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Microstructure Alignment and Mechanical Properties of Block Copolymer and Crystalline Polymer Thin FilmsYe, Changhuai January 2016 (has links)
No description available.
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Production of Highly-Ordered Nanocellular Foams by UV-Induced Chemical Foaming with Self-Assembled Block Copolymers / 自己組織化ブロック共重合体を用いた紫外線誘起化学発泡による高秩序ナノセルラー発泡体の作製Rattanakawin, Podchara 23 March 2022 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第23930号 / 工博第5017号 / 新制||工||1783(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 大嶋 正裕, 教授 山子 茂, 教授 佐野 紀彰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
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Study of the Morphology and Optical Properties of Propylene/Ethylene Copolymer FilmsFratini, Christopher M. 04 May 2006 (has links)
The development of a new catalyst system by The Dow Chemical Company has resulted in the production of isotactic polypropylene and propylene/ethylene copolymers with a unique defect and comonomer distribution. This work investigated the morphology and optical properties of cast and compression molded films made from the homopolymer and copolymers with up to 20 mol% ethylene comonomer. The defect distribution of the Dow Chemical copolymers resulted in materials with lower crystallinity than Ziegler-Natta or metallocene-made materials of similar ethylene content. These materials exhibited a gamma-phase crystal content ranging from 0-95%, depending on ethylene content, processing condition, and catalyst type.
The gamma-phase crystal content of quiescently crystallized copolymer films was found to significantly influence their bulk optical properties, presumably through a change in the spherulite birefringence. The bulk haze, clarity, and transparency of a homopolymer film were degraded through annealing treatments, which decreased the fraction of gamma-phase crystallinity and increased the thickness of existing lamellae, resulting in an increased intensity of scattered light and a corresponding degradation in the optical properties of the film. The haze, clarity, transparency, and gloss of the copolymer films were found to improve at higher comonomer content and higher cooling rates. The variation in the length scale and degree of disorder in the bulk morphology of films processed under different conditions was shown to correlate with the optical quality of the films, with smaller scale morphologies scattering less light and resulting in films with better optical properties.
It was also shown that no single metric can completely describe the optical quality of a polymer film; the relative importance of haze, transparency, and gloss, which depends on the intended application of the film, was discussed. The influence of surface scattering from the films was controlled through the compression molding of films using substrates of different surface roughness. The contribution of light scattered from the surface of the films was isolated and found to play a significant role in the degradation of optical quality. / Ph. D.
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Synthesis and Characterization of Multiphase Block Copolymers: Influence of Functional Groups on Macromolecular ArchitectureSaito, Tomonori 16 May 2008 (has links)
Low molecular weight liquid polybutadienes (1000 – 2000 g/mol) consisting of 60 mol% 1,2-polybutadiene repeating units were synthesized via anionic telomerization and conventional anionic polymerization. Maintaining the initiation and reaction temperature less than 70 °C minimized chain transfer and enabled the telomerization to occur in a living fashion, which resulted in well-controlled molecular weights and narrow polydispersity indices. MALDI-TOF mass spectrometry confirmed that the liquid polybutadienes synthesized via anionic telomerization contained one benzyl end and one protonated end.
Subsequently, 2-ureido-4[1H]-pyrimidone (UPy) quadruple hydrogen-bonding was introduced to telechelic poly(ethylene-co-propylene), and mechanical characterization of the composites with UPy-functionalized carbon nanotubes was performed. The composites enhanced the mechanical properties and the UPy-UPy association between the matrix polymer and carbon nanotubes prevented the decrease of an elongation at break. The matrix polymer was also reinforced without sacrificing the processability. Additionally, UPy groups were introduced to styrene-butadiene rubbers (SBRs). Introducing UPy groups to SBRs drastically changed the physical properties of these materials. Specifically, the SCMHB networks served as mechanically effective crosslinks, which raised Tg and enhanced the mechanical performance of the SBRs.
Novel site-specific sulfonated graft copolymers, poly(methyl methacrylate)-g-(poly(sulfonic acid styrene)-b-poly(tert-butyl styrene)), poly(methyl methacrylate)-g-(poly(tert-butyl styrene)-b-poly(sulfonic acid styrene)), and the corresponding sodium sulfonate salts were successfully synthesized via living anionic polymerization, free radical graft copolymerization, and post-sulfonation strategies. The graft copolymers contained approximately 9 – 10 branches on average and 4 wt% of sulfonic acid or sodium sulfonate blocks adjacent to the backbone or at the branch terminus. The mobility of the sulfonated blocks located at the branch termini enabled the sulfonated blocks to more readily interact and form ionic aggregates. The glass transition temperatures (Tg) of the sulfonated graft copolymers with sulfonated blocks at the branch termini were higher than that of copolymers with sulfonated blocks adjacent to the backbone. More facile aggregation of sulfonated blocks at the branch termini resulted in the appearance of ionomer peaks in SAXS whereas ionomer peaks were not observed in sulfonated graft copolymers with sulfonated blocks adjacent to the backbone.
In addition, similar analogues, novel site-specific sulfonated graft copolymers, poly(methyl methacrylate)-g-(poly(sulfonic acid styrene)-b-poly(ethylene-co-propylene)) (PMMA-g-SPS-b-PEP), poly(methyl methacrylate)-g-(poly(ethylene-co-propylene)-b-poly(sulfonic acid styrene)) (PMMA-g-PEP-b-SPS), and the corresponding sodium sulfonate salts were successfully synthesized. Estimated ï £N values predicted the phase separation of each block and differential scanning calorimetry (DSC) and dynamic mechanical analysis confirmed the phase separation of each block component of the graft copolymers. The aggregation of sulfonic acid or sodium sulfonate groups at the branch termini restricted the glass transition of the PEP block. This lack of the glass transition of the PEP block resulted in higher storage modulus than a sulfonated graft copolymer with sulfonated blocks adjacent to the backbone. The location of sulfonated blocks in both sulfonic acid and sodium sulfonate graft copolymers significantly affected the thermal, mechanical and morphological properties.
Lastly, symmetric (16000 g/mol for each block) and asymmetric (14000 g/mol and 10000 g/mol for each block) poly(ethylene-co-propylene)-b-poly(dimehtylsiloxane) (PEP-b-PDMS) were synthesized using living anionic polymerization and subsequent hydrogenation. The onset of thermal degradation for the PEP-b-PDMS diblock copolymer was higher than 300 ºC and PEP-b-PDMS was more thermally stable than the precursor diblock copolymer, polyisoprene-b-PDMS. DSC analysis of PEP-b-PDMS provided Tg of PDMS -125 ºC, Tg of PEP -60 ºC, Tc of PDMS -90 ºC, and Tm of PDMS -46 and -38 ºC, respectively. Appearance of thermal transitions of each PEP and PDMS block revealed the formation of phase separation. Estimated Ï N also supported the phase separation. / Ph. D.
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Cobalt Nanoparticle-Macromolecular Complexes and Their Conversion to Oxidatively Stable EntitiesBaranauskas, Victor Vincent 29 April 2005 (has links)
The goal of the research presented in this dissertation was to synthesize novel macromolecular materials that would afford oxidative stability to magnetic cobalt nanoparticles under ambient conditions. The cobalt nanoparticles were formed via the thermolysis of Co2(CO)8 in concentrated solutions of toluene containing the macromolecular dispersion stabilizers. The copolymers were designed to encapsulate the nanoparticles with a number of thin protective coatings to prevent their undesirable oxidation under ambient condtions. Cobalt nanoparticles encased with an organic glass were synthesized by stabilizing cobalt nanoparticles with poly(methyl methacrylate-co-2-vinylpyridine-g-dimethylsiloxane) whereas nanoparticles encapsulated with triazine networks were formed via the thermal treatment of cobalt particles complexed with poly(styrene-b-4-vinylphenylcyanate). Cobalt nanoparticles coated with a combination of carbonaceous and silica char were obtained by pyrolyzing cobalt particles stabilized with poly (4-vinylphenoxyphthalonitrile-co-4-vinylphenoxytriethoxysilane-g-dimethylsiloxane) graft copolymers. Moreover, cobalt nanoparticles encapsulated with either phthalonitrile networks or graphitic char were prepared via the thermal treatment of nanoparticles stabilized with poly(styrene-b-4-vinylphenoxyphthalonitrile).
Oxidatively-stable, magnetic cobalt nanoparticle complexes may be prepared by heating cobalt nanoparticles encapsulated in poly(styrene-b-4-vinylphenoxyphthalonitrile) block copolymers at elevated temperatures. The block copolymers were synthesized through the sequential anionic polymerization of styrene and tert-butyldimethylsilyloxystyrene. The silyl ether protecting groups on the second block were hydrolyzed under acidic conditions to afford poly(styrene-b-4-vinylphenol), and the pendent phenols of the diblock copolymer were chemically modified with 4-nitrophthalonitrile to afford poly(styrene-b-4-vinylphenoxyphthalonitrile). Stable suspensions of ~8-10 nm diameter cobalt metal nanoparticles were formed by thermolysis of dicobalt octacarbonyl in solutions of toluene containing poly(styrene-b-4-vinylphenoxyphthalonitrile). The cobalt-polymer nanoparticle complexes were pyrolyzed under argon to afford highly magnetic cobalt nanoparticles encased in graphitic coatings. Magnetic susceptibility measurements indicate that the cobalt-graphitic particles are oxidatively-stable and retain their high saturation magnetizations (~ 95-100 emu g-1) for at least a year under ambient conditions. / Ph. D.
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Structure–Property Relationships Of: 1) Novel Polyurethane and Polyurea Segmented Copolymers and 2) The Influence of Selected Solution Casting Variables on the Solid State Structure of Synthetic Polypeptide Films Based on Glutamate ChemistryKlinedinst, Derek Bryan 21 November 2011 (has links)
The foundational studies of this dissertation concern the characterization of segmented polyurethanes and polyureas synthesized without the use of chain extenders'molecules that are typically used to promote a microphase separated morphology that gives these materials their useful characteristics. Polyurethanes in which a single asymmetric diisocyanate comprising the whole of the hard segment were found to display poor microphase separation. Conversely, polyurethanes in which a single symmetric diisocyanate composed the hard segment were found to display good microphase separation. The more efficient packing of the symmetric hard segments also led to an increase in hard segment connectivity and hence higher values of storage moduli in these systems. When hydroxyl-terminated diisocyanates were replaced with amine-terminated diisocyanates, polyureas were formed. Here too, diisocyanate symmetry was found to play a key role with symmetric diisocyanates leading to better microphase separation. In addition, the polyurea materials displayed broader service temperature windows than their polyurethane counterparts as the relatively stronger bidentate hydrogen bonding replaced monodentate hydrogen bonding in these materials. A thread-like, microphase separated morphology was visually confirmed using atomic force microscopy. Other techniques such as ambient temperature tensile testing, and wide and small angle x-ray scattering were employed to confirm the presence of the microphase separated structure.
The investigation into the effects of diisocyanate chemistry and its symmetry was broadened to incorporate non-chain extended polyurethane materials with different soft segment molecular weights, as well as polyurethanes that did contain chain extenders. Once again the effect of using symmetric versus asymmetric diisocyanates was evident in the structure–property behavior of these systems, with symmetric diisocyanates forming materials that displayed better microphase separation and more connectivity of their hard domains.
Lastly, in a departure from the segmented copolymer area, a study was conducted into the influence of casting variables on the solid-state structure of synthetic polypeptide films based on glutamate chemistry. The effect of solvent evaporation was determined to play a key role in the morphology of these polypeptide films. Measured small angle light scattering patterns were compared to computer calculated patterns to reveal information about the structure, shape, and length scale of the polypeptide structure. / Ph. D.
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Solution-casting of Disulfonated Poly(arylene ether sulfone) Multiblock Copolymer Films for Proton Exchange MembranesLee, Myoungbae 09 June 2009 (has links)
The overall objective of the project, on which this thesis is based, is to develop a novel hydrocarbon-based proton exchange membrane (PEM) material that can produce a proton conductivity of 0.1 S/cm at the operating conditions of 50 % relative humidity and 120 oC, which is the performance target set by the U.S. DOE for automotive application. As a part of this project, our efforts have been focused on the investigation of the effects of solution-casting conditions on the final morphology and properties of disulfonated poly(arylene ether sulfone) multiblock copolymer films from the viewpoint of phase separation of block copolymers. Of equal importance to this work, is a possibility of utilizing a rheological technique for monitoring the transformation and kinetics of block copolymers during solvent removal process, which was initially examined in order to provide fundamental quantitative understanding and practical information on the solvent removal process.
Our results demonstrated that solvent selectivity and drying temperature as well as the block length had considerable effects on the final morphology and properties. The proton conductivity could be significantly increased by simply utilizing a selective solvent, dimethylacetamide (DMAC), which is good and marginal for the sulfonated and unsulfonated blocks, respectively, rather than N-methyl-2-pyrrolidone (NMP), a neutral solvent for both blocks. The drying temperature was also observed to have considerable effects on the final properties, being coupled with the effects of solvent selectivity. Also, it was shown that the multiblock copolymer consisting of longer blocks was more sensitive to the processing conditions. From the morphological study using transmission electron microscopy and small-angle X-ray scattering, evidences for the above observations were obtained.
In the second part of this dissertation, the evolution of GÎ and GË of the solutions of a styrene-butadiene-styrene (SBS) triblock copolymer in toluene was obtained as a function of concentration using a modified parallel-plate device and a rheology test scheme developed in this study in an effort to quantify the phase separation kinetics. Then, the information on the phase transformation and kinetics of the SBS block copolymer in the solution was obtained by analyzing the GÎ and GË data with the Avrami equation. The Avrami exponent was found to be approximately 1, which indicates that the phase transformation occurred by a one-dimensional growth mechanism. The rate constant showed a strong concentration-dependence. After the initial increase up to 45 vol %, the rate constant drastically decreased and, finally, converged to 0 at 70 vol %. It is believed that, at the concentration range below 45 vol %, the phase separation became more intense as the polymer molecules had more chances to interact owing to the concentration increase. However, above 45 vol %, the phase transformation became weaker due to the limited mobility of the polymer molecules, which finally led to a “kinetically frozen-in” structure, in which the polymer molecules could not move any longer. Thus, it can be concluded that the solvent removal rate is one of the dominant factors that decide the final microstructures of solution-cast block copolymer films. / Ph. D.
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Synthesis and Characterization of Highly Functional Substituted Stilbene Copolymers and Semi-crystalline Poly(aryl ether sulfone)sMao, Min 28 September 2007 (has links)
Novel, highly functional rod-like copolymers have been synthesized by alternating copolymerization of N, N, Nâ , Nâ -tetraalkyl-4, 4â -diaminostilbenes (TDAS) with maleic anhydride. Dynamic light scattering, 2H solid state NMR and persistence length measurement reveal high chain rigidity of the polymer backbone. Double quantum heteronuclear local field solid state NMR spectroscopy (2Q-HLF Solid State NMR) has been employed to investigate the chain structure of ¹³C labelled copolymer. The torsional angle of the H-13C-13C-H part of the anhydride ring was zero degrees, indicating an all cis configuration of the H-13C-13C-H moiety of the anhydride ring.
Rod-coil block copolymers containing rigid polyampholyte blocks were designed and synthesized by addition-fragmentation chain transfer (RAFT) copolymerization. The rigid polyampholytes blocks were formed by hydrolysis of alternating copolymers and the flexible coil block consists of poly(oligo(ethylene glycol) methacrylate). The rod-coil block copolymers form polyion complex (PIC) aggregates even when the polyampholyte blocks are charge imbalanced. The aggregates did not dissociate upon the addition of high concentrations of NaCl unlike the dissociation of flexible polyampholytes in NaCl solution. These unique solution properties are induced by 'like-charge attractions' of the rigid polyampholytic alternating copolymer chains.
An example, of what is birefringent to be a novel class of material, has been prepared which enables the control of the birefringence of a polymer film by controlling the rotation of aromatic groups pendant to the polymer backbone.
A linear rigid bisphenol monomer, 4,4′-dihydroxyterphenyl (DHTP), has been incorporated into poly(aryl ether sulfone)s (PAES) in a study to impart crystallization to these amorphous polymers. Three bisphenols, 4, 4′-isopropylidenediphenol, 4, 4′-(hexafluoroisopropylidene)diphenol and 4,4′-dihydroxybiphenyl have been copolymerized with DHTP and dichlorodiphenylsulfone. Only the segmented polysulfone containing 50% BP and 50% DHTP was semi-crystalline. This PAES had a melting temperature (Tm) 320°C in the first heating cycle of a DSC measurement and the presence of crystallites was confirmed by wide angle X-ray diffraction (WAXS). / Ph. D.
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Polydimethylsiloxane Containing Block Copolymers: Synthesis and Characterization of Alternating Poly(Arylene Ether Phosphine Oxide)-B-Siloxane and Segmented Nylon 6,6 -B-Siloxane CopolymersPolk, William David 10 December 2001 (has links)
Two novel classes of siloxane containing, organic-inorganic block copolymers were prepared using different synthetic approaches. The first copolymers were alternating poly(arylene ether phosphine oxide)-poly(dimethylsiloxane) systems, prepared via oligomeric silylamine-hydroxyl reactions. Secondly, segmented nylon 6,6-poly(dimethylsiloxane) block copolymers were synthesized via a non-aqueous adaptation of the "nylon 6,6 salt" hydrolytic polyamidization, using bis(aminopropyl) dimethylsiloxane oligomer as a co-reactant.
Three series of "perfectly" alternating block copolymers were produced from well characterized hydroxyl-terminated poly(arylene ether phosphine oxide) and dimethylamine-terminated poly(dimethylsiloxane) oligomers, in order to investigate both block length and chemical composition effects. Copolymerization in chlorobenzene resulted in high molecular weight materials capable of forming optically clear, nanophase separated films, which displayed unusual morphologies and good mechanical strength. Thermal gravimetric analysis showed high thermo-oxidative stability and increasing char yield with increasing siloxane content. Additional thermal and mechanical investigations provided evidence of selective phase mixing, particularly at shorter block lengths. Surface analysis showed an enrichment of the siloxane blocks at the air-polymer interface in comparison to the bulk state. This behavior increased in proportion to the length of the parent siloxane oligomers. Evaluation of selected optical properties, e.g., refractive indices, revealed linear trends resulting in values of compositionally weighted averages.
Conversely, a series of nylon 6,6-siloxane copolymers were produced from the polycondensation of preformed propylamine-terminated poly(dimethylsiloxane)s, solid nylon 6,6 salt and a corresponding amount of adipic acid to afford siloxane-amide semi-crystalline copolymers with siloxane content ranging from 10 to ~45 wt%. The characterization of high molecular weight and covalent siloxane-amide linkages was hindered by insolubility. For example, crystallinity of the nylon 6,6 precluded the use of common solution techniques, while the susceptibility of the siloxane blocks towards ionic redistribution prevented the use of strongly acidic solvents. However, development of a novel analytical technique using solid state 13C NMR and liquid-solid extraction provided evidence for the presence of covalent bonding between the dissimilar oligomer chains. Thermal gravimetric analysis of resultant copolymers revealed an increase in char yield with increasing siloxane content, a preliminary indicator of increased fire resistance, which was supported by subsequent qualitative Bunsen burner observations. Differential scanning calorimetry showed retention of the polyamide crystalline melt with levels of siloxane incorporation of up to 45 weight %.
In conclusion, two novel classes of polydimethylsiloxane containing block copolymers have been successfully synthesized, despite the complications created as a result of the polar/non-polar interactions developed between a semi-inorganic polydimethylsiloxane and the hydrocarbon based polyarylene ethers and nylon 6,6. / Ph. D.
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Block Copolymer Derived Porous Carbon Fiber for Energy and Environmental ScienceSerrano, Joel Marcos 26 April 2022 (has links)
As the world population grows, a persistent pressure on natural resources remains. Resource requirements have extensively expanded due to industrialization. Several technological advancements continually aim to alleviate these resource shortages by targeting existing shortcomings in effective and efficient material design. Practical, high-performing, and economical materials are needed in several key application areas, including energy storage, energy harvesting, electronics, catalysis, and water purification. Further development into high-performing and economical materials remain imperative. Innovators must seek to develop technologies that overcome fundamental limitations by designing materials and devices which address resource challenges.
Carbon serves as a versatile material for a wide range of applications including purification, separation, and energy storage owing to excellent electrical, physical, and mechanical properties. One-dimensional (1D) carbon fiber in particular is renowned for excellent strength with high surface-to-volume ratio and is widely commercially available. Although an exceptional candidate to address current energy and environmental needs, carbon fibers require further investigation to be used to their full potential. Emerging strategies for carbon fiber design rely on developing facile synthetic routes for controlled carbon structures. The scientific community has shown extensive interest in porous carbon fabrication owing to the excellent performance enhancement in separation, filtration, energy storage, energy conversion, and several other applications. This dissertation both reviews and contributes to the recent works of porous carbon and their applications in energy and environmental sciences. The background section shows recent development in porous carbon and the processing methods under investigation and current synthetic methods for designing porous carbon fibers (PCF). Later sections focus on original research.
A controlled radical polymerization method, reversible addition-fragmentation chain transfer (RAFT), enabled a synthetic design for a block copolymer precursor, poly(methyl methacrylate) (PMMA) and polyacrylonitrile (PAN). The block copolymer (PMMA-b-PAN) possesses a unique microphase separation when electrospun and develop narrowly disperse mesopores upon carbonization. The PMMA and PAN domains self-assemble in a kinetically trapped disordered network whereby PMMA decomposes and PAN cross-links into PCF. The initial investigation highlights the block copolymer molecular weight and compositional design control for tuning the physical and electrochemical properties of PCF. Based on this study, mesopore (2 – 50 nm) size can be tuned between 10 – 25 nm while maintaining large surface areas, and the PAN-derived micropores (< 2 nm). The mesopores and micropores both contribute to the development of the unique hierarchical porous carbon structure which brings unprecedented architectural control. The pore control greatly contributes to the carbon field as the nano-scale architecture significantly influences performance and functionality.
The next section uses PCF to clean water sources that are often tainted with undesirable ions such as salts and pollutants. Deionization or electrosorption is an electrochemical method for water purification via ion removal. I employed the PCFs as an electrode for deionization because of their high surface area and tunable pore size. Important for deionization, the adsorption isotherms and kinetics highlight the capacity and speed for purification of water. I studied PCF capacitive filtration on charged organic salts. Because PCF have both micropores and mesopores, they were able to adsorb ions at masses exceeding their own weight. The PFC adsorption efficiency was attributed to the diffusion kinetics within the hierarchical porous system and the double layer capacitance development on the PCF surface. In addition, based on the mechanism of adsorption, the PCFs showed high stability and reusability for future adsorption/desorption applications. The PCF performance as an electrosorption material highlights the rational design for efficient electrodes by hierarchical interconnected porosity.
Another application of PFCs is updating evaporative desalination methods for water purification. Currently distillation is not widely used as a source of potable water owing to the high cost and energy requirement. Solar desalination could serve as a low-cost method for desalination; however, the evaporation enthalpy of water severely limits practical implementation. Here I apply the pore design of PCF as a method for water nano-confinement. Confinement effects reduce water density and lowers evaporation enthalpy. Desalination in PCF were studied in pores < 2 nm to 22 nm. The PCF pore size of ~ 10 nm was found to be the peak efficiency and resulted in a ~ 46% reduction in enthalpy. Interestingly, the PCF nano-confinement also contributed to the understanding in competing desorption energy for evaporation in micropores. The pore design in PCF also shows confinement effects that can be implemented in other environmental applications.
Lastly, the block copolymer microphase morphology was explored in a vapor induced phase separation system. The resulting PCF properties showed a direct influence from the phase separation caused by nonsolvent. At low nonsolvent vapor, a disordered microphase separation occurred, however upon application of nonsolvent vapor, the polymer chains reorganized. The reorganization initially improved mechanical properties by developing more long-range ordered graphic chains in the PAN-derived carbon. However, at higher nonsolvent vapor concentrations, the fibers experienced polymer precipitation which resulted in bead and clump formation in the fiber mats. The beads and clumps lowered both mechanical properties and electrochemical performance. The vapor induced phase separation showed a method for enhancing mechanical properties without compromising electrochemical performance in flexible carbon fibers. / Doctor of Philosophy / Nanomaterials possess mechanical, physical, and electrical properties to address important growing demands for precious resources such as clean water and energy. Many advancements in nanomaterials focus on improving fine-tune architectures which facilitate efficiency in composites, filtration systems, catalytic systems, energy storage devices, and electronics. Carbon material has remained a valuable candidate in these fields owing to its abundancy economical cost, and excellent properties. Several carbon forms provide unique characteristics including 0D dots, 1D fibers, 2D sheets, and 3D monoliths. Of these, 1D fibers possess excellent strength, resiliency, and conductivity and have been commercially employed in modern automotive, airplanes, membranes, and conductors. However, traditional carbon fiber fabrication does not match the growing needs in performance. Therefore, in this dissertation I explore the design and processing of carbon fibers for controlled architectures. These designs were then systematically studied in filtration systems, solar desalination, and flexible electronics.
Block copolymers provide a new way to combine polymers for drastically new materials and effects. Firstly, I conducted a comprehensive study on the synthesis and composition of this block copolymer which laid the foundation for future carbon fiber design. The polymer consists of two chains – one chain to develop carbon structures upon heating; the second which decomposes into pores upon heating. Therefore, with these two chains, a highly porous carbon fiber can be created. The reaction I studied could mostly be controlled with time to change the length of each chain. Ultimately, the pore size and surface area depend on the relative lengths of each chain. Future studies, including ones in this work, could therefore tune pore size and surface area for many applications.
Carbon fibers with graphitic structure are inherently conductive and thereby attract charged molecules in a solution. Diffusion and capacity serve as major factors in these types of systems. With the aforementioned control of the carbon fibers a diffusion study was conducted with charged pollution ions. Owing to the conductive nature, a voltage supply was attached to the fibers, which would adsorb ions electrostatically, termed "electrosorption". The electrosorption performance within the carbon fibers elucidated the interconnected porous structure and how ions orientate themselves along the surface of the fibers. In addition, with the development of ion orientation along the surface of the fibers, a greater than 1:1 ratio of carbon weight to ion weight adsorbed developed owing to the diffusion and ion stacking capabilities. Additionally, the study provides deeper investigation into movement of ions within confined nano-porous material.
The ever-growing need for renewable resources such as fresh water has pressured development into more efficient material. Solar desalination has attractive qualities which makes it a focus for micro-scale studies. One of the major limitations lies in the high energy input change liquid water into vapor. At 100 °C for boiling, desalination lacks sufficient efficiency for large-scale applications in evaporation. However, by utilizing nano-scale material, the fundamental properties of water can be altered. The carbon fibers were then created with various nano-pore sizes which revealed nano-confinement effects when subject to solar heating. With the shrinking of pore sizes, the density of water also decreased. A lower density means less energy was required to convert water from a liquid to a vapor state. The carbon fibers helped reveal real applications into confinement effects on water based on pore size. Apart from just desalination, this means future environmental application can utilize this knowledge for more effective and smart designs.
The carbon fibers outstanding electrical and mechanical properties have spurred research and development since the mid-1900s. Since then, carbon fiber technologies have grown from facile and efficient productions means, to high end, high performance smart design. The work presented here furthers two major components: first, the high-performance design of porous carbon fiber; second, the fundamental principles in nano-material properties and their applications. By first constructing a design of polymer synthesis and then subsequent studies, development of nano-porous carbon energy progresses knowledge on smart and efficient designs. These materials provide a platform for future energy and environmental sciences.
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