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1. Thermal and Mechanical Properties of Lignin Derivative–Sulfur Composites

   https://doi.org/10.1002/pol.20240566  

   Kapuge_Dona, Nawoda L; Sauceda‐Oloño, Perla Y; Smith, Rhett C (February 2025, Journal of Polymer Science)

   ABSTRACT Lignin, comprising 20%–35% of lignocellulosic biomass, is the second most abundant biopolymer after cellulose. As the bioethanol industry expands, the accumulation of lignin by‐products necessitates innovative valorization strategies. This study explores the synthesis and characterization of lignin‐derived composites. Specifically, the reaction of 20 wt. % lignin‐derived guaiacol or syringol with 80 wt. % elemental sulfur gives composites GS₈₀and SS₈₀, respectively. The chemical structures of composites were elucidated using GC–MS,¹H NMR, and UV–Vis spectroscopy, revealing the formation of both SC_aryland SC_alkylbonds. Thermal and morphological analysis (via TGA, DSC, PXRD, and SEM‐EDS) indicated SS₈₀has higher crystallinity and thermal stability than GS₈₀, attributed to a higher degree of crosslinking and a greater content of dark sulfur. Mechanical testing showed SS₈₀exhibits superior compressional and flexural strengths, and enhanced Young's modulus and Shore hardness, compared to GS₈₀. Notably, the mechanical strength parameters for SS₈₀are comparable to those of C62 class bricks used in construction applications. These findings suggest that lignin‐derived composites, particularly those incorporating syringol, can provide viable alternatives to traditional materials in various applications, contributing to both waste valorization and sustainable materials science. 

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2. Superlubricity of pH-responsive hydrogels in extreme environments

   https://doi.org/10.3389/fchem.2022.891519  

   Chau, Allison L.; Getty, Patrick T.; Rhode, Andrew R.; Bates, Christopher M.; Hawker, Craig J.; Pitenis, Angela A. (August 2022, Frontiers in Chemistry)

   Poly(acrylamide- co -acrylic acid) (P(AAm- co -AA)) hydrogels are highly tunable and pH-responsive materials frequently used in biomedical applications. The swelling behavior and mechanical properties of these gels have been extensively characterized and are thought to be controlled by the protonation state of the acrylic acid (AA) through the regulation of solution pH. However, their tribological properties have been underexplored. Here, we hypothesized that electrostatics and the protonation state of AA would drive the tribological properties of these polyelectrolyte gels. P(AAm- co -AA) hydrogels were prepared with constant acrylamide (AAm) concentration (33 wt%) and varying AA concentration to control the amount of ionizable groups in the gel. The monomer:crosslinker molar ratio (200:1) was kept constant. Hydrogel swelling, stiffness, and friction behavior were studied by systematically varying the acrylic acid (AA) concentration from 0–12 wt% and controlling solution pH (0.35, 7, 13.8) and ionic strength ( I = 0 or 0.25 M). The stiffness and friction coefficient of bulk hydrogels were evaluated using a microtribometer and borosilicate glass probes as countersurfaces. The swelling behavior and elastic modulus of these polyelectrolyte hydrogels were highly sensitive to solution pH and poorly predicted the friction coefficient ( µ ), which decreased with increasing AA concentration. P(AAm- co -AA) hydrogels with the greatest AA concentrations (12 wt%) exhibited superlubricity ( µ = 0.005 ± 0.001) when swollen in unbuffered, deionized water (pH = 7, I = 0 M) and 0.5 M NaOH (pH = 13.8, I = 0.25 M) ( µ = 0.005 ± 0.002). Friction coefficients generally decreased with increasing AA and increasing solution pH. We postulate that tunable lubricity in P(AAm- co -AA) gels arises from changes in the protonation state of acrylic acid and electrostatic interactions between the probe and hydrogel surface. 

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3. Titanium Oxysulfate‐Derived 1D Lepidocrocite Titanate Nanostructures

   https://doi.org/10.1002/admi.202400866  

   Maity, Sukanya; Ibrahim, Mohamed; Badr, Hussein; Reji, Treesa; Hassig, Mary Q; Zhang, Tongjie; Li, Christopher; Rosén, Johanna; Barsoum, Michel W (November 2024, Advanced Materials Interfaces)

   Abstract Nanostructured titania, TiO₂, holds significant importance in various scientific fields and technologies for their distinctive properties and multipurpose characteristics. In this article, the facile, economical, and scalable synthesis of 1D lepidocrocite, 1DL, titania nanostructures derived from a water‐soluble Ti precursor, titanium oxysulfate (with oxidation of Ti⁺⁴) at temperature <100 °C under atmospheric pressure is discussed. Titanium oxysulfate with tetramethyl ammonium hydroxide, TMAH, is simply reacted to yield individual lepidocrocite titania‐based chain‐forming nanofilaments, NFs, 6 × 6 Ųin minimal cross‐section and aspect ratios of ≈20 1DLs. If only ethanol is used for washing, the 1DL self‐assemble into ≈10 µm, porous mesostructured particles, PMPs. If water is used, quasi‐2D sheets form instead. Characterization of the resulting powders showed them to be quite similar to those derived from TiB₂, and other water‐insoluble Ti precursors. The 1DL bandgap energies are ≈4 eV, due to quantum confinement. They adsorbed rhodamine 6G. The latter also sensitized the 1DLs and allowed for dye degradation using only visible light. Used as electrodes in supercapacitors, the 1DLs can be cycled over 1.6 V and result in high power densities (300 W kg⁻¹). Stronger birefringence started to appear in samples with concentrations >15 gL⁻¹indicating the formation of a liquid crystal phase. This new synthesis protocol enables the cheaper scalable production of 1DLs with significant implications across various fields. 

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4. Scalable, Bottom‐Up Synthesis of Transition Metal–Doped Quantum Confined, 1D Titanate‐Based Lepidocrocite Nanofilaments, Their Electronic Structures and Oxygen Evolution Reactivity

   https://doi.org/10.1002/admi.202500681  

   Ibrahim, Mohamed A; Singh, Devraj; McMoil, Aidan; Hassig, Mary Qin; Janani, Raja; Snyder, Joshua D; Barsoum, Michel W (February 2026, Advanced Materials Interfaces)

   ABSTRACT This work presents a scalable, bottom‐up approach for doping quantum confined, 1D lepidocrocite (1DL) titanate nanofilaments (NFs) with transition metal (TM) cations Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, and Cu²⁺ to enhance their photo‐ and electrocatalytic properties. Here we react titanium oxysulfate with tetramethylammonium hydroxide at 80°C for 12 h at one atmosphere. By incorporating metal salts during synthesis, uniform doping within the 1DL backbone is achieved. The resulting TM‐doped 1DL NFs all exhibit lower bandgap energies, E_g, than the undoped samples (3.89 eV); some by as much as 0.8 eV for Mn²⁺ at 1 mol% doping, extending optical absorption into the visible region. X‐ray diffraction, scanning electron microscopy, UV–Vis spectroscopy, inductively coupled plasma analysis, and X‐ray photoelectron spectroscopy confirm the successful doping and structural integrity of our materials. The photocatalytic performance of the 1 mol% doped NFs is significantly enhanced, with a 95% degradation of rhodamine 6G dye under visible light in just 30 min, compared to only 65% degradation for the undoped 1DL NFs. In electrocatalysis, the Ni‐doped 1DL NFs show superior oxygen evolution reaction (OER) activity, with an overpotential of 319 mV at 10 mA cm⁻², which is lower than the 383 mV for undoped 1DL NFs. The Ni‐doped 1DL also has the lowest Tafel slope of 145 mV/dec at 1 mol% doping and 143 mV/dec at 5 mol%, compared to 204 mV/dec for the undoped 1DLs, indicating faster reaction kinetics. The Ni‐doped NFs also exhibit excellent stability, maintaining a constant potential at 10 mA cm⁻²for > 50 h. Adding methanol to all colloidal suspensions results in their gelation within seconds. These findings highlight the potential of TM doping as an effective strategy to optimize 1DL's electronic and photochemical catalytic properties. 

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5. Rapid, Micron‐Resolution 3D Printing of Nd:YAG Ceramic with Optical Gain

   https://doi.org/10.1002/smll.202403130  

   Liu, Luyang; Wang, Wenbo; Feng, Shuai; Liu, Siying; Sun, Haofan; Nian, Qiong; Yang, Sui; Chen, Xiangfan (May 2024, Small)

   Abstract Polycrystalline yttrium aluminum garnet (YAG) ceramic doped with neodymium (Nd), referred to as Nd:YAG, is widely used in solid‐state lasers. However, conventional powder metallurgy methods suffer from expenses, time consumption, and limitations in customizing structures. This study introduces a novel approach for creating Nd:YAG ceramics with 3D free‐form structures from micron (∼70 µm) to centimeter scales. Firstly, sol‐gel synthesis is employed to form photocurable colloidal solutions. Subsequently, by utilizing a home‐built micro‐continuous liquid interface printing process, precursors are printed into 3D poly(acrylic acid) hydrogels containing yttrium, aluminum, and neodymium hydroxides, with a resolution of 5.8 µmpixel⁻¹at a speed of 10 µm s⁻¹. After the hydrogels undergo thermal dehydration, debinding, and sintering, polycrystalline Nd:YAG ceramics featuring distinguishable grains are successfully produced. By optimizing the concentrations of the sintering aids (tetraethyl orthosilicate) and neodymium trichloride (NdCl₃), the resultant samples exhibit satisfactory photoluminescence, emitting light concentrated at 1064 nm when stimulated by a 532 nm laser. Additionally, Nd:YAG ceramics with various 3D geometries (e.g., cone, spiral, and angled pillar) are printed and characterized, which demonstrates the potential for applications, such as laser and amplifier fibers, couplers, and splitters in optical circuits, as well as gain metamaterials or metasurfaces. 

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