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Synthesis and Characterization of Crystalline Assemblies of Functionalized Hydrogel Nanoparticles

Description: 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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Date: December 2005
Creator: Cai, Tong
Partner: UNT Libraries

FTIR-ATR Characterization of Hydrogel, Polymer Films, Protein Immobilization and Benzotriazole Adsorption on Copper Surface

Description: Plasma polymerization techniques were used to synthesize and deposit hydrogel on silicon (Si) substrate. Hydrogel is a network of polymer chains that are water-insoluble and has a high degree of flexibility. The various fields of applications of hydrogel include drug release, biosensors and tissue engineering etc. Hydrogel synthesized from different monomers possess a common property of moisture absorption. In this work two monomers were used namely 1-amino-2-propanol (1A2P) and 2(ethylamino)ethanol (2EAE) to produce polymer films deposited on Si ATR crystal. Their moisture uptake property was tested using FTIR-ATR technique. This was evident by the decrease in -OH band in increasing N2 purging time of the films. Secondly, two monomer compounds namely vinyl acetic acid and glycidyl methacrylate which have both amine and carboxylic groups are used as solid surface for the immobilization of bovine serum albumin (BSA). Pulsed plasma polymerization was used to polymerize these monomers with different duty cycles. Initial works in this field were all about protein surface adsorption. But more recently, the emphasis is on covalent bonding of protein on to the surface. This immobilization of protein on solid surface has a lot of applications in the field of biochemical studies. The polymerization of vinyl acetic acid and glycidyl methacrylate were shown as successful method to attach protein on them. Chemical mechanical polishing (CMP) of Cu is one of the processes in the integrated chips manufacturing industry. Benzotriazole is one of the constituents of this CMP slurry used as corrosion inhibitor for Cu. Benzotriazole (C6H5N3) is a nitrogen heterocyclic derivative having three nitrogen atoms, each with an unshared pair of electrons, forming five-membered ring structure. This molecule coordinates with Cu atoms by loosing a proton from one of its nitrogen atom and thereby forming a film which is polymeric in nature that prevents further oxidation of Cu. ...
Date: December 2007
Creator: Pillai, Karthikeyan
Partner: UNT Libraries

Humic Substances in Natural Waters and their Complexation with Trace Metals and Radionuclides : a Review

Description: Section I introduces the material contained in the rest of the report. Section II presents the origin and characteristics of humic materials as we understand them today and outlines the methods that have been used to separate and analyze these substances. Section III focuses on the general problem of metal-organic interactions and treats some of the factors that are important in chelating and complexing of metal ions by humic substances. Section IV deals specifically with the complexing of radionuclides by organic substances, treated from the standpoint of both empirical and experimental studies.
Date: July 1985
Creator: Boggs, Sam; Livermore, David & Seitz, Martin G.
Partner: UNT Libraries Government Documents Department

Actinide Recovery Using Aqueous Biphasic Extraction: Initial Developmental Studies

Description: Aqueous biphasic extraction systems are being developed to treat radioactive wastes. The separation technique involves the selective partitioning of either solutes or colloid-size particles between two scible aqueous phases. Wet grinding of plutonium residues to an average particle size of one micron will be used to liberate the plutonium from the bulk of the particle matrix. The goal is to produce a plutonium concentrate that will integrate with existing and developing chemical recovery processes. Ideally, the process would produce a nonTRU waste stream. Coupling physical beneficiation with chemical processing will result in a substantial reduction in the volume of mixed wastes generated from dissolution recovery processes. As part of this program, we will also explore applications of aqueous biphasic extraction that include the separation and recovery of dissolved species such as metal ions and water-soluble organics. The expertise and data generated in this work will form the basis for developing more cost-effective processes for handling waste streams from environmental restoration and waste management activities within the DOE community. This report summarizes the experimental results obtained during the first year of this effort. Experimental efforts were focused on elucidating the surface and solution chemistry variables which govern partitioning behavior of plutonium and silica in aqueous biphasic extraction systems. Additional efforts were directed toward the development of wet grinding methods for producing ultrafine particles with diameters of one micron or less.
Date: August 1992
Creator: Chaiko, David J.; Mensah-Biney, R.; Mertz, C. J. & Rollins, A. N.
Partner: UNT Libraries Government Documents Department

Characterization, Properties and Applications of Novel Nanostructured Hydrogels.

Description: 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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Date: December 2006
Creator: Tang, Shijun
Partner: UNT Libraries

Synthesis and study of crystalline hydrogels, guided by a phase diagram.

Description: Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid (AA) have been synthesized and used as building blocks for creating three-dimensional networks. The close-packed PNIPAM-co-allylamine and PNIPAM-co-AA nanoparticles were stabilized by covalently bonding neighboring particles at room temperature and at neutral pH; factors which make these networks amicable for drug loading and release. Controlled release studies have been performed on the networks using dextran markers of various molecular weights as model macromolecular drugs. Drug release was quantified under various physical conditions including a range of temperature and molecular weight. These nanoparticle networks have several advantages over the conventional bulk gels for controlling the release of biomolecules with large molecular weights. Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) can self-assemble into crystals with a lattice spacing on the order of the wavelength of visible light. By initiating the crystallization process near the colloidal crystal melting temperature, while subsequently bonding the PNIPAM-co-allylamine particles below the glass transition temperature, a nanostructured hydrogel has been created. The crystalline hydrogels exhibit iridescent patterns that are tunable by the change of temperature, pH value or even protein concentration. This kind of soft and wet hydrogel with periodic structures may lead to new sensors, devices, and displays operating in aqueous solutions, where most biological and biomedical systems reside. The volume-transition equilibrium and the interaction potential between neutral PINPAM particles dispersed in pure water were investigated by using static and dynamic light-scattering experiments. From the temperature-dependent size and energy parameters, the Sutherland-like potential provides a reasonable representation of the inter-particle potential for PNIPAM particles in swollen and in collapsed phases. An aqueous dispersion of PNIPAM particles can freeze at both high and low temperatures. At low temperatures, the freezing occurs at a large particle volume fraction, similar to that in a hard-sphere system; while at high temperature, the freezing occurs at ...
Date: December 2004
Creator: Huang, Gang
Partner: UNT Libraries

Fabrication and light scattering study of multi-responsive nanostructured hydrogels and water-soluble polymers.

Description: 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 ...
Date: December 2003
Creator: Xia, Xiaohu
Partner: UNT Libraries