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McGrath, Jonathan G. "Synthesis and Characterization of Core/Shell Hydrogel Nanoparticles and Their Application to Colloidal Crystal Optical Materials." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14537.
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This dissertation describes the use of spherical micro- and nanoparticles as building blocks for the fabrication of colloidal crystals. The polymer component used in all of the projects that are described herein is poly-N-isopropylacrylamide (pNIPAm). The polymeric identity of particles composed of this soft, hydrogel material, which is also thermoresponsive, contributes to particle self-assembly to form ordered structures. Specifically, particles that possess a core/shell topology were investigated to allow for the localization of distinct polymeric properties. Chapter 2 examines a characterization technique using fluorescence resonance energy transfer (FRET) that was explored to investigate the structure of pNIPAm particles that possess this core/shell topology. Chapters 4-6 investigate strategies to impart both stability and flexibility to the particles so that these properties could assist in particle self-assembly as well as provide a stable construct for the production of robust crystalline materials. Styrene was used as the main monomer component in a copolymer synthesis with NIPAm to achieve poly(styrene-co-N-isopropylacrylamide particles (pS-co-NIPAm) that exhibited both hard and soft properties. Simple drying procedures were used to form crystal assemblies with these particles and the application of these pS-co-NIPAm particle suspensions as processable, photonic inks is also investigated. Chapter 7 examines the ability to physically cross-link colloidal crystals composed of pS-co-NIPAm particles by simple heating methods to produce robust films. The optical properties of these crystal films could be tuned by simple rehydration of the film due to the hydrogel character of the crystal building blocks. Chapters 3 and 5 examine the synthesis and self-assembly strategies of core/shell particles using the properties of pNIPAm shell layers that have been added to different types of core particles (silver or pS-co-NIPAm) for the purposes of fabricating colloidal crystals with enhanced properties using thermal annealing procedures. Chapter 8 explores the use of silver particles as tracers for the characterization of colloidal crystals composed of thermally annealed colloidal crystals composed of pNIPAm hydrogel particles.
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Johnson, Elizabeth Edna. "Colloidal gas aphron foams : a novel approach to a hydrogel based tissue engineered myocardial patch /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10579.
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Cho, Jae Kyu. "The dynamics and phase behavior of suspensions of stimuli-responsive colloids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31682.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Victor Breedveld; Committee Member: Eric W. Weeks; Committee Member: Hang Lu; Committee Member: J. Carson Meredith; Committee Member: L. Andrew Lyon. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Duret, Bérénice. "Mise au point de dispersiοns aqueuses de particules d’huiles gélifiées et applications à la prοtectiοn de la peau." Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMLH39.
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Cette thèse vise à développer des formules cosmétiques éco-responsables à faible nombre d’ingrédients, en lien avec le contexte actuel du « Clean-label » dans ce secteur. Nous nous sommes intéressés à des dispersions de particules d’huile gélifiée, nommées « dispersions de gélosomes », encore inexplorées pour une utilisation cosmétique. Connues pour être stables et capables d’encapsuler des actifs hydrophobe, la question de leur texture et de leur application sur la surface de la peau reste aujourd’hui non renseignée. Elles sont préparées par émulsification à chaud d’un organogel, composé d’huile et de gélifiant lipophile (acide 12-hydroxystéarique), en présence d’un agent stabilisant (alcool polyvinylique hydrolysé à 80%). L’émulsion formée conduit, après refroidissement, à une dispersion de particules d’organogel. Nous avons d’abord démontré la possibilité de réaliser des dispersions de gélosomes avec des huiles cosmétiques et un conservateur. Des textures très variées ont été obtenues allant de liquides fluides à des gels fermes et cassants. L’analyse physico-chimique et l’observation microscopique de ces nouvelles formules ont permis d’identifier leurs microstructures : dans certaines conditions, des connexions se forment entre les gélosomes, et un hydrogel colloïdal est obtenu. L’étude des interactions à l’interface a permis de déterminer les facteurs et les mécanismes menant à des gélosomes individualisés ou connectés. Les dispersions de gélosomes, même les plus fluides, ont montré une grande stabilité. Enfin, de nouvelles dispersions de gélosomes ont pu être formulées à partir de stabilisants de nature et de modes de stabilisation variés. La méthodologie employée au cours de ce travail a permis d’établir un lien entre le stabilisant et les propriétés des dispersions. Des mécanismes différents ont pu être identifiés, induisant des microstructures et des propriétés applicatives intéressantes et variées. Pour la première fois, les propriétés de texture des dispersions, caractéristiques d’une application topique ont été collectées sur l’ensemble des systèmes par une approche combinée d’analyses rhéologiques in vitro et d’analyses sensorielles in vivo ; les perceptions ont été décrites et explicitées en fonction de l’influence de la nature de l’huile, du stabilisant et du type de microstructureThis thesis aims to develop eco-responsible cosmetic formulas with a low number of ingredients, in line with the current context of “Clean-label” in this sector. We focused on dispersions of gelled oil particles, called “gelosome dispersions”, which have not yet been explored for cosmetic use. Known to be stable and capable of encapsulating hydrophobic active ingredients, the question of their texture and their application onto the surface of the skin remains unanswered to date. They are prepared by hot emulsification of an organogel, composed of oil and a lipophilic gelator (12-hydroxystearic acid), in the presence of a stabilizing agent (80% hydrolyzed polyvinyl alcohol). Upon cooling, the emulsion leads to a dispersion of organogel particles. We first demonstrated the possibility of making gelosome dispersions with cosmetic oils and a preservative. A wide variety of textures was obtained, ranging from fluid liquids to firm and brittle gels. Physicochemical analysis and microscopic observation of these new formulas made it possible to identify their microstructures: under certain conditions, connections are formed between the gelosomes, and a colloidal hydrogel is obtained. The factors and mechanisms leading to individualized or connected gelosomes were determined by the study of interactions at the interface. Gelosome dispersions, even the most fluid, showed great stability. Finally, new dispersions of gelosomes were formulated using stabilizers of various types and stabilization modes. The methodology used during this work enabled the establishment of a link between the stabilizer and the properties of the dispersions. Different mechanisms could be identified, inducing interesting and varied microstructures and application properties. For the first time, the texture properties of the dispersions, characteristic of a topical application, were collected across all systems using a combined approach of in vitro rheological analyzes and in vivo sensory analyses; the perceptions were described and explained according to the influence of the nature of the oil, the stabilizer and the type of microstructure
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Mohammadi, Aliasghar. "Dynamics of colloidal inclusions in hydrogels." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104772.
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The electric-field-induced response of colloidal particles in hydrogels isused as a diagnostic method for probing colloid-hydrogel interfaces, where we measure the electrokinetic potential of polystyrene particles in polyacrylamide hydrogels using an optical tweezers setup with back-focal-plane interferometry and feed-back control to compensate low-frequency drift. A generalization of pertinent relations in the standard electrokinetic model is used to interpret the experiments, showing how the electrokinetic potential depends on ionic strength, surface chemistry, and polymer content of the suspending medium. A similar behaviour for the influence of ionic strength and surface chemistry on the surface potential of polystyrene particles in both hydrogels and deionized water is observed. Whereas the cross-linking ratio, defined as the molar ratio of cross-linking units to the total number of monomers, has a small effect on the colloidal inclusion surface potential, the influence of monomer concentrationis significant. Also, we present theoretical calculations of the dynamics of uncharged spherical inclusions in charged, compressible polymer skeletons to facilitate accurate interpretations of classical and electrical micro-rheology, and electroacoustics. Moreover, we undertake the theoretical analysis of the dynamic response of hydrogels in a parallel-plate channel to external stimuli, such as a pressure gradient and/or electric field.Le champ electrique induit par la reponse de particules colloidales dans des hydrogels est utilise comme une methode de diagnostic pour sonder interfaces colloide-hydrogel, ou l'on mesure le potentiel electrocinetique des particules de polystyrene dans des hydrogels de polyacrylamide en utilisant une configuration de pinces optiques par interferometrie arriere-plan focal et controle de feed-back pour compenser la derive a basse frequence. Une generalisation de relations pertinentes dans le modele standard electrocinetique est utilise pour interpreter les experiences, en montrant comment le potentiel electrocintique depend de la force ionique, la chimie de surface, et la teneur en polymere du milieu de suspension. Un comportement similaire de l'inuence de la force ionique et de la chimie de surface sur le potentiel de surface des particules de polystyrene dans les deux hydrogels et de l'eau demineralisee est observee. Alors que le taux de reticulation, defini comme le rapport molaire de reticulation unites et le nombre total de monomeres, a un faible effet sur le potentiel de surface collodale inclusion, l'influence de la concentration en monomeres est importante. En outre, nous presentons des calculs theoriques de la dynamique des inclusions non charges spherique chargee, squelettes polymere compressible pour faciliter l'interpretation exacte de classique et electrique micro-rheologie, et l'electroacoustique. En outre, nous nous engageons l'analyse thorique de la reponse dynamique des hydrogels dans un canal a plaques paralleles a des stimuli externes, comme un gradient de pression et/ ou d'un champ electrique.
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Chen, Yunhua. "Multiple hydrogen bond arrays reinforced polymer colloidal materials." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/54479/.
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We demonstrate the combination of supramolecular chemistry (multiple hydrogen bonding) with polymer colloidal sciences in the creation of interesting materials. This provides us an access to the unique structures and properties that [sic] not possible to [sic] traditional materials. We first developed cellular polymer films made from 2-ureido-4[H]-pyrimidinone (UPy) quadruple hydrogen bonded soft latexes. The films show colloidal crystalline-type Bragg diffraction features when exposed to solvents, and do not suffer excessive and deteriorative uptake of water and, more remarkably can absorb high amounts of organic solvents. Impressively, Pickering high internal phase emulsion gels can be prepared by using these UPy functionalized particles as stabilizers under extremely low shear stress and short time. Moreover, we first used the UPy functionalzed macromonomer as non-colvalently [sic] crosslinker to prepare thermo-sensitive nanogel particles which are conventionally made using covalent-bond crosslinkers. Templated high internal phase emulsion hydrogel monoliths stabilzed by these nanogels can be prepared through injection moulding, which also exhibit excellent thermo-responsive properties. Alternatively, we also first created interesting Janus micro-beads with highly anisotropic and tunable internal architecture based on complementary hydrogen bonding interactions, rather than UPy self-complementary interactions, by single emulsion-droplet microfluidic technique.
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Ma, Manlung. "Exploration of peptide-based hydrogels /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202008%20MA.
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Debord, Justin. "Synthesis, characterization and properties of bioconjugated hydrogel nanoparticles." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131123/unrestricted/debord%5Fjustin%5F200405%5Fphd.pdf.
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Zainuddin. "Synthesis and calcification of hydrogel biomaterials /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18693.pdf.
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Aufderhorst-Roberts, Anders. "Microrheological characterisation of Fmoc derivative hydrogels." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608155.
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Yang, Zhimou. "Molecular hydrogels : design, synthesis, enzymatic regulation, and biological applications /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202006%20YANG.
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Reynolds, Jason Kurt Faculty of Science UNSW. "Hydrogel determined metal bioaccessibility in acid sulfate-affected landscapes." Awarded by:University of New South Wales, 2008. http://handle.unsw.edu.au/1959.4/41436.
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Exposure of sulfidic sediments to atmospheric conditions can under various environmental and anthropogenic influences. The oxidation of sulfides results in the production of acidity, dissolution of aluminosilicates and pedogenci development. This process has acid sulfate landscapes throughout the world identified as major emitters of elevated concentrations of chemical metals. This emission of acidity and metals alters the bioaccessibility and subsequently has a deleterious impact on the surrounding biologic environment. Despite this, the examination of the biologic impact in these landscapes has received only minimal attention. Passive and dynamic hydrogel techniques were used to measure the bioaccessibility of metals in sediments and waters. The technique involved the construction of a restricted pore-size thin-film hydrogel that allowed for the diffusion of the bioaccessible fraction, composed of the free-ion and easily dissociable metal-complexes. The dynamic hydrogel technique contained a resin sink, which allowed for a time-integrated flux concentration to be calculated. The dynamic hydrogel technique was trialled and found to correlate with the pygmy mussel (Xenostrobus securis) aluminium uptake for short exposure periods (24 hours).The dynamic hydrogel metal concentration was also found to correlate to indpendantly measured pore water and simultaneously extracted metal (SEM) concentrations. The hydrogel techniqe was further applied to investigate the sediment-water interface in drained and non-drained acid suflate landscapes. The studied Australian and Finnish acid sulfate landscapes showed contrasting relationships between the acid volatile sulfides (AVS) and SEM fractions. In the Australian sediments, a conversion of AVS-S to FeS2-S occurs with depth driven by a polysulfide pathway, whilst the Finnish sediments displayed a persistence of AVS-S with depth with limited conversion to FeS2-S. Distinct variations exist at the sediment-water interface of the two contrasting landscapes, with AVS-S to FeS2-S ratios of 2.5 for the Australian and 0.2 in the Finnish sediments. The sediment geochemistry regulated metal mobility. A two-dimensional passive and dynamic hydrogel approach illustrated microniches and supply zones of aluminium iron, manganese and zinc at varying depths near the sediment-water interface. The measurement of bioaccessibility using an in situ technique in acid sulfate landscapes is a first for both Australia and Finland, and this research provides an important avenue for future water and sediment quality monitoring.
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Tang, Shijun Hu Zhibing. "Characterization, properties and applications of novel nanostructured hydrogels." [Denton, Tex.] : University of North Texas, 2006. http://digital.library.unt.edu/permalink/meta-dc-5605.
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Lu, Xihua. "Polymer hydrogel nanoparticles and their networks." Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc3232/.
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The thermally responsive hydroxypropyl cellulose (HPC) hydrogel nanoparticles have been synthesized and characterized. The HPC particles were obtained by chemically crosslinking collapsed HPC polymer chains in water-surfactant (dodecyltrimethylammonium bromide) dispersion above the lower critical solution temperature (LCST) of the HPC. The size distributions of microgel particles, measured by dynamic light scattering, have been correlated with synthesis conditions including surfactant concentration, polymer concentration, and reaction temperature. The swelling and phase transition properties of resultant HPC microgels have been analyzed using both static and dynamic light scattering techniques. By first making gel nanoparticles and then covalently bonding them together, we have engineered a new class of gels with two levels of structural hierarchy: the primary network is crosslinked polymer chains in each individual particle, while the secondary network is a system of crosslinked nanoparticles. The covalent bonding contributes to the structural stability of the nanostructured gels, while self-assembly provides them with crystal structures that diffract light, resulting in colors. By using N-isopropylacrylamide copolymer hydrogel nanoparticles, we have synthesized nanoparticle networks that display a striking iridescence like precious opal but are soft and flexible like gelatin. This is in contrast to previous colored hydrogels, which were created either by adding dyes or fluorescent, or by organic solvent or by embedding a colloidal crystal array of polymer solid spheres . Creating such periodic 3D structures in materials allows us to obtain useful functionality not only from the constituent building blocks but also from the long-range ordering that characterizes these structures. Hydroxypropyl cellulose (HPC) and poly (acrylic acid ) (PAA) complexes were studied using turbidity measurement and laser light scattering. The phase transition temperature of the complexes is found to depend on pH and molecular weights of PAA and HPC. The driving force for this phenomenon is due to the hydrogen bonding and hydrophobic interaction of the macromolecules. Based on the principle of the PAA/HPC complexes, the PAA nanoparticles were synthesized in 0.1wt % HPC aqueous solution at room temperature.
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Lee, Jinhyun. "Development of an anisotropic swelling hydrogel for tissue expansion control over the degree, rate and direction of hydrogel swelling /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31693.
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Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.Committee Chair: David G. Bucknall; Committee Member: Haskell W. Beckham; Committee Member: L. Andrew Lyon; Committee Member: Yadong Wang; Committee Member: Yonathan Thio. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Holdforth, Rachel Katherine. "Conductive carbon nanotube-hydrogel composites for nerve repair." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609184.
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Egidio, Fernanda do Carmo. "O uso de RMN para estudar a estrutura da água em interfaces e sistemas coloidais." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250164.
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Orientador: Edvaldo Sabadini, Fred Yukio FujiwaraTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-19T09:00:39Z (GMT). No. of bitstreams: 1 Egidio_FernandadoCarmo_D.pdf: 2263055 bytes, checksum: 940b47bd50de20f4597683b091bd3faf (MD5) Previous issue date: 2011
Resumo: O modelo de dois sítios, utilizado nos estudos de relaxação do solvente em soluções de carboidratos, pode ser transposto de forma satisfatória para soluções de polímeros hidrofílicos. Polímeros que possuem hidrogênios lábeis, isto é, que possuem hidrogênios disponíveis para troca química com os hidrogênios da água, causam aumento da taxa de relaxação spin-spin do solvente, R2, em relação ao valor obtido para a água pura O efeito torna-se mais intenso na medida em que a concentração dos polímeros aumenta. Polímeros que não possuem hidrogênios lábeis não alteram significativamente o R2 do solvente, pois o mecanismo de troca química não é estabelecido. A relaxação do solvente pode ser usada para estudar o processo de transição sol-gel em sistemas poliméricos. Conforme o gel e formado, as moléculas de água começam a ser confinadas e a taxa de relaxação do solvente aumenta significativamente. A estrutura de hidrogéis supramoleculares formados entre PEG e a-CD, a qual possui uma cavidade hidrofóbica em relação ao seu exterior hidrofílico, dependem das concentrações de seus constituintes e da massa molar do polímero. Quanto maior a massa molar do polímero, menor o numero de pontos de reticulação e mais frágil será o hidrogel. A partir da entrada de 2 moléculas de a-CD em uma cadeia de PEG linear 1.470 Da, a complexação torna-se mais intensa, levando ao recobrimento de toda a cadeia polimérica. A cinética de gelação entre a-CD e PEG, estudada por medidas do tempo de relaxação spin-spin (T2 = 1/R2) do solvente, fornece um perfil de curva que pode explicar o processo de complexação e formação do gel como um todo. A liberação e o confinamento de moléculas de água são refletidos no tempo de relaxação spin-spin destas. Ao liberar moléculas de água, observa-se uma diminuição nos valores de R2 da água até um ponto mínimo, a partir do qual os valores começam a aumentar devido ao confinamento destas moléculas
Abstract: The two sites model used in the studies of solvent relaxation in carbohydrate solutions was also applied for hydrophilic polymer solutions. Polymers with labile hydrogen atoms, meaning they have hydrogen available for chemical exchange with the hydrogen atoms of water, increase the solvent spin-spin relaxation rate, R2, relative to the pure water. The effect becomes more intense as the polymer concentration increases. Polymers without labile hydrogen do not affect significantly R2 of the solvent, because the chemical exchange mechanism is not established in this case. The solvent relaxation can be used to study the process of sol-gel transition in polymer systems. When the gel is formed, the water molecules become confined and the solvent relaxation rate increases significantly. The structure of supramolecular hydrogels formed from PEG and a-CD, which has a hydrophobic cavity and exterior hydrophilic, depends on the concentration of the constituents and the molar mass of the polymer. The higher is the molar mass of the polymer, the fewer is the crosslinking points and more the fragile is hydrogel. Since the inclusion of two a-CD molecules in a chain of linear PEG 1470 Da, the complexation becomes more intense, leading to the full inclusion complex. The kinetics of hydrogel formation between a-CD and PEG was studied by relaxation time measurements of the spin-spin (T2 = 1/R2) of the solvent, provides a curve, whose shape can used to explain the process of complexation and the gelation process at all. The release and confinement of water molecules of the gel are affect spin-spin relaxation the time of the water molecules. The releasing of the water molecules, results in the decreasing of R2 up to a minimum value, and beyond this point the values increases again, due to confinement of these molecules
Doutorado
Físico-Química
Doutor em Ciências
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Cai, Tong. "Synthesis and Characterization of Crystalline Assemblies of Functionalized Hydrogel Nanoparticles." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4976/.
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Two series monodispersed nanoparticles of hydroxylpropyl cellulose (HPC) and functionalized poly-N-isopropylamide (PNIPAM) particles have been synthesized and used as building blocks for creating three-dimensional networks, with two levels of structural hierarchy. The first level is HPC nanoparticles were made from methacrylated or degradable cross-linker attached HPC. These nanoparticles could be stabilized at room temperature by residual methacrylate or degradable groups are present both within and on the exterior of HPC nanoparticles. Controlled release studies have been performed on the particle and networks .The nearly monodispersed nanoparticles have been synthesized on the basis of a natural polymer of hydropropylcellulose (HPC) with a high molecular weight using the precipitation polymerization method and self-assembly of these particles in water results in bright colors. The HPC nanoparticles can be potential using as crosslinkers to increase the hydrogels mechanical properties, such as high transparency and rapid swelling/de-swelling kinetics. The central idea is to prepare colloidal particles containing C=C bonds and to use them as monomers - vinylparticles, to form stable particle assemblies with various architectures. This is accomplished by mixing an aqueous suspension of hydrogel nanoparticles (PNIPAM-co-allylamine) with the organic solvent (dichloromethane) to grow columnar crystals. The hydrogels with such a unique crystal structure behavior not only like the hydrogel opals, but also have a unique property: anisotropy.
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Miller, Darren A. "The ionic conductivity of p(2-hydroxyethyl methacrylate) hydrogels /." Title page, contents and summary only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phm6483.pdf.
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Tang, Shijun. "Characterization, Properties and Applications of Novel Nanostructured Hydrogels." Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5605/.
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The characterization, properties and applications of the novel nanostructured microgel (nanoparticle network and microgel crystal) composed of poly-N-isopropylacrylanmide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid(AA) have been investigated. For the novel nanostructured hydrogels with the two levels of structure: the primary network inside each individual particle and the secondary network of the crosslinked nanoparticles, the new shear modulus, drug release law from hydrogel with heterogeneous structure have been studied. The successful method for calculating the volume fraction related the phase transition of colloid have been obtained. The kinetics of crystallization in an aqueous dispersion of PNIPAM particles has been explored using UV-visible transmission spectroscopy. This dissertation also includes the initial research on the melting behavior of colloidal crystals composed of PNIPAM microgels. Many new findings in this study area have never been reported before. The theoretical model for the columnar crystal growth from the top to bottom of PNIPAM microgel has been built, which explains the growth mechanism of the novel columnar hydrogel colloidal crystals. Since the unique structure of the novel nanostructured hydrogels, their properties are different with the conventional hydrogels and the hard-sphere-like system. The studies and results in this dissertation have the important significant for theoretical study and valuable application of these novel nanostructured hydrogels.
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Tamirisa, Prabhakar A. "Plasma polymerized hydrogel thin films for applications in sensors and actuators." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19827.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2007.Committee Chair: Hess, Dennis W.; Committee Member: Henderson, Cliff L.; Committee Member: Hunt, William D.; Committee Member: Meredith, J. Carson; Committee Member: Prausnitz, Mark R.
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Herman, Emily Sue. "Exploring complex interactions within microgels and microgel assemblies." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52998.
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Hydrogels are water-swellable cross-linked polymeric networks that are capable of incorporating a variety of functionalities and responsivities. The stable colloidal form of a hydrogel is known as a microgel and ranges in size from the nano- to the micrometer scale. Microgels can exhibit similar properties to hydrogels, but the colloidal size of the microgel creates differences in their responsive behavior, such as faster reaction kinetics, as compared to their macrogel counterpart. Microgels have been explored for a broad range of applications, either as individual entities or within large scale assemblies. Although these materials have shown a great deal of utility and versatility, microgels have also demonstrated a great deal of complexity due to the fact that they exhibit both polymeric and colloidal properties. This so-called polymer/colloid duality creates intricacies in characterizing the behavior of these materials, especially when coupled with an oppositely charged component within multilayered assemblies. In this dissertation, work is focused primarily on building a greater fundamental understanding of microgels and their behavior within large scale assemblies. This is done through the development of new characterization techniques or through a direct visualization of the interactions of microgels with their surrounding environment with emphasis on their interaction with an oppositely charged linear polyelectrolyte. From these studies, a more developed fundamental understanding of microgels and their assembly into complex structures is obtained, and these findings will aide in the development of future applications of microgel assemblies.
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Price, Capri Ann. "Early Detection of Corrosion via Hydrogel-based Spectroelectrochemical Sensors." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4637.
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The backbone of the industrialized world is comprised of refined, zerovalent metal, a material which thermodynamically favors an oxidative return to more chemically stable states. There are many methods used to slow or delay this process, such as protective coatings, sacrificial anodes, and alloys, but no method can entirely prevent corrosion. This body of work instead proposes detecting the earliest chemical markers of corrosion: that is, metal ions as they solubilize from a metal surface. Such information would allow maintenance personnel to make informed decisions about the necessity or lack thereof of preventive maintenance, and intervene before advanced damage has a chance to occur.
This dissertation finds that hydrogel-based sensors are capable of such detection and offer a multisensory response, with colorimetric, electrical, volumetric and vibrational changes. Both the colorimetric and electrical trends were calibrated and used for quantification of metal ions both in solution and directly from metal substrate surfaces. Observing how the hydrogels responded to various metal ions contributed to a greater understanding of how ion-headgroup associations can affect the sensory responses of a hydrogel, something that can be exploited in future sensor work. The ability of the sensors to detect ions directly from metal surfaces allowed for an investigation of the protective quality of fatty acids as corrosion inhibitors. A range of chain lengths were tested using the hydrogels, and the comparison to current characterization techniques showed good correlation. This accessible technique, beyond contributing to the current meager literature of fatty acids as corrosion inhibitors, can also allow for the determination of acceptable benchmarks of corrosion, information that is sorely needed to efficiently steward global infrastructure.
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Bayer, Frank Markus [Verfasser], and Klaus [Akademischer Betreuer] Huber. "Hydrogen bond induced hetero-assembly in binary colloidal systems / Frank Markus Bayer. Betreuer: Klaus Huber." Paderborn : Universitätsbibliothek, 2011. http://d-nb.info/1036227960/34.
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Ozbas, Bulent. "Hydrogels constructed via self-assembly of beta-hairpin molecules." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 3.04 Mb., 225 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3221086.
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Reilly, Meghan J. "Enhancing the mechanical properties of a peptide-based hydrogel via covalent crosslinking." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 56 p, 2008. http://proquest.umi.com/pqdweb?did=1605146941&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Thesis (M.Ch.E.)--University of Delaware, 2008.Principal faculty advisors: Joel P. Schneider, Dept. of Chemistry & Biochemistry; and Eric M. Furst, Dept. of Chemical Engineering. Includes bibliographical references.
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Swami, Salesh N., University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Radiation synthesis of polymeric hydrogels for swelling-controlled drug release studies." THESIS_CSTE_SFH_Swami_S.xml, 2004. http://handle.uws.edu.au:8081/1959.7/698.
Full textAbstract:
Hydrogels are three dimensional networks of hydrophilic homopolymers or copolymers generally covalently or ionically crosslinked. They interact with aqueous media by swelling to some equilibrium value by retaining the aqueous media in their structures. This study concerns the investigation of the swelling and the controlled drug release behaviour of hydrogels synthesized via the photopolymerisation process. The study of hydrogels in this project was oriented towards their biomedical applications as controlled drug delivery devices. It is a known fact that the complete conversion of monomers to polymers may not be achieved in the polymerisation process thus there is always a certain component of unreacted toxic monomers still remained in the polymer matrix. These monomers have the tendency to leach out of the polymer matrices when the polymers are in contact with an aqueous medium thus rendering the hydrogel to be nonbiocompatable. The polymers synthesized in this work were washed thoroughly in milli-Q-water and then evaluated in vitro for any possible toxic effect on human keratinocyte (HaCaT)v cells using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diaphenyl tetrazolium bromide (MTT) cell proliferation assay. The cytotoxicity results indicated that the hydrogels understudy sustained and allowed a positive growth of the HaCat cells in the duration of the cytotoxicity experiment, thus proving to be satisfactorily compatible.Doctor of Philosophy (PhD)
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Appel, Eric. "Cucurbit(n)uril-based supramolecular hydrogels : from fundamentals to applications in drug delivery." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/252287.
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Tonsomboon, Khaow. "Fibre-reinforced hydrogels : biomimetic scaffolds for corneal tissue engineering." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709044.
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Brink, Kelly Sinclair. "Degradative properites and cytocompatibility of a mixed-mode hydrogel containing oligo[poly(thylene glycol) fumarate] and thiol-poly(Ethylene Glycol)-Thiol." Thesis, Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22607.
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Knee injuries are a major cause of orthopedic disabilities in the United States. Current reconstruction techniques for torn anterior cruciate ligaments (ACL) require extensive surgery and long physical rehabilitation times since the tissue does not heal upon injury. A common ACL injury occurs where the gap at the rupture site remains open after injury and fails to heal, which can lead to premature osteoarthritis and disability. Hydrogels are a popular material used for tissue engineering applications due to their ability to retain water and good biocompatibility. Previous work has shown that hydrogels can be made through the mixed-mode reaction of radically crosslinked thiol groups and acrylate end groups. This project explores mixed-mode oligo[poly(ethylene glycol) fumarate] (OPF)-based hydrogels as alternate carriers for regeneration of partial tear ligament defects. The main purpose of this project was to determine the degradative properties of and cell response to thiol-PEG-thiol (PEG-diSH), a novel hydrogel material. The swelling and degradative properties of hydrogels containing three components OPF, PEG-diacrylate (PEG-DA), and PEG-diSH were characterized by their fold swelling. In addition, cell viability, morphology changes, proliferation and collagen production were analyzed in tri-ratio hydrogels with and without the presence of RGD over three weeks.
Results showed that the hydrogels containing PEG-diSH demonstrated significantly larger fold swelling and promoted cell clustering (as shown by increased area of clusters), probably due to the larger mesh size and possibly due to the presence of free thiol functional groups present in the network from the mixed-mode reaction. However, an increase in cell number was not found in these gels up to eight days, suggesting that cell migration may play a role in the appearance of clusters. Additionally, increased cell spreading in response to RGD was observed inside gels containing PEG-diSH; no spreading was seen in the non PEG-diSH gels (± RGD), possibly because the mesh size was too small to allow for clustering or spreading within the matrix.
Results from this work suggest that the presence of PEG-diSH could promote cell-cell contact within the clusters which could be useful in systems where direct contact promotes tissue formation or cell differentiation.
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Spiller, Kara Lorraine Lowman Anthony M. "Semi-degradable, multi-functional hydrogels for the repair of articular cartilage defects /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3263.
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Vernengo, Jennifer Lowman Anthony M. "Injectable bioadhesive hydrogels for nucleus pulposus replacement and repair of the damaged intervertebral disc /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1315.
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Dong, Liang-Chang. "Thermally reversible hydrogels for controlled drug delivery and enzyme immobilization /." Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/8009.
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Xia, Xiaohu. "Fabrication and light scattering study of multi-responsive nanostructured hydrogels and water-soluble polymers." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4374/.
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Monodispersed microgels composed of poly-acrylic acid (PAAc) and poly(N-isopropylacrylamide) (PNIPAM) interpenetrating networks were synthesized by 2-step method with first preparing PNIPAM microgel and then polymerizing acrylic acid that interpenetrates into the PNIPAM network. The semi-dilute aqueous solutions of the PNIPAM-PAAc IPN microgels exhibit an inverse thermo-reversible gelation. Furthermore, IPN microgels undergo the reversible volume phase transitions in response to both pH and temperature changes associated to PAAc and PNIPAM, respectively. Three applications based on this novel hydrogel system are presented: a rich phase diagram that opens a door for fundamental study of phase behavior of colloidal systems, a thermally induced viscosity change, and in situ hydrogel formation for controlled drug release. Clay-polymer hydrogel composites have been synthesized based on PNIPAM gels containing 0.25 to 4 wt% of the expandable smectic clay Na-montmorillonite layered silicates (Na-MLS). For Na-MLS concentrations ranging from 2.0 to 3.2 wt%, the composite gels have larger swelling ratio and stronger mechanical strength than those for a pure PNIPAM. The presence of Na-MLS does not affect the value of the lower critical solution temperature (LCST) of the PNIPAM. Surfactant-free hydroxypropyl cellulose (HPC) microgels have been synthesized in salt solution. In a narrow sodium chloride concentration range from 1.3 to 1.4 M, HPC chains can self-associate into colloidal particles at room temperature. The microgel particles were then obtained in situ by bonding self-associated HPC chains at 23 0C using divinyl sulfone as a cross-linker. The volume phase transition of the resultant HPC microgels has been studied as a function of temperature at various salt concentrations. A theoretical model based on Flory-Huggins free energy consideration has been used to explain the experimental results. Self-association behavior and conformation variation of long chain branched (LCB) poly (2-ethyloxazoline) (PEOx) with a CH3-(CH2)17 (C18) modified surface are investigated using light scattering techniques in various solvents. The polymer critical aggregation concentration (cac) strongly depends on solvent polarity, decreasing as the solvent becomes more hydrophobic.
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Hule, Rohan A. "Structure-property relationships in self-assembling peptide hydrogels, homopolypeptides and polysaccharides." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 209 p, 2009. http://proquest.umi.com/pqdweb?did=1679684291&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Kim, Se-Ho [Verfasser], Dierk [Akademischer Betreuer] Raabe, and Christina [Akademischer Betreuer] Scheu. "Engineering impurities in colloidal nanostructures used in 'green hydrogen' generation / Se-Ho Kim ; Dierk Raabe, Christina Scheu." Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://d-nb.info/1240615728/34.
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Swami, Salesh N. "Radiation synthesis of polymeric hydrogels for swelling-controlled drug release studies." Thesis, View thesis, 2004. http://handle.uws.edu.au:8081/1959.7/698.
Full textAbstract:
Hydrogels are three dimensional networks of hydrophilic homopolymers or copolymers generally covalently or ionically crosslinked. They interact with aqueous media by swelling to some equilibrium value by retaining the aqueous media in their structures. This study concerns the investigation of the swelling and the controlled drug release behaviour of hydrogels synthesized via the photopolymerisation process. The study of hydrogels in this project was oriented towards their biomedical applications as controlled drug delivery devices. It is a known fact that the complete conversion of monomers to polymers may not be achieved in the polymerisation process thus there is always a certain component of unreacted toxic monomers still remained in the polymer matrix. These monomers have the tendency to leach out of the polymer matrices when the polymers are in contact with an aqueous medium thus rendering the hydrogel to be nonbiocompatable. The polymers synthesized in this work were washed thoroughly in milli-Q-water and then evaluated in vitro for any possible toxic effect on human keratinocyte (HaCaT)v cells using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diaphenyl tetrazolium bromide (MTT) cell proliferation assay. The cytotoxicity results indicated that the hydrogels understudy sustained and allowed a positive growth of the HaCat cells in the duration of the cytotoxicity experiment, thus proving to be satisfactorily compatible.
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Hendrickson, Grant R. "Harnessing microgel softness for biointerfacing." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50252.
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Hydrogel materials have become a heavily studied as materials for interfacing with biology both for laboratory investigations and the development of devices for biomedical applications. These polymers are water swellable and can be made responsive to many different stimuli by choice of monomers, co-monomers, and cross-linkers or functionalization with pendent ligands, substrates, or charged groups. The high water content, low moduli and potential responsively of these polymers make good candidates for biomaterials. A specific type of hydrogel called a microgel or a hydrogel micro/nanoparticle has similar properties to bulk hydrogel materials. Many of the interesting results and utility of the microgels in bioapplications are due to their inherent softness of the material. Here, the softness, flexibility, and conformability of these water swollen particles is used to create an interesting sensor platform, studied in the context of a microgel passing through a pore, and used as an emulsifier to create a drug delivery platform. The unifying theme of this dissertation is the softness of microgels which is critical for all of these experiments. However, the study of individual microgel softness is challenging and complex, since the softness is composed of two different components. The first is that the microgel is a swollen polymer which can be deswollen by an external stimuli or force. The second is that the microgel is a volume conserving elastic colloid which can deform without deswelling under the certain conditions. Throughout, this dissertation will discuss the ramifications of the complex softness of microgels in each experimental result and potential application.
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Pillai, Karthikeyan Chyan Oliver Ming-Ren. "FTIR-ATR characterization of hydrogel, polymer films, protein immobilization and benzotriazole adsorption on copper surface." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5132.
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Perakslis, Eric D. Lowman Anthony M. "Determination of the in vitro and in vivo oral drug delivery capabilities of complexation hydrogels /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1305.
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Huo, Hongguang. "Tailored cell attachment and cytotoxicity in PEG-based polysaccharide-derivatized hydrogels." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 117 p, 2007. http://proquest.umi.com/pqdlink?did=1253510481&Fmt=7&clientId=79356&RQT=309&VName=PQD.
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Lee, Seung Geol. "Structure-property relationship of hydrogel: molecular dynamics simulation approach." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44844.
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We have used a molecular modeling of both random and blocky sequence hydrogel networks of poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate) (P(VP-co-HEMA)) with a composition of VP:HEMA = 37:13 to investigate the effect of the monomeric sequence and the water content on the equilibrium structures and the mechanical and transport properties by full-atomistic molecular dynamics (MD) simulations. The degree of randomness of the monomer sequence for the random and the blocky copolymers, were 1.170 and 0.104, respectively, and the degree of polymerization was fixed at 50. The equilibrated density of the hydrogel was found to be larger for the random sequence than for the blocky sequence at low water contents (< 40 wt %), but this density difference decreased with increasing water content. The pair correlation function analysis shows that VP is more hydrophilic than HEMA and that the random sequence hydrogel is solvated more than the blocky sequence hydrogel at low water content, which disappears with increasing water content. Correspondingly, the water structure is more disrupted by the random sequence hydrogel at low water content but eventually develops the expected bulk-water-like structure with increasing water content. From mechanical deformation simulations, the stress-strain analysis showed that the VP is found to relax more efficiently, especially in the blocky sequence, so that the blocky sequence hydrogel shows less stress levels compared to the random sequence hydrogel. As the water content increases, the stress level becomes identical for both sequences. The elastic moduli of the hydrogels calculated from the constant strain energy minimization show the same trend with the stress-strain analysis. Ascorbic acid and D-glucose were used to study the effect of the monomeric sequence on the diffusion of small guest molecules within the hydrogels. By analyzing the pair correlation functions, it was found that the guest molecule has greater accessibility to the VP units than to the HEMA units with both monomeric sequences due to its higher hydrophilicity compared to the HEMA units. The monomeric sequence effect on the P(VP-co-HEMA) hydrogel is clearly observed with 20 wt % water content, but the monomeric sequence effect is significantly reduced with 40 wt % water content and disappears with 80 wt % water content. This is because the hydrophilic guest molecules are more likely to be associated with water molecules than with the polymer network at the high water content. By analyzing the mean square displacement, the displacement of the guest molecules and the inner surface area, it is also found that the guest molecule is confined in the system at 20 wt % water content, resulting in highly anomalous subdiffusion. Therefore, the diffusion of the guest molecules is directly affected by their interaction with the monomer units, the monomeric sequence and the geometrical confinement in the hydrogel at a low water content, but the monomeric sequence effect and the restriction on the diffusion of the guest molecule are significantly decreased with increasing the water content.
We also investigated the de-swelling mechanisms of the surface-grafted poly(N-isopropylacrylamide) (P(NIPAAm)) brushes containing 1300 water molecules at 275 K, 290 K, 320 K, 345 K, and 370 K. We clearly observed the de-swelling of the water molecules for P(NIPAAm) above the lower critical solution temperature (LCST) (~305 K). Below the LCST, we did not observe the de-swelling of water molecules. Using the upper critical solution temperature (UCST) systems (poly(acrylamide) brushes) for comparison purposes, we did not observe the de-swelling of water molecules at a given range of temperatures. By analyzing the pair correlation functions and the coordination numbers, the de-swelling of the water molecules occurred distinctly around the isopropyl group of the P(NIPAAm) brush above the LCST because C(NIPAAm) does not offer sufficient interaction with the water molecules via the hydrogen bonding type of secondary interaction. We also found that the contribution of the N(NIPAAm)-O(water) pair is quite small because of the steric hindrance of the isopropyl group. By analyzing the change in the hydrogen bonds, the hydrogen bonds between polar groups and water molecules in the P(NIPAAm) brushes weaken with increasing temperature, which leads to the de-swelling of the water molecules out of the brushes above the LCST. Below the LCST, the change in the hydrogen bonds is not significant. Again, the contribution of the NH(NIPAAm)-water pairs is insignificant; the total number of hydrogen bonds is ~20, indicating that the interaction between the NH group and the water molecules is not significant due to steric hindrances. Lastly, we observed that the total surface area of the P(NIPAAm) brushes that is accessible to water molecules is decreased by collapsing the brushes followed by the de-swelling of water molecules above the LCST.
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Butterick, Lisa Ann. "Design of self-assembling beta-hairpin peptide-based hydrogels for tissue engineering applications." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 248 p, 2008. http://proquest.umi.com/pqdweb?did=1597619011&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Tuesca, Anthony D. Lowman Anthony M. "Synthesis, characterization, and application of polyethylene glycol modified insulin for oral delivery using complexation hydrogels /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2715.
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Wu, Xiaojun. "Development of optical biosensors based on oxidases and hydrogels performing in organic phase and aqueous phase solvents." HKBU Institutional Repository, 2002. https://repository.hkbu.edu.hk/etd_ra/423.
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Smith, Michael Hughes. "The design of multifunctional hydrogel nanoparticles for drug delivery." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43609.
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Hydrogel micro- and nanoparticles (microgels and nanogels) are a promising class of drug delivery vehicles. Composed of hydrophilic polymers arranged into a cross-linked network structure, nanogels show several attractive features for the delivery of macromolecule therapeutics. For instance, the hydrated, porous internal cavity of the nanogel may serve as a high capacity compartment for loading macromolecules, whereas the periphery of the nanogel may be used as a scaffold for conjugating cell-specific targeting moieties. This dissertation presents recent investigations of nanogels as targeted delivery vehicles for oligonucleotides to cancer cells, while exploring new nanogel chemistries that enable future in vivo applications. For instance, synthetic efforts have produced particles capable of erosion into low molar mass constituents, providing a possible mechanism of particle clearance after repeated administration in vivo. In another example, the microgel network chemistry was tuned to promote the encapsulation of charged proteins. In parallel with those synthetic efforts, new light scattering methodologies were developed to accurately quantify the particle behaviors (e.g. loading, erosion). Using multiangle light scattering (MALS), changes in particle molar mass and radius were measured, providing a quantitative and direct approach for monitoring nanogel erosion and macromolecule encapsulation. The new particle chemistries demonstrated, together with enabling light scattering methods, will catalyze the development of improved delivery vehicles in the near future.
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Sato, Jun. "Transient Rheology of Stimuli Responsive Hydrogels: Integrating Microrheology and Microfluidics." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-10272006-133420/.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007.Andreas S. Bommarius, Committee Member ; L. Andrew Lyon, Committee Member ; J. Carson Meredith, Committee Member ; William J. Koros, Committee Member ; Victor Breedveld, Committee Chair.
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Goetz, Lee Ann. "Preparation and analysis of crosslinked lignocellulosic fibers and cellulose nanowhiskers with poly(methyl-vinyl ether co maleic acid) â " polyethylene glycol to create novel water absorbing materials." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45893.
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The search for cellulosic based products as a viable alternative for petroleum-based products was the impetus for covalently crosslinking lignocellulosic fibers and nanocellulose whiskers with poly(methyl vinyl ether) co maleic acid (PMVEMA) - polyethylene glycol (PEG). The lignocellulosics used were ECF bleached softwood (pine) and ECF bleached birch kraft pulp. This thesis also tests the hypothesis that water absorption and retention can be improved by grafting PMVEMA-PEG to the surface of ECF bleached kraft pulp hardwood and softwood fibers via microwave initiated crosslinking. The crosslinking of the PMVEMA to hardwood and softwood kraft ECF bleached pulp fibers resulted in enhanced water absorbing pulp fibers where the PMVEMA is grafted onto the surface of the fibers. The crosslinking was initiated both thermally and via microwave irradiation and the water absorption and water retention was measured as the percent of grafted PMVEMA. This was the first application of microwave crosslinking of pulp fibers with the goal of creating water absorbing pulp fibers. Ultimately, the water absorption values ranged from 28.70 g water per g dry crosslinked pulp fiber (g/g) to 230.10 g/g and the water retention values ranged from 26% to 71% of the water retained that was absorbed by the crosslinked pulp fibers. The microwave initiated crosslinked fibers had comparable results to the thermally crosslinked fibers with a decreased reaction time, from 6.50 min (thermal) to 1 min 45 sec (microwave).
Cellulose nanowhiskers, crystalline rods of cellulose, have been investigated due to their unique properties, such as nanoscale dimensions, low density, high surface area, mechanical strength, and surface morphology and available surface chemistry. Prior to this study, the crosslinking of cellulose whiskers with the matrix via solution casting of liquid suspensions of whiskers and matrix had not been explored. The hypothesis to be investigated was that incorporating cellulosic whiskers with the PMVEMA-PEG matrix and crosslinking the whiskers with the matrix would yield films that demonstrate unique properties when compared to prior work of crosslinking of PMVEMA-PEG to macroscopic ECF bleached kraft pulp fibers.
Solution cast composites of cellulose nanowhiskers-PMVEMA-PEG were crosslinked at 135 °C for 6.5 min and analyzed for crosslinking, thermal stability, strength and mechanical properties, whisker dispersion, and water absorption and uptake rates. The whisker-composites demonstrated unique properties upon crosslinking the whiskers with PMVEMA-PEG, especially the elongation at break and tensile strength upon conditioning of the final materials at various relative humidities. In addition, the whiskers improved the thermal stability of the PMVEMA-PEG matrix. This is significant as methods of improving processing thermal stability are key to developing new materials that utilize cellulose whiskers, PMVEMA, and PEG. This thesis addresses the hypothesis that cellulose nanowhiskers that are crosslinked with a matrix can create new whisker-matrix composites that behave differently after crosslinking.
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Zhou, Bo. "The preparation and characterization of thermo-sensitive colored hydrogel film and surfactant-free porous polystyrene three-dimensional network." Thesis, University of North Texas, 2001. https://digital.library.unt.edu/ark:/67531/metadc3019/.
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Polymer hydrogel films change their properties in response to environmental change. This remarkable phenomenon results in many potential applications of polymer hydrogel films. In this thesis colored thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel film was prepared by firstly synthesizing polymer latex and secondarily crosslinking the nanoparticles and casting the polymers onto glass. The shape-memory effect has been observed when changing the environmental temperature. The temperature-dependent of turbidity of polymer hydrogel film was measured by HP UVVisible spectrophotometer. This intelligent hydrogel might be used in chemomechanical systems and separation devices as well as sensors. Polymer adsorption plays an important role in many products and processes. In this thesis, surfactant-free three-dimensional polystyrene (PS) nanoparticle network has been prepared. The infrared spectroscopy and solubility experiment are performed to prove the crosslinking mechanism, also the BET method was used to measure the adsorption and desorption of polystyrene network. The BET constant (C) is calculated (C=6.32). The chemically bonded polymer nanoparticle network might have potential applications as catalyst or used for chromatographic columns.
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Phelps, Edward Allen. "Bio-functionalized peg-maleimide hydrogel for vascularization of transplanted pancreatic islets." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45899.
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Type 1 diabetes affects one in every 400-600 children and adolescents in the US. Standard therapy with exogenous insulin is burdensome, associated with a significant risk of dangerous hypoglycemia, and only partially efficacious in preventing the long term complications of diabetes. Pancreatic islet transplantation has emerged as a promising therapy for type 1 diabetes. However, this cell-based therapy is significantly limited by inadequate islet supply (more than one donor pancreas is needed per recipient), instant blood-mediated inflammatory reaction, and loss of islet viability/function during isolation and following implantation. In particular, inadequate revascularization of transplanted islets results in reduced islet viability, function, and engraftment. Delivery of pro-vascularization factors has been shown to improve vascularization and islet function, but these strategies are hindered by insufficient and/or complex release pharmacokinetics and inadequate delivery matrices as well as technical and safety considerations. We hypothesized that controlled presentation of angiogenic cues within a bioartificial matrix could enhance the vascularization, viability, and function of transplanted islets. The primary objective of this dissertation was to enhance allogenic islet engraftment, survival and function by utilizing synthetic hydrogels as engineered delivery matrices. Polyethylene glycol (PEG)-maleimide hydrogels presenting cell adhesive motifs and vascular endothelial growth factor (VEGF) were designed to support islet activities and promote vascularization in vivo. We analyzed the material properties and cyto-compatibility of these engineered materials, islet engraftment in a transplantation model, and glycemic control in diabetic subjects. The rationale for this project is to establish novel biomaterial strategies for islet delivery that support islet viability and function via the induction of local vascularization.