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In preparation of gelant solution for making crosslinked polymer gels for water shutoff applications unpublished experiments plus chemical intuition suggest that, unless hydrolyzed polyacrylamide (HPAM) polymer is fully hydrated before addition of crosslinker, the final gel will have lower than optimum mechanical strength. It is suggested so because polymer chains need to be unfolded before proper crosslinking can occur. We have evaluated gel strengths of “flowing” gels for water shut off in natural fractures and other non-matrix features as a function of time of addition of crosslinker relative to time of hydration of polymer. Gels were prepared from moderately high molecular weight HPAM crosslinked with chromium(III) acetate (CrAc) or polyethyleneimine (PEI). Crosslinker was added after either (1) initial wetting of solid polymer particles or (2) complete hydration of polymer. HPAM can be purchased as a fine particulate hydrocarbon slurry or as a solution concentrate, either of which, when diluted into makeup water, rapidly provides fully hydrated polymer solution. However, dry HPAM is often preferred because of lower overall cost of active material and smaller storage footprint than slurry or liquid concentrates. The down side of using the solid product is that it generally requires two or more large blending tanks in order to fully hydrate polymer for large volume gel treatments. However, if conditions exist where crosslinker can be added to wetted but not fully hydrated polymer, then dry polymer and crosslinker can be blended in a small continuous flow unit, with full hydration occurring downhole prior to gelation. Gel strengths were determined using a common qualitative coding system for gels prepared in identical manner except for timing of crosslinker addition. Crosslinker was added immediately after wetting of polymer or after polymer had been agitated until complete hydration. Samples were prepared in fresh water or 4% NaCl brine and at ambient temperature or 122 °F. For almost all samples of polymer gels prepared with identical concentrations of HPAM and CrAc, there was no observable difference in gel strength regardless of time of addition of crosslinker. HPAM/CrAc polymer gels with 4wt% NaCl make up water were lower in strength by one code level with respect to those prepared with fresh water. For polymer gels hydrated at 122 °F with 4wt% NaCl there was no gel strength code level difference with respect to those prepared at ambient temperature with 4wt% NaCl. For HPAM/PEI polymer gels the majority of the samples showed similar gel strengths regardless of the timing of crosslinker addition. A few polymer gels showed weaker gel strengths when prepared from partially hydrated polymer solution before crosslinker addition. Presence of 4wt% NaCl in the makeup water gave weaker gel strengths than those prepared with fresh water with an average difference of four code levels. The pre-gel viscosity of a polymer solution was also compared to the timing of crosslinker addition at ambient temperature. For HPAM/PEI system the overall polymer solution viscosity decreased when PEI was added whereas for HPAM/CrAc system the polymer solution viscosity remained similar after crosslinker was added to the completely hydrated polymer solution but increased when crosslinker was added to partially hydrated polymer solution. The most significant result of this work is the demonstration that for most field applications optimum quality gel can be obtained using dry polymer and a small continuous mixing system for initial wetting of the polymer after which the crosslinker can be added to the polymer solution on the fly. This practice can decrease the footprint, equipment requirements and labor and thus the cost of large volume flowing gel treatments.

No / Polymer gel electrolytes (PGE) based on polyvinylidene fluoride (PVDF), lithium salts and appropriate solvent systems, developed at Leeds University, have been shown to form tough rigid films with conductivities approaching 10¿2 S cm¿1. A continuous process has now been developed for the construction of rechargeable lithium cells by extruding the PGE as a melt and directly laminating between the anode and cathode electrodes. On cooling, the solid PGE acts as electrolyte and separator and binds the cell laminate together from within requiring no external case. This process has been successfully applied for the fabrication of cells with electrodes developed by SpectraPower Inc. in a commercial process enabling cell laminates with PGE thickness less than 0.1 mm and with energy densities approaching 170 Wh kg¿1. A prototype manufacturing facility has been set up to produce rechargeable cells of high specific capacity and high energy density. Future developments will enable rechargeable lithium ion cells to be produced on a continuous process as flat sheets opening the way for novel battery geometries.

Polymer gels undergo the volume phase transition in response to an infinitesimal environmental change. This remarkable phenomenon results in many potential applications of polymer gels. This dissertation systematically investigates the chemical and physical properties of polymer gels. It is found that infrared radiation laser not only induces a volume phase transition in N-isopropylacrylamide (NIPA) gel, but also causes the gel to bend toward the laser beam. The transmission of visible laser light through a NIPA gel can also be controlled by adjusting the infrared laser power. A new class of environmentally responsive materials based on spatial modulation of the chemical nature of gels has been proposed and demonstrated. Three simple applications based on the modulated gels are presented: a bi-gel strip, a shape memory gel, and a gel hand. The bending of bi-gels has been studied as a function of temperature, acetone aqueous solution, and salt solution. As the polymer network concentration increases, the behavior of shear modulus of acrylamide (PAAM) gels deviates significantlyfromthe classical theory. The ionic NIPA gels undergo two sequential volume phase transitions: one occurs in dilute NaCl solution, the other occurs in concentrated NaCl solution. An interpenetrating polymer network (IPN) of PAAM--NIPA has also been synthesized using free radical polymerization. It is found that the IPN gels preserve the essential properties of individual components. The volume phase transition of the IPN gels can be triggered by multiple external stimuli including temperature, acetone concentration, and salt concentration.

Polymer gels undergo a volume phase transition in solvent in response to an infinitesimal environmental change. This remarkable phenomenon has resulted in many potential applications of polymer gels. The understanding of its mechanical properties has both scientific and technological importance. For this purpose, we have developed a novel method for measuring Poisson's ratio, which is one of the most important parameters determining the mechanical property of gels. Using this method, Poisson's ratio in N-isopropyacrylamide (NIPA) and polyacrylamide (PAAM) gels has been studied.

Gels are a special class of materials which are composed of 3D networks of crosslinked polymer chains that encapsulate liquid/air in the matrix. They can be classified into organogels or hydrogels (organic solvent for organogel and water for hydrogel). For hydrogels that contain metallic elements in the form of ions, the term of metallo-supramolecular polymer hydrogel (MSPHG) is often used. The aim of this project is to develop a kind of new MSPHG and investigate its properties and possible applications. The commercial polymeric anhydride poly(methyl vinyl ether-alt-maleic anhydride) (PVM/MA) is converted by reaction with NaOH to give poly(methyl vinyl ether-alt-monosodium maleate) (PVM/Na-MA). By addition of AgNO3-solution, the formation of the silver(I) supramolecular polymer hydrogel poly[methyl vinyl ether-alt-mono-sodium maleate]∙AgNO3 is obtained. Freeze-dried samples of the hydrogel show a mesoporous network of polycarboxylate ligands that are crosslinked by silver(I) cations. The supercritical CO2 dried silver(I) hydrogel was characterized by FT-IR, SEM-EDAX, TEM, TGA and Physical adsorption (BET) measurements. The intact silver(I) hydrogel was characterized by cryo-SEM. In the intact hydrogel, ion-exchange studies are reported and it is shown that Ag+ ions can be exchanged by copper(II) cations without disintegration of the hydrogel. The silver(I) hydrogel shows effective antibacterial activity and potential application as burn wound dressing.

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Phase transitions of the gelatin – water and agaroza - water systems have been studied using the cloud-point method. Phase diagrams of these systems are constructed at different values of pH of medium. It is shown that pH of medium influences on the melting temperature of gelatin and agaroza gels. / Методом точек помутнения изучены фазовые переходы в системах желатин – вода и агароза – вода. Построены фазовые диаграммы систем при разных pH среды в магнитном поле и вне поля. Установлено, что pH среды влияет на температуру плавления гелей желатина и агарозы.

Technologies such as horizontal wells and multi-stage hydraulic fracturing have made ultra-low permeability shale and tight gas reservoirs productive but the industry is still on the learning curve when it comes to addressing various production issues. Some of the problems encountered while hydraulically fracturing these reservoirs are the absence of frac barriers, thinner shales and the increased presence of geological hazards. Induced vertical fractures sometimes extend to an underlying aquifer and become a conduit to the well. We have developed a low-concentration, low-viscosity and delayed-crosslink polymeric gel system as a water shutoff agent for hydraulically-fractured tight gas and shale reservoirs, where some fractures might connect to water rich zones. The system also is a significant improvement over traditional flowing gels for fracture water shutoff in conventional reservoirs because of these features. The gel uses high molecular weight hydrolyzed polyacrylamide (HPAM) at low polymer concentrations with a delayed organic crosslinker. This crosslinker is more environmentally benign and provides much longer gelation time and stronger final gels than comparable polymer loadings with chromium carboxylate crosslinkers at higher temperatures. The low viscosity system allows low-pressure extrusion of gelant into the narrow-aperture fractures present in unconventional gas reservoirs. The gelant can be pumped at low pressures due to lower polymer concentrations and delayed gelation point. This allows the potential to seal problem zones that are producing excess water even when the fractures conducting water have very narrow apertures. By impeding water production, the gel system developed here can effectively delay water loading thereby avoiding abandonment or installation of expensive equipment with increased operational costs, thus extending life and reserves of unconventional gas wells.