Block copolymer-derived nanoporous materials are featured with microstructures defined by the microphase separation of constituent blocks, enabling various applications in energy storage. Dictated by the molecular weights and volume fractions of constituent blocks, the microphase separation forms nanoscale microstructures of 1-100 nm. Selective removal of a sacrificial phase produces nanopores with tailored pore width, continuity, and tortuosity. The remaining phase customizes the properties of resulting nanoporous materials, including specific surface area, electrical conductivity/insulation, and mechanical performance. Therefore, block copolymer-derived porous materials are felicitous for use in high-performance energy storage. This dissertation presents the utilization of block copolymers to derive nanoporous materials: i) high-modulus polyimide separators for lithium-metal batteries, and ii) high-surface-area carbon electrodes for fast-charging zinc-ion batteries. In lithium-metal batteries, the dendritic growth of lithium leads to deteriorating performance and severe safety concerns. Suppressing lithium dendrites is imperative to guarantee both high performance and safe cycling. Mesoporous polyimide separators are promising for dendrite suppression: i) the mesopores are smaller than the width of lithium dendrites, preventing lithium dendrites from penetrating the separator. ii) The high-modulus polyimide ceases the growth of lithium dendrites. Herein, this dissertation reports a mesoporous polyimide separator produced by thermalizing polylactide-b-polyimide-b-polylactide at 280 °C. The mesoporous polyimide separator exhibits a median pore width of 21 nm and a storage modulus of 1.8 GPa. When serving as a dendrite-suppressing separator in lithium-metal batteries, the mesoporous polyimide separator enables safe cycling for 500 hours at a current density of 4 mA/cm2. In zinc-ion batteries, developing cathodes compatible with fast charging remains a challenge. Conventional MnO2 gravel cathodes suffer from low electrical conductivity and slow ion (de-)insertion, resulting in poor recharging performance. In this dissertation, porous carbon fiber (PCF) supported MnO2 (PCF@MnO2), comprising nanometer-thick MnO2 deposited on block copolymer-derived PCF, serves as a fast-charging cathode. The high electrical conductivity of PCF and fast ion (de-)insertion in nanometer-thick MnO2 both contribute to a high rate capability. The PCF@MnO2 cathode, with a MnO2 loading of 59.1 wt%, achieves a MnO2-based specific capacity of 326 and 184 mAh/g at a current density of 0.1 and 1.0 A/g, respectively. This dissertation investigates approaches to utilizing block copolymers-derived nanoporous materials for high-performance energy storage. Those approaches are envisaged to inspire the design of block copolymer-derived nanoporous materials, and advance the development of "beyond Li-ion" energy storage. / Doctor of Philosophy / When we talk with friends on mobile phones, accomplish works on laptops, drive back home and see family's smiling faces under lamplights, we must have noticed that our daily life significantly relies on electrical energy. Although being predominantly employed in today's rechargeable energy storage, lithium-ion batteries using graphite anodes have approached their theoretical energy limits. We are expecting better-performance batteries for a more convenient life: to fully charge our phones faster, to use our laptops for a longer time, and to drive our electric cars for a further distance. Lithium-metal batteries and aqueous zinc-ion batteries stand out for "beyond lithium-ion" energy storage because they deliver more energy and charge faster. The commercialization of lithium-metal batteries and zinc-ion batteries may benefit from revolutionary porous materials derived from block copolymers. On one hand, lithium-metal batteries employ metallic lithium anodes, storing about 10 times of energy compared to equal-weight graphite anodes and allowing faster charging rates. However, the lithium-metal anodes grow needle-shaped dendrites during cycling. Those lithium dendrites traverse the battery separator through its large pores, causing internal short circuits and even fire hazards. Suppressing lithium dendrites is imperative for safe lithium-metal batteries. Stiff separators with small pores can suppress lithium dendrites. The small pores prevent lithium dendrites from traversing, and the stiff separators cease the dendritic growth. This dissertation introduces a dendrite-suppressing separator derived from block copolymers comprising stiff polyimide blocks and vulnerable blocks. When those block copolymers form films, the vulnerable blocks spontaneously disperse as a network embedded in the polyimide. Then, the vulnerable blocks are removed at elevated temperatures to create interconnected small pores. This porous polyimide separator suppresses lithium dendrites to allow safe cycling for 500 hours, surpassing today's separators which encounter short circuits within 60 hours. On the other hand, zinc-ion batteries require fast-charging cathodes for high charging rates. A fast-charging cathode demands both good electrical conductivity and fast ion insertion. Herein, this dissertation reports a porous carbon fiber supported MnO2 cathode. The block copolymers comprise a polyacrylonitrile block and a vulnerable block. The vulnerable blocks form a network dispersing in the polyacrylonitrile fibers. At elevated temperatures, polyacrylonitrile is converted to graphitic carbon fibers, and the vulnerable network decomposes to create interconnected pores. The porous carbon fibers afford a large surface area, allowing a high loading of MnO2 to deposit as nanometer-thick sheaths. The resulting cathode combines good electrical conductivity of porous carbon fibers and the fast ion insertion in thin MnO2 sheaths, therefore, exhibiting superior fast-charging performance. This dissertation reports the methods of using block copolymers to produce porous materials for high-performance batteries. We envisage those methods to inspire the design of block copolymer-derived porous materials, and advance the development of high-performance energy storage for a more convenient life.

Bottlebrush polymers are intriguing topologies that have become more significant in various applications, including drug delivery, elastomers, photonic crystals, anti-fouling coatings, nanoporous materials, and electronic and transport substrates. Polymeric side chains are tightly grafted to a polymer backbone in these macromolecules. Bottlebrush polymers' densely bonded structure causes steric repulsion between nearby polymer chains, leading them to exhibit a chain-extended conformation. Even though these extraordinary macromolecules have several uses, the transformational promise of the bottlebrush polymer architecture has yet to be realized due to the difficulty in synthesizing large molecular weight bottlebrush polymers. This dissertation illustrates the ability of the optimized grafting-through strategy to create controlled supramolecular polymeric networks (SPNs) and different types of topologies, including block copolymers and tapered bottlebrush polymers. We show that the optimized synthesis of bottlebrush polymers using a direct-growth approach results in a controlled product and monomodal size exclusion chromatography (SEC) peaks. The optimization of the direct-growth approach depends on two factors: monomer type and percentage of monomer to polymer conversion in the reversible-deactivation radical polymerization (RDRP) step. Moreover, performing ring-opening metathesis polymerization (ROMP) initiated by Grubbs 3rd generation catalyst (G3) on a norbornene functionalized macromolecules allows for creating polymers with bulky side chains. This strategy was implemented to create methylated, acetylated, and native poly(β-cyclodextrin) that reached a degree of polymerization of 150 and molecular weights > 150 kg/mol. These results were 10-fold higher than the reported method using atom transfer radical polymerization (ATRP) with β-cyclodextrin functionalized with methacrylate group. Furthermore, multiple macromonomers were prepared using ATRP and photoiniferter polymerization that are functionalized with norbornene. These macromonomers were used in the following ROMP reaction to result in multiple series of amphiphilic bottlebrush block copolymers and tapered bottlebrush polymers. The surface tension measurements on the self-assembled amphiphilic bottlebrush block copolymer series in water revealed an ultralow critical micelle concentration (CMC), 1-2 orders of magnitude lower than its linear counterpart. Combined with coarse-grained molecular dynamics simulations, fitting small-angle neutron scattering traces (SANS) allowed us to evaluate solution conformations of micellar nanostructures for self-assembled macromolecules. Furthermore, the tapered bottlebrush polymer series SANS traces were collected to investigate their molecular arrangement in dilute solution. For the first time, summation scattering models describing both bottlebrush polymer shape and side chain polymer conformations were utilized. Using these models, we extracted physical parameters of the polymers, including bottlebrush radius and length as well as side chain excluded volume parameter and correlation length. / Doctor of Philosophy / Bottlebrush polymers are intriguing topologies that have become more significant in a variety of applications, including photonic crystals and nanoporous materials. In these macromolecules, polymeric side chains are densely grafted to a polymer backbone which causes steric repulsion between nearby polymer chains. However, even though these extraordinary macromolecules have several uses, the transformational promise of the bottlebrush polymer architecture has yet to be realized due to the difficulty in synthesizing large molecular weight bottlebrush polymers. This dissertation illustrates the ability of the optimized grafting-through strategy to create controlled supramolecular polymeric networks (SPNs) and different types of topologies, including block copolymers and tapered bottlebrush polymers. This dissertation shows that the optimized synthesis of bottlebrush polymers using direct-growth approach results in a controlled synthesis. The optimization of the direct-growth approach depends on two factors: monomer type and percentage of monomer to polymer conversion in creating the macromonomer step. In addition, performing ring-opening metathesis polymerization (ROMP) initiated by Grubbs 3rd generation catalyst on a norbornene functionalized macromolecules allows for creating polymers with bulky side chains. This strategy was implemented to create methylated, acetylated, and native poly(β-cyclodextrin) that reached a degree of polymerization of 150 and molecular weights > 150 kg/mol. Multiple macromonomers were prepared using ATRP and photoiniferter polymerization that are functionalized with norbornene. These macromonomers were used in the following ROMP reaction to result in multiple series of amphiphilic bottlebrush block copolymers and tapered bottlebrush polymers. The surface tension measurements on the self-assembled amphiphilic bottlebrush block copolymer series in water revealed an ultralow critical micelle concentration (CMC). In addition, fitting of small-angle neutron scattering traces (SANS) allowed us to evaluate solution conformations for micellar nanostructures for self-assembled macromolecules. Furthermore, the tapered bottlebrush polymer series SANS traces were collected to investigate their molecular arrangement in dilute solution. Finally, for the first time, models were used to extract physical parameters of the polymers, including bottlebrush radius and length as well as side chain excluded volume parameter and correlation length.

Lyotropic and thermotropic high strength liquid crystalline polymers have become an important area of research and development in polymeric, high performance materials. These materials have afforded excellent high temperature stability and high strength in the oriented direction, but not in the transverse direction. Hence, "balancing" the properties in both directions is an important area of research. Segmented polymers composed of an amorphous, glassy engineering thermoplastic, and an anisotropic, liquid crystalline polymer were synthesized and investigated. The isotropic phase is based upon a ductile poly(arylene ether sulfone), while the anisotropic segment is based on a rigid poly(arylate) moiety. The difunctionally terminated, controlled molecular weight poly(sulfone) oligomers were synthesized via a nucleophilic aromatic substitution reaction. Functional end groups included phenolic, acetate and carboxyl. The structure and reactivity of these oligomers was characterized by analytical techniques, including FT-IR, NMR, and polymer physical characterization methods such as, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and thermal mechanical analysis (TMA), and dynamic mechanical thermal analysis (DMTA). The well characterized, difunctionally terminated poly(sulfone) oligomers were then utilized along with ester forming monomers in a subsequent melt acidolysis reaction to form segmented poly(sulfone)-poly(arylate) co- or terpolymers. Earlier work by Lambert (281-283) showed that solution and interfacial techniques could only be utilized to synthesize segmented polymers with low poly(arylate) contents. The melt acidolysis technique allowed the synthesis of poly(sulfone)- poly(arylate) polymers with poly(arylate) contents as high as 90 weight percent. Along with a high degree of agitation, the melt acidolysis technique utilized chlorobenzene as a solvent in the initial stage of the reaction to enhance the mixing of the poly(sulfone) oligomers and ester forming monomers, allowing true segmented polymers to be formed. This was proven by FT-IR and extraction studies, which determined that very little of the original poly(sulfone) oligomer was extracted by refluxing chloroform. The morphology of these polymers was studied by polarized optical microscopy, and wide angle X-ray scattering. Low weight fraction poly(arylate) co- and terpolymers were determined to be amorphous, while higher poly(arylate) weight fraction polymers (15 weight percent or greater) were found to be semi-crystalline or liquid crystalline. Thermal analysis (DSC) also gave evidence that these materials were semi-crystalline or liquid crystalline. Also, as the weight fraction of poly(arylate) was increased, a significant improvement in solvent resistance was observed as well as an improvement in the modulus and tensile strength. / Ph. D.

Two methods for the preparation of bisphenol-A polycarbonate-polydimethylsiloxane multi-block or segmented copolymers have been investigated. The first is a solution reaction which utilized the interaction of a preformed, α,ω-dimethylamino terminated polydimethylsiloxane with a preformed, α,ω-hydroxyl terminated polycarbonate. This synthesis produces perfectly alternating block copolymers wherein the block molecular weights are equal to the number average molecular weights of the respective well-characterized oligomeric precursors. This silylamine-hydroxyl reaction is clean, efficient and can be utilized to produce copolymers which consist of a variety of block sizes ranging from approximately dimeric to 25,000-30,000 g/mole. Intrinsic viscosities of 1.0 di/g. are easily attained and mechanical properties range from being elastomeric to rigid depending on the overall bulk composition. However, these copolymers do incorporate the relatively hydrolytically unstable [the molecular geometry of the bonds between Si—O—C] moiety as the link between the block structures. Thermal analysis of these perfectly alternating block copolymers reveals their two-phase nature even at block molecular weights as low as ~ 2000 g/mole. Surface analysis of the copolymer films performed by X-ray photoelectron spectroscopy (known as ESCA) indicates preferential surface migration of the siloxane component in all cases studied. In addition, preliminary ESCA studies of blends of these materials with a commercial polycarbonate homopolymer show siloxane on the surface even when bulk percentage of siloxane is as low as 0.05 wt.%. A method for estimating the percentage of the surface area sampled by ESCA which is comprised of siloxane was developed. Results derived from this procedure indicate the particular importance of the siloxane block size in determining surface composition. The second synthetic method investigated was a phase transfer catalyzed reaction which produced a more randomly coupled block copolymer. Preformed hydroxypropyl, hydroxybutyl, or carboxypropyl terminated siloxane oligomers were used whereas the polycarbonate blocks were produced in situ. These reactions, in general, were found to be less efficient than the "silylamine reaction." However, promising results were obtained using the hydroxyl-terminated siloxanes in two cases: 1, when siloxanes of <Mn> ≃ 5000 g/mole were used and, 2, when the siloxane oligomers were capped with the dichloroformate of bisphenol-A prior to the interfacial step. When these phase transfer catalyzed reactions were carried out utilizing the carboxyfunctional oligomeric siloxanes, reasonably high molecular weight copolymers could be obtained. The best results were achieved when an anhydrous "pre-phosgenation" step was utilized. In contrast to the perfectly alternating copolymer systems previously described, these randomly coupled block copolymers contain the ≡SiC≡ bond which may be preferable in some applications (e.g. biomaterials). One problem which must be addressed for the synthesis of block copolymers derived from preformed oligomers is the separate synthesis of those oligomers. The techniques for the preparation of hydroxybutyl and carboxypropyl terminated siloxane oligomers were developed in this research. Moreover, a novel, facile method for the production of polycarbonate oligomers of well-controlled number average molecular weights was also devised. This procedure involves monofunctional capping of a calculated fraction of the phenolic end-groups prior to oligomerization by the direct phosgenation route. The hydroxyl end-groups can then be regenerated by selective hydrolysis of the protecting groups. Trimethylsilyl chloride, trifluoroacetic acid and trifluoroacetic anhydride were shown to be suitable capping reagents. Additional information pertaining to the physical characteristics of these novel copolymers was derived from collaborative studies with other colleagues at this university and at the University of Akron. / Ph. D.

The diversity of adhesive/adherend pairs has created innumerable unique combinations of thermodynamic, kinetic, chemical, physical and rheological contributions with which to explain adhesion processes. So complex are the interrelationships of these contributions to the overall composite system that little information can be extracted about the role of the adhesive properties themselves. This study attempts to simplify the number of variables influencing the strength of adhesive joints by employing a series of styrene-isoprene-styrene linear triblock copolymers as model hot-melt adhesives for titanium 6-4 alloy substrates. The block copolymer samples have narrow molecular weight distributions and styrene contents ranging from 20 to 60% by weight. For these systems a finite number of "dominant" variables are defined including 1) adherend wettabf lity, 2) mechanical properties, 3) rheology, 4) adhesive and adherend contamination, and 5) temperature-pressure cycles for joint formation. Characterization of the block copolymer series in each of these areas is presented. Copolymer morphology emerges as an important variable affecting the material and adhesive properties of these systems. The adhesive joints prepared from these samples are simple lap shear specimens. Comparative joint strengths and joint fracture energies of the series of copolymer adhesives are rationalized in terms of styrene content, styrene domain connectivity and domain orientation. Scanning electron microscopy is employed to examine the surface characteristics of the fractured adhesives. Distinctive failure features are associated with the styrene content and dissipative capacities of the adhesives. / Master of Science

Models of multiple component, multiple phase adhesives were developed to examine the conflicting demands placed on modern adhesion technology. Styrene and isoprene based block copolymers were investigated 511 order to understand their adhesive properties. The structure of the microphase separated morphology of the materials studied was found to influence the adhesive behavior in applications as hot melt/structural type adhesives and as pressure sensitive adhesives. The thermal and the dynamic mechanical behavior of linear styrene/isoprene/styrene triblock copolymers (40% and 50% by weight styrene) was determined for free films and for films bonding together two rigid adherends. Damping phenomena indicated a broader mechanical relaxation spectrum occurring at higher i temperatures in the bonded assemblies. Microphase separation in the melts of these triblock materials was interpreted as contributing to the formation of residual stresses in both free films and bonded joints under appropriate thermal and pressure histories, illustrating the importance of sample preparation. in the evaluation of multiple phase adhesive systems. / Ph. D. / incomplete_metadata

A series of perfectly alternating polyimide/ poly(dimethylsiloxane) microphase separated block copolymers ranging from 0-50 wgt. % poly(dimethylsiloxane) have been measured for permeability characteristics. The polyimide segment of the copolymers was based on oxydiphthalicdianhydride (ODPA) and 1,4-Bis(4-amino-1,1- dimethylbenzyl)benzene (Bis P). The polysiloxane was an aminopropyl terminated poly(dimethylsiloxane). Randomly segmented block copolymers of =20 wet. % poly(dimethylsiloxane) with different segment lengths were also studied, based on the same materials for the sake of comparison with the perfectly alternating versions of the same block copolymers. Permeability measurements were performed on tough, microphase separated, transparent films with O₂, N₂, CH₄, and CO₂ gases in that order. The effects of the chemical composition and block lengths on permeability coefficients and selectivity values were evaluated. The permeability of copolymer films to gases was found to be highly sensitive to the morphology of the copolymer. The morphology was found to be controlled by varying the amount and the segment length of each component and this allowed for fine control of the permeability characteristics. Conversely, the measurement of permeability characteristics can lead to more information about the morphology of complicated microphase separated block copolymers. / Master of Science

The principal purpose of this investigation was to synthesize and hydrogenate well-characterized linear and star-branched block copolymers based on butadiene and isoprene. Sequential anionic addition techniques initiated by homogeneous organolithium species in hydrocarbon solvents were employed to prepare several series of butadiene-isoprene copolymers varying in block size and architecture. Linear A–B–A poly(butadiene–isoprene–butadiene) triblock copolymers were synthesized by two different living addition techniques, e.g., three-stage process using a monofunctional anionic initiator and a two-stage process using a difunctional anionic initiator. Alternatively, the synthesis of star block copolymers involved the sequential polymerization of poly(butadiene-isoprene) diblock arms which were then linked into stars via divinylbenzene. Hydrogenation of unsaturated polymers has widely attracted attention since this provides an alternate method for improving and optimizing the mechanical, thermal, oxidative and chemical resistance properties of these technological important materials. Homogeneous catalytic hydrogenation was employed to chemically modify these linear and star-branched copolymer into thermoplastic elastomers. Hydrogenation successfully converted the soft polybutadiene blocks into hard semicrystalline polyethylene segments, while the central polyisoprene blocks resulted in the formation of amorphous alternating rubbery copolymers of propylene-ethylene. The hard semicrystalline blocks form morphological domains that serve as physical crosslinking and reinforcement sites. The presence of semicrystalline segments in both the linear and starâ branched copolymers has important significance for processing. Above the endothermic melting temperature of the semicrystalline end. blocks, the now amorphous system can approach the melt behavior of a singlephase melt, that is, displaying negligible "physical" network structure in the melt. Overall, these systems display a valuable combination of good melt processability together with physical properties characteristic of A-B-A architectures. / Master of Science

Structure-property behavior of free radical synthesized polydimethylsiloxane (PDMS) - polystyrene and PDMS-styrene derivative block polymers have been studied. The block polymers were provided by Dr. J. V. Crivello from GE. Two different types of segmented polytetramethyleneoxide (PTMO) based ionene elastomers were also investigated. The PTMO-dihalide ionenes were obtained through the courtesy of Dr. C. M. Leir in 3M, while the PTMO-dipyridinium ionenes were synthesized by Dr. B. Lee in Prof. McGrath’s research group at VPI&SU. In the free radical synthesized PDMS-PS block polymers, the molecular weight (MW) and the molecular weight distribution (MWD) of the PS blocks varied with the PDMS block length (block MW) comprising the macroinitiators, and the styrene conversion level. As the PDMS block length or the conversion level increased, the average PS block MW increased, and the molecular weight distribution of the PS block became broader. Multi-modal molecular weight distribution of the PS blocks was observed on the high conversion polymers with large PDMS blocks. As the MW and the MWD of the PS blocks changed, the morphology, the degree of phase mixing, and bulk properties of these PDMS-PS block polymers were altered as expected. At constant conversion level, the morphology of these block polymers changed from spherical PS domains in the PDMS matrix to a lamellar structure as the PDMS block length increased. As expected, their mechanical properties were also changed as morphology varied. At constant PDMS content, the systems with shorter PDMS blocks displayed elastomeric properties, while the polymers having large PDMS blocks behaved like a plastic due to a continuous lamellar morphology. The degree of phase mixing also decreased with an increase of the PS block length because of the increased incompatibility between the two block components. For a constant PDMS block length, the PS block length increased and the MWD of the PS blocks became broader when the styrene conversion level increased. Consequently, the morphology, the degree of phase mixing as well as the bulk properties of the block polymer also varied with conversion level. Addressing the segmented PTMO based ionene elastomers, these materials displayed excellent elastomeric properties which result from the ion clustering or ionic domain formation in a continuous PTMO matrix. The morphology and bulk properties of these ionene systems were strongly dependent on the strength of ionic association. By varying the ion content, the type of counter ion, or hard segment, the ionic association was changed. Therefore, the morphology and the bulk properties were also altered. Morphological textures of these ionene systems were studied by Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). Due to the strong ion clustering, an ionene rod-like morphology was observed in the PTMO-dihalide ionene elastomers by both TEM and SAXS at low volume fraction of ionene content (<7 vol%). It is the first time that these two analytical methods have distinctly led to the same end result for any ionomer system! This morphological structure is not predicted by any of existing theories of ion clustering in ionomers nor the classical theories of block/segmented polymers. Finally, the morphology of these ionene systems was altered with ion content. When the ion content was decreased by increasing the PTMO segment length, the long-range ordered structure disappeared as well as the rod-like microphase structure. A very unique phenomenon, a highly reversible modulus "jump" with increasing temperature, has been observed for these ionene materials which has not been reported before. This "jump" is directly related to the ion content, type of counter ion and the hard segment. Based on experimental evidence, the "jump" is tentatively speculated to be caused by a conformational change in the ionene hard segments. However, further investigations are needed to support or disprove this speculation. / Ph. D.

Surface and bulk properties have been studied in terms of composition and morphology of siloxane containing block copolymers and their blends with homopolymers. X-ray Photoelectron Spectroscopy (XPS) has been used to obtain the compositional information from the top 60 angstroms or so at the surface. Transmission Electron Microscopy (TEM) was utilized to probe the bulk morphology. An attempt is made to compare the bulk and the surface and find possible mechanisms governing them. It is found that solvent-cast neat block copolymers have a uniform layer at the surface that is rich in siloxane whereas their bulk has a microphase-separated domain structure. In case of blends, siloxane enrichment is quite pronounced even at bulk concentrations as low as 0.05% w/w siloxane. Amount of surface siloxane as a function of bulk content is studied with the help of XPS. At the same time, the bulk morphology of these blends is studied by TEM. The changes occurring in the surface and the bulk are found to have similar patterns. It is shown that the observed surface behavior may be related to the bulk morphology. Molecular weight of the blocks in the copolymers is found to be a very important parameter governing both the surface and the bulk properties in the neat copolymers as well as their blends. / Master of Science