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Synthesis of Polyaldehydes

Description: Part one of this thesis concerns the polymerizability of some α,β-unsaturated monaldehydes and also relates the synthesis of some new polyaldehydes which have not been reported in the literature. Part two concerns the polymerization of glyoxal, the simplest dialdehyde, and the structure elucidation of this new polymer.
Date: June 1964
Creator: O'Neal, Hubert Ronald
Partner: UNT Libraries

Hydrolytic polymerization of chromium (III) hydroxides in the aquatic environment

Description: Products of hydrolytic polymerization of Cr(III) hydroxide were investigated in Milli-Q water and in natural water matrices. Products were first fractionated on Sephadex column using eluents of increasing strength. Ion chromatography (IC) with UV detection at 436 nm was then used to separate the ionic species.
Date: December 1991
Creator: Mbamalu, Godwin E.
Partner: UNT Libraries

Polymerization of the E and Z Isomers of Bis-(Triethoxysilyl)-2-Butene

Description: We have synthesized the Z and E isomers of 1,4-bis(triethoxysilyl)-2- butene and polymerized them under acid and base catalyzed sol-gel conditions. As expected the E system formed crosslinked, insoluble gels. The Z isomer, by nature of its geometry, formed high molecular weight, soluble polymeric products under acidic conditions. We were able to prepare and isolate both the cyclic disilsesquioxane monomer, and its dimer. Comparison of their spectral characterization with that of the soluble polymers suggests that the cyclics are present within the polymers. lle synthesis of a dimer likely present at some early stage of the polymerization suggests that we may be able to control the reaction and form rigid polymers with controllable tacticity. In addition, most of the gels were found to be non-porous indicating that the gels were, in fact, more compliant than ethenylene-bridged polysilsesquioxanes leading to collapse of pores during drying.
Date: May 11, 1999
Creator: Carpenter, J.P. Dorhout, K.; Loy, D.A.; Shaltout, R.M. & Shea, K.J.
Partner: UNT Libraries Government Documents Department

Cyclization Phenomena in the Sol-Gel Polymerization of a,w-Bis(triethoxysilyl)alkanes and Incorporation of the Cyclic Structures into Network Silsesquioxane Polymers

Description: Intramolecular cyclizations during acid-catalyzed, sol-gel polymerizations of ct,co- bis(tietioxysilyl)aWmes substintidly lengtien gelties formonomers witietiylene- (l), propylene- (2), and butylene-(3)-bridging groups. These cyclizations reactions were found, using mass spectrometry and %i NMR spectroscopy, to lead preferentially to monomeric and dimeric products based on six and seven membered disilsesquioxane rings. 1,2- Bis(triethoxysilyl)ethane (1) reacts under acidic conditions to give a bicyclic drier (5) that is composed of two annelated seven membered rings. Under the same conditions, 1,3- bis(triethoxysilyl)propane (2), 1,4-bis(triethoxysilyl)butane (3), and z-1,4- bis(triethoxysilyl)but-2-ene (10) undergo an intramolecular condensation reaction to give the six membemd and seven membered cyclic disilsesquioxanes 6, 7, and 11. Subsequently, these cyclic monomers slowly react to form the tricyclic dirners 8,9 and 12. With NaOH as polymerization catalyst these cyclic silsesquioxanes readily ~aeted to afford gels that were shown by CP MAS z%i NMR and infr=d spectroscopes to retain some cyclic structures. Comparison of the porosity and microstructwe of xerogels prepared from the cyclic monomers 6 and 7 with gels prepared directly from their acyclic precursors 2 and 3, indicate that the final pore structure of the xerogels is markedly dependent on the nature of the precursor. In addition, despite the fact that the monomeric cyclic disilsesquioxane species can not be isolated from 1-3 under basic conditions due to their rapid rate of gelation, spectroscopic techniques also detected the presence of the cyclic structures in the resulting polymeric gels.
Date: January 4, 1999
Creator: Alam, T.M.; Carpenter, J.P.; Dorhout, P.K.; Greaves, J.; Loy, D.A.; Shaltout, R. et al.
Partner: UNT Libraries Government Documents Department

Application of NMR Spectroscopy and Multidimensional Imaging to the Gelcasting Process and in-situ Real-Time Monitoring of Cross-Linking Polyacrylamide Gels

Description: In the gelcasting process, a slurry of ceramic powder in a solution of organic monomers is cast in a mold. The process is different from injection molding in that it separates mold-filling from setting during conversion of the ceramic slurry to a formed green part. In this work, NMR spectroscopy and imaging have been conducted for in-situ monitoring of the gelation process and for mapping the polymerization. ¹H nuclear magnetic resonance spectra have been obtained during polymerization of a premix of soluble reactive methacrylamide (monomer) and N, N'-methylene bisacrylamide (cross-linking molecules). The premix was polymerized by adding ammonium persulfate (initiator) and tetramethyl-ethylene-diamine (accelerator) to form long-chain, cross-linked polymers. The time-varying spin-lattice relaxation times T₁ during polymerization have been studied at 25 and 35 C, and the variation of spectra and T₁ with respect to extent of polymerization has been determined. To verify homogeneous polymerization, multidimensional NMR imaging was utilized for in-situ monitoring of the process. The intensities from the images are modeled and the correspondence shows a direct extraction of T₁ data from the images.
Date: April 1995
Creator: Ahuja, S.; Dieckman, S. L.; Gopalsami, Nachappa; Raptis, A. C. & Omatete, Oritsegbemi O.
Partner: UNT Libraries Government Documents Department

Dystroglycan loss disrupts polarity and beta-casein induction inmammary epithelial cells by perturbing laminin anchoring

Description: Precise contact between epithelial cells and their underlying basement membrane is critical to the maintenance of tissue architecture and function. To understand the role that the laminin receptor dystroglycan (DG) plays in these processes, we assayed cell responses to laminin-111 following conditional ablation of DG expression in cultured mammary epithelial cells (MECs). Strikingly, DG loss disrupted laminin-111-induced polarity and {beta}-casein production, and abolished laminin assembly at the step of laminin binding to the cell surface. DG re-expression restored these deficiencies. Investigations of mechanism revealed that DG cytoplasmic sequences were not necessary for laminin assembly and signaling, and only when the entire mucin domain of extracellular DG was deleted did laminin assembly not occur. These results demonstrate that DG is essential as a laminin-111 co-receptor in MECs that functions by mediating laminin anchoring to the cell surface, a process that allows laminin polymerization, tissue polarity, and {beta}-casein induction. The observed loss of laminin-111 assembly and signaling in DG-/-MECs provides insights into the signaling changes occurring in breast carcinomas and other cancers, where DG's laminin-binding function is frequently defective.
Date: February 17, 2006
Creator: Weir, M. Lynn; Oppizzi, Maria Luisa; Henry, Michael D.; Onishi,Akiko; Campbell, Kevin P.; Bissell, Mina J. et al.
Partner: UNT Libraries Government Documents Department

THE RADIATION PROCESSING RESEARCH AND DEVELOPMENT PROGRAM AT BROOKHAVEN NATIONAL LABORATORY

Description: A review of various ways in which nuclear energy can be used in the chemical process industry is presented. Data are included on aspects of radioinduced polymerization of ethylene. Flowsheets are included for radiochemonuclear, thermochemonuclear, electrochemonuclear, and photochemonuclear reactors. Other information is included on irradiation loops. (J.R.D.)
Date: February 1, 1963
Creator: Steinberg, M. & Manowitz, B.
Partner: UNT Libraries Government Documents Department

Surface polymerization agents

Description: This is the final report of a 1-year, Laboratory-Directed R&D project at LANL. A joint technical demonstration was proposed between US Army Missile Command (Redstone Arsenal) and LANL. Objective was to demonstrate that an unmanned vehicle or missile could be used as a platform to deliver a surface polymerization agent in such a manner as to obstruct the filters of an air-breathing mechanism, resulting in operational failure.
Date: December 1, 1996
Creator: Taylor, C. & Wilkerson, C.
Partner: UNT Libraries Government Documents Department

Heterogeneous oxidative and polymerization processes

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). We performed experiments directed at understanding novel catalysts and the use of supercritical carbon dioxide as a reaction medium for catalytic reactions. We participated in program development activities with individual companies and with trade organizations to develop research and funding strategies for catalysis on a national level. This work has helped to identify scientific and technological opportunities for catalysis research in industry and for large national initiatives such as global climate change. Our work has poised the Laboratory to participate in a spectrum of activities where catalysis science and technology will play a role.
Date: November 1, 1998
Creator: Tumas, W.; Ott, K. & Baker, R.T.
Partner: UNT Libraries Government Documents Department

Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

Description: Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.
Date: April 4, 2000
Creator: RAHIMIAN,KAMYAR & LOY,DOUGLAS A.
Partner: UNT Libraries Government Documents Department

Characterization of Methyltrimethoxysilane Sol-Gel Polymerization and the Resulting Aerogels.

Description: Methyl-functionalized porous silica is of considerable interest as a low dielectric constant film for semiconductor devices. The structural development of these materials appears to affect their gelation behaviors and impact their mechanical properties and shrinkage during processing. 29Si solution NMR was used to follow the structural evolution of MTMS (methyltrimethoxysilane) polymerization to gelation or precipitation, and thus to better understand the species that affect these properties and gelation behaviors. The effects of pH, water concentration, type of solvents, and synthesis procedures (single step acid catalysis and two-step acid/base catalysis) on MTMS polymerization were discussed. The reactivity of silicon species with different connectivity and the extent of cyclization were found to depend appreciably on the pH value of the sol. A kinetic model is presented to treat the reactivity of both silicon species involved in condensations separately based on the inductive and steric effects of these silicon species. Extensive cyclization in the presence of acid, which was attributed to the steric effects among numerous reaction pathways for the first time, prevents MTMS gelation, whereas gels were obtained from the two-step method with nearly random condensations. The experimental degree of condensation (DC) at the gel point using the two-step procedure was determined to be 0.86, which is considerably higher than that predicted by the current accepted theories. Both chemical and physical origins of this high value were suggested. Aerogels dried by supercritical CO2 extraction were characterized by FTIR, 13C and 29Si solid-state NMR and nitrogen sorption. The existence of three residual groups (Si-OH, Si-OCH3, and Si-OC2H5) was confirmed, but their concentrations are very low compared to silica aerogels. The low concentrations of the residual groups, along with the presence of Si-CH3, make MTMS aerogels permanently hydrophobic. To enhance applicability, MTMS aerogels were successfully prepared that demonstrated shrinkage less than 10% after supercritical ...
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Date: August 2003
Creator: Dong, Hanjiang
Partner: UNT Libraries

Investigation of Lead Hydrolytic Polymerization and Interactions with Organic Ligands in the Soil/Sediment-Water Environment

Description: The objective of this research was to investigate lead speciation in the soil/sediment-water environment and to better understand how the species affect lead mobility under different environmental conditions. The research involved both field soil and sediment samples as well as standard lead solutions. Field samples were fully characterized and extracted by aqueous and organic solvents. The results were compared and evaluated with the metal speciation model, MINTEQA2. Hydrolytic polymerization and organic complexation studies were conducted with standard lead solutions under controlled experimental conditions. Results of the field samples showed that pH, dissolved cations, ionic strength, dissolved organic matter, and nature of the soil/sediment matrix play major roles in the distribution and mobility of lead (Pb) from contaminated sites. In the aqueous equilibration experiment, the magnitude of Pb2+ solubilization was in the order of pH4>pH7>pH9. The results were in good agreement with MINTEQA2 predictions. An important finding of the research is the detection of Pb polymerization species under controlled experimental conditions. At pH 5.22, Pb polymeric species were formed at rate of 0.03 per day. The role of Pb complexation with organic matter was evaluated in both field and standard samples. Different methodologies showed three types of organically bound Pb. A very small fraction of Pb, in the ppb range, was extractable from the contaminated soil by polar organic solvents. Sequential extractions show that 16.6±1.4 % of the Pb is organically complexed. Complexation of Pb with fulvic acid provided new information on the extent of Pb association with soluble organic matter. The overall results of this research have provided new and useful information regarding Pb speciation in environmental samples. The results, in several instances, have provided verification of MINTEQA2 model's prediction. They also revealed areas of disagreement between the models prediction and the experimental results. A positive note regarding the experimental ...
Date: December 2002
Creator: Sanmanee, Natdhera
Partner: UNT Libraries

Polymerization, shock cooling and ionization of liquid nitrogen

Description: The trajectory of thermodynamic states passed through by the nitrogen Hugoniot starting from the liquid and up to 10{sup 6} GPa has been studied. An earlier report of cooling in the doubly shocked liquid, near 50 to 100 GPa and 7500 K, is revisited in light of the recent discovery of solid polymeric nitrogen. It is found that cooling occurs when the doubly shocked liquid is driven into a volume near the molecular to polymer transition and raising the possibility of a liquid-liquid phase transition (LLPT). By increasing the shock pressure and temperature by an order of magnitude, theoretical calculations predict thermal ionization of the L shell drives the compression maxima to 5-6 fold compression at 10 Mbar (T {approx} 3.5 10{sup 5} K) and at 400 Mbar (T {approx} 2.3 10{sup 6} K) from K shell ionization. Near a pressure of 10{sup 6} GPa the K shell ionizes completely and the Hugoniot approaches the classical ideal gas compression fourfold limit.
Date: July 21, 2005
Creator: Ross, M & Rogers, F
Partner: UNT Libraries Government Documents Department