京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18522号 / 工博第3914号 / 新制||工||1601(附属図書館) / 31408 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 辻井 敬亘, 教授 金谷 利治, 教授 山子 茂 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This dissertation describes the use of spherical micro- and nanoparticles as building blocks for the fabrication of colloidal crystals. The polymer component used in all of the projects that are described herein is poly-N-isopropylacrylamide (pNIPAm). The polymeric identity of particles composed of this soft, hydrogel material, which is also thermoresponsive, contributes to particle self-assembly to form ordered structures. Specifically, particles that possess a core/shell topology were investigated to allow for the localization of distinct polymeric properties. Chapter 2 examines a characterization technique using fluorescence resonance energy transfer (FRET) that was explored to investigate the structure of pNIPAm particles that possess this core/shell topology. Chapters 4-6 investigate strategies to impart both stability and flexibility to the particles so that these properties could assist in particle self-assembly as well as provide a stable construct for the production of robust crystalline materials. Styrene was used as the main monomer component in a copolymer synthesis with NIPAm to achieve poly(styrene-co-N-isopropylacrylamide particles (pS-co-NIPAm) that exhibited both hard and soft properties. Simple drying procedures were used to form crystal assemblies with these particles and the application of these pS-co-NIPAm particle suspensions as processable, photonic inks is also investigated. Chapter 7 examines the ability to physically cross-link colloidal crystals composed of pS-co-NIPAm particles by simple heating methods to produce robust films. The optical properties of these crystal films could be tuned by simple rehydration of the film due to the hydrogel character of the crystal building blocks. Chapters 3 and 5 examine the synthesis and self-assembly strategies of core/shell particles using the properties of pNIPAm shell layers that have been added to different types of core particles (silver or pS-co-NIPAm) for the purposes of fabricating colloidal crystals with enhanced properties using thermal annealing procedures. Chapter 8 explores the use of silver particles as tracers for the characterization of colloidal crystals composed of thermally annealed colloidal crystals composed of pNIPAm hydrogel particles.

As devices and new technologies continue to shrink, nanocrystalline multi-metal compounds are becoming increasingly important for high efficiency and multifunctionality. However, synthetic methods to make desirable nanocrystalline multi-metallics are not yet matured. In response to this deficiency, we have developed several solution-based methods to synthesize nanocrystalline binary alloy and intermetallic compounds. This dissertation describes the processes we have developed, as well as our investigations into the use of lithographically patterned surfaces for template-directed self-assembly of solution dispersible colloids. We used a modified polyol process to synthesize nanocrystalline intermetallics of late transition and main-group metals in the M-Sn, Pt-M’, and Co-Sb systems. These compounds are known to have interesting physical properties and as nanocrystalline materials they may be useful for magnetic, thermoelectric, and catalytic applications. While the polyol method is quite general, it is limited to metals that are somewhat easy to reduce. Accordingly, we focused our synthetic efforts on intermetallics comprised of highly electropositive metals. We find that we can react single-metal nanoparticles with zero-valent organometallic Zinc reagents in hot, coordinating amine solvents via a thermal decomposition process to form several intermetallics in the M’’-Zn system. Characterization of the single-metal intermediates and final intermetallic products shows a general retention of morphology throughout the reaction, and changes in optical properties are also observed. Following this principle of conversion chemistry, we can employ the high reactivity of nanocrystals to reversibly convert between intermetallic phases within the Pt-Sn system, where PtSn2 ↔ PtSn ↔ Pt3Sn. Our conversion chemistry occurs in solution at temperatures below 300 °C and within 1 hour, highlighting the high reactivity of our nanocrystalline materials compared to the bulk. Some evidence of the generality for this process is also presented. Our nanocrystalline powders are dispersible in solution, and as such are amenable to solution-based processing techniques developed for colloidal dispersions. Accordingly, we have investigated the use of lithographically patterned surfaces to control the self-assembly of colloidal particles. We find that we can rapidly crystallize 2-dimensional building blocks, as well as use epitaxial templates to direct the formation of interesting superlattice structures comprised of a bidisperse population of particles.

As devices and new technologies continue to shrink, nanocrystalline multi-metal compounds are becoming increasingly important for high efficiency and multifunctionality. However, synthetic methods to make desirable nanocrystalline multi-metallics are not yet matured. In response to this deficiency, we have developed several solution-based methods to synthesize nanocrystalline binary alloy and intermetallic compounds. This dissertation describes the processes we have developed, as well as our investigations into the use of lithographically patterned surfaces for template-directed self-assembly of solution dispersible colloids. We used a modified polyol process to synthesize nanocrystalline intermetallics of late transition and main-group metals in the M-Sn, Pt-M', and Co-Sb systems. These compounds are known to have interesting physical properties and as nanocrystalline materials they may be useful for magnetic, thermoelectric, and catalytic applications. While the polyol method is quite general, it is limited to metals that are somewhat easy to reduce. Accordingly, we focused our synthetic efforts on intermetallics comprised of highly electropositive metals. We find that we can react single-metal nanoparticles with zero-valent organometallic Zinc reagents in hot, coordinating amine solvents via a thermal decomposition process to form several intermetallics in the M''-Zn system. Characterization of the single-metal intermediates and final intermetallic products shows a general retention of morphology throughout the reaction, and changes in optical properties are also observed. Following this principle of conversion chemistry, we can employ the high reactivity of nanocrystals to reversibly convert between intermetallic phases within the Pt-Sn system, where PtSn2 ↔ PtSn ↔ Pt3Sn. Our conversion chemistry occurs in solution at temperatures below 300 °C and within 1 hour, highlighting the high reactivity of our nanocrystalline materials compared to the bulk. Some evidence of the generality for this process is also presented. Our nanocrystalline powders are dispersible in solution, and as such are amenable to solution-based processing techniques developed for colloidal dispersions. Accordingly, we have investigated the use of lithographically patterned surfaces to control the self-assembly of colloidal particles. We find that we can rapidly crystallize 2-dimensional building blocks, as well as use epitaxial templates to direct the formation of interesting superlattice structures comprised of a bidisperse population of particles.

Tissue response to PNIPAM and HPC nanoparticles has been studied by implantation method. The results suggest that both PNIAPM and HPC nanoparticles possess good biocompatibility and they may serve as a good carrier for the applications of controlled delivery. Rheological properties of dispersions of IPN microgels composed of PNIPAM and PAAc have been studied. It is found that the IPN microgel dispersion can undergo a sol-gel transition at temperature above 33°C. In vivo drug release experiments suggest that the gelation procedure creates a diffusion barrier and thus leads to slow release. An emulsion method has been used to grow columnar crystals by mixing PNIPAM microgel dispersions with organic solvents. Effect of both temperature and microgel concentration on formation of columnar crystals has been studied. PNIPAM-co-NMA microgels have been used for the fabrication of crystalline hydrogel films by self-crosslinking microgels. The hydrogel film exhibits an iridescent. The thermally responsive properties and mechanical properties of this film have been studied. Melting temperature (Tm) of colloidal crystals self-assembled with PNIPAM-co-AAc microgels has been investigated as a function of pH, salt concentration and microgel concentration. It is revealed that Tm increases as pH value increases; Tm decreases with increase of salt concentration; Tm increases as microgel concentration increases. Phase behavior of PNIPAM-co-HEAc microgel dispersions has been investigated. It is observed that these microgel dispersions exhibit liquid, crystal, and glass phase. As microgel size increases, crystal phase shifts to low concentration range. As temperature increases, crystal phase shifts to high concentration ranges. These colloidal crystals can be stabilized by NaOH-induced gelation. Effect of NaOH concentration on formation of physical gelation has been investigated.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23232号 / 工博第4876号 / 新制||工||1761(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 宮原 稔, 教授 松坂 修二, 教授 山本 量一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

No description available.

Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling. Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling. The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied. Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles. Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour. Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.

Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling. Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling. The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied. Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles. Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour. Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.

The efficiency of an organic photovoltaic cell depends mainly on its morphology where an exciton has to migrate to a p-n junction to create a photocurrent. Therefore the distance from the bulk of the cell to a junction interface should not exceed the diffusion length of the exciton. In this thesis, two novel lithographical methods, to produce specific polymer morphologies, were developed and evaluated. In the first method, called embedded annealing, self-assembled polystyrene colloids were embedded in a polydimethylsiloxane (PDMS) film and annealed under an electric field to produce a bi-polymer structure consisting of polymer columns in a thin film of PDMS. Polymer colloids were successfully assembled into two dimensional hexagonally close packed arrays. However, the annealing process was unsuccessful. The second method, imprint annealing, aimed to increase the aspect ratio (height/width) of thermally imprinted micrometer sized polystyrene features by annealing them in uniform electric fields. The results showed that the aspect ratio of imprinted features can be significantly increased, 21-fold, while maintaining the periodicity of the original imprint. This is in contrast to previous results where smooth polymer films annealed in uniform fields where the periodicity of the resulting structures cannot be independently controlled, and are highly sensitive to the electrode spacing. Feature sizes down to 1 µm and aspect ratios up to 4.5 were achieved using imprint annealing. / Verkningsgraden hos en hos en solcell beror, för givna material, framförallt på dess uppbyggnad. För att bidra till fotoströmmen måste en genererad exciton vandra till en pn-övergång. På grund av detta bör det längsta avståndet till närmaste pn-övergång i solcellen inte vara längre än excitonens diffusionslängd. I detta examensarbete testas två olika litografiska metoder för att åstadkomma en specifik filmgeometri lämpad för organiska solceller. Den första metoden, kallad embedded annealing, går ut på att bädda in spontant ordnade sfäriska polystyrenkolloider i en polydimetylsiloxan (PDMS) -film för att sedan vid förhöjd temperatur applicera ett elektiskt fält över filmen. Förhoppningen var att på detta sätt töja ut kolloiderna till pelare genom PDMS-filmen. I det första steget ordnades kolloiderna sponant i tätpackade hexagonala tvådimensionella gitter på kiselsubstrat. Experimenten lyckades inte med hjälp av elektriska fält töja ut kolloiderna. Den andra metoden, imprint annealing, syftar till att öka höjd/bredd -förhållandet och minska diametern hos präglade polystyrenstrukturer. Dessa ursprungliga topografiska stukturer skapas med hjälp av en tryckpressmetod kallad nanoimprinting. Dessa strukturer värmdes upp, och ett uniformt elekrisk fält applicerades över dem. Mina resultat visar att man med elektriska fält avsevärt kan öka höjd-breddförhållandet hos polymerstrukturer och samtidigt bevara periodiciteten hos de ursprungliga strukturerna. Detta står i kontrast mot tidigare resultat på släta filmer, där periodiciteten inte kan kontrolleras oberonde av andra parametrar. Med imprint annealing ökades höjd-breddförhållandet hos enskilda strukturer upp till 21 gånger. Diametrar ner till 1 µm och höjd/breddförhållanden upp till 4,5 uppnåddes.