Covalent organic frameworks (COFs) are a recently discovered class of nanoporous polymeric materials with ultra-high specific surface areas, which makes them highly attractive for applications in nanofiltration, gas capture and storage, and catalysis. However, the macroscopic morphology of COFs is maintained by relatively weak physical interactions between crystallites, which limits the applications of COFs where they may experience significant physical stresses. Herein, fillers are added to three-dimensional TAPB-PDA COF aerogels synthesized to improve the mechanical strength and functionality through the formation of a composite material by physically implanting the fillers in the macropores present in the gel network. Boron nitride loading is shown to double the Young’s modulus of the aerogel, from 11 kPa to 22 kPa, at 20 relative weight percent loading, while only causing a 10% decrease in accessible nanoporous surface area, normalized to the mass of COF in the sample. Poly(acrylic acid) added at 5 relative weight percent loading and crosslinked increases the Young’s modulus to 21 kPa and simultaneously increases the elastic limit of the aerogel from 10% to 65% strain, while inducing a 38% decrease in accessible nanoporous surface area, normalized to the mass of COF in the sample. This work demonstrates the potential for macroscopic composites with COFs forming the majority phase of the material, showing the possibility for mechanical reinforcement without significant hinderance of the adsorbent functionality of the material.

Crystalline polymeric materials play an increasingly important role in daily life.Understanding and controlling the development of crystallinity is integral to improving the performance of crystalline polymers in packaging, drug delivery, water treatment, gas separations, and many other industries. Herein, fluorescence and Raman spectroscopy have been applied for the first time to study the crystallinity of polymers, including traditional semicrystalline thermoplastics and covalent organic frameworks (COFs; an emerging class of crystalline polymers with highly ordered pore structures). On one hand, by incorporating a fluorescent dye segment into a semicrystalline polymer matrix, it is feasible to accurately monitor its crystallization and melting. The flexibility of dye incorporation allows for new fundamental insights into polymer crystallization in the bulk and at/near interfaces that may otherwise be out of reach for established techniques like differential scanning calorimetry (DSC). On the other hand, Raman spectroscopy has been identified as a technique sensitive to the crystallinity of COFs and applied alongside well-established characterization techniques (X-ray diffraction and N2 adsorption) to monitor the crystallization of COFs during synthesis. This has enabled careful control of COF crystallinity during solvothermal synthesis for improved application in the field of drug delivery. The monitoring of COF crystallinity has been extended to more complex film geometries produced by interfacial polymerization. The high molecular sieving potential of COFs remains out of reach in part due to a lack of understanding of the interplay between crystallinity, crystallite orientation, and filtration performance. A careful study of these relationships is suggested for future work to provide key insight toward applying COFs as molecular sieving materials in water treatment and other separation applications.

The properties of block polymers (BPs) are intricately coupled to the dynamic and rich nature of the nanostructured assemblies which result from the phase separation between blocks. The introduction of strong secondary forces, such as electrostatics and hydrogen bonding, into block polymers greatly influences their self-assembly behavior, and therefore affects their physical and electrochemical properties often in non-trivial ways. The recent surge of work expanding scientific understanding of complex spherical packing in block polymers (BPs) has unlocked new design space for the development of advanced soft materials. The continuous matrix phase which percolates throughout spherical morphologies is ideal for many applications involving transport of ions or other small molecules. Thus, determining the accessible parameter range of such morphologies is desirable. Bulk zwitterion-containing BPs hold great potential within the realm of electroactive materials while remaining relatively untapped. In this work, architecturally and compositionally asymmetric diblock polymers were prepared with the majority block having zwitterions tethered to side chain termini at different ratios. Thermally reversible Frank-Kasper phases are observed in multiple samples with significant signs of kinetic arrest and influence. The kinetic influences are validated and described by the temperature-dependent static permittivity. Polyzwitterions combine the attractive features of zwitterions with the mechanical support and processability of polymeric materials. Among these attractive features is a potential for superior permittivity which is limited by the propensity of zwitterions to pack into strongly associating structures. Block polymer self-assembly embodies a plethora of packing frustration opportunities for optimizing polyzwitterion permittivity. The capabilities of this novel approach are revealed here, where the permittivity of a polyzwitterionic block is enhanced to a level comparable to that of pure liquid zwitterions near room temperature (εs ~ 250), but with less than a third the zwitterion concentration. The mechanistic source of permittivity enhancement from a single zwitterion-tethered block polymer is realized deductively through a series of thermal pathways and control sample experiments. Tethered zwitterions within the mixed block interface are frustrated when subject to segmental segregation under sufficient interfacial tension and packing while non-interfacial zwitterions contribute very little to permittivity, highlighting the potential for improvement by several fold.

As society moves to reduce the effects of climate change, there is a growing needfor the use of polymer science in technologies to mitigate the emission of carbon dioxide. Networks containing quaternary ammonium groups with corresponding HCO3 ions providing the mobile counter-charge in the networks have been reported to capture carbon dioxide directly from the atmosphere through a moisture swing mechanism, among other mechanisms. In this work, microstructural analysis of synthesized polystyrene-based anion exchange networks is conducted using known characterization techniques to better understand if variations in sorbent microstructure adjust the distances between the quaternary ammonium groups. Additional surface morphology studies of these sorbents are conducted. X-Ray Diffraction (XRD) spectra reveal the amorphous structure of these polymers and the ability to adjust the distance between quaternary ammonium groups by introducing different spacer groups and various anions into the networks, which may affect the spontaneity of the CO2 to chemisorb to these sorbents. However, Wide Angle X-Ray Scattering (WAXS) conflicts with the XRD data, indicating a change in distance between these groups is not achieved. Additionally, WAXS data indicates an ability to increase the homogeneity of structure in these materials by introducing larger counterions into the networks. Small Angle X-Ray Scattering (SAXS) reveals no obvious large morphological features in these sorbents, which is supported by Scanning Electron Microscopy (SEM) images. In conclusion, XRD and WAXS experiments exhibit conflicting data regarding the ability to adjust the distances between the quaternary ammonium groups in these networks. Proposed actions to resolve this conflict are presented. Finally, SEM sheds light on particle size and morphological features of these materials.

Additive manufacturing, also known as 3D printing, has revolutionized modern manufacturing in several key areas: complex geometry fabrication, rapid prototyping and iteration, customization and personalization, reduced material waste, supply chain flexibility, complex assemblies and consolidated parts, and material innovation. As the technology continues to evolve, its impact on manufacturing is expected to grow, driving further innovation and reshaping traditional production processes. Some innovation examples in this field are inspired by natural or bio-systems, such as honeycomb structures for internal morphological control to increase strength, bio-mimetic composites for scaffold structures, or shape memory materials in 4D printing for targeted drug delivery. However, the technology is limited by its ability to manipulate multiple materials, especially tuning their submicron characteristics when they show non-compatible chemical or physical features. For example, the deposition and patterning of nanoparticles with different dimensions have seen little success, except in highly precise and slow 3D printing processes like aerojet or electrohydrodynamic. Taking inspiration from the layered patterns and structures found in nature, this research aims to demonstrate the development and versatility of a newly developed ink-based composite 3D printing mechanism called multiphase direct ink writing (MDIW). The MDIW is a multi-materials extrusion system, with a unique nozzle design that can accommodate two immiscible and non-compatible polymer or nano-composite solutions as feedstock. The intricate internal structure of the nozzle enables the rearrangement of the feedstock in alternating layers (i.e., ABAB...) and multiplied within each printed line. This research will first highlight the design and development of the MDIW 3D printing mechanism, followed by laminate processing to establish the requirements of layer formation in the XY-axis and the effect of layer formation on its microstructural and mechanical properties. Next, the versatility of the mechanism is also shown through the one-step fabrication of shape memory polymers with dual stimuli responsiveness, highlighting the 4D printing capabilities. Moreover, the MDIW's capability of dual nanoparticle patterning for manufacturing multi-functional carbon-carbon composites will be highlighted. Comprehensive and in-depth studies are conducted to investigate the morphology-structure-property relationships, demonstrating potential applications in structural engineering, smart and intelligent devices, miniature robotics, and high-temperature systems.

Engineering polymers are critical for contemporary high-performance applications where toughness, thermal stability, and density are at a premium. These materials often demand high-energy processing conditions or highly reactive monomers that hold negative impacts on human and environmental health. Thus, this work serves to remediate the negative impacts of engineering polymer synthesis by addressing toxicity and processing at the monomer level, while maintaining or exceeding previous thermomechanical and stimuli-responsive performance. Polyurethanes (PUs) represent a class of engineering polymers that possess highly modular properties due to the diverse monomer selection available for their synthesis. The efficient reaction between isocyanates and hydroxyls impart stellar properties and flexible processing modalities, however recent scrutiny regarding the toxicity of the isocyanate precursors has driven the search for non-isocyanate polyurethane (NIPU) pathways. The advancement of bis-carbonylimidazolide (BCI) monomers for the synthesis of NIPU thermoplastics and foams is thoroughly investigated in this work. Remarkably, a novel decarboxylation pathway for BCI monomers controlled by catalyst loading enabled in-situ CO2 generation during crosslinking with trifunctional amines, and resulted in a facile synthetic route for NIPU foams. Further explorations into catalyst considerations revealed Dabco® 33-LV as a suitable mechanism for controlling reaction times and careful selection of surfactant concentration provided control over pore size and geometry. This led to a library of flexible and rigid NIPU foams that displayed a wide range of thermomechanical properties. Furthermore, sequestration of the imidazole byproduct through an efficient Michael reaction identified maleimide and acrylate additives as a viable pathway to eliminate post-processing steps resulting in NIPU foam synthesis that is amenable to current industrial standards. This route held advantages over the isocyanate route, as condensate removal drove molecular weight increase and ultimately achieved the first reported phase separation behavior of a NIPU thermoplastic containing a poly(ethylene glycol) soft segment. Furthermore, sustainable considerations for engineering polymers were explored with the introduction of a novel cyclobutane bisimide monomer that readily installs into various polymeric systems. Direct installation of this monomer, CBDA-AP-I, into a polysulfone backbone enabled controlled photo-cleavage, while further hydroxy ethyl functionalization allowed for incorporation into PU systems for photo-cleavable high-performance adhesive applications.

In this report, a PDMS network formed from catalysis of a linear, bifunctional polymer by Ashby-Karstedt’s catalyst is analyzed. An exploration of the crosslink density, shear plateau modulus, and glass transition temperature is performed to display some of the material’s mechanical, chemical, and thermal properties. The softness of this network in addition to the biocompatibility and thermal stability of PDMS make this elastomer useful for a broad spectrum of applications.

Advancements in three-dimensional (3D) additive manufacturing techniques have opened up new possibilities for healthcare systems and the medical industry, allowing for the realization of concepts that were once confined to theoretical discussions. Among these groundbreaking research endeavors is the development of intricate magnetic structures that can be actuated through non-invasive methods, including electromagnetic and magnetic actuation. Magnetic actuation, in particular, offers the advantage of untethered operation. In this study, a photopolymerizable resin infused with Fe3O4 oxide nanoparticles is employed in the printing process using the micro-continuous liquid interface production technique. The objective is to optimize the manufacturing process to produce microstructures featuring smooth surfaces and reduced surface porosity, and enhanced flexibility and magnetic actuation. Various intricate structures are fabricated to validate the printing process's capabilities. Furthermore, the assessment of the flexibilty of these 3D-printed structures is conducted in the presence of an external magnetic field using a homemade bending test setup, allowing for a comprehensive characterization of these components. This research serves as a foundation for the future design and development of micro-robots using micro-continuous liquid interface production technique.

In the search for ever more sustainable manufacturing techniques, additive manufacturing through light driven 3D printing processes is growing rapidly as a field, specifically the production of “living” materials which can be repaired and or reprocessed through the reactivation of polymer chain ends. Currently research in the production of these living materials is largely focused on radical polymerization methods. Cationic polymerizations have been developed for this purpose, although there is still much work to be done. This work seeks to explore a transition-metal free system to produce living materials through cationic reversible addition fragmentation chain-transfer (C-RAFT).Cationic polymerization is known for its rapid propagation. This is due to the highly reactive active center which also readily reacts with nucleophiles in unwanted chain transfer reactions. For this reason, reagents in living cationic polymerizations are subject to rigorous purification steps involving the distillation of monomer and solvent, freeze—pump—thaw cycles, and running the reaction under an inert environment1. These restrictions make living cationic polymerizations unattractive for 3D printing processes. New systems for rapid water tolerant C-RAFT photopolymerization will provide for new materials to be produced through this more sustainable manufacturing process. In this work, living cationic polymerization of isobutyl vinyl ether (IBVE) is achieved using a synthesized cationic RAFT agent and an initiating system consisting of camphorquinone (CQ), ethyl 4-(dimethylamino)benzoate, and iodonium salt HNu-254. Molecular weights of 12 kg/mol are achieved with a dispersity of 1.4. The polymerization mechanism is probed and shows rapid kinetics consistent with living polymerizations in addition to photo-controllability as indicated by light on-off experiments. Chain extension experiments display re-activation of the trithiocarbonate chain end. This feature is then used to produce block-copolymers using ethyl vinyl ether and cyclohexyl vinyl ether.