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京都大学 / 新制・課程博士 / 博士(工学) / 甲第23913号 / 工博第5000号 / 新制||工||1780(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 作花 哲夫, 教授 安部 武志, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The synthesis and characterization of step-growth polymers with novel monomers provided materials with tailored properties for emerging technologies. Specifically, multiphase materials (i.e., microphase separated block copolymers) exploit the synergistic relationship of combining polymers with disparate thermal and mechanical properties. The introduction of intramolecular interactions such as hydrogen and ionic bonding into these polymers further tailored their properties for applications including elastomers, electromechanical transducers, and additive manufacturing (AM). A review of recent literature revealed the material properties required for polymeric materials in electromechanical transducers, which aided in the design of polymers for this application. An isocyanate-, catalyst-, and solvent-free approach facilitated the synthesis of segmented polyureas with tunable thermal and mechanical properties. These materials found use as high dielectric elastomers and water-soluble polymers for extrusion-based AM dependent on the backbone composition. Vat photopolymerization (VP) AM served as a technique to 3D printed novel unsaturated polyester resins (UPR). Incorporating a phosphonium ionic liquid as a reactive diluent replaced styrene and reduced the volatility of commonly used UPRs. VP successfully provided 3D structures from these UPRs that demonstrated limited ionic conductivities. An extensive review of the literature surrounding the structure-property relationships of charged block copolymers with varying architectures helped to inform the synthesis of novel, cationic step-growth polymers. The synthesis of a new phosphonium IL facilitated the synthesis of a segmented polyurethane containing a phosphonium-functionalized soft segment for the first time. This phosphonium polyurethane exhibited ionic conductivities comparable to literature examples of block copolymers used for ionic polymer transducers, which suggests that these materials may serve for this application as well. Carbonyldiimidazole provides a novel route towards synthesizing imidazolium ionenes with unique backbone structures. The coupling of poly(ethylene glycol) dibromides with a bis-carbonylimidazole monomer and a commercial aliphatic dibromide led to the formation of segmented imidazolium ionenes. These polymers exhibited significant atmospheric water uptake as well as water solubility. However, the physical properties of the materials suggested that the synthetic procedure resulted in low molecular weights. Suggested future work provides methods for circumventing this issue and proposes next steps for all the projects discussed herein. / Doctor of Philosophy / Emerging technologies require new polymeric materials with intentionally designed properties. Step-growth polymers such as polyesters, polyurethanes, and polyureas find use in many applications of our everyday lives. Although these materials have served mainly as commodity plastics historically, a reimagining of their syntheses and chemical structures makes them accessible for modern technologies. For example, applying green chemistry principles to the synthesis of polyureas resulted in a less toxic synthetic procedure. Polyureas synthesized through this method exhibited elastic properties comparable to classical polyureas and displayed high dielectric constants, which lend them towards use in dielectric elastomer actuators. This chemistry also allowed for the synthesis of water-soluble polyureas, which served as a material for low temperature extrusion additive manufacturing, colloquially known as 3D printing. Vat photopolymerization describes another type of 3D printing that involves the selective curing of liquid resins with light to form a 3D structure. Employing a reactive ionic liquid monomer with a commercially-relevant unsaturated polyester allowed for a nontoxic method of printing these materials, which also imparted ionic conductivity. Finally, the synthesis of positively charged polyurethanes and ionenes led to the production of ionically conductive materials that may find use in polymeric transducers.

The present thesis investigates the application of pressurized mixtures of imidazolium-based ionic liquids with traditional organic solvents for the dissolution and extraction of lignocellulosic biomass, with bamboo as a specific example of renewable biomass. The approach has been unconventional in that the focus has been on solvent mixtures in which the ionic liquid is the minor component. The objective has been to combine the solvating power of the ionic liquid with a traditional solvent such as ethanol to modulate the outcomes of solubility and extractions by tuning the parameters of fluid composition, temperature, and pressure. Working with mixtures of ionic liquids in traditional solvents as process solvents lowers the viscosity of the medium and thus reduces the transport limitations that are often encountered when working with pure ionic liquids. Among other potential advantages are the reductions in overall process cost that are associated with ionic liquids, potentially easier recovery of post-extraction products, and the recycling of the ionic liquids. This thesis has also addressed another important question regarding the thermal stability of the ionic liquids as a processing medium at elevated temperatures and pressures over time, which may negatively impact their recovery and reuse, and may lead to environmentally unacceptable consequences. The dissolution experiments were carried out in a specially designed high-pressure view-cell equipped with sapphire windows for visual or optical observations. Evaluations were made employing standard characterization tools such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, and Scanning Electron Microscopy (SEM). Thermal stability studies were carried out using a combination of a view-cell and fiber optic UV-Vis capability at high pressures (up to 350 bar) and temperatures (up to 150 ℃). The dissolution of bamboo was first explored using mixtures of 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) with ethanol at temperatures from 100 to 150 ℃ and pressures from 35 to 350 bar over 4 or 24 h extraction times. The fluid mixtures employed were in the range of 1 - 40 wt % ionic liquid, which is in contrast to relevant dissolution experiments reported in the literature which either use pure ionic liquids or have the ionic liquids as the majority component. The effects of changing the temperature, pressure, and solvent composition on the removal of different components of the bamboo were assessed. Temperature played the most significant role in the amount of material extracted from the bamboo, with higher temperatures resulting in the removal of more lignin than cellulose and greater conversion of crystalline cellulose to the less recalcitrant amorphous form of cellulose. The concentration of ionic liquid in solution was also important, with higher concentrations resulting in more dissolved biomass. Finally, increasing the pressure resulted in higher amounts of dissolved biomass. The next series of studies focused on rigorously assessing the stability of 1-alkyl-3-methylimidazolium acetate and chloride ionic liquids with alkyl chain lengths from 2 to 10 under both isothermal and non-isothermal conditions via thermogravimetric analysis. Isothermal degradation experiments were conducted at temperatures ranging from 100 to 225 ℃ over time periods ranging from two hours to three weeks. Non-isothermal degradation experiments were conducted at heating rates of 5, 10, 15, and 20 ℃/min from room temperature to 650 ℃. The activation energies and pre-exponential factors were assessed with isoconversional integral methods; the activation energies () ranged from 115 to 157 kJ/mol, and the pre-exponential factors (()) ranged from 24-38. The degradation reactions could be described as 1st order, as they often are in the literature, but were best fit by the 3-dimensional reaction model. Ionic liquids with longer alkyl chains on their imidazolium rings decomposed more quickly and at lower temperatures. The thermal stability of the most promising ionic liquids ([EMIM]Ac, [BMIM]Ac, [EMIM]Cl, and [BMIM]Cl) were then assessed more closely at the possible biomass processing conditions that were being considered. The primary interest was determining the effects of various cosolvents on the thermal stability of these ionic liquids at the process temperatures and pressures, from 100 to 150 ℃ and 35 to 350 bar. These evaluations were carried out in the same high-pressure view cell in which the extraction experiments were conducted. To assess the degradation of the ionic liquids, time-evolved UV spectra of the mixtures were generated. It was found that more protic solvents such as water attenuated the degradation of the ionic liquids, whereas aprotic solvents such as DMF significantly exacerbated their degradation. Among the ionic liquids evaluated, it was found that [BMIM]Cl had the greatest stability in ethanol at 150 ℃. The bamboo extraction experiments were then continued with mixtures of [BMIM]Cl in ethanol. The results showed that higher temperatures are necessary to extract lignin and cellulose, with [BMIM]Cl's thermal stability at these temperatures giving it the advantage over [EMIM]Ac. In this system as well it was shown that higher concentrations of ionic liquid facilitated the extraction of more biomass. However, biomass constituents that dissolve into mixtures with lower concentrations of ionic liquid readily precipitate back out of solution when the mixture is returned to room conditions. Along with the results of the studies with [EMIM]Ac, the experiments conducted with [BMIM]Cl show that an increase in pressure results in greater amounts of dissolved biomass holding other conditions constant. The thesis, in summary, presents for the first time (a) the use of ionic liquids as a minor component in organic solvents as a potential biomass processing media, (b) the thermal stability of ionic liquids in a cosolvents at high pressures and temperatures, and (c) experimental results showing that pressure can enhance the amount that can be extracted from biomass with mixtures of ionic liquids in a cosolvent like ethanol. / Doctor of Philosophy / The purpose of the work detailed in the present thesis is to better understand the effects of mixtures of ionic liquids and traditional solvents on woody biomass. Ionic liquids are organic salts with melting points below 100 ℃, and they possess unique physical and chemical properties that can facilitate the dissolution or extraction of otherwise recalcitrant materials. There is a rapidly growing need for greener and more sustainable methods of processing woody biomass, which consist of primarily cellulose, lignin, and hemicelluloses. Industrial use of these liquids as processing solvents for woody biomass is limited by their relatively high viscosity, cost, and the difficulty of separating dissolved materials back out of solution. One method used to address these limitations is to mix the ionic liquids with other solvents, such as ethanol. The studies detailed in this thesis also seek to understand the effects of temperature and pressure on both the dissolution of woody biomass and on the degradation of the ionic liquids. The studies employ both traditional characterization equipment and a custom-designed view-cell which allowed for observation and characterization at high temperatures and pressures. The first part of the study investigated the dissolution of bamboo with mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate, [EMIM]Ac, and ethanol. The effects of changing the temperature, pressure, and solvent composition on the removal of different components of the bamboo were assessed. It was found that temperature played the most significant role in the amount of material extracted, with higher temperatures resulting in the removal of more lignin than cellulose. The concentration of ionic liquid in solution was also important, with higher concentrations resulting in more dissolved biomass. Finally, increasing the pressure resulted in higher amounts of dissolved biomass. The next parts of the study focused on the degradation of the ionic liquids at elevated temperatures. The type of ionic liquids used in this study do not boil or evaporate at high temperatures, but instead break down into constituents that are themselves volatile. The thermal degradation of the ionic liquid used in the initial biomass dissolution experiments was investigated along with a series of similar ionic liquids. Their degradation behavior was assessed both by measuring their mass over time at a single constant temperature, and by heating them at a constant rate until they fully degraded. This behavior was mathematically modeled. The thermal stability of the most promising ionic liquids were then investigated in mixtures with other solvents in the high-pressure experimental cell under the same temperature and pressure conditions used in the biomass dissolution experiments. The ionic liquid found to have the best stability in ethanol in those experiments was 1-butyl-3-methylimidazolium chloride, [BMIM]Cl. Further dissolution experiments were carried out with mixtures of this ionic liquid in ethanol. These experiments took the insights gained from the previous investigations to further clarify the effects of temperature, concentration, and pressure on the dissolution of bamboo in mixtures of ionic liquid and ethanol. It was again shown that higher temperatures are necessary to extract lignin and cellulose. It was also shown that higher concentrations of ionic liquid facilitate the extraction of more biomass. However, it was also shown that biomass dissolved into mixtures with lower concentrations of ionic liquid readily precipitates back out of solution when the mixture is returned to room conditions. Pressure was again shown to have a favorable effect on the amount of material extracted.

This dissertation aims to investigate and correlate structure, dynamics and transport properties of several novel soft materials systems using multiple Nuclear Magnetic Resonance (NMR) methodologies, including solid-state NMR (SSNMR), diffusometry, and imaging, and with the help of X-ray scattering. First, we report the investigation of structure and dynamics of three polymeric membranes: hydroxyalkyl-containing imidazolium homopolymers, poly(arylene ether sulfone) segmented copolymers, and disulfonated poly(arylene ether sulfone) random copolymers using a wide array of SSNMR techniques, including: 1) ¹³C cross-polarization magic angle spinning (CPMAS) with varying cross-polarization (CP) contact time, 2) ¹³C single-pulse magic angle spinning (MAS) with varying delay time, 3) ²³Na single-pulse MAS, 4) two dimensional phaseadjusted spinning sideband (2D PASS), 5) proton spin−lattice relaxation (T₁), 6) rotating frame spin−lattice relaxation (T₁ρ), and 7) center-band-only detection of exchange (CODEX). These various types of SSNMR spectroscopic methods provide a wealth of structural and dynamic information over a wide range of time scales from a few nanoseconds to seconds. We further present a picture of rich structural and transport behaviors in supramolecular assemblies formed by amphiphilic wedge molecules using a combination of ²³Na solid-state NMR, ¹H/²H PFG NMR diffusion, relaxation and grazing-incidence small-angle X-ray scattering. Our results show that the liquid crystalline domains in these materials undergo a transition from columnar to bicontinuous cubic phases with a simple increase in humidity, while the amorphous domain boundaries consist of individual wedge molecules with a significant fraction (~ 10%) of total wedge molecules. Multiple-component diffusion of both wedges and water further confirms the structural and dynamic heterogeneity, with the bicontinous cubic phase being able to facilitate much faster water and ion transport than the columnar phase. We then develop a quantitative approach to probe the migration of two novel “theranostic” polymeric agents (combining “therapeutic” and “diagnostic” functions) into bulk hydrogels using two distinct time-resolved magnetic resonance imaging (MRI) methods. To the best of our knowledge, this is the first work that combines time-resolved MRI experiments to reliably quantify diffusivity of paramagnetic and superparamagnetic nanoparticles in bulk biological media. Our results agree closely with those obtained from fluorescence techniques, yet the capability of our approach allows the analysis of actual nanoparticles diffusion through biogels on mm to cm scales during a range of time periods. Finally, we employ a combination of NMR techniques to obtain a comprehensive understanding of ion clustering and transport behaviors of ionic liquids inside the benchmark ionic polymer Nafion. Spin relaxation shows that anion relaxation is more influenced by the fixed sulfonate groups than cation relaxation. 2D ¹H-¹⁹F heteronuclear Overhauser effect spectroscopy (HOESY) and 1D ¹⁹F¹⁹F selective nuclear Overhauser effect (NOE) spectroscopy confirm our assumption of the formation of ion clusters at low water content in the ionomer. While we observe non-restricted diffusion behavior for cations, anion diffusion is strongly restricted both between domain boundaries and within domains in the absence of water. The restricted anion diffusion can serve as a reliable probe for detailed multiscale structures of the ionomer. / Ph. D.

The present thesis explores the volumetric and transport properties of complex fluid mixtures under pressure in order to develop a better, more holistic understanding of the relationship between the volumetric properties, derived thermodynamic properties, and viscosity. To accomplish this broad objective, two different categories of fluid mixtures were examined using a combination of experimental data and models. These included base oils and their mixtures with polymeric additives, used in lubricants and ionic liquids, with cosolvent addition, for use in biomass and polymer processing. Experimental density data were collected using a variable-volume view-cell at pressures up to 40 MPa and temperatures up to 398 K. A unique high pressure rotational viscometer was developed to study the effect of pressure, temperature, and shear rate on viscosity while also allowing for the simultaneous examination of phase behavior. Viscosity data were collected at pressures up to 40 MPa, temperatures up to 373 K, and shear rates up to 1270 s-1. Experimental density and viscosity data were fit to a pair of coupled model equations, the Sanchez-Lacombe equation of state and the free volume theory respectively. From density, derived thermodynamic properties, namely isothermal compressibility, isobaric thermal expansion coefficient, and internal pressure, were calculated. By generating these models, viscosity could be viewed in terms of density, allowing for a direct link with thermodynamic properties. In the first part of the study, the effect of composition on density, thermodynamic properties, and viscosity was examined for base oils used in automotive lubricants. Six different base oils, four mineral oils and two synthetic oils, were studied to develop a better understanding on how the thermodynamic properties, particularly isothermal compressibility and internal pressure, vary with the concentration of cyclic molecules in the oil stock. Isothermal compressibility was found to decrease with cycloalkane content, while internal pressure increased. Additionally, the effect of two different polymeric additives on the volumetric properties and viscosity of a base oil composed of poly(α olefins) was examined. Both additives are polymethacrylate based, one with amine functionality, and are used as viscosity index modifiers in engine oils and automatic transmission fluids. The polymer with amine functionality was found to have a significant effect on internal pressure, seen as a large drop at high polymer concentration (7 mass percent), due to the addition of repulsive intermolecular interactions. In the second part of the study, six ionic liquids with the 1-alkyl-3-methylimidazolium cation and their mixtures with ethanol were examined. Two anions were used, chloride and acetate. The effect of ethanol addition on the derived thermodynamic properties and viscosity was studied in terms of chain length of the alkyl group on the cation. In addition, a method of estimating Hildebrand solubility parameter was employed, allowing for solubility parameter to be put in terms of pressure, temperature, and composition. The effect of cosolvent addition on the thermodynamic properties was changed by the length of the alkyl group on the cation. As the cation became bulkier, anion-cation interactions weakened, allowing for an increase in the anion-cosolvent interactions. / Doctor of Philosophy / The present thesis aims to understand both the density and viscosity of various fluid mixtures at high pressures and temperatures through both experiments and modeling. By studying these properties simultaneously, a more holistic view of a fluid can be developed to predict its usefulness for a specific application. This is especially important in the case of fluid mixtures, where, in addition to temperature and pressure, composition needs to be taken into account. To accomplish the experimental portion of this work, a new high pressure rotational viscometer was developed to measure viscosity as a function of temperature and pressure in conjunction with a preexisting technique for measuring density. This experimental data was used to create models, allowing for a better understanding of the effect of temperature, pressure, and composition on both density and viscosity along with certain thermodynamic properties. In the first part of the study, oils and additives used to make lubricants with automotive applications, such as engine oils and automatic transmission fluids, were studied. By studying the properties of these mixtures under pressure, a better understanding of how properties key to lubricant effectiveness are related to temperature, pressure, and composition can be developed. In the second part of the study, ionic liquids, salts with melting points below 100oC, and their mixtures with ethanol were studied. Ionic liquids have unique properties and have been studied for use in batteries, polymer processing, biomass processing, and gas capture. Due to the wide range of potential ionic liquids with various properties that can be made, these salts have been described as tailorable solvents. By adding an additional solvent, the resulting mixture can be tuned through temperature, pressure, and composition. Using the set of tools employed in the present work, important properties for process design were calculated. In particular, the Hildebrand solubility parameter was estimated as a function of temperature, pressure, and composition. The solubility parameter is a useful tool in predicting whether or not a material will dissolve in the solvent of choice.

Adsorption is a ubiquitous phenomenon that plays key roles in numerous applications including molecule separation, energy storage, catalysis, and lubrications. Since adsorption is sensitive to molecular details of adsorbate molecule and adsorbent materials, it is often difficult to describe theoretically. Molecular modeling capable of resolving physical processes at atomistic scales is an effective method for studying adsorption. In this dissertation, the adsorption of small molecules in three emerging materials systems: porous liquids, room-temperature ionic liquids, and atomically sharp electrodes immersed in aqueous electrolytes, are investigated to understand the physics of adsorption as well as to help design and optimize these materials systems. Thermodynamics and kinetics of gas storage in the recently synthesized porous liquids (crown-ether-substituted cage molecules dispersed in an organic solvent) were studied. Gas molecules were found to store differently in cage molecules with gas storage capacity per cage in the following order: CO2>CH4>N2. The cage molecules show selectivity of CO2 over CH4/N2 and demonstrate capability in gas separation. These studies suggest that porous liquids can be useful for CO2 capture from power plants and CH4 separation from shale gas. The effect of adsorbed water on the three-dimensional structure of ionic liquids [BMIM][Tf2N] near mica surfaces was investigated. It was shown that water, as a dielectric solvent and a molecular liquid, can alter layering and ordering of ions near mica surfaces. A three-way coupling between the self-organization of ions, the adsorption of interfacial water, and the electrification of the solid surfaces was suggested to govern the structure of ionic liquid near solid surfaces. The effects of electrode charge and surface curvature on adsorption of N2 molecules near electrodes immersed in water were studied. N2 molecules are enriched near neutral electrodes. Their enrichment is enhanced as the electrode becomes moderately charged but is reduced when the electrode becomes highly charged. Near highly charged electrodes, the amount of N2 molecules available for electrochemical reduction is an order of magnitude higher near spherical electrodes with radius ~1nm than near planar electrodes. The underlying molecular mechanisms are elucidated and their implications for development of electrodes for electrochemical reduction of N2 are discussed. / Doctor of Philosophy / Adsorption is a ubiquitous phenomenon that plays key roles in numerous applications including molecule separation, energy storage, catalysis, and lubrications. Since adsorption is sensitive to molecular details of adsorbate molecule and adsorbent materials, it is often difficult to describe theoretically. Molecular modeling capable of resolving physical processes at atomistic scales is an effective method for studying adsorption. In this dissertation, the adsorption of small molecules in three emerging materials systems: porous liquids, room-temperature ionic liquids, and atomically sharp electrodes immersed in aqueous electrolytes, are investigated to understand the physics of adsorption as well as to help design and optimize these materials systems. Thermodynamics and kinetics of gas storage in the recently synthesized porous liquids (crown-ether-substituted cage molecules dispersed in an organic solvent) were studied. Gas molecules were found to store differently in cage molecules with gas storage capacity per cage in the following order: CO2>CH4>N2. The cage molecules show selectivity of CO2 over CH4/N2 and demonstrate capability in gas separation. These studies suggest that porous liquids can be useful for CO2 capture from power plants and CH4 separation from shale gas. The effect of adsorbed water on the three-dimensional structure of ionic liquids [BMIM][Tf2N] near mica surfaces was investigated. It was shown that water, as a dielectric solvent and a molecular liquid, can alter layering and ordering of ions near mica surfaces. vi A three-way coupling between the self-organization of ions, the adsorption of interfacial water, and the electrification of the solid surfaces was suggested to govern the structure of ionic liquid near solid surfaces. The effects of electrode charge and surface curvature on adsorption of N2 molecules near electrodes immersed in water were studied. N2 molecules are enriched near neutral electrodes. Their enrichment is enhanced as the electrode becomes moderately charged but is reduced when the electrode becomes highly charged. Near highly charged electrodes, the amount of N2 molecules available for electrochemical reduction is an order of magnitude higher near spherical electrodes with radius ~1nm than near planar electrodes. The underlying molecular mechanisms are elucidated and their implications for development of electrodes for electrochemical reduction of N2 are discussed.