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Tunable hydrogels have gained significant attention in the bioengineering field due to their designer preparation approach. Towards this end, gelatine stands out as a promising candidate owing to its desirable attributes, such as biocompatibility, ability to support cell adhesion and proliferation, biodegradability, and cost-effectiveness. This study presents the preparation of a robust gelatine hydrogel employing sacran aldehyde (SDA) as a natural cross-linker. The resulting SDA-cross-linked gelatine hydrogels (GSDA) display an optimal compressive stress of 0.15 MPa at 50% strain, five times higher than pure gelatine hydrogel. As SDA cross-linking concentration is increased, the swelling capacity of GSDA declines. This decline in swelling capacity, from 80% to 40%, is a result of strong crosslinking of gelatin with SDA. Probing further with FT-IR spectroscopy and SEM at the micron scale unveiled a dual-cross-linking mechanism within the hydrogels. This mechanism encompasses both short- and long-range covalent cross-linking, along with thermo-induced physical cross-linking, resulting in a significant enhancement of the load-bearing capacity of the fabricated hydrogels. [ABSTRACT FROM AUTHOR]

Shellac, a naturally degradable material, was used as a carrier to load some functional and active compounds in the packaging fields. It is rarely used directly as a substrate to prepare packing films due to its unsatisfactory solubility and mechanical properties. In this research, ammonia was used as a solvent to dissolve shellac which helped form a smooth and tough shellac film via the interaction between shellac and ammonia. Moreover, a shellac composite film was formed by additional cellulose nanofibers (CNF). The properties of the shellac composite films (SAmCxPS) were regulated by modulating the concentrations of ammonia and CNF. The prepared films were characterized by a scanning electron microscope (SEM), NanoS Zetasizer, thermogravimetric analysis (TGA), and UV-Vis spectrophotometer, and their tensile strength was also determined. The results revealed that the shellac composite films were successfully prepared and were very thermally stable. The maximum tensile stress of the shellac composite films with 0.9 wt% CNF could reach 20.5 MPa. Such a high tensile stress indicated significantly improved mechanical properties. Moreover, the shellac composite films also showed good UV barrier properties, which reduced the ripeness of the fruit. Overall, the improvement in the stability and mechanical and UV barrier properties of shellac can broaden its application in the field of packaging. [ABSTRACT FROM AUTHOR]

Due to the utilization of the potentially hazardous monomer, isocyanate compound, polyurethanes (PUs) with good properties are restricted in several fields, such as bio‐engineering. Non‐isocyanate polyurethanes (NIPUs) with high overall performance and self‐healing properties were synthesized by dicarbamate, bio‐based isosorbide (IS) and polycarbonate diols (PCDLs) through a solvent‐free and ecologically friendly melt polycondensation route. Previously, few bio‐based monomers have been introduced into polycondensation reactions of PUs. Chemical structures of NIPUs were analyzed by Fourier transform‐infrared spectroscopy (FT‐IR), proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). With changing the IS content and the molecular weight of PCDL, the obtained NIPUs had linear structures and high molecular weights ranging from 3.3 × 104 to 5.9 × 104 g/mol. Results of tensile testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) suggested NIPUs had well thermal and mechanical properties, with Td,5% above 286.2°C and tensile strength between 8.0 and 16.7 MPa due to the crystallization and the hydrogen bonding interactions. Furthermore, the NIPUs exhibited self‐healing ability and recyclability, having great potential for industrialization. [ABSTRACT FROM AUTHOR]

Low critical solution temperature (LCST) of commonly used thermoresponsive polymers in water is basically dominated by hydrophobic interactions. Herein, a novel thermoresponsive system based on electrostatic interactions is reported. By simply loading aluminum chloride (AlCl3) into non‐responsive poly(2‐hydroxyethyl acrylate) (PHEA) hydrogels, PHEA‐Al gels turn to have reversible thermoresponsive behavior between transparent and opaque without any volume change. Further investigations by changing metal ion‐polymer compositions unravel the necessity of specific electrostatic interactions, namely, cation‐dipole bonding interactions between hydroxy groups and trivalent metal ions. The thermoresponsive hydrogel demonstrates high transparency (≈95%), excellent luminous modulation capability (>98%), and cyclic reliability, suggesting great potential as an energy‐saving material. Although LCST control by salt addition is widely known, salt‐induced expression of thermoresponsiveness has barely been discussed before. This design provides a new approach of easy fabrication, low cost, and scalability to develop stimuli‐responsive materials. [ABSTRACT FROM AUTHOR]

The mechanical properties for paper sheets composited with glucose (Glc), methyl cellulose (MC), and carboxymethyl cellulose (CMC) were investigated. The paper composites were prepared by immersing paper sheets in aqueous solutions of these materials and drying at 100 °C for 30 min. The stress–strain curves for these paper composites were measured by a uniaxial tensile apparatus with a stretching speed of 2 mm/min. The breaking stress and strain for untreated paper were 24 MPa and 0.016, respectively. The paper composites demonstrated stress–strain curves similar to the untreated paper; however, the breaking point largely differed for these composites. The breaking strain and breaking stress for the Glc composite slightly decreased and those for the MC composite gradually increased with the concentration of materials composited. Significant increases in the mechanical properties were observed for the CMC composite. The breaking stress, breaking strain, and breaking energy for the 3 wt.% CMC composite were 2.0-, 3.9-, and 8.0-fold higher than those for untreated paper, respectively. SEM photographs indicated that the CMC penetrated into the inner part of the paper. These results strongly suggest that the mechanical improvement for CMC composites can be understood as an enhancement of the bond strength between the paper fibrils by CMC, which acts as a bonding agent. It was also revealed that the breaking strain, breaking stress, and breaking energy for the CMC composites were at maximum at the first cycle and decreased gradually as the immersion cycles increased. [ABSTRACT FROM AUTHOR]