Madison I. Bardot

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent environmental contaminants that cause negative health effects. These health concerns and impending regulations motivate demand for PFAS removal technologies. Such technologies must be capable of high-throughput, continuous-flow operation, and maintaining treatment performance at large-scales in municipal and industrial treatment systems. Many PFAS remediation technologies rely on particle-based sorbents, which are subject to mass-transfer limitations in large-scale flow-through systems that can limit PFAS removal performance. Recently, we introduced monolithic sorbents for PFAS removal based on styrene-functionalized β-cyclodextrin polymers whose porosity can reduce these mass-transfer limitations. The first monolith formulations were prepared by photoinitiating polymerization within flow-through columns, which limited the monolith’s practical scalability. Here, we address this limitation by using a redox initiation process at room temperature, which is compatible with the high internal phase emulsion and enables scalable fabrication across column dimensions. Mercury porosimetry revealed a bimodal pore size distribution and a larger characteristic maximum pore size in the redox-initiated monoliths compared to the monomodal pore size distribution observed in the photoinitiated materials. Chemical composition and batch adsorption performance remained consistent across redox-initiated monoliths scaled to 36 times the original monolith cross-sectional area. Redox-initiated monoliths outperformed photoinitiated monoliths in flow-through columns, showing later breakthrough of the short-chain PFAS, perfluorobutanoic acid. We also evaluated the PFAS removal performance of scaled redox-initiated monoliths in columns of increasing diameters (0.5, 1, and 1.5 cm). Their performance was consistent across scales, indicating that redox-initiated monoliths with larger cross-sectional areas maintain their promising sorption performance.

Molecular electron spin qubits are an emerging platform for quantum technologies due to their atomic-scale synthetic tunability. Supramolecular structures can also place these qubits at precise positions within ordered arrays, allowing the scale-up of qubit architectures through a bottom-up approach. Here, we introduce the first three-dimensional paired-ion framework (PIF), VO-3D-PIF-1, which is composed of a concentrated array of S = 1/2 vanadyl porphyrin spin qubits arranged by ionic lattice interactions. The PIF was characterized using electron paramagnetic resonance spectroscopy to demonstrate the impact of framework structure and spin density on spin–lattice relaxation (T1) and spin decoherence (Tm). The high vanadyl porphyrin spin density within the framework (0.125 spins/nm3) promotes dipolar-driven decoherence, with Tm = 200–400 ns over a temperature range of 140–5 K. Spin–lattice relaxation mirrors that of vanadyl porphyrins in dilute solution, suggesting that the weak ionic interactions assembling the porphyrins within the secondary coordination sphere do not adversely affect phonon-induced T1 relaxation.

Mechanical bonds impart unique mechanical properties to polymers. However, forming polymers with many mechanical bonds is traditionally difficult and has limited the study of mechanically interlocked materials (MIMs) to milligram-scale amounts and/or sparse incorporation of interlocked components. We recently introduced a two-dimensional polymer architecture in which every repeat unit contains a mechanical bond through a copolymerization reaction between crystalline and diffusible monomers. Here we described a significantly accelerated variant of this polymerization that enabled scaling to >100 g batches of the polymer and the preparation of >500 g of the polymer in total using equipment found in most academic research laboratories. This polymer is produced in a two-step procedure in which a tetrafunctional phenol monomer is crystallized into a mechanically interlocked structure supported by hydrogen bonding, after which polymerization occurs by reaction with dimethyldichlorosilane in hexanes, a nonsolvent for the crystal. Improved polymerization efficiency and kinetics were realized by incorporating triethylamine, which accelerates siloxane bond formation and incorporates into the monomer crystal in a single-crystal-to-single-crystal transformation. Crystallization procedures to produce monomer crystals in 50-g batches and polymerization techniques to produce the 2D MIM in 100-g batches are reported. TPE-PhO[Si(CH₃)₂]₂ produced at these larger scales shows consistent chemical composition by X-ray photoelectron spectroscopy and NMR spectroscopy and the expected 2D morphology by scanning electron microscopy and atomic force microscopy. These findings introduce 2D MIMs as a unique yet readily accessible polymer architecture.

During the past decade, researchers have designed and synthesised a variety of artificial molecular pumps capable of the active transport of macrocycles (rings) from free solution into mechanically interlocked states. In their ability to drive non‐equilibrium transport, these artificial molecular pumps imitate natural transmembrane transporters, which are widespread in living organisms. Despite this resemblance, ring‐threading molecular pumps have not previously been operated in aqueous supramolecular assemblies in imitation of their natural counterparts. Here, we demonstrate the active transport of charged macrocycles from aqueous solution into micellar assemblies of polymer chains, which remain stable after pumping has occurred. While micelles are used routinely to encapsulate and solubilise hydrophobic small molecules in aqueous solution, this report, by contrast, shows that artificial molecular pumps can harness external energy to drive hydrophilic molecules into micelles where they are stored at concentrations far from equilibrium.

During the past decade, researchers have designed and synthesised a variety of artificial molecular pumps capable of the active transport of macrocycles (rings) from free solution into mechanically interlocked states. In their ability to drive non‐equilibrium transport, these artificial molecular pumps imitate natural transmembrane transporters, which are widespread in living organisms. Despite this resemblance, ring‐threading molecular pumps have not previously been operated in aqueous supramolecular assemblies in imitation of their natural counterparts. Here, we demonstrate the active transport of charged macrocycles from aqueous solution into micellar assemblies of polymer chains, which remain stable after pumping has occurred. While micelles are used routinely to encapsulate and solubilise hydrophobic small molecules in aqueous solution, this report, by contrast, shows that artificial molecular pumps can harness external energy to drive hydrophilic molecules into micelles where they are stored at concentrations far from equilibrium.

Mechanical bonds arise between molecules that contain interlocked subunits, such as one macrocycle threaded through another. Within polymers, these linkages will confer distinctive mechanical properties and other emergent behaviors, but polymerizations that form mechanical bonds efficiently and use simple monomeric building blocks are rare. In this work, we introduce a solid-state polymerization in which one monomer infiltrates crystals of another to form a macrocycle and mechanical bond at each repeat unit of a two-dimensional (2D) polymer. This mechanically interlocked 2D polymer is formed as a layered solid that is readily exfoliated in common organic solvents, enabling spectroscopic characterization and atomic-resolution imaging using advanced electron microscopy techniques. The 2D mechanically interlocked polymer is easily prepared on multigram scales, which, along with its solution processibility, enables the facile fabrication of composite fibers with Ultem that exhibit enhanced stiffness and strength.

Two-dimensional covalent organic frameworks (2D COFs) form as layered 2D polymers whose sheets stack through high-surface-area, noncovalent interactions that can give rise to different interlayer arrangements. Manipulating the stacking of 2D COFs is crucial since it dictates the effective size and shape of the pores as well as the specific interactions between functional aromatic systems in adjacent layers, both of which will strongly influence the emergent properties of 2D COFs. However, principles for tuning layer stacking are not yet well understood, and many 2D COFs are disordered in the stacking direction. Here, we investigate effects of pendant chain length through a series of 2D imine-linked COFs functionalized with n-alkyloxy chains varying in length from one carbon (C1COF) to 11 carbons (C11COF). This series reveals previously unrecognized and unanticipated trends in both the stacking geometry and crystallinity. C1COF adopts an averaged eclipsed geometry with no apparent offset between layers. In contrast, all subsequent chain lengths lead to some degree of unidirectional slip stacking. As pendant chain length is increased, trends show average layer offset increasing to a maximum of 2.07 Å in C5COF and then decreasing as chain length is extended through C11COF. Counterintuitively, shorter chains (C2–C4) give rise to lower yields of weakly crystalline materials, while longer chains (C6–C9) produce greater yields of highly crystalline materials, as confirmed by powder X-ray diffraction and scanning electron microscopy. Molecular dynamics simulations corroborate these observations, suggesting that long alkyl chains can interact favorably to promote the self-assembly of sheets. In situ proton NMR spectroscopy provides insights into the reaction equilibrium as well as the relationship between low COF yields and low crystallinity. These results provide fundamental insights into principles of supramolecular assembly in 2D COFs, demonstrating an opportunity for harnessing favorable side-chain interactions to produce highly crystalline materials.

3D printing by fused deposition modelling (FDM) enables rapid prototyping and fabrication of parts with complex geometries. Unfortunately, most materials suitable for FDM 3D printing are non-degradable, petroleum-based polymers. The current ecological crisis caused by plastic waste has produced great interest in biodegradable materials for many applications, including 3D printing. Poly(lactic acid) (PLA), in particular, has been extensively investigated for FDM applications. However, most biodegradable polymers, including PLA, have insufficient mechanical properties for many applications. One approach to overcoming this challenge is to introduce additives that enhance the mechanical properties of PLA while maintaining FDM 3D printability. This review focuses on PLA-based nanocomposites with cellulose, metal-based nanoparticles, continuous fibers, carbon-based nanoparticles, or other additives. These additives impact both the physical properties and printability of the resulting nanocomposites. We also detail the optimal conditions for using these materials in FDM 3D printing. These approaches demonstrate the promise of developing nanocomposites that are both biodegradable and mechanically robust.