How Gellan gum gelation is affected by acyl substituents: from hierarchical organization to simple viscoelastic behavior.

Mechanistic insights into gelation and rheological behavior of Pluronic F127-based thermoresponsive hydrogels

An integrated analysis of gelation kinetics, micellization thermodynamics, and viscoelastic properties (G′, G″) of Pluronic F127-based hydrogels is provided to support the rational design of thermoresponsive hydrogels and identify critical knowledge gaps to guide future research in advanced therapeutic biomaterials.

Correlating Structure and Rheology in Ionically Crosslinked Alginate Biopolymer Hydrogels - A Case for Why “Less” can be “More”

We probe the structural and rheological properties of ionically crosslinked alginate, a model biopolymer hydrogel, using microscopy, rheology and viscosity dependent molecular probes. This combination of techniques enables the quantification and correlation of microstructure, microviscosity, bulk viscoelasticity and yielding dynamics. By adjusting the stoichiometric ratio, R, between the alginate biopolymer and its cation crosslinks, we observe a transition from a homogeneous network-like structure to a coarse bundle-like structure at high (R>0.67) stoichiometric ratio. Intriguingly, these bundle-like structures have distinct and counter-intuitive rheological properties. Using molecular probes, we observe a continuous decrease in microviscosity that is correlated with a decrease in bulk elastic modulus and an increase in energy dissipation. This is accompanied by a transition in the hydrogel yielding under strain from a sharp, well-defined yield point to a continuous ductile-like yielding. We ascribe these surprising transitions to the looser intermolecular interaction between alginate biopolymers in the bundle-like state, as previously predicted by x-ray scattering experiments. These findings reveal new and counter-intuitive structure-property relations that demonstrate high crosslink concentration does not necessarily translate to optimal mechanical performance. Significance Alginate is a polysaccharide biopolymer naturally found in brown seaweed cell walls. Extracted alginate forms ionically crosslinked hydrogels that are strong, flexible and increasingly valuable in the biomedical, packaging and food industries. A large part of the utility of these hydrogels stems from the ease with which their mechanics can be tuned through adjusting the stoichiometry between alginate and its ionic crosslinks. However, little is known about how the material properties of alginate hydrogels, in particular their rheology and dynamics, are affected by microscale structural transitions at high stoichiometric ratios. Here, we use a multi-modal approach to describe and correlate hydrogel material properties and to demonstrate that increased polymer crosslinking can, counterintuitively, sometimes weaken hydrogel performance.

Alginate-Based Hydrogel Blends with Uncrosslinked Polymers: Multiscale Structure and Its Relationship with Viscoelastic Properties

The multiscale architecture of alginate–gelatin–hyaluronic acid (AGH) hydrogels was elucidated using a synergistic approach of swelling tests, mechanical characteristics, TEM, and SAXS; it was demonstrated that, in AGH, a crosslinked alginate network coexists with non-interconnected cavities composed of uncrosslinked polymer strands. While swelling analysis yields a mesh size of ξS = (12 ± 3) nm corresponding to the alginate network, mechanical measurements reveal an effective mesh size ξM–eff = (44 ± 2) nm, reflecting the combination of the viscoelastic network and cavity contributions. SAXS identifies two rod-like crosslink-site populations (∼1 and ∼4 nm); the latter was directly validated by TEM, and these populations were found in the swollen and dried states to be independent of alginate content. These findings establish the porosity of the cavities, ϕ, as the key structural parameter to predict AGH mechanical properties from those of pure alginate, providing a framework for designing complex bio-based composites.

Self-Degradable Temporary Plugging Agent Based on Dynamic Covalent Bond-Crosslinked Double-Network Hydrogels

Rheological Characterization of Yeast Protein–Sanxan Composite Hydrogels via SAOS, LAOS and Thermal Analysis

Future foods are driving an urgent need for sustainable and functional protein resources, and synthetic biology is emerging as a powerful platform to produce such proteins efficiently. Here, we designed a yeast protein (YP)–sanxan composite hydrogel obtained. The introduction of YP significantly improved thermal stability (by 5–15 °C) and ensured polymer compatibility. Rheological analysis indicated a frequency-dependent weak gel (tan δ = 0.1–0.3), making it suitable for safe swallowing. The material exhibited Type III nonlinear viscoelastic behavior, characterized by inter-cycle strain softening and a weak overshoot in G″, with Lissajous curves revealing a strain-induced transition from solid-like to fluid-like behavior. Crucially, YP-reinforced gels (5–20%) exhibited higher elastic moduli, indicating that the incorporation of YP strengthened the gel network and increased its structural rigidity, as further confirmed by Strain Sweep. With its tunable rheology and superior thermal stability, this hydrogel holds great potential for functional foods, 3D food printing, delivery systems, and biomedical scaffolds.

Double-modified guar gum dual-network hydrogels with balanced mechanical and swelling properties.

Polysaccharide-based hydrogels suffer from an inherent trade-off between mechanical strength and swelling capacity, along with poor structural stability under complex conditions, which severely restricts their industrial scalability. Herein, a targeted dual-side-chain modification strategy (hydroxypropylation combined with phosphation) was developed, and a rigid-flexible dual-network (DN) hydrogel was constructed via the interpenetrating of modified guar gum derivatives with polyacrylamide (PAM). A critical crosslinking density threshold of 0.1 g/10 g system was identified, where the rigid modified guar gum backbone and flexible PAM network formed a homogeneous interpenetrating structure. This unique structure enabled the hydrogel to achieve a compressive strength exceeding 500 ± 26 kPa and swelling ratio of 46-fold, realizing an excellent balance between mechanical performance and swelling behavior. For extreme agricultural scenarios, the borate-ion-crosslinked B(OH)4--HPG/PAM hydrogel retained 85% of its mechanical properties under high temperature and salinity. For acidic complex wounds, the phosphorylated Ca2+-PGG/PAM hydrogel (esterification degree 0.12 ± 0.01) exhibited a superior swelling ratio via pH-responsive dissociation of coordination bond. This scenario-adaptive bio-based hydrogel constructed via rational molecular modification provides a feasible solution for agricultural water retention in extreme environments and advanced dressings for complex wounds, and offers a design paradigm for polysaccharide-based hydrogels with balanced mechanical-swelling properties.