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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 54 for “"polycondensation"”.
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Polycondensation of Bridged Amino-Functionalized Trialkoxysilanes.
… of such material is done by hydrolysis and polycondensation of trialkoxysilane. The fastest gelation was observed at reaction in the absence of acids or bases. However, addition of surfactant to the reaction mixture catalyzed formation of silsesquioxanes in acidic media. Obtained materials …
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Acid-base catalysts for polycondensation of acetaldehyde in flow
… is used as a bio-oil model compound in a polycondensation reaction over two acid-base catalysts, pelletized Evonik P25 TiO₂ and an activated hydrotalcite-like compound (HTlc), to produce high molecular weight molecules in the transportation fuel range. The catalytic performance of these …
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Kinetic studies of solid-phase polycondensation in two polyamides and a polyester
The effects of polymer particle size, temperature, and time on the continued condensation of two polyamides: poly(hexamethylene adipamide) and poly(hexamethylene sebacamide), and a polyester, poly(ethylene terephthalate), were studied experimentally. The polyamides were held at elevated …
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Functional polybithiophenes: Novel syntheses approaches, characterization and application aspects
This work is a study of an organometallic polycondensation process based on a modified Stille coupling reaction. This polymerization methodology was investigated with the use of various aryl monomeric units. This polycondensation process uses hexabutylstannane, Bu3SnSnBu3, to react with …
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A study of tribopolymerization under fretting conditions
… Monomers, capable of polymerizing either by polycondensation or addition processes, were used at 1 % concentration in hexadecane. Under the conditions used (90N load, 65Hz frequency, 200μm peak-to-peak amplitude, 1 hour), the monomers tested reduced friction or wear or both. Fourier Transform …
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The catalytic role of birnessite in the Maillard reaction and the abiotic formation of humic substances
… The Maillard (browning) reaction involving the polycondensation of carbohydrates and amino acids has been postulated as being an important abiotic pathway for humic substance formation. However, the catalytic role of minerals common in soils and sediments in the Maillard reaction and the …
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Using Branching and Endgroups to Control the Physical Properties of Macromolecules: Systematic Studies of Etherimide Polymers
… groups were used to terminate an AB2-type polycondensation reaction, generating capped hyperbranched polymers (HBPs). The composition and constitution of the end groups controlled the solubility and thermal properties of the HBPs. For the same polymer backbone, different end groups were …
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Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles
… urea. The work herein presents an improved melt polycondensation synthetic methodology, which strategically harnesses the spontaneous pyrolytic degradation of urea to afford a series of PDMS polyureas via reactions at high temperatures in the presence of telechelic amine-terminated oligomeric …
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Synthesis and Chacterization of Novel Polybenzimidazoles and High-Solids Meta-Polybenzimidazoles
… which uses polyphosphoric acid (PPA) as both the polycondensation agent and the casting solvent. This one-pot process, called the 'PPA Process', allows for the synthesis of high molecular weight polymer membranes with high acid-loading levels and good mechanical properties.</p>
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Synthesis and characterization of pH/temperature dual sensitive multiblock copolymer for drug delivery
… molecular weight of 42000 Da was synthesized by polycondensation between an acid-labile ketal linker, 2,2-bis(aminoethoxy)propane (BAP) and Pluronic® P104 using L-lysine diisocyanate ethyl ester (LDI) or 1,6-Diisocyanatohexane (HDI). The gelation temperature of 20% (w/v) MBCP was in the range of …
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Mesoporous Functionalized Materials for Post-Combustion Carbon Dioxide Capture.
… organic-inorganic materials were synthesized by polycondensation of bis[3-(trimethoxysilyl)propyl]amine in presence of cationic and anionic surfactants. Reaction media strongly affected gelation time. Thus, in basic media gelation occurred immediately while acid increased gelation time. Material …
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Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures
… solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The …
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Topology and Telechelic Functionality Control in Polyester Design
… branched topology were synthesized using melt polycondensation for pressure sensitive adhesive applications. Relationships between molecular weight, polymer composition, and adhesive performance were investigated. Melt rheological studies and the characterization of adhesive properties …
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Novel Polyphenylquinoxaline and Polybenzimidazole Proton Exchange Membranes For High Temperature Fuel Cell Systems
… membranes. PPQs were synthesized via the polycondensation of 3,3',4,4'-tetraaminobiphenyl and 1,4-bisbenzil in polyphosphoric acid. It was found that PPQ homopolymers were unable to form stable gel membranes via the PPA Process. Thus, PPQ copolymers with PBI were investigated. A series of …
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Synthesis of a renewable sourced thermotropic polyester with 2,5-furandicarboxylic acid
… was then used to synthesize the FDCA monomer. A polycondensation reaction involving 4-hydroxybenzoic acid, hydroquinone, and FDCA was subsequently carried out to produce a random mesogenic polyester. ATR-FTIR spectroscopy was used to analyze the backbone structure of the polymer. Thermal analysis …
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Étude des propriétés optiques et électrochimiques du pentoxyde de vanadium préparé par la méthode sol-gel
… soit par des réactions d'hydrolyse et de polycondensation d'un alcoxyde. La structure des films V$ \ Sb2$O$ \ sb5$ déposés sur différents substrats a été examinée par spectroscopie infrarouge ATR. Les conditions de dépôt pour obtenir des films V$ \ Sb2$o$ \ sb5$ servant de …
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Synthesis and characterization of high performance polybenzoxazoles
… have been synthesized via low temperature polycondensation and a novel catalytic cyclization reaction. Preliminary experiments involved the synthesis of poly(hydroxy amide)s and polybenzoxazoles based on a bisphenol-A aminophenol and isomeric acid chlorides. The polymers exhibited …
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The ring-opening polymerization of cyclosiloxanes in the presence of bis ([alpha], [omega]-aminopropyl)-1,3-tetramethyldisiloxane
… was prepared using both bulk and solution polycondensation techniques. Copolymers based on polybutylene terephthalate were highly insoluble, due to the presence of crystallinity in the systems. The incorporation of some isophthalate linkages increased the solubility of the polymer products, …
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