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Publication Designing Bottlebrush Polymer Surfactants for Segregation to Fluid Interfaces(2024-09) Seong, Hong-GyuThis dissertation focuses on the synthesis, characterization, and application of amphiphilic bottlebrush copolymers and bottlebrush electrolytes, emphasizing how variations in polymer shape and size significantly influence interfacial assembly kinetics, packing efficiency, and mechanical properties. The use of a highly reactive yet stable ruthenium benzylidene catalyst (Grubbs catalyst) enabled the facile synthesis of bottlebrush polymers with different backbone and side-chain degrees of polymerization through ring-opening metathesis polymerization. This versatility allowed precise control over the resulting polymers’ shape and size. Notably, this work explores the assembly behavior of amphiphilic bottlebrush random and block copolymers at liquid interfaces, revealing distinct interfacial assembly kinetics, packing efficiency, and mechanical properties depending on the microstructure. Additionally, bottlebrush polyelectrolytes containing acrylic acid repeating units were synthesized and studied for their co-assembly with oligomeric, amine-containing counterparts in the oil phase, highlighting design principles for using bottlebrush polyelectrolytes as soft nanoparticles in liquid printing techniques. Furthermore, the amphiphilicity of core-shell bottlebrush copolymers, comprising a pH-responsive core with a hydrophobic shell, was shown to be adjustable by modulating the water pH, triggering an inversion process governed by the enthalpic penalty associated with inter-side-chain steric repulsions. Lastly, the shape and size of bottlebrush polymers was tuned during synthesis by adjusting the monomer/catalyst ratio, and through embedding redox-responsive disulfide groups along the backbone. Disulfide cleavage triggered backbone degradation, altering the final shape and size of the bottlebrush polymers.Publication Leveraging the Dynamic Nature of Allyl Sulfides for Stress, Relaxation, Recycling, and Adhesion(2024-09) Mineo, AutumnInspired by the adaptable nature of allyl sulfides, this dissertation examines how addition-fragmentation-transfer (AFT) of allyl sulfides can be leveraged to relax stress in polymer coatings, recycle vinyl-derived plastics, and improve fusion bonding between mixed materials. Our approach to designing stress dissipation in polymer coatings involved post-polymerization modification of azlactone-bearing prepolymers to install allyl sulfide linkages which rearrange to relax stress on irradiation. Film relaxation was monitored using a custom-built optical cantilever, which revealed the complete relaxation of residual stress in allyl sulfide containing coatings. In addition to eliminating residual stress and curvature defects in polymer coatings, our work expanded the chemical library of dynamic AFT materials and furthered the field of covalent adaptable networks (CANs) by highlighting synergy between dynamic bonding and coating applications. Motivated to reduce the amount of plastic waste polluting the environment, and recognizing the unique radical rearrangement of allyl sulfides, I developed a cyclic allyl sulfide (CAS) monomer that copolymerizes with an array of vinyl monomers and affords main chain allyl sulfide vii connectivity for closed-loop chemical recycling. Vinyl-derived copolymers with the additive CAS monomer possessed similar thermal properties to their homopolymer counterparts, indicating minimal changes in processability, however, allyl sulfide containing copolymers were able to be broken down by radical scission and reformed by free radical extension. Our method of chemical recycling by chain extension has the benefit of being tailorable with respect to recovery molar mass and can be easily modified to synthesize higher value products, i.e. upcycle. While the capabilities of the cyclic allyl sulfide comonomer additive are unparalleled, a dramatic relationship between molar mass and CAS copolymerization suggested the presence of undesired transfer during polymerization. In efforts to limit undesired transfer by modifying reaction conditions, CAS copolymerization was found to be compatible with atom transfer radical copolymerization, reversible addition fragmentation transfer copolymerization, emulsion copolymerization, and emulsion extension copolymerization. Undesired transfer was ultimately mitigated by non-selective radical compartmentalization in emulsion polymerization to afford high molar mass products with high concentrations of dynamic allyl sulfide linkages. Both the ability to synthesize high molar mass CAS copolymers and CAS copolymers with radically liable end groups, motivated the discovery of unprecedented AFT self-initiation by dithiobenzoate thermolysis and the use of this advancement to enable allyl sulfide exchange during ultrasonic welding as an enhanced joining technique for immiscible polymers.Publication Functional Polymer Coatings Fabricated by Chemical Vapor Deposition(2024-09) Kim, MyoungukThe overall goal of this dissertation is to fabricate functional polymer coatings by the initiated chemical vapor deposition (iCVD). The iCVD has immense potential for producing highly uniform, conformal coatings on complex surfaces with precise control over chemical composition and film thickness. The dissertation consisted of three independent chapters and the Appendix. The first chapter was “Liquid Crystalline Polymer Coatings Fabricated by Chemical Vapor Deposition”. This study aimed to deposit liquid crystalline polymer (LCP) thin films for the first time and tried to control the molecular alignments of LCPs by adjusting the surface free energy of the poly(vinyl alcohol) substrates via vapor phase reaction. We observed the different birefringence and surface topography of LCP thin films depending upon the molecular alignments. The second chapter was “Strain-Induced Order Parameter Control of Ultrathin Liquid Crystalline Polymer Films on Soft Elastic Substrates”. In this study, we used the previous knowledge of wrinkle fabrication of LCP thin film on the soft polydimethylsiloxane (PDMS) substrates by compressive strain development during the iCVD process. We controlled the wrinkle structure of LCP thin films varying the elastic moduli of PDMS substrates according to the surface wrinkle theory. We tried to align the LCPs along the stretching direction by applying the external uniaxial strain and found the effects of both strain on the order parameter of LCP thin films on the soft substrate. The third chapter was “Characterization of Ultrathin PNIPAM Copolymer Films with Different Crosslinker Flow Rates Fabricated by Chemical Vapor Deposition”. In this work, we fabricated a series of PNIPAM copolymer films with different crosslinker flow rates and found that the crosslinker flow rate affected the properties of PNIPAM copolymer films in the thin film regime. We approached the deposition kinetic to reveal the reaction order of polymerization of PNIPAM copolymer film and characterized the physical properties, thermal stability in terms of activation energy and the lowest critical solution temperature (LCST) as a function of crosslinker flow rate. Then, we summarized the conclusion of whole chapters in the dissertation and give future perspectives of functional polymers as well as the iCVD. This dissertation provided valuable insights for new chemistry and application of vapor-deposited functional polymer thin films. These findings were by not only introducing liquid crystal to the monomer library of the iCVD but also expanding our knowledge in crosslink density-dependent properties and their applications as stimuli-sensitive actuators of temperature-responsive polymer ultrathin films fabricated by chemical vapor deposition. Lastly, we showed some actual application of PNIPAM copolymer films discussed in the chapter 4 in the Appendix titled “Ultrathin PNIPAM Copolymer Film Acuators Under External Stimuli”. This work demonstrated the application of poly(N-isopropylacrylamaide), PNIPAM copolymer films as thin film actuators. We fabricated the bilayer structures of PNIPAM copolymer films; 1) on the mesoscale polymer ribbon with high aspect ratio by flow coating, and 2) free-standing thin film with gold layer deposited by sputter coating. We confirmed the PNIPAM copolymer films as actuators triggered by external stimuli using their temperature-responsive properties.Publication Self-Assembly of Linear and Bottlebrush Copolymers: Bulk and Thin Films Studies(2024-09) Hu, MingqiuMoore’s law predicts that the areal density of transistors in semiconductor devices doubles every two years. The self-assembly of copolymers have emerged as a promising alternative to yield sub-10 features on Silicon substrates. In this work, we presented a solid-state hydrolysis strategy, where a hydrophobic-hydrophobic copolymer was hydrolyzed into a hydrophilic-hydrophobic copolymer in spin-coated thin films. The solid-state hydrolysis bypassed the poor solubility of high-chi copolymers. We introduced photoacid generators into the spin-coated copolymer films so that the solid-state hydrolysis can be achieved through exposure to UV light, aligning the self-assembly closer to currently used photolithography approaches in industry. To assist characterization of film thickness and X-ray scattering analysis, we developed an open-source Python package allowing X-ray scattering and specular reflectivity to be measured at the same areal detector. The orientation of the self-assembled patterns in thin films needs to be carefully controlled because only vertical orientation is suitable for pattern transfer into substrate through sequential etching. We developed a depth-sensitive characterization method using grazing-incidence small-angle neutron scattering. We identified that the horizontal patterns persist through the entire film while the vertical patterns only exist near the polymer-air and polymer-substrate interfaces and get randomized in depths away from the interfaces. Promoting vertical orientation of the self-assembled patterns is essential for pattern transfer. We developed block copolymers with low-surface-area junctions that assemble into vertical lamellae in spin-coated thin films. The self-assembly occurred on unmodified Silicon substrates without any surface modification or external field. Moving on from linear copolymers to bottlebrush copolymers, we first summarized recent progress on the architectural effect on polymer self-assembly in a review article. It is commonly believed that bottlebrush copolymers self-assemble more rapidly than their linear analogs due to the absence of entanglements. However, we found that high-chi bottlebrush copolymers are trapped in meta-stable poorly ordered status unlike their linear analogs, which evolve into better lateral order after thermal annealing. For low-chi bottlebrush copolymers, we highlighted the conformation of the molecular backbone in the self-assembled lamellar morphologies. Bottlebrush copolymers at lower grafting densities have the backbone looping back and forth between the two sidechain domains.Publication Investigation into the Sintering Phenomena of Ultra-High Molecular Weight Polyethylene (UHMWPE)(2024-09) Zhou, YingThis dissertation investigates the sintering of Ultra-High-Molecular-Weight Polyethylene (UHMWPE) using in-situ techniques. Despite its widespread use, the manufacturing process of UHMWPE is not fully understood. Specifically, the short processing time under moderate pressure contradicts analytical models predicting particle coalescence and interfacial strength buildup, given its low surface energy and high viscosity. This research represents one of the first systematic studies dedicated to qualitatively identifying the macroscopic volume change during the overall sintering process of nascent UHMWPE powder. The goal is to monitor and reveal deformation during the manufacturing process, ultimately for a better understanding of the structure-process-property relationships of UHMWPE. The study begins with pressure-free sintering of UHMWPE nascent powder to investigate the influence of compaction pressure on the subsequent deformation of the sintering stage. Without pressure during sintering, significant expansion is observed during heating through the α-relaxation and melting. This large expansion impedes the porosity removal during isothermal sintering, therefore leading to high porosity remaining in the sintered UHMWPE and insufficient properties for applications. Since pressure is essential for porosity removal, a customized pressure sintering apparatus are developed, providing in-situ density evolution. Specifically, five distinct processes are identified including: (1) room temperature compaction; (2) subsequent densification through the α-relaxation, (3) enthalpy-driven melt explosion via crystal melting; (4) entropy-driven melt explosion due to non-equilibrium melt; (5) recrystallization under pressure. Thus, this in-situ density is applied to study varying external processing parameters and molecular architecture. The mechanical properties of sintered UHMWPE are evaluated, focusing on impact behaviors and using fracture mechanics to compare crack resistance under severe conditions. Both metallocene-catalyzed- and Ziegler-Natta-catalyzed- UHMWPE exhibit ductile fracture behaviors with significant plastic deformation, evidenced by fibrils observed through microscopy. Additionally, higher molecular weight reduces diffusion, leading to weak interface and the formation of grain boundaries. Finally, the blends of UHMWPE-HDPE is studied aiming to enhance the processibility. Interesting results are observed with a mass concentration of 20% UHMWPE in the blends. Preliminary results indicate that 20% UHMWPE can enhance load transfer ability while maintaining higher crystallinity.Publication Synthesis and Characterization of Novel Anisotropic Foams(2024-09) Daguerre-Bradford, JohnThis dissertation pertains to the investigation of innovative technologies to generate high performance anisotropic microcellular materials with unusual morphologies to understand the mechanisms of anisotropic formation and systems to control the structure and ultimate properties. First, a convenient and energy efficient method to produce anisotropic high performance polymeric foams via radically initiated cationic frontal polymerization (RICFP) coupled with chemical blowing agents (CBA) is presented. The results illustrate the development of anisotropy within frontal polymerization (FP) foam formation results from the propagating front working in concert with foam volume expansion. This can be controlled through changes in boundary conditions and front initiation position, which affect the microcellular structure and the physical and mechanical properties. Formulation changes, through the addition of nanoparticles, also affect the properties, microcellular characteristics, and kinetics of the FP process. Additionally, a similar method was developed where the microcellular structure and anisotropy is dictated by the directionality of the propagating front during RICFP from a free-standing gel and not by external confinement. This is DocuSign Envelope ID: 0570F892-1B1E-4799-9F90-7FDB4E1F15C3 viii achieved by first creating a gel where the crosslink density can be tuned by UV intensity and cure time, after which can be foamed while simultaneously creating a second network via RICFP. In this case, the microcellular morphology and ultimate properties are dictated and can be tuned through manipulating the crosslink density of the gel precursor or the formulation. Moreover, by patterning the crosslink density of the initial gel through controlled UV exposure, complex microcellular structures can be formed that are not possible in conventional foaming processes. Solid-state foaming was performed via supercritical-CO2 and superheated-water as green solvents, on an anisotropic media (e.g., fiber) to investigate how molecular orientation affects the resulting anisotropic microcellular structure. Further investigation into the use of this strategy to generate complex microcellular hierarchical constructs by templating assemblies of helically biased fibers was performed to understand their effect on the corresponding deformation. It was found that the anisotropic microcellular structure follows the direction of molecular orientation, resulting in a complex deformational response imposed by the template. That is, foams generated to create a helical bias are shown to undergo torsional deformation commensurate with uniaxial deformation when compressed uniaxially.Publication Monitoring Intermolecular Interactions and Interfacial Reactions through the Wetting Behavior of Thin Polymer Films(2024-09) Petek, EvonThe wetting behaviors of thin polymer films are known to be unique in comparison to bulk material and influenced by interfacial effects in an unknown, complex manner. Our approach to studying intermolecular interactions and their effects on wetting involves the investigation of contact angle measurements on multilayered, ultrathin polymer films and their dependence on film thickness. A large critical thickness (~100 nm) for the dependence of water contact angle measurements on polystyrene (PS) films is observed across literature. This highlights a gap in the current understanding of wetting in the ultrathin length scale, where the additive contributions from long-range vdW forces cannot fully explain the observed thickness dependence of contact angle measurements. Two crosslinked polymer bilayer systems of PS and poly(methyl methacrylate) (PMMA) are used to deconvolute wetting contributions from changes in material properties due to geometric confinement and interfacial effects due to additive, long-range van der Waals forces. Additionally, several challenges to fabricating ultrathin polymer film samples for contact angle measurements are identified. Initiated chemical vapor deposition (iCVD) is explored as a technique to fabricate large-scale, uniform polymer films of sub-10 nm thickness advantageous for wettability studies. It is determined that deposited film topography depends on iCVD conditions and the wetting favorability of the substrate. The concentration of monomer at the substrate surface (Pm/Psat) is shown to be a key variable to dictate the resulting film topography. In turn, contact angles on the films are shown to depend on iCVD conditions. This is highlighted by the development of a data management system for uniform analysis of advancing/receding contact angle (ACA/RCA) measurements, which uncovered correlations between the contact angle measurements. The need for uniform analysis of ACA/RCA is discussed, which motivates the development of an automated method to uniformly process data by a mathematical definition. This method is used to process all ACA/RCA measurements. In addition, a novel method to investigate the wettability of reactive interfaces in real-time is developed. Multiple representations of wettability as surface functionalization are achieved within a singular experiment. Overall, these findings contribute to a further understanding of the unique wetting behaviors of thin polymer films and guide future investigation of wetting via contact angle measurements.Publication Functionalization of Polycyclooctene using Thiol-ene Click Chemistry: Strategy towards Polymer-to-Polymer Upcycling(2024-09) John Chethalen, RoshniThe growing production of plastics has led to an increase in waste, posing considerable environmental challenges. Polyethylene, a significant component of landfills, does not decompose under ambient conditions. Traditional mechanical recycling often diminishes the material qualities of polyethylene, limiting its long-term usefulness. An innovative technique, upcycling through dehydrogenation and functionalization, addresses this issue by enhancing the utility of recycled materials. This study explores several methods of functionalizing dehydrogenated polyethylene, using polycyclooctene (PCOE) as a model substrate, to produce materials suitable for a wide range of applications, including adhesives and elastomers. A comprehensive investigation into the structure-property relationships was conducted to understand the impact of chemical alterations on macroscopic properties, advancing the potential applications of upcycled polyethylene. In Chapter 2, thiol-ene click chemistry with mercaptoethanol was employed to functionalize PCOE with polar OH groups. The degree of C=C conversion was linked to reaction parameters, and the functionalization significantly enhanced mechanical properties, most notably increasing ultimate shear strength in a lap joint arrangement by approximately tenfold. This suggests potential for lower temperature melt processing applications. Further research may be focused to explore how varying the molecular weight of PCOE affects its structural, thermal, and mechanical properties. Chapter 3 examines the modification of PCOE with three acid-terminated linear pendants that do not require acid group protection. Increased COOH fractions improved surface polarity while influencing crystallinity and melting temperature. Although the rubbery modulus decreased, there was no significant change in the glassy modulus as determined by DMA characterization. Broadband dielectric spectroscopy revealed multiple relaxations in highly functionalized polymers, indicating potential for self-assembly applications. Chapter 4 details the successful synthesis of linear EVSA copolymers with varying degrees of thioacetate functionalization, resulting in greater stretchability and elasticity. The EVSA-25 sample demonstrated excellent elongation and intrinsic crosslinking during melt pressing, indicating a sustainable and cost-effective method for creating specialty materials. Broadband dielectric spectroscopy showed rapid relaxation of pendant groups, suggesting potential for self-healing applications. The EVSA-25 sample also exhibited exceptional elastic recovery and reprocessing capability, maintaining material properties through multiple recycling cycles. The functionalization of PCOE with polar OH groups through thiol-ene click chemistry significantly enhanced the adhesive strength, while modifications with acid-terminated linear pendants improved surface polarity and influenced crystallinity and melting temperature. Additionally, synthesizing linear EVSA copolymers with varying degrees of thioacetate functionalization resulted in greater stretchability, elasticity, and reprocessable capabilities, maintaining elasticity through two recycling cycles. These studies highlight the potential for upcycling polyethylene using environmentally friendly processes, presenting promising avenues for developing functional materials.Publication Self-Assembly of Collagen Type II in Solutions and Hyaluronan Networks(2024-09) Chen, XuhongThe aging of the vitreous body in human eyes is associated with the aggregation of collagen type II fibrils within hyaluronan (HA) networks, leading to the formation of opacities, collapse of the vitreous, and impaired vision. This dissertation primarily explored the behaviors of native collagen type II self-assembly in solutions and HA networks. We discussed the contribution of electrostatics to the collagen self-assembly and calculated the electrostatic free energy of the staggered packing of collagen type II triple helices under varying physicochemical conditions. Using light scattering and microscopy techniques, we systematically studied the effects of ionic strength, collagen concentration, pH, and temperature on the kinetics and equilibrium structure of collagen type II in vitro fibrillization in solutions. We concluded the kinetics-structure relationship of collagen self-assembly: slow kinetics of collagen self-assembly promotes the formation of large collagen fibrils, while fast kinetics results in a high concentration of small aggregates. Under physiological conditions, the organization of collagen type II is not affected by the presence of HA in solutions. However, increasing the HA gel elasticity significantly retarded the self-assembly of collagen type II and decreased the degree of fibrillization, as probed by atomic force microscopy and fluorescence microscopy. The two components exhibit weak enthalpic interactions and mutual steric exclusion. Little effect of collagen fibrils on the swelling equilibrium of HA gels was observed under physiological conditions. Additionally, the two networks mutually reinforce in an additive way with a higher degree of reinforcement at low salt concentrations. This work provides a deeper understanding of the driving forces of collagen fibrillization and its interplay with HA networks, contributing to our knowledge of the vitreous body's failure and development of potential therapeutic approaches.Publication UNTANGLING THE MORPHOLOGY AND MECHANICAL PROPERTIES OF FLEXIBLE, FILAMENTOUS MESOSCALE POLYMER RIBBON ARRAYS(2024-05) Moed, Demi E. K.Nature leverages densely packed, high aspect ratio surface structures to moderate surface attachment. For example, the helically coiled geometry of rod-like bacterial pili allows the microorganisms to maintain surface attachment even when subjected to high rates of flow through plastic deformation. While many synthetic systems have sought to replicate these high aspect ratio structures, stiff, inflexible micro- and nanopillar surfaces are frequently limited in their aspect ratios by capillary forces. In this work, we develop and characterize high aspect ratio (100,000) arrays of flexible mesoscale polymer ribbons. These thin, filamentous mesoscale polymer ribbons offer numerous advantages over existing systems, including environmentally tunable 3D geometries, entanglements with proximal ribbons, and numerous material compositions. In this dissertation, we explore methods to fabricate and characterize pili-inspired mesoscale polymer ribbon arrays and elucidate key properties of their morphology and mechanics. We fabricate mesoscale polymer ribbon arrays through flow coating, and then visualize their 3D morphology using confocal microscopy. We identify individual ribbon positions in 3D space using computational image analysis techniques adapted from fiber composite materials and calculate key quantitative descriptors to directly compare morphological changes across samples and environmental conditions. We demonstrate and provide a scaling relationship for the decrease in ribbon curvature over time due to surface tension-induced creep. We show that drag forces dominate any morphological changes that may arise from changes to the environment’s pH. Through microcantilever bending, we measure the stress-strain curve and modulus of single mesoscale polymer ribbons and demonstrate their sensitivity to confinement effects. We showcase that mesoscale polymer ribbon arrays tangled about a cantilever follow a load-sharing model, and that the failure of the array is sensitive to both the strength of each individual ribbon and the strength of the ribbon-cantilever grip. Coating the cantilever tip with adhesive polydimethylsiloxane can improve adhesion at the ribbon-cantilever interface. Mesoscale polymer ribbons even exhibit collective wrapping behavior about droplets of perfluorodecalin. These results outline key design parameters for engineering at the mesoscale, which brings mesoscale polymer ribbon arrays closer to applications as adhesives and filters.Publication NANOMATERIALS AT LIQUID INTERFACES: FROM STRUCTURE AND DYNAMICS TO MACROSCOPIC PROPERTIES(2024-05) Fink, Zachary MarcLiquid surfaces decorated with nanoparticles (NPs) afford a promising route to materials with unique and technologically important properties and an ideal platform from which to probe particle adsorption, rearrangement, and structure. Probing these two-dimensional (2D) assemblies can reveal the kinetics, dynamics, and ordering of assemblies that possess inherently interesting optical, chemical, or physical properties. This topic has received renewed interest from the condensed matter community, yet directly visualizing the assemblies in-situ and leveraging the unique properties of NPs at these interfaces remains challenging. The thesis work detailed herein connects 2D NP assembly fundamentals to striking plasmonic, photonic, electronic, and reconfiguration properties afforded by the inherent NP properties and the fluid nature of the interface. The real time NP structure and dynamics at an ionic liquid–vacuum interface were revealed by single particle tracking using scanning electron microscopy (SEM). Upon approach to jamming, the dynamics trends were strongly particle size dependent due to the increase in particle lubrication facilitated by the ligand brush layer. Unfortunately extending the in-situ SEM technique to liquid–liquid interfaces was not possible; instead, a suite of complementary techniques including: GISAXS, GIXPCS, UV-Vis reflection spectroscopy, and pendant drop tensiometry, were used to probe the assemblies. The phase separation of plasmonic and non-plasmonic NP mixtures was examined and showed that NP size disparity and non-plasmonic NP number fraction significantly influence the adsorption process and equilibrium packing of gold NPs. Electronic or photonic properties were incorporated into liquid–liquid interfaces by the careful selection of the polymer used. Phytic acid (PA) and sulfonated polyaniline (S-PANI) ink phases showed enhanced electrical performance due to the dense packing of PA/S-PANI complexes at the interface. 3D printed all-liquid circuits could self-repair on demand after the conductive pathway was mechanically broken. Block copolymers were used to generate well-ordered interfacial films, where all colors across the visible spectrum were obtained. Finally, future directions and the design of a liquid cell TEM are discussed. Understanding how collective NP characteristics direct interfacial self-assembly is a promising step in improving current nanotechnologies to confront challenges in renewable and green energy, energy storage, and materials transportation.Publication EMBEDDING THIOLS INTO CHOLINE PHOSPHATE POLYMER ZWITTERIONS: SYNTHESIS AND INTEGRATION INTO BIOMOLECULAR MATERIALS(2024-05) Cassaro-Snyder, Deborah JThe compositional scope of polymer zwitterions has grown significantly in recent years and now offers designer synthetic materials that are broadly applicable across numerous areas, including supracolloidal structures, electronic materials interfaces, and macromolecular therapeutics. Among recent developments in polymer zwitterion syntheses are those that allow insertion of reactive functionality directly into the zwitterionic moiety, yielding new monomer and polymer structures that hold potential for maximizing the impact of zwitterions on the macromolecular materials chemistry field. This dissertation describes the preparation of zwitterionic choline phosphate (CP) methacrylates containing either aromatic or aliphatic thiols embedded directly into the zwitterion. The polymerization of these functional CP methacrylates by reversible addition-fragmentation chain-transfer (RAFT) methodology yields polymeric zwitterionic thiols (PZTs) containing protected thiol functionality in the zwitterionic units. After polymerization, the protected thiols are liberated to yield thiol-rich polymer zwitterions which serve as precursors to subsequent reactions that produce polymer networks as well as polymer-protein bioconjugates through reversible disulfide formation or by permanent addition mechanisms. Moreover, the aromatic PZTs are found to stabilize oil-in-water interfaces when evaluated by pendant drop tensiometry. Overall, PZTs represent a novel and versatile materials platform to access a variety of properties and chemistries with wide ranging potential applications in the macromolecular field, from stimuli-responsive surfactants to polymer-protein therapeutics.Publication From Micromotors to Solid Surfactants: Synthesis and Applications of Heterogeneous Polymer Particles(2024-05) McGlasson, Alex MichaelColloid science has classically concerned itself with the investigation of properties of dispersed phases in a bulk medium. This has led to the development of a rich amount of chemistry, physics, and engineering that have facilitated the evolution and maturation of this field. One of the many developments made over the last 30 years is the introduction of colloidal particles that are heterogenous in both chemistry and shape. These heterogeneities can introduce behaviors that are not achievable in homogeneous systems and that are specific to the type and class of nonuniformity. This has led to the development of numerous technologies, two of which are Janus micromotors and solid surfactants. In this dissertation, we will develop new methods to synthesize and characterize these two heterogeneous polymer particle systems. In Chapter 1, we give an overview of the field of heterogeneous particles and techniques one can use to synthesize them. We then discuss the current state of the field for both solid surfactants and Janus micromotors. In Chapter 2 we develop dynamic light scattering as a characterization method to study the bulk three-dimensional active motion of Janus micromotors. From this work we find that dynamic light scattering can successfully characterize the non-steady state bulk active motion of Janus micromotor systems. This work positions dynamic light scattering to become an advanced characterization technique for Janus micromotor systems. In Chapter 3, we study the assembly mechanism of Janus particle solid surfactants at immiscible interfaces using dynamic pendant drop tensiometry. We find that by tuning the properties of the Janus particle that one can simultaneously both the binding energy but also the kinetics of assembly. In Chapter 4, we develop a new dimensionless number termed the active Bond number which can be used to analyze the deformation of immiscible interfaces by active matter and self-propelled colloids. We find that the active bond number is highly successful at predicting deformations for multiple experimental systems and can be broadly useful. We then conclude the dissertation with a summary of work and a future perspective on the fields of heterogeneous particles.Publication Bottlebrush Networks: An Emerging Architecture(2024-05) Clarke, Brandon R.Recent advances in our fundamental understanding of soft tissues and robotics have spurred a desire to create intricate, robust devices suited to a variety of applications (e.g. wound dressings, soft actuators, additive manufacturing, etc). This revolution is currently constrained by the bottleneck of contemporary soft materials available to researchers. To truly expound upon these growing research areas, the next generation of soft materials must be tailored to host unique, multifunctional properties. Such materials are realizable in the form of polymeric networks, which are ubiquitous as the basis for a large range of materials with a continuum of properties (e.g. adhesives, membranes, and structural materials). The precise, coded design of polymeric building blocks will expand the available window of materials to include those hosting the unique properties required for next-generation device fabrication. Of specific interest among such polymeric building blocks are bottlebrush networks (BBNs). BBNs contain a large array of architectural parameters that position them strongly to serve as a foundation upon which chemists may engineer desirable properties. Despite the apparent malleability of the BBN architecture, a lack of chemical diversity has severely hindered its progression as a materials platform. This shortcoming stems largely from the architecture’s origin in the physics discipline, where BBNs have historically been synthesized via radical polymerization methods using low Tg side chains (resulting in BBEs). This dissertation focuses on building out the BBN platform using the unique benefits of living polymerization methods—specifically ring-opening metathesis polymerization (ROMP). Chapter 1 details fundamental BBN knowledge, providing a solid foundation for which to build upon for the remainder of the thesis. Chapter 2 focuses almost entirely upon synthesis, in particular macromonomers and bottlebrush controls by which to gauge BBN kinetic chain lengths (RKs). Chapter 2 further illustrates BBN syntheses by detailing the first homopolymer BBNs synthesized with poly(ethylene glycol) [PEG]. Chapter 3 focuses on the synthesis and characterization of bottlebrush amphiphilic polymer co-networks (B-APCNs) containing both PEG and poly(dimethyl siloxane) [PDMS] side chains. Synthesized B-APCNs are shown to have tunable mechanical properties controlled by manipulating the volume fractions of either PEG or PDMS side chains, suppressing the organization of chains into discrete crystalline domains. Chapter 4 demonstrates how the level of molecular defects in BBEs synthesized via free radical polymerization and ROMP affect their mechanical properties through the development of a new parameter coined the “structural efficiency ratio”. This SER demonstrates that ROMP-based PDMS BBEs form stress-supporting strands rather ineffectively (14%) at [0.11 M] concentrations. Chapter 5 illustrates how manipulation of RK during living polymerization impacts the structure and mechanical properties of networks, importantly introducing the concept of “network constitutional isomers” [NCIs]. These NCIs are demonstrated to have dramatically different molecular structures because of minor variations in polymerization chemistry—the amount of catalyst and type of catalyst. Chapter 6 combines insights from chapters 3-4 to build defects into BBEs—a design philosophy termed “defect-driven design” (D3)—by synthesizing ultra-low crosslink density samples. These D3 BBEs are further demonstrated to perform exceptionally well as pressure sensitive adhesives, with the hydrophobic PDMS side chains used allowing for underwater adhesion to become possible.Publication Effects of Polymer-Nanoparticle Interactions on the Dynamics of Attractive Polyhedral Oligomeric Silsesquioxane Nanocomposites(2024-02) Young, Walter WPolyhedral oligomeric silsesquioxane (POSS) had long been recognized as a critical building block for inorganic-organic hybrid materials with unique and desirable properties and performance. Through synthesis and characterization of polymer/POSS nanocomposites, direct insights into the significant effects of the polymer/POSS interactions on the resulting material properties are obtained. Random copolymers of a hydrogen-bond accepting monomer and a non-interacting monomer are synthesized and loaded with a model amine-functionalized hydrogen bond donating POSS molecule via solution casting, to create a material with well-controlled dynamical heterogeneity. The increase in the glass transition temperature (Tg) of these materials is found to strongly depend on the number of interacting groups in the system. Essentially, the effect of increasing the POSS loading is the same effect as increasing the number of interacting monomers in the copolymer. Likewise, POSS molecules with a variable number of amines were synthesized and loaded into a hydrogen bond accepting homopolymer. Similar to what was observed for the random copolymers, increasing the functionality of the nanofiller increased the Tg enhancement effect. To probe the purported effects of POSS molecules on entanglement dynamics, composites were prepared with a range of polymer molar masses. Across these materials, critical rheological timescales were observed which point to a relaxation process that occurs independently of the presence of entanglements, and scales exponentially with POSS loading. Attempts to probe this process with other experimental techniques such as dielectric relaxation spectroscopy were inconclusive due to competing experimental effects at similar frequencies. Overall, these results on highly controlled model materials reveal the role of specific nanofiller interactions on the properties of polymer composites.Publication Harnessing Nanocellulose for Sustainable Carbon Capture: Synthesis, Processing, and Performance Evaluation(2024-02) Wassgren, Jerred CScientists and governments have recognized the need for environmental remediation, most notably with the adoption of the Paris Agreement in 2016. One of the major concerns is the production of greenhouse gases (GHGs). The major GHG is carbon dioxide (CO2) in which humans emit over 36 gigatons yearly. Atmospheric CO2 is responsible for 60% of the heat retained by the earth – resulting in rising temperatures, melting ice caps, and increasing ocean acidification. Therefore, a major goal of the Paris Agreement was to reduce GHG emissions as well as the capture of CO2 from the atmosphere. Here within, a sustainable nanocellulose aerogel is synthesized and characterized for the intended application of CO2 capture. First, arginine, a sustainable amino acid with high amine content, is grafted onto the surface of cellulose nanofibers. Through the water-soluble coupling reactions known as EDC/NHS coupling, it was possible to achieve an arginine loading of 0.78 mmol/g; or near 100% maximum possible grafting of arginine. Following this grafting, aerogels of both the grafted and ungrafted cellulose nanofibers are then processed into aergoels using a sustainable process pioneered by the Carter group. This process results in mechanically robust aerogels, with a modulus of 15.4 MPa, one the highest moduli for highly porous nanocellulose aerogels. These aerogels are then subjected to CO2 adsorption studies using a custom laboratory built instrument. When grafted, we find that the arginine significantly improves the CO2 adsorption compared to the unmodified fibers. Furthermore, this adsorption is relatively fast (< 5 minutes), significantly faster than current nanocellulose CO2 adsorbents.Publication Developing Nanostructured Carbonaceous Material (Graphene and Porous Carbon) from Polymers for Energy Storage Devices(2024-02) Bhardwaj, AyushCarbonaceous material including porous carbon and graphene are extensively investigated and employed in numerous application areas especially energy storage and conversion, filtration, catalysis, and mechanical metamaterial enabled by their exceptional properties. However, producing these material often demand precise control over structure property relationship and also involve extremely high temperature in inert atmosphere with long processing time which has been a limiting factor in their high throughput production. This dissertation presents technological innovation in producing carbonaceous material (i.e., graphene and porous carbon) using simple yet effective and scalable approach with the focus on improving their energy storage capabilities for both micro and structural devices. Chapter 1 introduces the concept of supercapacitors a promising next generation energy storage devices with the brief discussion on the current fabrication method of porous carbon and graphene as a super capacitive electrode material. Chapter 2 presents a photothermal method for fast, efficient, and scalable preparation of high-quality, few-layer graphene films on large area. The process involves one step photothermal conversion of polymeric material into graphene using high intensity xenon flash lamp at ambient conditions without any catalyst. Of various polymeric material investigated, cyclized polyacrylonitrile resulted in the graphene with less defects in its structure as confirmed by Raman spectra. The mechanism of photo thermal conversion of polymeric material into graphene is also elucidated. Moreover, the utility of the photothermally produced graphene is demonstrated by preparing graphene film electrodes onto a carbon fiber current collector for supercapacitors. The graphene electrodes exhibited capacitance of 3mF/cm2 a nominal regime for carbon-based devices. Chapter 3 builds upon the previous chapter and focuses on the preparation of high-performance supercapacitor using the already developed photothermal processing. Specifically, polyaniline a rod like polymer resulted in the graphene with interconnected porous structure and oxygen doping a desired trait for supercapacitors. Along with it, polyaniline offered several additional advantages as compared to polymers explored in previous chapter for graphene preparation such as it can be grown electrochemically on conducting substrates enabling the rapid synthesis of polymeric material directly onto the desired substrate, including carbo fiber. A remarkable capacitance in excess of 150 mF/cm2 (at least fortyfold increase compared to graphene produced conventionally) is obtained for polyaniline derived graphene without any post processing/modification. Furthermore, the photothermal strategy allowed the one-step preparation of supercapacitor devices on areas exceeding 100 cm2, yielding an absolute areal capacitance of 4.5 F. The proportional increase in capacitance with device area facilitates scaling and suggests the commercial applicability of this sustainable approach for low-cost, energy-efficient, and high-throughput production of lightweight, high-performance graphene-based supercapacitor devices. Chapter 4 introduces the preparation of large-pore (40 nm) ordered mesoporous carbon by rapid thermal annealing (RTA) of precursor films structured by brush block copolymer-mediated self-assembly. Ultrafast RTA processing (~50oC/s) at elevated temperatures (up to 1000oC) allowed the generation of stable, conductive, turbostratic mesoporous carbon films in minutes. Porous carbon prepared on stainless steel at 900oC demonstrated exceptionally high areal and volumetric capacitances of 6.3 mF/cm2 and 126 F/cm3 (at 0.8 mA/cm2 using 6M KOH as the electrolyte), and 91% capacitance retention after 10,000 galvanostatic charge/discharge cycles. Post-RTA conformal V2O5 deposition yielded pseudo capacitors with 10-fold increases in energy density (20 μWh cm-2 μm-1) without adversely affecting the high-power density (450 μW cm-2 μm-1). The use of RTA coupled with BBCP templating opens avenues for scalable, rapid fabrication of high-performing carbon-based micro-pseudocapacitors. Chapter 5 builds upon the previous chapter by integrating the self -assembled of brush block copolymer with nano imprinting lithography to increase the performance of micro-supercapacitor on limited footprint area. In this project, high aspect ratio nanofeature of porous carbon was prepared to increase the accessible surface area per unit area. Mechanical properties of nanoporous carbon were also determined. Remarkably, these material exhibit ultrahigh strength similar to or even higher than the tenth of Young's modulus (E), the most widely used approximation of a fundamental upper limit of material breaking strength. None of the engineering materials exhibit a comparable combination of density, strength, deformability, and damping capability. The results of this study provide a great promise of amorphous carbon nanopillars and their nanoporous structures as a superior structural nanomaterial.