Hydrogel composites in an aqueous media with viscoelastic properties and elastic modulus that can be precisely tailored are desirable to mimic many biological tissues ranging from mucus, vitreous humor, and nucleus pulposus as well as build up biosensors. Without altering the chemistry, tuning the physical interactions and structures to govern the viscoelastic properties of the hydrogels is indispensable for their applications but quite limited. Here we design a complexation gel composite and utilize the physical principle of topologically frustrated dynamical state to tune the correlated structures between the guest polycation chains and negatively charged host gels. We precisely quantify the mesh size of the host gel and guest chain size. By designing various topologically correlated structures, a viscoelastic moduli map can be built up, ranging from tough to ultrasoft, and from elastic-like with low damping properties to viscous-like with high damping properties. We also tune the swelling ratio by using entropy effect and discover an Entropy-driven Topologically Isovolumetric Point. Our findings provide essential physics to understand the relationship between entropy-driven correlated structures and their viscoelastic properties of the complexation hydrogel composites and will have diverse applications in tissue engineering and soft biomaterials.

Hard carbon anodes face the critical challenge of low initial coulombic efficiency (ICE) and capacity fading arising from insufficient control of the closed-pore structure, which must be addressed to advance sodium-ion batteries (SIBs). In this work, we present a carbon structure engineering strategy to enhance anode performance by treating cyano-functionalized phenolic resin-derived carbon microspheres with NH₃. Cyano side groups increase crosslinking density during resin curing, facilitating the formation of closed-pore structures with low specific surface areas. Stepwise carbonization in ammonia and nitrogen atmospheres tailors the closed-pore structure and surface morphology. Small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HR-TEM) reveal that the closed-pore walls undergo mild etching, inducing pore surface defects. Compared with nitrogen treatment, NH₃ significantly enhances nitrogen incorporation and electrochemical activity. The optimized sample carbonized at 1200 °C exhibits a specific surface area of 1.87 m² g⁻¹, an ICE of 81.81%, and a first-cycle discharge capacity of 373.3 mAh g⁻¹ at a current density of 30 mA g⁻¹. In situ X-ray Diffraction (XRD) and the galvanostatic intermittent titration technique (GITT) reveal a three-step sodium storage mechanism: adsorption, intercalation, and pore-filling, with rough pore surfaces accelerating filling kinetics. This strategy provides a scalable approach for designing high-performance carbon-based anodes.

Carbon aerogels (CAs) had been well applied in extreme condition thermal insulation, but achieving a balance between mechanical robustness and thermal insulation remains challenging. We present a novel strategy to fabricate carbon aerogels with tunable mechanical properties and thermal insulation properties by tailoring their skeleton architecture via molecular assembly. Carbon precursor aerogel with thick neck particle packing structure was obtained by strong hydrogen-bonding-induced self-assembly between polyurethane-urea oligomer (PUU) and phenolic resin (PF), and carbon aerogel retained robust interparticle connections after pyrolysis, resulting in excellent mechanical properties. The presence of PUU leads to denser packing of resin molecules, promotes graphitization of the carbon and formation of nanocrystalline structures at 1400 °C, resulting in optimized compression modulus and strength. The closed pore structure of carbon skeleton was further studied by Small-Angle X-ray Scattering (SAXS), while moderate pore width (0.4–0.6 nm) optimizes the balance between strength (110 MPa) and thermal conductivity (0.30 W/(m·K)). This work demonstrates that molecular-level assembly combined with pyrolysis control enables precise tuning of carbon aerogel structures and properties, providing new insights for high-temperature thermal insulation applications.