Yifei Wang

Solvents play a critical role in chemical reactivity. Ternary solvent systems—such as combinations of water, a water-miscible polar organic solvent, and a water-immiscible oil—have been shown to organize into nanophase-structured domains. However, the influence of these nanophases on reaction kinetics remains largely unexplored. In this study, we investigate how nanophase structuring within ternary solvents impacts the kinetics of strain-promoted azide-alkyne click reactions. Ternary solvents were designed to either promote or suppress nanophase structuring, with dynamic light scattering being used to assess nanoscale domain formation. High-throughput UV-Vis kinetic analysis revealed that hydrophobic reactants exhibited significantly enhanced reaction rates within ternary solvents, beyond the hydrophobic effects induced within water-containing binary solvents. Rates were elevated for ternary compositions within a small, specific region of the ternary phase diagram expected to contain oil-in-water nanophases. This kinetic enhancement effect was removed when hydrophilic reactants were used or when nanophase stability was reduced. These findings suggest that the structure of ternary solvent nanophases can be harnessed to modulate reaction kinetics and have influence beyond that of the bulk solvent properties like the polarity or water-induced hydrophobic interactions between reagents. This insight has broad implications for solvent design in synthetic chemistry, biocatalysis, and prebiotic chemistry, offering insight into controlling chemical reactivity in complex, multicomponent solvent systems.

Solid–liquid composites (SLCs) combine the properties of solids and liquids, enhancing functionalities and expanding potential applications. Traditional methods for creating SLCs often face challenges such as low mass transfer efficiency, difficulty in controlling separation behavior, and substantial waste production. Herein, we report a new approach to solve these challenges by using disulfide-based responsive polymeric capsule shells to make liquid-filled monoliths for carbon capture. The capsules are prepared through interfacial polymerization and contain either non-polar poly(α-olefin)₄₃₂ or highly polar 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][TFSI]) at 74–82 wt%. Upon gentle heating, the dynamic disulfide bonds of the isolated capsules undergo bond exchange, leading to the fusion of capsule shells into free-standing monoliths that retain >89 wt% of their liquid core and remain stable for at least two weeks. These monoliths demonstrate CO₂ absorption rates and capacities comparable to their capsule counterparts; further, in response to radiofrequency (RF), they reach the CO₂ desorption temperature in only ∼31 s. This innovative system addresses the limitations of conventional SLC fabrication techniques, offering a versatile and practical approach to fusing polymer capsule shells for applications across separation, energy storage, and carbon capture applications.

Polymeric capsules with core-shell structures have been widely explored for molecule separations, energy storage, and catalysis, among other applications. To tailor the application-oriented performance of these structures, researchers have imparted stimuli-responsive properties to the shells. In contrast to capsules with "static" shells, stimuli-responsive capsule shells not only protect the core from the external environment, but also aid in handling and impart properties such as on-demand release of cargo and varied shell permeability, as well as provide a platform for the fabrication of advanced structures. The composition and properties of polymer shells can be tuned through incorporation of dynamic covalent bonds into the polymer backbones, or introduction of segments or pendant side chains which can leverage intermolecular (e.g., hydrogen bonding) or electrostatic interactions to give response. Most reports on responsive polymer capsules focus on their application in cargo delivery, a topic that is heavily reviewed elsewhere. In complement, this minireview addresses responsive polymer capsules and their applications beyond drug delivery, focusing on structure-property relationships. We first highlight the most common fabrication techniques for core-shell structures including hard template, soft template, and microfluidic methods, among which we emphasize our utilization of interfacial polymerization and polymer precipitation within a Pickering emulsion template. We then provide a concise review of commonly employed chemistries for responsive polymer shells based on stimuli, including our contribution on the incorporation of dynamic covalent polymer backbones into thermo-responsive capsule shells. Application-oriented performances of the responsive core-shell structures are then highlighted. Finally, we outline opportunities for advancing the performance-related properties of responsive capsules, wherein we propose new directions where responsive polymer-based capsules can have critical impact in the development of new technologies. This minireview addresses responsive polymer capsules and their applications beyond drug delivery, focusing on structure-property relationships.

Salt hydrate phase change materials are important in advancing thermal energy storage technologies for the development of renewable energies. At present, their widespread use is limited by undesired undercooling and phase separation, as well as their tendency to corrode container materials. Herein, we report a direct ink writing (DIW) additive manufacturing technique to print noncorrosive salt hydrate composites with thoroughly integrated nucleating agents and thermally conductive additives. First, salt hydrate particles are prepared from nonaqueous Pickering emulsions and then employed as rheological modifiers to formulate thixotropic inks with polymer dispersions in toluene serving as the matrix. These inks are successfully printed at room temperature and cured by solvent evaporation under ambient conditions. The resulting printed and cured composites, containing up to 70 wt % of the salt hydrate, exhibit reliable thermal cyclability for 10 cycles and suppressed undercooling compared to the bulk salt hydrate. Remarkably, the composites consistently maintain their structural integrity and thermal performance throughout the entirety of both the melting and solidification processes. We demonstrate the versatility of this approach by utilizing two salt hydrates, magnesium nitrate hexahydrate (MNH, T_m = 89 °C) and zinc nitrate hexahydrate (ZNH, T_m = 36 °C), to achieve desired thermal characteristics across a wide range of temperatures. Further, we establish that the incorporation of carbon black in these inks enhances the thermal conductivity by at least 33%. This approach consolidates the strengths of additive manufacturing and salt hydrate phase change materials to harness customizable thermal properties, well suited for targeted thermal energy management applications.

Porous MXene-polymer composites have gained attention due to their low density, large surface area, and high electrical conductivity, which can be used in applications such as electromagnetic interference shielding, sensing, energy storage, and catalysis. High internal phase emulsions (HIPEs) can be used to template the synthesis of porous polymer structures, and when solid particles are used as the interfacial agent, composites with pores lined with the particles can be realized. Here, we report a simple and scalable method to prepare conductive porous MXene/polyacrylamide structures via polymerization of the continuous phase in oil/water HIPEs. The HIPEs are stabilized by salt flocculated Ti ₃ C ₂ T _x nanosheets, without the use of a co-surfactant. After polymerization, the polyHIPE structure consists of porous polymer struts and pores lined with Ti ₃ C ₂ T _x nanosheets, as confirmed by scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The pore size can be tuned by varying the Ti ₃ C ₂ T _x concentration, and the interconnected Ti ₃ C ₂ T _x network allows for electrical percolation at low Ti ₃ C ₂ T _x loading; further, the electrical conductivity is stable for months indicating that in these composites, the nanosheets are stable to oxidation at ambient conditions. The polyHIPEs also exhibit rapid radio frequency heating at low power (10 °C s ⁻¹ at 1 W). This work demonstrates a simple approach to accessing electrically conductive porous MXene/polymer composites with tunable pore morphology and good oxidation stability of the nanosheets.