Browsing by Subject "Polymers--Industrial applications"
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Item Mechanistic modeling, design, and optimization of alkaline/surfactant/polymer flooding(2008-12) Mohammadi, Hourshad, 1977-; Pope, Gary A.; Delshad, MojdehAlkaline/surfactant/polymer (ASP) flooding is of increasing interest and importance because of high oil prices and the need to increase oil production. The benefits of combining alkali with surfactant are well established. The alkali has very important benefits such as lowering interfacial tension and reducing adsorption of anionic surfactants that decrease costs and make ASP a very attractive enhanced oil recovery method provided the consumption is not too large and the alkali can be propagated at the same rate as a synthetic surfactant and polymer. However, the process is complex so it is important that new candidates for ASP be selected taking into account the numerous chemical reactions that occur in the reservoir. The reaction of acid and alkali to generate soap and its subsequent effect on phase behavior is the most crucial for crude oils containing naphthenic acids. Using numerical models, the process can be designed and optimized to ensure the proper propagation of alkali and effective soap and surfactant concentrations to promote low interfacial tension and a favorable salinity gradient. The first step in this investigation was to determine what geochemical reactions have the most impact on ASP flooding under different reservoir conditions and to quantify the consumption of alkali by different mechanisms. We describe the ASP module of UTCHEM simulator with particular attention to phase behavior and the effect of soap on optimum salinity and solubilization ratio. Several phase behavior measurements for a variety of surfactant formulations and crude oils were successfully modeled. The phase behavior results for sodium carbonate, blends of surfactants with an acidic crude oil followed the conventional Winsor phase transition with significant three-phase regions even at low surfactant concentrations. The solubilization data at different oil concentrations were successfully modeled using Hand's rule. Optimum salinity and solubilization ratio were correlated with soap mole fractions using mixing rules. New ASP corefloods were successfully modeled taking into account the aqueous reactions, alkali/rock interactions, and the phase behavior of soap and surfactant. These corefloods were performed in different sandstone cores with several chemical formulations, crude oils with a wide range of acid numbers, brine with a wide range of salinities, and a wide range of temperatures. 2D and 3D sector model ASP simulations were performed based on field data and design parameters obtained from coreflood history matches. The phenomena modeled included aqueous phase chemical reactions of the alkaline agent and consequent consumption of alkali, the in-situ generation of surfactant by reaction with the acid in the crude, surfactant/soap phase behavior, reduction of surfactant adsorption at high pH, cation exchange with clay, and the effect of co-solvent on phase behavior. Sensitivity simulations on chemical design parameters such as mass of surfactant and uncertain reservoir parameters such as kv/kh ratio were performed to provide insight as the importance of each of these variables in chemical oil recovery. Simulations with different permeability realizations provided the range for chemical oil recoveries. This study showed that it is very important to model both surface active components and their effect on phase behavior when doing mechanistic ASP simulations. The reactions between the alkali and the minerals in the formation depend very much on which alkali is used, the minerals in the formation, and the temperature. This research helped us increase our understanding on the process of ASP flooding. In general, these mechanistic simulations gave insights into the propagation of alkali, soap, and surfactant in the core and aid in future coreflood and field scale ASP designs.Item Water-dispersible, conductive polyaniline for organic thin-film electronics(2007-12) Lee, Kwang Seok, 1973-; Loo, Yueh-Lin, 1974-; Sanchez, Isaac C., 1941-Water-dispersible, conductive polyaniline is an attractive candidate for organic thin-film electronics due to its solution-processability which facilitates low-cost processing. The successful incorporation of water-dispersible, conductive polyaniline into organic electronic applications relies on the development of proper processing techniques for material deposition and the elucidation of how processing conditions affect structural development and macroscopic properties of the material. This thesis focuses on understanding the processing-structure-property relationships of a waterdispersible, conductive polyaniline that is doped with poly(2-acryl-amido-2-methyl-1- propanesulfonic acid), or PANI-PAAMPSA. Such understanding has facilitated the incorporation of PANI-PAAMPSA into functional organic thin-film transistors (TFTs). We have developed simple, direct patterning techniques by exploiting the wetting and adsorption characteristics of PANI-PAAMPSA. Conductive PANI-PAAMPSA features can be selectively patterned in the hydrophilic regions on a molecular template. Conductive PANI-PAAMPSA features, which are directly patterned on insulating substrates, can be used as functional electrical components immediately after patterning. PANI-PAAMPSA features as small as 5μm can be routinely created with average electrical conductivity of 0.2S/cm. The patterned PANI-PAAMPSA features effectively function as source and drain electrodes in pentacene thin-film transistors (TFTs). Specifically, bottom-contact pentacene TFTs with PANI-PAAMPSA electrodes exhibit an average mobility of 0.2cm2 /V-s and on/off current ratios of 104 , which are on par with the requirements for backplane circuits for driving display applications. In bottom-contact devices, PANIPAAMPSA makes efficient electrical contact to pentacene by promoting growth of continuous pentacene grains across the channel/electrode interface. Pentacene at such an interface adopts upright orientation, i.e., the fused rings of pentacene are oriented perpendicular to the surface, which leads to more efficient charge injection and extraction at the pentacene/PANI-PAAMPSA interface compared to a pentacene/gold interface. Despite the fact that PANI-PAAMPSA has enhanced charge injection and extraction at the channel/electrode interface in pentacene TFTs, the bulk resististivity of this material remains high (≅5Ωcm). We have successfully reduced the bulk resistivity of PANI-PAAMPSA by more than two orders of magnitude through a simple dichloroacetic acid (DCA) treatment. Our characterization reveals that DCA induces drastic structural changes of PANI-PAAMPSA. DCA moderates the ionic interactions between PANI and PAAMPSA. PANI-PAAMPSA chains can thus rearrange from the “compact-coil” to the “extended chain” conformation. Efficient charge transport is thus enabled through such “extended chain” PANI-PAAMPSA conformation. The use of DCA-treated PANIPAAMPSA as functional electrodes increases device performance (i.e., mobilities and on/off currnet ratios) of TFTs utilizing functionalized acenes by more than an order of magnitude. Specifically, bottom-contact triisopropylsilyl pentacene TFTs with DCAtreated PANI-PAAMPSA electrodes exhibit mobilities and on/off current ratios as high as 0.12 cm2 /V-s and 105 , respectively. Lastly, we show that the molecular structure of vacuum-deposited organic semiconductor molecules, i.e., pentacene and dihexylthiophene anthracene (DHT-ANT) can be drastically different depending on the nature of the surface chemistry of the substrates. Specifically, pentacene and DHT-ANT grow two-dimensional (2D) grains when the molecule-substrate interactions are weak. In these 2D grains, the fused rings of the molecules are generally oriented upright on the substrate surface. On the other hand, if the molecule-substrate interactions are strong, the molecules tend to grow onedimensional (1D) grains. The fused rings of the molecules are generally parallel to the substrate surface. The details of the molecular orientation in turn significantly influence the electronic band structures of the organic semiconductors. Specifically, molecules with fused rings lying flat on substrate surfaces exhibit higher work functions compared to molecules with fused rings oriented upright. We demonstrated several examples showing how the processing-structureproperty relationships of PANI-PAAMPSA facilitate its incorporation in organic TFTs. Such relationships are beneficial for organic electronics as the field moves towards real applications on a commercial scale.