we prepared polyphosphazene-organic polymer diblock structures using macromolecular phosphoranimines. The second part of the research was devoted to the preparation of new branched and hyperbranched polymers by controlled radical polymerization. We used atom transfer radical polymerization (ATRP) to prepare hyperbranched polystyrenes and polyacrylates. In addition, the novel class of compounds being simultaneously monomers and initiators (AB ̀‚monomers or inimers) were used successfully to design and prepare polymers and copolymers with novel topologies, compositions and functionalities. We prepared first molecular bottle-brush structures, multi arm star block and star diblock copolymers and also novel polar thermoplastic elastomers by entirely radical processes.
Author: Mario Gleria
Publisher: Nova Publishers
ISBN: 9781590334232
Category : Science
Languages : en
Pages : 1066
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The main aim of this book is to provide a complete picture of current research on phosphazene compounds carried out around the world. The book opens with a general introduction, then moves on to cover synthetic aspects of phosphazene polymers, their characterization in solution and from the theoretical, thermal, and mechanical points of view; application aspects of poly(organophosphazenes); and the synthesis, characterization, and practical utilization of cyclophosphazenes. There is particular focus on the use of cyclophosphazenes as hydraulic fluids and additives, as cores for star polymers or dendrimers, and as starting substrates for supramolecular chemistry and nanostructured materials. The spectroscopic characterization of these compounds by NMR and Raman techniques is also discussed. Annotation : 2004 Book News, Inc., Portland, OR (booknews.com).
Author: Youngtai Yoo
Publisher:
ISBN:
Category : Polymerization
Languages : en
Pages : 522
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Author: David Eric Dana
Publisher:
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Category : Phenols
Languages : en
Pages : 466
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Author: Sebastian S. Plamthottam
Publisher:
ISBN:
Category : Graft copolymers
Languages : en
Pages : 192
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