Cellulose nanocrystals (CNCs) are commonly produced with carboxylic acid surface functionalities, as it aids the dispersion in aqueous solvents. However, the carboxylic acid-functionalized CNCs (CNC-COOHs) exhibit poor dispersibility in nonaqueous solvents due to their self-aggregation, limiting their integration into many biosourced solvent-based technologies, such as inkjet printing, spin-coating, etc. Aimed at improving the dispersibility of CNCs in nonaqueous solvents, molecular dynamics simulations were performed to study the underlying reasons for the low dispersibility of CNC-COOHs in biosourced ethanol and investigate how surface functionalization impacts their self-aggregation tendency in this solvent. The potential of mean force (PMF) calculations revealed that the aggregation of CNC-COOHs through their hydrophilic surfaces drives their low dispersibility in ethanol and that the functionalization of CNC-COOHs with alkyl groups (CNC-COOH-alkyl, with alkyl being ethyl, butyl, hexyl, and octyl) reduces their aggregation tendency. The lower binding tendency of the alkylated CNCs than CNC-COOHs stems from a higher binding entropy loss and a lower attraction between their surfaces, as alkylation increases the distance between bound CNCs. The higher binding entropy loss of CNC-COOH-alkyls is attributed to alkyl groups' reduced degrees of freedom at the contact point between CNC-COOH-alkyls. As a result, the highest dispersibility can be achieved when the CNC-COOHs are functionalized with the longer alkyl groups, i.e., hexyl and octyl. PMF-derived binding free energy values predict the dispersibility trend as CNC-COOH-octyl ≈ CNC-COOH-hexyl > CNC-COOH-butyl > CNC-COOH-ethyl > CNC-COOH. Experimental tests for synthesized CNC-COOH-alkyls with ethyl, butyl, and hexyl groups confirmed simulation predictions, wherein the increasing size of the alkyl chain increased CNC dispersibility. CNC-COOH-hexyl dispersed well in ethanol and remained stable for 1 day. The findings of this research enhanced our understanding of how functionalization of the CNCs improves their stability in biosourced nonaqueous solvents such as ethanol and opens the avenue for their integration in biosourced solvent-based technologies.

Dynamic liquid crystalline polymers (dLCPs) incorporate both liquid crystalline mesogens and dynamic bonds into a single polymeric material. These dual functionalities impart order-dependent thermo-responsive mechano-optical properties and enhanced reprocessability/programmability enabling their use as soft actuators, adaptive adhesives, and damping materials. While many previous works studying dynamic LCPs utilize dynamic covalent bonds, metallosupramolecular bonds provide a modular platform where a series of materials can be accessed from a single polymeric feedstock through the variation of the metal ion used. A series of dLCPs were prepared by the addition of metal salts to a telechelic 2,6-bisbenzimidazolylpyridine (Bip) ligand endcapped LCP to form metallosupramolecular liquid crystal polymers (MSLCPs). The resulting MSLCPs were found to phase separate into hard and soft phases which aids in their mechanical robustness. Variations of the metal salts used to access these materials allowed for control of the thermomechanical, viscoelastic, and adhesive properties with relaxations that can be tailored independently of the mesogenic transition. This work demonstrates that by accessing phase separation through the incorporation of metallosupramolecular moieties, highly processable yet robust MSLCP materials can be realized. This class of materials opens the door to LCPs with bulk flow behavior that can also be utilized as multi-level adhesives.

Memory-forming properties introduce a new paradigm to the design of adaptive materials. In dense suspensions, an adaptive response is enabled by non-Newtonian rheology; however, typical suspensions have little memory, which implies rapid cessation of any adapted behavior. Here we show how multiple adaptive responses can be achieved by designing suspensions where different stress levels trigger different memories. This is enabled by the interplay of interactions based on frictional contact and dynamic chemical bridging. These two interactions lead to novel rheology with several well-delineated shear thinning and thickening regimes, which enable stress-activated memories associated with opposite time-dependent trends. As a result, in response to different stress levels, the suspension can evolve by either softening or stiffening and is trainable, exhibiting targeted viscosity and energy dissipation with repeated low-velocity impact. Such behavior, usually associated with mechanical metamaterials, suggests that dense suspensions with multiple memories can be viewed as trainable rheological metafluids.

Organic Ionic Plastic Crystals (OIPCs) are a unique class of polycrystalline solid-state electrolytes that combine long-range structural order with localized rotational disorder, enabling both mechanical compressibility and ion transport. Unlike conventional crystalline or amorphous solid electrolytes, OIPCs undergo thermotropic phase transitions, where molecular reorientation significantly influences transport properties. As polycrystalline materials, OIPCs inherently contain grain boundaries (GBs), which are hypothesized to play a crucial role in ionic conductivity. However, no direct visualization of the multigrain structure and GBs in OIPCs has been reported, leaving a fundamental gap in understanding their role in ion transport. In this study, we present the first direct optical visualization of GBs in pure OIPCs, addressing the long-standing question of how GB networks influence ion transport in pristine plastic crystal electrolytes. Using polarized optical microscopy (POM), we resolve GB morphology and track its evolution across different thermotropic phases, revealing phase-dependent variations in GB connectivity and microstructure. To establish a direct structure-transport correlation, we integrate simultaneous interdigitated electrode (IDE) impedance spectroscopy and POM imaging, enabling real-time electrochemical characterization of visually resolved GBs. Our results demonstrate that GBs are not passive defects but active facilitators of ion transport, with specific GB structures enhancing percolation pathways while others impede conductivity. To further investigate how salt doping modifies GB morphology and ion transport, we introduce sodium bis(fluorosulfonyl)imide (NaFSI) and tetrabutylphosphonium bis(fluorosulfonyl)imide () into OIPCs and monitor their impact on phase behavior, GB structure, and ionic conductivity. Our preliminary results indicate that NaFSI and systematically alter GB connectivity, leading to tunable transport pathways. The correlation between GB structure and conductivity confirms that grain boundary engineering through composition control is a viable strategy for optimizing sodium-ion conducting solid electrolytes. This work provides a comprehensive, multi-scale assessment of GB-mediated ion transport in IPCs, offering critical insights into how polycrystalline morphology dictates bulk ionic conductivity. By combining direct GB visualization, real-time electrochemical measurements, and phase-dependent morphological analysis, our study establishes a framework for the rational design of high-performance sodium-based solid electrolytes, contributing to the development of next-generation sodium-ion batteries. Funding Acknowledgments: This work was primarily supported by the University of Chicago Materials Research Science and Engineering Center (MRSEC) through a Seed Project, funded by the National Science Foundation under Award No. DMR-2011854. Additional support was provided by the National Science Foundation Partnerships for Research and Education in Materials (PREM) under Award No. 2425025.

Introducing dynamic covalent chemistries into polymer networks allows access to complex linear viscoelasticity, owing to the reversible nature of the dynamic bonds. While this macroscopic mechanical behavior is influenced by the dynamic exchange of these chemistries, connecting the microscopic dynamics to the bulk properties is hindered by the time scale conventional techniques can observe. Here, light scattering passive microrheology is applied to probe short-time dynamics of dynamic covalent networks that consist of telechelic benzalcyanoacetate (BCA) Michael acceptors and thiol-functionalized cross-linkers. The mean-squared displacement of probe particles embedded in the dynamic covalent networks is analyzed to explore the microscopic short-term dynamics and relaxation behavior. A series of Michael acceptors with varying equilibrium constants when reacted with thiols confirms that the observed microscopic relaxation arises from the bond dissociation. The data suggest the particles undergo local superdiffusivity, suggesting that bond breaking and bond reformation exert external force on the probe particles driving this non-Brownian anomalous diffusion.

In materials, the ability to retain the memory of applied stresses or strains opens up new opportunities for enhancing their performance adaptively via training. In dense suspensions, a stress-adaptive response is enabled by non-Newtonian rheology; however, typical suspensions have little memory, which implies rapid cessation of any adapted behavior. Here, we show how multiple adaptive responses can be achieved by designing suspensions where different stress levels trigger different memories. This is achieved through the interplay of particle interactions based on frictional contact and dynamic chemical bridging. These two interactions give rise to stress-activated memories associated with opposite time-dependent trends. As a result, a suspension can be trained to adapt to applied stress either by softening or stiffening, exhibiting targeted viscosity and energy dissipation in response to low-velocity impact. Such behavior, usually associated with mechanical metamaterials, suggests that dense suspensions with multiple memories can be viewed as trainable rheological metafluids.

Slide-ring polycatenane networks (SR-PCNs) are covalent polymer networks that contain interlocked doubly threaded rings that serve as additional topological constraints. These rings are catenated by the covalent polymer network, enabling them to slide along the polymer backbone between the covalent crosslinks. Herein, the SR-PCN synthesis is achieved by reacting a metal-templated doubly threaded pseudo[3]rotaxane (P3R) crosslinker with a chain extender and a covalent crosslinking moiety. The focus of this work is to explore the impact that monomer structure has on the SR-PCN synthesis, with the goal of increasing the reaction kinetics of the P3R to optimize ring incorporation in the network and minimize side reactions. It is shown that through monomer optimization it is possible to synthesize SR-PCNs with high gel fractions and ring content, allowing a detailed evaluation of the influence of the rings on the properties of these interlocked networks. Compared with control covalent networks and a tangled network, formed using a 1 : 2 metal-ligand complex, SR-PCNs exhibit enhanced swelling and frequency-dependent viscoelastic behavior, which are attributed to the motion of the rings. Molecular simulations of model interlocked networks elucidate the underlying mechanisms governing the mechanical behavior and provide insights into the structural changes induced by the rings. In addition, the responsive behavior of these SR-PCNs is explored upon exposure to stimuli that impact the ring mobility, such as changes in solvent, metalation, and protonation of the ligand moieties.

High-T g, epoxy-amine networks are used ubiquitously across various industries as lightweight adhesives; however, a cross-cutting need is improved ductility in these glassy materials. Tailoring the location of photoactive azobenzene moieties (interstitial, pendent, or at the cross-link) within high-T g networks elucidated several structural relationships to mechanical responses and improvements in ductility. Within the linear viscoelastic regime, probed using dynamic mechanical analysis, the mechanical changes during irradiation were strongly dependent on light intensity, with a glass-to-rubber transition realized as the intensity increased from 330 to 3000 mW/cm2. Using embedded thermocouples, a bulk thermal contribution to the material softening was estimated, helping to decouple the photothermal and photomechanical response in the activated networks. Nonuniform light penetration during quasi-static testing of thick (6 mm) sample specimens illustrated a trade-off in performance with azobenzene concentration. Improvements in high-rate impact performance relied on a change in failure mechanisms within the impacted plate caused by the local change in ductility with irradiation. Maintaining the rapid (similar to 10 s) mechanical response within these materials across several testing length-scales and deformation rates highlights a relatively unexplored avenue to manage an "on-demand" mechanical response.

Versatile technologies that can deliver both RNA and protein payloads could streamline development, simplify manufacturing and expand the capabilities of combination therapies. Here we demonstrate an efficient approach to forming ca. 100 nm polymer vesicles (polymersomes) capable of rapid self-assembly without organic solvents, avoiding the need for post-encapsulation purification. Block copolymers are designed with a lower critical solution temperature that renders them soluble in aqueous medium under standard refrigeration, but they spontaneously assemble at room temperature into large batches of nanoparticles with predictable size and morphology. The nanomaterials are designed with charged and biofunctional moieties to drive payload affinity and in vivo targeting, while both siRNA and proteins can be encapsulated during warming at >75% loading efficiencies. Formulations can be stored in a dry state for greater hydrolytic stability under standard refrigeration and can be diluted directly from the vial, bypassing the need for purification required for high scalability. We use our system for in vivo delivery in protein subunit vaccination, immune tolerance induction and siRNA interference therapy in cancer.

The structural and transport properties of an organic ionic plastic crystal (OIPC), triisobutyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1444FSI) with the addition of lithium bis(fluorosulfonyl)imide (LiFSI) have been investigated with a combined experimental and computational approach. After establishing the effect of thermal processing on structural and transport properties of P1444FSI, a consistent processing procedure was established to understand how P1444FSI properties change with increasing temperature and LiFSI concentration. Elevated rotational motions of ions on the plastic crystalline lattice coincides with and may facilitate solid-solid phase transitions in P1444FSI, while the transport of lithium cations within LiFSI-doped P1444FSI was found to be dominated by increased translational diffusivity with little change in rotational diffusivity. The trade-off between increased ion conductivity in the solid-state and decreased mechanical robustness with increasing LiFSI concentration presents an important challenge for P1444FSI-based solid-state electrolytes moving forward.

Training has emerged as a promising materials design technique in which function can be achieved through repeated physical modification of an existing material rather than by direct chemical functionalization, cutting, or reprocessing. This work investigates both the ability to train for function and then to erase that function on-demand in macroscopic metamaterials made from liquid crystal elastomers. We first show that the Poisson's ratio of these disordered arrays can be tuned via directed aging to induce an auxetic response. We then show that the arrays can be reset and retrained for another local mechanical function, allostery, thus demonstrating pluripotent functionality.

The thia-Michael reaction, i.e., the addition of a thiol to an α,β-unsaturated carbonyl moiety, has recently gained significant attention within the field of dynamic covalent chemistry. Interestingly, including an additional electron-withdrawing group at the α-position of the Michael acceptor can result in room temperature (rt), catalyst-free dynamic thia-Michael reactions. Importantly, the electronic nature of the Michael acceptor can be used to tune the equilibrium constant (Keq) of these reactions. Herein we report how sterics can be used to enhance the Keq of these rt dynamic bonds. A series of benzalcyanoacetate, benzalcyanoacetamide, and benzalisoxazolone-based Michael acceptors with varying substituents in the ortho-position of their β-phenyl rings were investigated. By placing substituents in such a position, out-of-plane twisting was created between the β-phenyl ring and the α,β-unsaturated carbonyl, raising the overall energy of the reactants and leading to significant increases in Keq. By modulating the size of the ortho-substituent, the magnitude of Keq could be increased by 1.3 to 6.8 times relative to their para-substituted counterparts. The ortho-substituted acceptors could still be tuned electronically through the para-position, allowing access to r.t., dynamic covalent bonds whose Keq could be tuned from 10 to 1.8 × 106 M-1 across the three acceptor families.

Redox targeting flow batteries (RTFBs) allow for enhanced energy density over traditional flow batteries by including immobilized redox-active solids in the tank, charged and discharged via soluble redox mediators (RMs). This study presents a nonaqueous polymeric RTFB using crosslinked poly[(4-(N,N-dimethylaminomethyl)ferrocenylmethyl)styrene] hexafluorophosphate (xPs–[(FcNMe2)+][PF6–]) as the polymeric redox target (polyRT) and evaluates three RM systems: a single-mediator redox targeting (SMRT) system with [FcNMe₃⁺][PF₆⁻] or MEEPT, and a dual-mediator redox targeting (DMRT) system combining MEEPT and Fc. Discharge capacity utilizations of 90% and 63% were achieved for the [FcNMe₃⁺][PF₆⁻]- and MEEPT-based SMRT systems, respectively, while the DMRT system reached 106%, indicating near-complete or enhanced accessibility through cooperative RM action. In particular, MEEPT and Fc enabled staged discharge across different redox potentials, reducing voltage losses and improving voltage efficiency. A Nernstian thermodynamic model was applied to rationalize the performance trends by coupling RM and polyRT state-of-charge (SOC) profiles. Two metrics were introduced: η_RM, the accessible fraction of mediator discharge capacity, and η_RT^*, the model predicted accessibility of the polyRT. The model showed reasonable agreement with experimental data, highlighting that small redox potential offset and high η_RM are critical for optimal SMRT performance. Together, these results establish design criteria for selecting and pairing RMs with polyRT, offering a practical framework for advancing high-capacity, high-efficiency RTFBs.

The solution-state fluxional behavior of bullvalene, first investigated over 60 years ago, has fascinated physical organic and supramolecular chemists alike. Little effort, however, has been put into investigating bullvalene applications in the bulk, partially due to difficulties in characterizing such dynamic systems. To address this fundamental knowledge gap, herein we probe whether bullvalene Hardy-Cope rearrangements can be mechanically perturbed in bulk polymer networks. We first demonstrate the impact of bullvalene fluxionality in bulk thermoset elastomers using modulated differential scanning calorimetry; enhanced enthalpic relaxation events are observed in the non-reversing heat flow for bullvalene-containing materials relative to “static” control networks. Then, we use dynamic mechanical analysis to demonstrate that the activation barrier to glass transition is significantly elevated for bullvalene-containing materials (ca. 90 kcal/mol) relative to “static” control networks (ca. 50 kcal/mol). Furthermore, bullvalene rearrangements can be “mechanically activated” at low temperature in the glassy region; such behavior facilitates energy dissipation (at least ca. 3-fold increase in hysteresis energy) and polymer chain alignment to stiffen the material (at least ca. 2-fold increase in Young’s modulus) under load. Collectively, this work showcases bullvalene as a reversible chemical mechanophore in the modulation of viscoelastic behaviors.

The morphological features of particles, notably shape anisotropy, critically influence the rheological properties of dense suspensions, spanning both natural and engineered systems. This work explores the potential of using shape memory particles to dynamically regulate suspension fluid flow through controllable shape transformations. First, we synthesize shape-memory particles with programmable anisotropy from liquid crystal elastomers, such that the stiffness and shapes of the particles can be tuned by manipulating temperature. Our findings reveal that suspensions from such particles exhibit significant tunability in shear thickening behavior, transitioning from discontinuous shear thickening to a Newtonian-like response within a narrow temperature range of 60 [Formula: see text]C. This capability to modulate rheological responses in situ presents an approach for addressing processing challenges in many applications where control over flow behavior is paramount. Furthermore, we also show that suspensions composed of these anisotropic particles can undergo physical aging, and evolve into a glassy state. This state can be escaped upon activation of the shape memory effect. This reversibility underscores the potential for using such materials to engineer systems that can enter or come out of kinetic arrest by leveraging internal mechanical responses to external stimuli. The insights gained here not only broaden our understanding of the interplay between particle geometry and suspension dynamics but also pave the way for leveraging ensembles of stimuli-responsive objects to precisely control collective behaviors in many-body systems.

Carboxylic acid functionalized cellulose nanocrystals have been obtained from biomass and evaluated as aqueous, environmentally sustainable alternatives to conventional polyvinylidene difluoride binders for cathodes of lithium-ion batteries.

This study seeks to explore the relationship between particle polarity and the electrochemical accessibility of organo-disulfide-based redox-active particles. Micron-sized poly(glycidyl methacrylate) (PMGA) particles were synthesized and subsequently cross-linked with thiadiazole disulfide to produce redox-active particles (DS-RAPs). The residual glycidyl units underwent reactions with various side chains to modulate the polarity of the DS-RAPs. These side chains vary from nonpolar aliphatic N-methylbutylamine (MBA) to the more polar oligoethylene glycol amine (EGA) and glycidyl carbonate (GC) moieties. Cyclic voltammetry reveals that functionalization with polar side chains enhances electrochemical accessibility, with DS-RAP(GC) demonstrating the highest accessibility in both acetonitrile and tetraglyme-based electrolytes. Testing the DS-RAP derivatives as cathode electrodes in a lithium cell with a LiTFSI/tetraglyme electrolyte indicates that DS-RAP(GC) yields the highest specific capacities, energy efficiency, and best kinetics at 0.1C. Conversely, C-rate dependence measurements show that DS-RAP(EGA) has higher specific capacities at faster C-rates and is more resilient to mass transport limitations compared to DS-RAP(GC) and DS-RAP(MBA). This is attributed to greater electrolyte swelling in DS-RAP(EGA) and higher ion diffusivity, as evidenced by galvanostatic intermittent titration technique (GITT) measurements. Lastly, long-term cycling tests at 0.1C indicate minimal degradation, with the resulting capacity fade attributed to charge trapping during the continuous reversible oxidation/reduction of disulfides. Overall, these findings contribute significantly to the development of effective RAPs for energy storage applications, highlighting the pivotal role of chemical modifications via side chain engineering in controlling particle polarity to enhance charge transport and overall electrochemical performance.

Control of frictional interactions among liquid-suspended particles has led to tunable, strikingly non-Newtonian rheology via the formation of strong flow constraints as particles come into close proximity under shear. Typically, these frictional interactions have been in the form of physical contact, controllable via particle shape and surface roughness. We investigate a different route, where molecular bridging between nearby particle surfaces generates a controllable constraint to relative particle movement. This is achieved with surface-functionalized colloidal particles capable of forming dynamic covalent bonds with telechelic polymers that comprise the suspending fluid. At low shear stress this results in particles coated with a uniform polymer brush layer. Beyond an onset stress σ* the telechelic polymers become capable of bridging and generate shear thickening. Over the size range investigated, we find that the dynamic brush layer leads to dependence of σ* on particle diameter that closely follows a power law with exponent -1.76. In the shear thickening regime, we observe an enhanced dilation in measurements of the first normal stress difference N1 and reduction in the extrapolated volume fraction required for jamming, both consistent with an effective particle friction that increases with decreasing particle diameter. These results are discussed in light of predictions for suspensions of hard spheres and of polymer-grafted particles.

Cellulose nanocrystal (CNC)-reinforced composites are gaining commercial attention on account of their high strength and sustainable sourcing. Grafting polymers to the CNCs in these composites has the potential to improve their properties, but current solution-based synthesis methods limit their production at scale. Utilizing dynamic hindered urea chemistry, a new method for the melt-functionalization of cellulose nanocrystals has been developed. This method does not require toxic solvents during the grafting step and can achieve grafting densities competitive with state-of-the-art solution-based grafting methods. Using cotton-sourced, TEMPO-oxidized CNCs, multiple molecular weights of poly(ethylene glycol) (PEG) as well as dodecane, polycaprolactone, and poly(butyl acrylate) were grafted to the CNC surface. With PEG-grafted nanoparticles, grafting densities of 0.47 chains nm-2 and 0.10 chains nm-2 were achieved with 2000 and 10,000 g mol-1 polymer chains respectively, both of which represent significant improvements over previous reports for solution-based PEG grafting onto CNCs. image

Several FDA-approved adjuvants signal through the NLRP3 inflammasome and IL-1β release. Identifying small molecules that induce IL-1β release could allow targeted delivery and structure–function optimization, thereby improving safety and efficacy of next-generation adjuvants. In this work, we leverage our existing high throughput data set to identify small molecules that induce IL-1β release. We find that ribociclib induces IL-1β release when coadministered with a TLR4 agonist in an NLRP3- and caspase-dependent fashion. Ribociclib was formulated with a TLR4 agonist into liposomes, which were used as an adjuvant in an ovalbumin prophylactic vaccine model. The liposomes induced antigen-specific immunity in an IL-1 receptor-dependent fashion. Furthermore, the liposomes were coadministered with a tumor antigen and used in a therapeutic cancer vaccine, where they facilitated rejection of E.G7-OVA tumors. While further chemical optimization of the ribociclib scaffold is needed, this study provides proof-of-concept for its use as an IL-1 producing adjuvant in various immunotherapeutic contexts.