Nyalaliska W. Utomo

Challenges posed by the chemical incompatibility between nanoparticles and polymer matrices hinder the widespread use of polymer nanocomposites as the material platform for many innovations. In this study, we demonstrate the effectiveness of a versatile approach to the surface functionalization of commercial nanoparticles. To illustrate the importance of proper surface functionalization, the process was used to functionalize high-moment iron nanoparticles to enhance the magneto-mechanical performance of nanoparticle-based magnetorheological elastomers (MREs). We successfully grafted off-the-shelf iron nanoparticles with poly(dimethylsiloxane) (PDMS) ligands, and then used them to fabricate nanoparticle-based anisotropic MREs with reduced stiffness and improved magnetic properties compared with MREs fabricated with the original nonfunctionalized particles. Structural analysis revealed a regular arrangement of nanoparticles with reduced agglomeration within the elastomeric matrix when functionalized particles were used. Mechanical testing showed enhanced deflection and bending performance for these MREs. Furthermore, this improvement of magneto-mechanical performance was obtained at lower effective magnetic content compared with nonfunctionalized particle elastomers. Magnetic characterization, in turn, revealed amplified magnetic anisotropy and improved chain ordering inside the functionalized-particle MREs. Our findings highlight the potential of surface functionalization of magnetic nanoparticles to improve performance in nanocomposites, such as nanoparticle-based MREs with superior mechanical and magnetic properties.

Solid-state electrolytes (SSEs) are challenged by complex interfacial chemistry and poor ion transport through the interfaces they form with battery electrodes. Here, we investigate a class of SSE composed of micrometer-sized lithium oxide (Li ₂ O) particles dispersed in a polymerizable 1,3-dioxolane (DOL) liquid. Ring-opening polymerization (ROP) of the DOL by Lewis acid salts inside a battery cell produces polymer-inorganic hybrid electrolytes with gradient properties on both the particle and battery cell length scales. These electrolytes sustain stable charge-discharge behavior in Li||NCM811 and anode-free Cu||NCM811 electrochemical cells. On the particle length scale, Li ₂ O retards ROP, facilitating efficient ion transport in a fluid-like region near the particle surface. On battery cell length scales, gravity-assisted settling creates physical and electrochemical gradients in the hybrid electrolytes. By means of electrochemical and spectroscopic analyses, we find that Li ₂ O particles participate in a reversible redox reaction that increases the effective CE in anode-free cells to values approaching 100%, enhancing battery cycle life.

Complementary characterization results show that chemical dissolution of transition metal in LiMn ₂ O ₄ is caused by solvolysis-generated HF, which can be suppresed by rational design of a group of nonsolvolytic electrolytes.

A highly stretchable, tunable, self-healing elastomer is realized by separately synthesizing cationic and anionic polymer chains and complexing them.

Solid‐state electrolytes (SSEs) formed inside an electrochemical cell by polymerization of a liquid precursor provide a promising strategy for overcoming problems with electrolyte wetting in solid‐state batteries. Hybrid solid‐state polymer electrolytes (HSPEs) created by in situ polymerization of a conventional liquid precursor containing electrochemically inert nanostructures are of particular interest because they offer a mechanism for selectively reinforcing or adding new functionalities to the electrolyte—removing the need for high degrees of polymerization. The synthesis, structure, chemical kinetics, ion‐transport properties and electrochemical characteristics of HSPEs created by Al(OTf)₃‐initiated polymerization of 1,3‐dioxolane (DOL) containing hairy, nano‐sized SiO₂ particles are reported. Small‐angle X‐ray scattering reveals the particles are well‐dispersed in liquid DOL. Strong interaction between poly(ethylene glycol) molecules tethered to the SiO₂ particles and poly(DOL) lead to co‐crystallization—anchoring the nanoparticles in their host It also enables polymerization–depolymerization processes in DOL to be studied and controlled. The utility of the in‐situ‐formed HSPE, is demonstrated first in Li|HSPE|Cu half cells, which manifest Coulombic efficiencies (CE) values approaching 99%. HSPEs are also demonstrated in solid‐state lithium–sulfur–polyacrylonitrile (SPAN) composite full‐cell batteries. The in‐situ‐formed Li|HSPE|SPAN cells show good cycling stability and thus provide a promising path toward all‐solid‐state batteries.

The weight-average molecular weights of six native cellulose samples in ionic liquids were determined through steady shear viscosity measurements in the ionic liquid butyl methyl imidazolium chloride. The intrinsic viscosity [η] in ethyl methyl imidazolium acetate (EMImAc) is measured using a gravity-driven glass capillary viscometer and found to be independent of temperature in the range of 30–80 °C, disproving a literature report of [η] in EMImAc, exhibiting a strong temperature dependence. Findings are contrasted with values of intrinsic viscosity in cupriethylenediamine hydroxide, the most widely used solvent to dissolve and analyze the molecular weight of cellulose pulps in industry. Differences are tentatively attributed to the different temporary association properties of cellulose chains in the two solvents. Finally, it is demonstrated that cellulose adsorbs at the air/solution interface in three different ionic liquids to create a viscoelastic liquid interfacial layer of higher concentration. Adsorption at the air/solution interface gives an extra contribution to the measured torque in various rotational rheometer geometries, which apparently simply adds to the torque from the pure bulk solution.

Dry native cellulose solutions in 1-butyl-3-methylimidazolium methylphosphonate (EMImMPO₃H), 1-butyl-3-methylimidazolium acetate (EMImAc), and 1-butyl-3-methylimidazolium chloride (BMImCl) ionic liquids (IL) were investigated using subambient linear viscoelastic oscillatory shear. Glass transition temperatures (T_g) of solutions with various cellulose concentrations up to 8.0 wt% were observed as the peaks of loss tangent tan(δ) and loss modulus G′′ in descending temperature sweeps at 1 rad s⁻¹. Cellulose/IL solutions showed a minimum in T_g at ∼2.0 wt% cellulose content before increasing with cellulose concentration, suggesting a perturbation of the strongly structured IL solvents by the cellulose chains. Isothermal frequency sweeps in the vicinity of T_g were used to construct time–temperature-superposition master curves. The angular frequency shift factor a_T as a function of temperature indicates Arrhenius behavior within a 9 K range near T_g, allowing calculation of fragility, which was found to be constant up to 8.0 wt% cellulose concentration. This result implied that increasing cellulose concentration initially decreases T_g due to disrupted ionic regularity of ILs, but does not seem to change their fragility.

Due to their distinctive molecular architecture, ABA triblock copolymers will undergo specific self-assembly processes into various nanostructures upon introduction into a B-block selective solvent. Although much of the focus in ABA triblock copolymer self-assembly has been on equilibrium nanostructures, little attention has been paid to the guiding principles of nanostructure formation during non-equilibrium processing conditions. Here we report a universal and quantitative method for fabricating and controlling ABA triblock copolymer hierarchical structures using solvent-non-solvent rapid-injection processing. Plasmonic nanocomposite hydrogels containing gold nanoparticles and hierarchically-ordered hydrogels exhibiting structural color can be assembled within one minute using this rapid-injection technique. Surprisingly, the rapid-injection hydrogels display superior mechanical properties compared with those of conventional ABA hydrogels. This work will allow for translation into technologically relevant areas such as drug delivery, tissue engineering, regenerative medicine, and soft robotics, in which structure and mechanical property precision are essential.

Cellulose coagulates upon adding water to its solutions in ionic liquids. Although cellulose remains in solution with much higher water contents, here we report the effect of 0–3 wt % water on solution rheology of cellulose in 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate. Fourier transform infrared spectroscopy, thermal gravimetric analysis, and polarized light microscopy were also used to study water absorbance to the solutions. Tiny amounts of water (0.25 wt %) can significantly affect the rheological properties of the solutions, imparting a yield stress, while dry solutions appear to be ordinary viscoelastic liquids. The yield stress grows linearly with water content and saturates at a level that increases with the square of cellulose content. Annealing the solutions containing small amounts of water at 80 °C for 20 min transforms the samples to the fully dissolved “dry” state.