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Enzyme-linked Immunosorbent Assay (ELISA) serves as a fundamental tool for the selective and sensitive detection of various analytes, including antibodies, pesticides, antibiotics, proteins, and pathogens, playing a crucial role in biomedical diagnosis, chemical quality control, and the detection of hazardous chemicals in foods and environments. Despite its widespread use, conventional ELISA faces limitations such as high costs, limited scalability and flexibility for personal use, challenges in simultaneously examining multi-target chemicals at low concentrations, and reliance on specialized instrumentation and trained personnel. In response to these challenges, paper-based ELISA (p-ELISA) emerged as an alternative, using fibrous and microporous platforms to offer increased surface area, reduced cost, and ease of use. However, the inherent heterogeneous structure of paper and fibrous membranes, particularly in the vertical direction, impedes the penetration of large biomolecules, leading to less biomolecule incorporation and, consequently, reduced sensitivity and inhomogeneous colorimetric signals. Addressing these deficiencies, this dissertation introduces a novel biosensing platform based on chemically modified melamine foam (MF) with a three-dimensional (3D) reticulated macroporous structure. Our study has proven that this foam-based ELISA (f-ELISA) platform to be rapid, sensitive, additive, and volume-responsive, showcasing its versatility across various ELISA methodologies, including direct, competitive, and sandwich ELISA. Moreover, the platform's adaptability to varied ligands, such as antibodies, nanobodies, and peptides, alongside its capability to accurately detect a wide range of targets, including biomarkers, antibiotics, environmental toxicants, pathogens, etc., underscores a substantial improvement upon conventional and paper-based ELISA techniques. Specifically, Chapter 1 summarizes the background information on current detection techniques and applications of melamine foam in varied fields. In Chapter 2, a novel, highly sensitive, naked-eye detectable colorimetric biosensor was developed based on chemically modified melamine foam (MF). This platform is designed for the rapid, on-site detection of various environmental hazards and toxicants in fluid systems. Using the unique three-dimensional reticulated macroporous structure of MF, this platform enables the fast and efficient transfer of biomolecules, ensuring enhanced sensitivity and broad applicability across multiple detection methods, including direct, competitive, and sandwich ELISA. This advancement of f-ELISA technology demonstrates significant improvements over traditional and paper-based ELISA methods, offering an alternative solution for environmental monitoring and potential healthcare applications.In Chapter 3, the application of f-ELISA in the detection of bacterial cells could further demonstrate the advantages of the macroporous features offered by the chemically modified MF as mentioned in Chapter 2. In essence, this study paves the way for a rapid, sensitive, and volume-flexible biosensing platform, using E. coli O157:H7 as a proof of concept, which holds promise for the rapid and ultrasensitive detection of various pathogenic bacteria in real-world applications.In Chapter 4, the study elaborates on refining the foam-based ELISA (f-ELISA) platform developed in Chapter 2 and Chapter 3, showcasing its expanded versatility and efficacy for onsite detection applications. Through different chemical modifications to melamine foam, the research developed a macroporous 3D substrate that effectively binds various ligands, including antibodies, nanobodies, and peptides. This study highlights the platform's adaptability, affordability, and user-friendly design, making it a versatile and effective tool in diagnostics, offering broader applications, and improving detection processes in various fields. Lastly, Chapter 5 summarizes the invention of the f-ELISA system and its applications under different scenarios.

Point-of-care (POC) diagnostics have emerged as a critical tool in modern healthcare and agriculture, offering the potential to revolutionize disease detection and management, particularly in resource-limited settings. By enabling rapid, on-site testing without the need for specialized laboratory equipment, POC diagnostics can significantly improve patient outcomes, reduce healthcare costs, and enhance disease surveillance capabilities. Polydiacetylenes (PDAs) are a unique class of polymers with conjugated backbones that undergo a colorimetric blue-to-red transition in response to various stimuli, making them promising candidates for simple, visual detection systems. This dissertation explores the development and optimization of PDA-based sensors for point-of-use diagnostic applications. A systematic investigation of liposome synthesis parameters is conducted, identifying optimal conditions for uniform and responsive PDA assemblies. The effects of diacetylene monomer structure and lipid doping on sensor performance are examined, revealing that shorter alkyl chains and moderate lipid incorporation enhance sensitivity while maintaining stability.Efforts to develop antibody-functionalized PDA sensors for detecting plant pathogens and model proteins are described, highlighting both the potential and limitations of this approach. To overcome challenges encountered with antibody-based systems, an alternative strategy using small-molecule ligands for protein detection is explored. Throughout the work, emphasis is placed on creating robust, reproducible protocols suitable for point-of-use applications.The insights gained from this research contribute to the broader understanding of PDA-based biosensors and provide a foundation for their future development as accessible diagnostic tools for healthcare and agricultural applications.

The following dissertation discusses the development of reactions that transform polyolefins, selectively cleave polyolefins, and furnish materials with circular economies to address the limitations of commodity plastics. These reactions include the synthesis of circular polymers from renewable natural sources that undergo reversible cleavage of siloxane linkages, derivatization of oxyfunctionalized polyethylenes to furnish materials of higher value with greater reuse, and incorporation of functional groups into the backbone of polyethylene to imbue new properties to the polymer and incorporate cleavable linkages for selective degradation of polyethylene. The development of transition metal-catalyzed C–H acyloxylation reactions of polyolefins will also be discussed.Chapter 1 is an overview on the synthesis, application, and limitations of polyolefins. Strategies that could potentially overcome the limitations of polyolefins and examples of them in the literature are discussed in detail.Chapter 2 discusses the synthesis of monomers from the hydrosilylation of plant oils to furnish polyesters, polycarbonates, polyamides, and polyurethanes with in-chain siloxane linkages that enable programmed depolymerization. Acid-catalyzed siloxane metathesis enables the depolymerization and repolymerization of select polymers at the siloxane linkages. Studies on the microbial digestion of isotopically labelled fragments after enzymatic hydrolysis of these polymers suggest that the main chain of the polymer is metabolized to carbon dioxide in soil.Chapter 3 discusses methods to derivatize pendent ketones and alcohols of oxyfunctionalized polyethylene to incorporate esters and oximes to the backbone to generate monofunctional polyethylenes that can be accessed from waste polymers. Judiciously selected conditions highlight the challenges of performing reactions on polymers. The esters and oximes imbue the monofunctional polyethylenes with enhanced properties when compared to unmodified polyethylene. In addition, these functional groups enable recovery through removal of the functional group or selective dissolution to recover the starting polymers for reuse.Chapter 4 discusses incorporation of in-chain amide linkages in polyethylene through Beckmann rearrangement. The resulting long-chain polyamides possess similar bulk properties as unmodified polyethylene yet have improved surface properties over unmodified polyethylene. These polyamides cannot be synthesized through step-growth or ring-opening polymerization. Hydrogenolysis of the amide linkages furnish telechelic alcohols and amines demonstrating a method to selectively cleave materials derived from polyethylene. These amine- and alcoholterminated fragments were reacted with diisocyanate linkers to furnish polyurea-urethane elastomers with valuable properties.Chapter 5 discusses the development of nickel-catalyzed C–H acyloxylation of polymers to furnish pendent esters in one chemical step. These ester-containing polymers have enhanced properties from unmodified polyethylene and can be accessed readily from abundant base metals and peroxides.

Materials engineering depends on a thorough understanding of the structure-property relationships in order to rationally design better materials. In polymer science, information about the structure of the material generally comes from scattering techniques, such as wide angle X-ray scattering or neutron scattering. These scattering experiments produce information about the material's structure in reciprocal space, so there can at times be ambiguity in the results when transitioning to real space. Transmission electron microscopy (TEM) is widely used in the materials science community to produce direct, atomic-scale images of hard materials. However, special techniques are needed to image polymeric materials with TEM due to the inherent radiation sensitivity in these soft materials. A series of techniques termed cryo-EM have been developed by the structural biology community to produce atomic-resolution images of proteins. Cryo-EM has only sparingly been applied to synthetic polymers, yet it is a promising tool to advance polymer science. This dissertation focuses on the application of cryo-EM techniques to study the atomic structure of synthetic polymers. The atomic-scale images of the polymers are combined with other material characterization data, molecular dynamics simulations, and TEM image simulations in order to understand the governing interactions that control self-assembly at the atomic level. The direct, atomic-scale imaging of synthetic polymer materials serves to advance material engineering by uncovering the structure-property relationships starting at the atomic scale. Chapters 2, 3, and 4 provide detailed studies in using polypeptoids, which are synthetic polymers with a monomer unit similar to peptides, to uncover the effect of single atom substitutions, ionic interactions, and fixed charges on the self-assembly of these materials. Polypeptoids are a great model system to study self-assembly because their unique submonomer synthesis method grants the ability to precisely vary single atoms within the polymer structure. Chapter 2 starts with using this ability to study the effect of halogen substitutions on the self-assembly and crystal motifs of polypeptoid nanosheets. Chapter 3 investigates the effect of fixed charges and condensed counterions in polypeptoid nanofibers. Chapter 4 details an investigation into the effect of fixed charges and charge density on polypeptoid self-assembly. Chapter 5 applies the same cryo-EM techniques to a conventional diblock copolymer in poly(ethylene oxide)-b-polystyrene (SEO). New synthetic routes were established to create single crystals of SEO with a lithium salt whereby the lithium salt was fully incorporated in the crystal. The single crystals of SEO were imaged with atomic-scale resolution to study how the arrangement of polymer chains changes in response to different amounts of lithium salt. Image simulation based on known crystal structures was used to bring greater understanding to the atomic-scale images.

Molecular weaving is the realization of a macroscopic principle on a molecular level. Whereas the concept of interlocking, as observed in chains and fences, can be translated to the molecular level by designing molecularly interlocked molecules (MIMs), the technique of weaving single threads into a pattern is not easily recreated. This can be attributed to the necessity for the formation of extended structures with a high degree of order as weaving fundamentally involves an ordered assembly of single strands into various patterns. Reticular chemistry is uniquely qualified to solve this problem as it involves the design and synthesis of multidimensional, crystalline, and porous extended framework structures by connecting different building blocks through strong bonds. By combining strategies from both MIMs and reticular chemistry, molecular weaving was first realized in 2016 in covalent organic frameworks (COFs) by the Yaghi lab. Because MIMs have been implemented as molecular machines and investigated for their mechanical behavior, the question of the effect of molecular weaving on the overall properties of the material remained unanswered.This dissertation focuses on elucidating the effect of molecularly woven nanocrystals as additives in polymer matrices. The challenge of capturing how molecular weaving influences a material’s properties lies within the small size of the synthesized crystals. As many mechanical engineering techniques are designed to analyze macroscopic samples, the nanometer-sized woven crystals aren’t easily characterized. By utilizing them as fillers in polymers, we are able to study the effect of molecular weaving on a macroscopic scale.Chapter I provides a general introduction into reticular chemistry and its potential to address important problems related to climate change and realize complex concepts such as molecular weaving. I will be discussing the history of reticular chemistry and its materials, followed by a clear definition of this field of chemistry. The chapter concludes with an outlook into the present and future of reticular materials in applications such as molecular weaving.Chapter II introduces the core concept of molecularly woven nanoparticles as additives in different polymers. By leveraging molecular weaving and the inherent porosity of the COF, polymers are able to interact with the pore system by threading through the framework. This leads to the formation of so-called polymer-COF junctions that are able to template polymer entanglement and provide additional pathways for energy dissipation during stress.Chapter III expands upon polymer-COF composites by investigating a molecularly interlocked framework and its effect on the mechanical behavior of the composites. By comparing the behavior of the interlocked COF as an additive both with the woven COF and the demetalated version of itself, more insight into the interactions between polymer matrix and mechanically bonded framework structure can be gained.Chapter IV delves into the scaling of woven COFs and their translation into polymer-COF composites with polycarbonate (PC) and polydimethylsiloxane (PDMS). Additionally, the scaling of a series of mechanically bonded COFs is discussed, and a new pathway to accessing metal-free woven structures is presented.Chapter V discusses the expansion of molecular weaving from three-dimensional (3D) to two-dimensional (2D) COFs. By controlling the angles of the linkers between the tetrahedral weaving nodes, the formation of 2D woven structures can be achieved from generally 3D-directing starting materials.Chapter VI covers an educational research study that introduced a group of high school students to cutting-edge research through an accessible, low-tech synthesis of a water harvesting MOF. Additionally, the participants learned about concepts such as water scarcity and the importance of finding alternate ways to access clean drinking water.Chapter VII serves as a conclusion to the topic of woven COFs and their ability to enhance the mechanical behavior of polymer-COF composites. This chapter also serves as a perspective for future investigations in this field of research.

Integrating sustainability into high-performance polymers is at the forefront of research efforts to reduce the environmental adverse impact of plastics. Recent approaches have benefited from the reversible chemistry to recycle and degrade materials. Among the promising strategies, Diels–Alder (DA) cycloaddition offers exceptional features, including synthetic ease, absence of catalysts, and the thermally-activated retro-DA (rDA) reaction. The implementation of accessible DA building blocks (e.g., furan and maleimide as the diene-dienophile pair) has provided the synthetic toolbox to fabricate self-healing and degradable thermosets. However, when used as reversible step-growth polymerization, the traditional diene-dienophile or two-component systems generally suffer from the inherent mismatch in stoichiometry, solubility, and/or low rDA temperature (i.e., ~100 °C for furan-maleimide adduct). In comparison, cyclopentadiene (Cp) can serve as a dual role via self-dimerization and thus, holds potential as a solvent-free and single-component platform. Furthermore, combined with the high rDA temperature of the Cp dimer (i.e., 150–180 °C) or Cp-maleimide adduct (i.e., ~150 °C), the application of Cp analogs in polymerization is promising to fabricate advanced functional polymers with enhanced sustainability. Despite its compelling chemistry, Cp is highly reactive with the propensity to isomerize, dimerize and oligomerize, making the monomer synthesis and polymerization notoriously challenging. In fact, Cp polymerization has remained uncontrolled since the first attempt by Staudinger in 1926. Herein, the successful stories of obtaining well-defined Cp polymer building blocks and controlling the Cp polymerization will be demonstrated, followed by the construction of complex and reversible materials based on the developed methodologies. The first part of the dissertation explores the efficient access to a well-defined tetra-functional Cp monomer under mild conditions via the optimized deprotection of a norbornadiene precursor using a tetrazine reagent. The controlled synthesis of a tough and degradable homopolymer network is subsequently showcased. The second part builds upon the deprotection platform to synthesize and study di-functional Cp derivatives with varied substituent effects. The goal is to understand and suppress uncontrolled cross-linking for the formation of reversible high-MW DA homopolymers. The utilization of a radical inhibitor, butylated hydroxytoluene, was discovered to prevent cross-linking, leading to the first general Cp homopolymerization. Notably, a Cp thermoplastic with the backbone derived from hydrogenated polybutadiene can be thermally recycled (i.e., Mn = 68 to 23 kDa and back to 68 kDa) three times without solvents and additional purification steps. The last three stories were developed by utilizing the well-defined Cp derivatives to fabricate degradable thermoplastic polyurethanes, a Cp-maleimide self-healing thermoset, and the stereo-chemical homopolymer networks. Through the development of controlled Cp polymerization, the expansion of DA chemical toolbox can be realized to fabricate a variety of promising materials with optimized mechanical performance and sustainability.

Natural network polymers are ubiquitous, leveraged for a diverse range of functions, and controlled by modular chemical motifs at the molecular level. Synthetically, there is a desire to borrow many of nature’s methods to build network materials with modular approaches for screening and engineering materials properties. Yet in spite of the range of chemical transformations available, most network development follows the classic approach of network formulation, formation, and examination. This conventional methodology often entails challenges in precise control of network structures, as well as limitations in functional group compatibility with network polymerization approaches. Consequentially, there is a need for modular, scalable synthetic strategies which can be performed as post polymerization modifications of network pendant motifs for facile derivatization and screening of materials properties. To address this, we can turn to active ester chemistry as a versatile, scalable platform for control and manipulation of network functionalities using mild conditions and simple wash protocols. Through integration of active ester containing monomer units into widely used free radical network polymerizations, this thesis demonstrates the utility of this straightforward approach for materials screening and design. Key discussions highlight the ability to install biomimetic metal-ligand crosslinking motifs; modulate an array of properties including mechanical, magnetic, and fluorescent behavior; and lastly leverage simple derivatization strategies to interrogate the impact of chemical substituents on nanoscale water transport behavior. To begin we can take direct structural inspiration from well characterized iron-catechol crosslinks of marine mussels and adapt these natural motifs to synthetic networks for tuning and patterning mechanical properties. Through utilization of a pentafluorophenyl acrylate as an active ester monomer unit, we can directly install catechol containing dopamine into the network, crucially without the need for protection or deprotection of phenolic moieties and avoiding their oxidation during substitution. Through this synthetic approach, large scale films could be prepared with an array of catechol and covalent crosslinking contents, followed by complexation and crosslinking of catechol groups with Fe3+ salts to achieve increases in elastic moduli of nearly two orders of magnitude. Moreover, by conceptually mirroring the mussels’ core-shell iron localization in the byssal thread, we can design diffusion controlled gradients in ion incorporation in catechol functionalized networks to prepare materials with patterned ion installation and heterogeneous, composite-like mechanical properties. Results demonstrated sub-millimeter scale resolution control and appreciable changes in mechanical behavior. Building from these approaches, we can turn to other biological inspirations for preparation of oxidation resistant materials which provide even greater degrees of tunability through increased metal chelation scope. While literature examples abound of potential ligands of interest, hydroxypyridinone (HOPO) motifs, adapted from the L-mimosine amino acid used in plants, present an enticing moiety to work with. Structurally, these ligands are similar to that of catechol moieties, but they have added benefits of increased oxidative stability and wider metal ion chelation scope through their altered ring structure. Present work builds on recent literature methods to prepare an active ester compatible, amine terminated HOPO ligand in a one pot approach, without the need for multiple protection and deprotection steps. Leveraging the active ester network platform, ligands could be installed and complexed with an array of metal salts, allowing for comparison mechanical reinforcement differences between catechol and HOPO functionalized materials after complexation. By building on prior patterning methods and utilizing the improved properties of the HOPO motif, materials with heterogeneous mechanical, magnetic, and fluorescent responses could be prepared, opening new doors for material preparation for soft robotic and encryption applications. Lastly, this topology consistent approach for network substituent modification was leveraged in hydrogel systems for measuring the impact of chemical identity on nanoscale water transport behavior. To conduct such measurements, Overhauser Dynamic Nuclear Polarization (ODNP) was leveraged as a combined electron paramagnetic and nuclear magnetic resonance (EPR and NMR) technique to measure interactions between passing water molecules and a nitroxide radical spin probe tethered to the network. Critically, ODNP measurements place significant restriction on sample geometry and must be conducted in narrow bore (0.6mm ID) capillaries. To address this challenge, prior work on active ester network polymerizations was extended to a biphasic flow synthesis, enabling the formation of microparticle networks with varied crosslinker and active ester content to modulate final water content and network substituents. Moreover, via this approach, large batches of parent materials could be prepared, split, and derivatized with both nitroxide spin labels and hydrophobic or hydrophilic sidechains, allowing for measurement of final hydrogel materials with consistent network topology and repeat unit sequence. Present results provide fundamental insight into nanoscale water behavior at the polymer network surface and highlight the impact of chemical identity on nanoscale water diffusivity, providing guiding design rules for next generation membrane materials.

Semiconducting polymers are an intriguing class of materials that have been attracting increasing attention over the years. As their name suggests, semiconducting polymers are used in similar fields as their inorganic counterparts, but they offer several advantages that make them particularly desirable. These polymers are solution-processable, flexible, and have intrinsically low thermal conductivity, all of which are important for applications such as wearable thermoelectric devices. The low thermal conductivity, in particular, contributes to the thermoelectric efficiency of these devices, making them a natural choice for such applications.However, like all materials in their developing stages, semiconducting polymers are not without drawbacks. In their pristine form, the use of semiconducting polymers in thermoelectric devices is limited by low electrical conductivity due to low intrinsic charge carrier density and mobility. To address these issues, we employ various dopants and doping methods to introduce carriers into semiconducting polymer thin films. Additionally, we developed a setup to rub-align semiconducting polymer thin films to study the effects of changing the molecular morphology on charge transport characteristics and doping. We characterize doped polymer films using techniques such as four-point probe conductivity, temperature-dependent conductivity, Seebeck coefficient measurements, Hall effect measurements, wide-angle X-ray scattering, and steady-state spectroscopy.The first part of this dissertation (Chapter 2) explores the effects of the ambient environment, particularly humidity, on semiconducting polymer films doped with a novel doping method recently reported in the literature called “anion-exchange.” The anion exchange doping method greatly enhances doping efficiency and also allows control of over the choice of counterion that accompanies the doped charge carrier. The counterion comes from an electrolyte solution, however, the electrolytes used are often made from hygroscopic salts. We show that these counterions can draw water into polymer films doped via anion exchange, which greatly reduces conductivity by acting as traps for carriers.The second part of the dissertation (Chapters 3 and 4) investigates the effect of rub-aligned polymer thin films on doping and charge transport. Charge transport in semiconducting polymer films is often limited by their semicrystalline nature, where poor mobility can be caused by structural defects like bends or kinks that create energetic barriers. One way to reduce such defects is through a novel “high-temperature rub-aligning” method to straighten and molecularly align the polymer chains. Our study showed that conductivity greatly improves with this method, however, we also found that literature reports of this improvement were exaggerated because the method to measure anisotropic conductivity is highly dependent on electrode geometry, and previous work did not take this into account. Additionally, rub-aligned films provide insights into the effect of different polymorphs on the doping process. We found that rub-aligning creates two polymorphs that happen to have face-on and edge-on structures. We found that face-on polymorph, whose structure is more similar to the final doped structure, has a lower barrier to doping than the edge-on polymorph, which requires a greater structural rearrangement to dope.For the final part of this dissertation (Chapter 5), we used a holistic approach to understanding the effect of different dopants, doping methods, and structure on charge transport in doped semiconducting polymer thin films. By taking advantage of temperature-dependent measurements and models based on the Boltzmann transport formalism, we demonstrated that the factor dominating charge transport in doped semiconducting polymer thin films is highly dependent on the type of dopants and the doping method. Our finding demonstrates that the relationship between the Seebeck coefficient and conductivity of doped P3HT films can be improved either by reducing Coulomb interactions or by adding additional charge transport pathways through doping the of amorphous regions. The latter is shown by an increase in the correlation length between domains.

Elastomeric materials, characterized by their elasticity and energy dissipation capabilities, are crucial in everyday life. Over the years, the development of elastomers with novel properties is driven by the growing demand for materials that can meet the increasingly complex and specific requirements in automotive, aerospace, medical, structural and industrial applications and enable new applications such as soft robotics and flexible electronics. Liquid crystal elastomer is one such material system that combines liquid crystals with rubbery polymers, which gave rise to several unique properties such as anisotropic elasticity, stimuli responsiveness and actuation, energy dissipation, photoelasticity and reversible adhesion. Since materials need to withstand multiple cycles of mechanical loading and exposure to thermal fields in real world applications, it is important to understand the rate and temperature dependent properties of liquid crystal elastomers, which will result in the development of robust materials and reliable engineering structures.In this dissertation, we first explore the rate and temperature dependent fracture properties of liquid crystal elastomers and develop predictions of the temperature of self-rupture for various geometries. Secondly, we develop an interpenetrating network strategy to improve the high temperature fracture and fatigue properties of liquid crystal elastomers, while preserving their actuation properties. Then, we develop a pressure sensitive adhesive using liquid crystal elastomers and explore the ultra-high rate dependence of adhesion energy. Finally, we study the enhanced adhesion of liquid crystal elastomers on various rough surfaces. We hope that the understanding of the fracture and adhesive properties of liquid crystal elastomers and the strategies developed to further improve these properties using materials chemistry will translate to real world in solving critical challenges in medical technology, robotics, automotive, aerospace and industrial applications

Plastic pollution is overrunning the planet. To combat this, it is important to be able to generate biodegradable alternative plastics and measure their biodegradability. The research aimed to develop a method for quantifying the biodegradation of these plastics using peroxide digestion with Fenton’s Reagent. The results show that peroxide digestion can be used in tandem with other analytical methods to quantify biodegradation, namely with mass loss, compression analysis, and supplemental FTIR spectroscopy.

This dissertation elucidates the significance of macromolecular design in two types of systems - (i) covalently-linked polyurethane networks and composites, and (ii) complexes of oppositely charged polymers (polyelectrolyte complexes) – unified by their macromolecular nature, yet distinguished by their design, governing principles, and applications. The first part of this dissertation highlights the profound effect of the chemistry of flexible polyurethane foams on their physico-mechanical and thermochemical properties; by harnessing these correlations, a simple strategy has been proposed for the facile classification of post-consumer-use flexible polyurethane foams for their chemical recycling. Following this, the upcycling of depolymerized polyurethane products (polyols) into lightweight high-strength organic-inorganic composites with superior thermal insulation and acoustic barrier performance has been discussed. The amenability of the compositing strategy with polyols from different sources, varying chemistries of the diisocyanate linker, and types of inorganic materials have been highlighted. This dual approach is a step toward enabling the circularity of post-consumer-use flexible polyurethane foam and informing the design of polyurethane-inorganic composites with unique properties. The second part of this dissertation delineates the phenomenon of polyelectrolyte complexation and examines the non-trivial role of salt ion valency and polyelectrolyte length asymmetry on complexation. Divalent ions have been shown to reverse the composition of PECs, favoring their sequestration in the complex phase, and hindering chain relaxation. Following this, the dramatic influence of polyelectrolyte length symmetry in controlling the polymer content of the complex phase has been discussed in the context of thermodynamics and the Voorn-Overbeek theory. Furthermore, length-asymmetry will be shown to alter the viscosity of the complex phase. These dual studies are aimed to serve as design guides for polyelectrolyte complexation occurring in environments (biological and medical systems, environmental and wastewater treatment applications) where little to no control can be exercised over the properties of the solution and polyelectrolytes.

This dissertation represents a broad exploration of polymer chemistry, anchored in the principles of the Circular Economy and sustainability. The work presented herein places a strong emphasis on utilizing monomers and polymers sourced from nature. We endeavor to enhance the utility of lignin-derived polymers for commercial applications by improving solubility and thermal properties, while also delving into the synthesis of aromatic-aliphatic polyesters from renewable resources. Lignin-derived poly(ether-amide)s are targeted initially, with the aim of overcoming their solubility limitations through thiol-ene reactions. By introducing small thiol-tagged molecules, the repeating double bonds are reduced, leading to increased chain flexibility and in turn, improved solubility and glass transition temperatures. We then explored the copolymerization of lignin-derived components with lactones for the synthesis of aromatic-aliphatic polyesters. Lactones, such as lactide and glycolide, are natural building blocks pervasive across nature. They were used in ring-opening polymerizations to produce aliphatic alcohol likers. The lactone linkers underwent condensation polymerizations with hydroxycinnamate dimers, creating sustainable, high molecular weight polyesters with desirable thermal properties. These approaches not only enhance the viability of polymers from biomass but also align with the ethos of sustainability by repurposing natural materials.We then pivot to focus on the development of hydrogel wound dressings, as a biomimetic extracellular matrix. Bioinspired polymers were used to initiate redox hydrogel crosslinking, leading to hydrogels with improved biocompatibility compared to the gold standard approach (APS and TEMED). Finally, this was expanded to the development of in situ forming hydrogel wound dressings that sequester and release antibiotics, analgesics, and hemostatic agents. These hydrogels exhibited rapid formation, controlled release of therapeutic agents, and biocompatibility, addressing the acute need for hemostasis and infection prevention in traumatic blast wounds. In vivo studies demonstrated the safety and efficacy of these hydrogel wound dressings in reducing bacterial burden and promoting wound healing. Overall, this work presents a holistic approach to polymer science, drawing inspiration from nature and rooted in sustainability. By harnessing the potential of natural monomers and polymers, we seek to advance the field while addressing pressing challenges in materials science and healthcare.

Additive Manufacturing, also commonly known as 3D Printing, has significant potential for personalized medicine and biomedical devices, owing to its streamlined design-to-production workflow. Unlike traditional manufacturing techniques, 3D printing allows for the creation of highly tailored products that can be precisely designed to meet the specific needs of individual patients. Current printable biomaterials are limited to synthetic and biological polymers and their range in material properties. Although synthetic polymers are tunable, they lack degradability. Unlike synthetic polymers, biopolymers are biodegradable, but their properties are limited to those found in nature. Therefore, there is a need for tunable and biodegradable materials in 3D printing to help expand its capability. In Chapter 1, the 3D printing hydrogel literature is surveyed, and polypeptides based on N-carboxyanhydride (NCA) are recognized as a potential feedstock that can diversify the printable material palette. In Chapter 2 and Appendix A, a library of star block copolypeptide composed of a consistent inner hydrophilic block and different β-sheet outer blocks were synthesized. By varying the β-sheet forming domains, shear-processable hydrogels with diverse microstructure and mechanical properties were prepared and structure-function relationships were determined. The versatile synthesis of these star block copolypeptides provides a robust platform to tune material properties based solely on molecular design. Utilizing these systems in 3D printing, specifically Direct Ink Writing (DIW), eliminates the necessity for additives and provides a synthetic handle to tailor its functionality.In Chapter 3 and Appendix B, photocrosslinkable groups were facilely integrated into the star block copolypeptide scaffold to allow subsequent chemical crosslinking with visible light after DIW. Escherichia Coli was integrated into these hydrogel inks and biological composites with complex geometries were achieved in these bioinert printing conditions. Furthermore, the tunable properties of different copolypeptide networks enable control over proliferation and colony formation for embedded microbes as demonstrated based on green fluorescent protein (GFP) expression. Opening the possibility of controlling integrated biological behavior through the molecular design of the star copolypeptide matrix.To demonstrate the ease of use of these star copolypeptides, Chapter 4 and Appendix C delve into their utilization as rheological modifiers within the widely used Gelatin Methacrylamide (GelMA) bioinks. The temperature stability of the star copolypeptide networks allows these GelMA hybrids to be extruded at physiological temperatures, facilitating their utilization for integrating mammalian cells for bioprinting. In contrast to conventional rheological modifiers, the star copolypeptide participates in photochemical crosslinking with GelMA while preserving its natural biodegradability. This approach, employing star copolypeptides as rheological modifiers for DIW, showcases the prospective integration of bioactive materials and fluids, paving the way for modular bioinks. This thesis aims to unveil the unexplored capabilities of star copolypeptides as a tailorable material, propelling the frontier of bioprinting.

Polymers containing a backbone of repeated Si–O bonds, referred to as siloxanes or silicones, are a ubiquitous class of materials due to their collection of unique properties. The exceptionally wide Si–O bond angle and high deformability of the backbone bonds results in a low glass transition temperature of –120 °C and a crystallization temperature below room temperature. Additionally, the high bond dissociation energy gives rise to decomposition temperatures above 300 °C and results in a chemically inert polymer. The combination of these features result in a massive temperature window while maintaining inert. With a market size of over $4 billion, polydimethylsiloxane (PDMS) is the most common siloxane and has been the subject of decades of research. These research and development efforts have led to the material being used in numerous environments ranging from cosmetics to aerospace. The utility of PDMS arises from the sophisticated methods used to tune the polymer chemistry, which result in a range of properties appropriate for numerous different applications. Robust chemical reactions, like hydrosilylation, have led to an extremely broad scope of functional groups that can be synthetically bonded to the siloxane backbone. This same strategy has been used to attach polymers, polymerization initiators, or polymerizable moieties to the siloxane chain, leading to a broad scope of possible siloxane-based copolymer architectures. One architecture that is lacking in synthetic versatility, however, is graft copolymers with a siloxane backbone and polymeric grafts based on vinyl monomers. Chapter 2 of this dissertation outlines a methodology to synthesize graft copolymers with siloxane backbones using a combination of thiol–ene click chemistry and atom-transfer radical polymerization. Optimization of polymerization conditions enabled the synthesis of graft copolymers with a range of grafting densities and molecular weights > 5 MDa. Degradation of the siloxane backbone enabled characterization of the polymerized grafts, showcasing dispersities around 1.2 and molecular weights close to the targeted values. In order to form a freestanding polymeric material, the siloxane must be crosslinked. The network architecture is an important parameter that can be manipulated to control the properties of the material. Additionally, novel functionality can be incorporated through the usage of a dynamic crosslinker. An example of such a material is Silly Putty, which is PDMS crosslinked through borosiloxane bonds. The method of synthesizing this material, however, has remained largely unchanged since the 1940s and remains a time and energy intensive process with limited tunabilty. In Chapter, 3 we demonstrate a novel methodology to synthesize polyborosiloxane networks using hydrosilylation in minutes. While the current state-of-the-art is limited to end-functionalized PDMS chains, our developed method gives access to backbone-functionalized PDMS starting materials, which drastically increases the degree of tunability over the final network properties. In Chapter 4, we expand upon this method by synthesizing boronate esters containing varying functional groups to investigate the impact of the crosslinker chemical environment on the stress relaxation dynamics. We demonstrate an unprecedented level of control over the rate of stress relaxation for polyborosiloxane materials while maintaining a facile and robust crosslinking method. The newly developed methodologies for graft copolymers and functional polymeric networks will enable future investigations into the properties of these materials and their incorporation into complex composite systems to expand upon the current availability of silicone materials.

In this research we present the novel technology that was developed using low-cost materials and 3D printing to allow for in operando nanoscale investigations of perfluorosulfonic acid membranes under vanadium oxygen fuel cell (VOFC) and direct methanol fuel cell (DMFC) conditions, using conductive atomic force microscopy. We detail the process of designing, iterating, fabricating, and validating our novel 3D printed imaging cell. The justifications for the design choices are explained in detail. Heating and relative humidity control are added to the cell as additional features for more accurate environmental simulation. Using the cell, we image Nafion membranes under VOFC conditions and compare our findings with previous research. We found that thinner membranes show higher current densities than thicker membranes. Furthermore, under VOFC conditions we observe the same shrinking behavior observed in previous research as the ionic strength of electrolytes that Nafion is exposed to increases. We imaged Nafion membranes under DMFC conditions and found that the operating temperature and anode catalysts play an important role in observing nanoscale proton conductivity. Finally, we detail the process of synthesizing low-valency vanadium/sulfuric acid electrolytes and end with an investigation into VO/TiO2 catalysts using density functional theory. This investigation helps to explain the atomic processes occurring on a model catalyst system that can catalyze the oxidative dehydrogenation of methanol to formaldehyde.

Soft responsive materials can undergo significant changes in their properties in response to external stimuli such as temperature, mechanical force, light, pH, magnetic, electric fields, and chemical agents. The efforts of this dissertation are mainly focused on understanding and exploiting the chemistry, physics, mechanics, and dynamics of soft responsive materials to develop new pathways of programmable properties including shape morphing and optical signal. This dissertation encompasses the engineering techniques of soft responsive materials across the spectrum from non-living (i.e., synthetic) to living systems. In non-living systems, we used synthetic stimuli-responsive soft materials, such as hydrogels and elastomers, to explore how material characteristics can be integrated into novel structural designs through additive manufacturing. We also modeled these material systems using computational methods to further understand and predict their behaviors. Extrusion-based 3D printing (i.e., direct ink writing), one of the techniques of additive manufacturing, was employed to create complex structures with precise control over material compositions and local architectures. We discuss the rationale of the structure design, from microscopic to macroscopic, to enable the desired functionality by leveraging the structure-property relationships. In living systems, we have integrated our synthetic adhesive hydrogel with plants to introduce new functionalities such as programmable shape morphing, on-demand plant control, and precise cargo delivery. We examine the engineering requirements for synthetic polymers to interface with living systems like plants, focusing on mechanical, chemical, and biocompatible characteristics. We present a method for achieving strong, yet reversible, adhesion to various plant surfaces, utilizing the Schiff's base reaction to establish dynamic imine bonds. This strategy paves the way for advanced nutrient delivery systems for plants, wearable sensors for early disease detection, and novel human-plant interaction modalities.

Cationic polymers are of broad interest in the biotechnology sector due to their potential use in drug conjugation, tissue engineering, gene delivery, water purification and chelation, and stimuli-responsive materials. Of particular interest in designing cationic polymers is control over their pKa—allowing for the presentation of a positive charge at specific pH, which is dependent on molecular weight, connectivity, and pendant group identity of the polymer. In this dissertation, we designed and synthesized a series of smoking-inspired monomers and polymers based on pyrrolidine, piperidine, and tocopherol—utilizing copolymerization and other polymer chemistry strategies to vary their molecular weight, dispersity, hydrophilicity/hydrophobicity, charge density, and pKa. These polymers are designed to mimic certain chemical structures present in tobacco alkaloids or other smoking-related compounds that have implications in human health. In this work, we explore the utility of amine-based polymers within and beyond the scope of innate immunity—playing important roles in solving bioengineering and tissue engineering problems. Exposure to certain chemical factors present in tobacco and smoking-related compounds leads to the elevated risk and greater symptom severity of several autoimmune conditions. While this link has remained mechanistically unclear, the presence of protein/DNA immune complexes in systemic lupus erythematosus (SLE) has been designated as an important marker of disease severity, seen more prevalently in smokers vs. never-smokers. The smoking-inspired polymer library developed in this study is used to mimic the features of these immune complexes. Investigation of these polymeric materials complexed with negatively-charged biological macromolecules shows notable differences in complex formation, biophysical structure, and subsequent innate immune activity. These results provide further evidence of the role of biophysical complex structure in innate immune activity, and the role that tobacco’s chemical structures may play in exacerbating disease. Additional work explores the interaction of DNA with cigarette smoke in vitro—demonstrating the formation of visible clew-like precipitates upon DNA exposure to cigarettes. These pellets, which resemble the precipitates formed by the condensation of oppositely-charged biomacromolecules, demonstrate a level of biophysical ordering and immune activity seen in immunomodulatory DNA complexes.