Physical Crosslinking Research Articles

High Self‐Supporting Chitosan‐Based Hydrogel Ink for In Situ 3D Printed Diabetic Wound Dressing

AbstractCustomizable 3D‐printed biopolymer hydrogels, highly sought after for diabetic wound management, face challenges in clinical application due to weak physical crosslinking within their constituent inks. In this study, a novel chitosan‐based hydrogel ink with a dense yet reversible physical crosslinking network is subtly designed for the rapid in situ fabrication of personalized diabetic wound dressing. This robust network is established through multiple electrostatic and hydrogen bonding interactions between unique carboxymethyl chitosan and nanoclay, further reinforced by the introduction of amide bonds, which act as double hydrogen bond donors/acceptors. Benefiting from this network, the ink with low nanoclay content exhibits remarkable self‐supporting properties, enabling high‐fidelity, large‐scale, and complex 3D printability without additional processing, while substantially retaining its inherent rheological properties after autoclave sterilization and the incorporation of active components. Given these advantages, this multifunctional 3D printable hydrogel can be rapidly in situ constructed on diabetic wounds. Simultaneously, the 3D‐printed hydrogel demonstrates biodegradability, anti‐swelling, and appropriate mechanical properties, along with remarkable in vitro antibacterial and pro‐angiogenic capabilities, leading to effective diabetic wound healing in vivo. This work offers a new strategy for creating highly self‐supporting biopolymer inks and paves the way for developing advanced personalized wound dressings.

Porous polyimide composite films containing mesoporous hollow silica nanospheres with ultralow dielectric constant and dissipation loss

Porous polyimide hybrid films with ultralow dielectric constant and dissipation loss were synthesized during chemical imidization and rapid evaporation of polymer solutions. Polyimide (PI) of bis(4-aminophenyl)-1,4-diisopropylbenzene (BISP) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) were synthesized in N-methylpyrrolidinone (NMP) to yield the corresponding poly(amic acid)s (PAA)s, which were then chemically imidized. To reduce the dielectric properties of the porous PI films, amine-functionalized, surface-modified hollow silica nanoparticles (AHNS) with various sizes from 100 nm to 1 μm, prepared via sol-gel process, were added with PAA at 3, 5, or 10 % weight content, followed by chemical imidization to produce the porous PI/AHNS films. To avoid the high-volume shrinkage of wet gels and maintain the high porosity of the PI with low polarizability, AHNS nanoparticles were added to the porous structure of the PI xerogels as a physical crosslinker. The polyimide hybrid film with 10 nm AHNS nanoparticles at 10 % weight content showed a dielectric constant of 1.151 and a dissipation rate of 0.001 at a frequency of 10 GHz.

Dual-Self-Crosslinking Effect of Alginate-Di-Aldehyde with Natural and Synthetic Co-Polymers as Injectable In Situ-Forming Biodegradable Hydrogel.

Injectable, in situ-forming hydrogels, both biocompatible and biodegradable, have garnered significant attention in tissue engineering due to their potential for creating adaptable scaffolds. The adaptability of these hydrogels, made from natural proteins and polysaccharides, opens up a world of possibilities. In this study, sodium alginate was used to synthesize alginate di-aldehyde (ADA) through periodate oxidation, resulting in a lower molecular weight and reduced viscosity, with different degrees of oxidation (54% and 70%). The dual-crosslinking mechanism produced an injectable in situ hydrogel. Initially, physical crosslinking occurred between ADA and borax via borax complexation, followed by chemical crosslinking with gelatin through a Schiff's base reaction, which takes place between the amino groups of gelatin and the aldehyde groups of ADA, without requiring an external crosslinking agent. The formation of Schiff's base was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. At the same time, the aldehyde groups in ADA were characterized using FT-IR, proton nuclear magnetic resonance (¹H NMR), and gel permeation chromatography (GPC), which determined its molecular weight. Furthermore, borax complexation was validated through boron-11 nuclear magnetic resonance (¹¹B NMR). The hydrogel formulation containing 70% ADA, polyethylene glycol (PEG), and 9% gelatin exhibited a decreased gelation time at physiological temperature, attributed to the increased gelatin content and higher degree of oxidation. Rheological analysis mirrored these findings, showing a correlation with gelation time. The swelling capacity was also enhanced due to the increased oxidation degree of PEG and the system's elevated gelatin content and hydrophilicity. The hydrogel demonstrated an average pore size of 40-60 µm and a compressive strength of 376.80 kPa. The lower molecular weight and varied pH conditions influenced its degradation behavior. Notably, the hydrogel's syringeability was deemed sufficient for practical applications, further enhancing its potential in tissue engineering. Given these properties, the 70% ADA/gelatin/PEG hydrogel is a promising candidate and a potential game-changer for injectable, self-crosslinking applications in tissue engineering. Its potential to revolutionize the field is inspiring and should motivate further exploration.

Super-Tough, Non-Swelling Zwitterionic Hydrogel Sensor Based on the Hofmeister Effect for Potential Motion Monitoring of Marine Animals.

Hydrogel-based electronic devices in aquatic environments have sparked widespread research interest. Nevertheless, the challenge of developing hydrogel electronics underwater has not been profoundly surmounted because of the fragility and swelling of hydrogels in aquatic environments. In this work, a zwitterionic double network hydrogel comprisedof polyvinyl alcohol (PVA), poly(sulfobetaine methacrylate) (PSBMA), and sulfuric acid (H2SO4) demonstrates super-tough and non-swelling performance. The Hofmeister effect of H2SO4 and PSBMA induces the PVA chains to form numerous nanocrystalline domains, which serve as the primary physical crosslinking points and provide effective energy dissipation. H2SO4 induces a strong salting-out effect to facilitate PVA crystallization and the formation of a dense and stable network structure that inhibits swelling. The resulting hydrogel exhibits an ultra-high toughness of 4.61MJm-3, non-swelling, and long-term stability for up to a month in pure water and seawater. Based on this, a hydrogel-based seawater strain sensor has been developed to monitor the underwater movements of marine animal models. Reliable and stable sensing performance ensures real-time collection of underwater motion signals, despite the impacts of water flow and the interference of ions. This study provides a facile approach to designing super-tough and non-swelling hydrogels and further expands the application of underwater electronic devices.

Recombinant Fibrous Protein Gels as Rheological Modifiers in Skin Ointments.

Rheological modifiers are an important component in the development of skin cream (SC) chassis for personal skin care products (PSCPs). The viscous behavior of a PSCP is critical to its effectiveness where its uniformity and material strength impact its processing, storage, and delivery of active ingredients. Due to the mildly acidic environment of the skin, PSCPs require a SC that will assist in maintaining their material strength at low pHs. We have investigated a coiled-coil protein hydrogel system for the ability to possess pH-responsiveness, where physical cross-linking and material strength is controlled by pH relative to the isoelectric point (pI) of the protein. We recently designed a coiled-coil protein hydrogel variant, Q5, which possesses a relatively low pI that we hypothesized to have improved supramolecular assembly into a hydrogel at acidic conditions. We demonstrate that Q5 can retain a partial solution-to-gel transition at pH 6.0 and acts as a soft hydrogel by rheology. We further tested Q5 to act as a rheological modifier in a standard SC at pH 6.0 and pH 8.0 to test conditions mediated by pH changes in the skin environment. Q5 reveals the ability to uniquely increase material strength at low pH in comparison to a standard rheological modifier like hydroxyethyl cellulose (HEC), suggesting modular protein-based coiled-coil rheological modifiers can be used in PSCPs.

Eco-Friendly Microwave Synthesis of Sodium Alginate-Chitosan Hydrogels for Effective Curcumin Delivery and Controlled Release.

In this study, we developed sodium alginate-chitosan hydrogels using a microwave-assisted synthesis method, aligning with green chemistry principles for enhanced sustainability. This eco-friendly approach minimizes chemical use and waste while boosting efficiency. A curcumin:2-hydroxypropyl-β-cyclodextrin complex was incorporated into the hydrogels, significantly increasing the solubility and bioavailability of curcumin. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed the structure and successful incorporation of curcumin, in both its pure and complexed forms, into the polymer matrix. Differential scanning calorimetry revealed distinct thermal transitions influenced by the hydrogel composition and physical cross-linking. Hydrogels with higher alginate content had higher swelling ratios (338%), while those with more chitosan showed the lowest swelling ratios (254%). Scanning Electron Microscopy (SEM) micrographs showed a porous structure as well as successful incorporation of curcumin or its complex. Curcumin release studies indicated varying releasing rates between its pure and complexed forms. The chitosan-dominant hydrogel exhibited the slowest release rate of pure curcumin, while the alginate-dominant hydrogel exhibited the fastest. Conversely, for curcumin from the inclusion complex, a higher chitosan proportion led to the fastest release rate, while a higher alginate proportion resulted in the slowest. This study demonstrates that the form of curcumin incorporation and gel matrix composition critically influence the release profile. Our findings offer valuable insights for designing effective curcumin delivery systems, representing a significant advancement in biodegradable and sustainable drug delivery technologies.

Study on Oil Resistance of Polyurethane Protective Material

Abstract The polyurethane protective tape is a new type of protective material made by coating high performance pressure-sensitive adhesive on polyurethane elastomers, which is widely used in aviation. During its operational life, the polyurethane protective tape inevitably comes into contact with oil, and its oil resistance directly impacts its lifespan. This study focuses on the polyurethane protective tape and conducts immersion tests in No. 15 aviation hydraulic fluid, aircraft gear oil 4450 and RP3 aviation kerosene at room temperature. A comparative analysis was also conducted on the tensile strength, tear resistance, fracture morphology, chemical structure, and thermophysical properties before and after immersion. The research indicates that the tensile properties of polyurethane protective tapes remain essentially unchanged after immersion in RP3 aviation kerosene. After being immersed in No.15 aviation hydraulic fluid and aircraft gear oil 4450, the tensile strength of the polyurethane protective tape gradually decreases. Furthermore, compared to No.15 aviation hydraulic fluid, the rate of tensile strength reduction in polyurethane protective tape immersed in aircraft gear oil 4450 is more rapid. The resistance to tearing of polyurethane protective tapes diminishes gradually with prolonged immersion, with the rate of decline being greater for aircraft gear oil 4450 than for No.15 aviation hydraulic fluid, and even greater for RP3 aviation kerosene. The decrease in mechanical properties of polyurethane protective tapes after immersion in oil is attributed to the swelling effect of the oil, which reduces the intermolecular forces within the polyurethane material and leads to a decrease in physical cross-linking. This process is physical aging, with no evident chemical aging occurring.

Effect of Mercerization on the Properties of Cellulose Fiber and Cellulose Hydrogel Extracted from Pineapple Leaf Fiber

AbstractThis study investigated the effects of alkaline treatment on the pineapple leaf fiber (PALF) cellulose extraction and the properties of cellulose hydrogel. PALF was treated with different concentrations of sodium hydroxide (NaOH) (2 to 10 wt %) and at room temperature (RT) and 80 °C. Then, extracted cellulose was then dissolved in N,N’‐dimethyl acetamide (DMAc)/lithium chloride (LiCl) solvent system and formed into hydrogel by phase inversion method. The Fourier transform infrared spectra shows the peak disappearance at 1606 cm−1 proves that lignin was removed starting from 6 and 4 wt % NaOH at RT and 80 °C, respectively. Higher NaOH concentrations treatment increased thermal stability and the crystallinity (71 to 79 %) of the fibers. Higher NaOH concentration and treatment temperature enhanced cellulose extraction from PALF, leading to more physical crosslinking during hydrogel formation. High amount of cellulose extracted decreased the hydrogel's swelling equilibrium and increased the gel fraction. The highest transmittance (87.8 %) and the lowest intensity of absorbance (at 280 nm corresponding to lignin) were obtained by the hydrogel prepared with PALF treated with 8 wt % NaOH at 80 °C. Clearly, this research findings provide new insights into optimizing cellulose extraction using alkaline treatment specifically for cellulose hydrogel formation.

Boosting electrochemical performance by regulating rigid-flexible microphase separation of multiblock copolymers

The growth of lithium dendrites and associated safety issues hinder the further development of liquid lithium metal batteries. A novel rigid-flexible multiblock copolymer PBC-mb-PBS was successfully synthesized based on molecular design. Incorporating crystalline rigid phase polybutylene succinate (PBS) into PBC-mb-PBS significantly enhances its tensile strength and low-temperature toughness through physical crosslinking. The flexible polydibutyl 2-(2-cyanoethyl)malonate (PBC) phase with side-chain cyano groups facilitate ionic conduction, forming a LiN-rich stabilized interfacial layer, thereby improving oxidative stability and high-voltage cathode compatibility. A series of multiblock copolymers with varying segment lengths were synthesized to balance mechanical properties and ionic conductivity by adjusting microphase separation. The quasi-solid-state polymer electrolyte (QSPE), derived from PBC-mb-PBS with the molar block ratio of 0.42, exhibits optimal electrochemical performance with ionic conductivity of 6.20 × 10−5 S cm−1 at 30 °C and 4.22 × 10−4 S cm−1 at 60 °C. Due to its bicontinuous microphase structure, it also shows excellent mechanical strength and promotes uniform lithium deposition at high current densities. Li//LiFePO4 and Li//LiNi0.83Co0.05Mn0.12O2 cells demonstrate high capacity retention, confirming the potential of this polymer electrolyte in high-voltage applications. This design strategy offers insights for developing quasi-solid-state lithium metal batteries with superior overall performance.

Microcapsules with condensates and liposomes composite membranes fabricated via soy protein simple coacervation

Coacervation is a common phenomenon in plant proteins which however has yet been well recognized. This study systematically investigated the properties of soy glycinin coacervates, explored the wetting behavior between the condensates and oil droplets in order to obtain microcapsules with core-shell structure, and furthermore figured out the strategy to stabilize the condensate membranes. Fluidity of glycinin coacervates was characterized by viscosity and fluorescence recovery after photo bleaching which was highly dependent on solution parameters and intriguingly increased with prolonged time due to protein structure reorganization. Complete engulfment of oil droplets by coacervates leading to core-shell structure formation was achieved at salinity≥0.1M NaCl and pH≥7 above room temperature. Core-shell structure could be preserved by membranization using liposome coating as it prevented the coalescence between coacervates. Condensate membranes were further hardened by a combination of physical and enzymatic crosslinking using calcium ions and transglutaminase respectively which enabled the microcapsules to survive in the gastric environment. This study is important as it paves way for fabricating well designed microcapsules based on the simple coacervation of plant proteins which are biocompatible and widely abundant.

Double-crosslinked polyvinyl alcohol/starch bioplastic with superior water-resistance and flame retardancy

The high water solubility and flammability of polyvinyl alcohol (PVA) limits its further widespread use in areas such as bioplastic and green packaging. In this study, double-crosslinked polyvinyl alcohol/starch bioplastics (named PDA) were fabricated using PVA, dialdehyde starch (DAS), and phytic acid (PA), resulting in a material with superior water resistance, flame retardancy, and excellent degradability. PA not only plays the role of catalyst for the chemical crosslinking but also as the physical crosslinker to form the intermolecular hydrogen bonds with PVA and DAS. This chemically and physically double cross-linked network structure results in PDA bioplastics with excellent toughness and water resistance. Specifically, the optimal formulation with 15 % PA content, designated as PDA15, exhibited a high toughness of 35.5 MJ/m3 and demonstrated prolonged shape retention in the boiling water. Additionally, PA also serves as a flame-retardant and antibacterial agent; the PDA15 achieved a high limit oxygen index (LOI) value of 40.0 % and passed the UL-94 V-0 rating without melt dripping, along with better degradability compared to pure PVA film. These outstanding performances make the PDA bioplastics highly promising for various applications, particularly in disposable plastics and laminated flexible packaging materials.

Adsorption of silver ions onto chitosan hydrogel: Structural studies

Chitosan indicate a significant potential in the field of water treatment due to polymer high porosity, large specific surface area and its ability to bind strongly heavy metal ions form aqueous solutions. Therefore, chitosan based hydrogels have been fabricated by physical crosslinking of the polymer chains via sol–gel method using sodium β-glycerophosphate (β-GP) for silver ions (Ag) removal from water solutions. The aim of this study was to provide experimental studies under batch conditions to perform adsorption isotherm and evaluate the effect of silver adsorption onto chitosan hydrogel morphological and structural changes using SEM, XRD, FTIR and EDX analyses. Obtained results provides the data on the structural changes in the chitosan hydrogels under Ag adsorption process. The FTIR spectra confirmed that the C-NH2 and OH groups contribute to the formation of chitosan - silver ion complexes. The presence of adsorbed Ag in the samples < 0.8 gAgL−1 were evidenced by the characteristic peak at 2θ = 46.35°. Regarding to EDX analysis the adsorption efficiency toward Ag ions, rises with an increase in Ag initial concentration, resulting in L-type isotherm. The percentage removal of silver ions efficiency obtained 34 % for the highest Ag initial concentration (10 gAg L−1). SEM micrographs after Ag adsorption performed morphology as homogeneous porous network and reveals Ag present in the structure resulting from effective Ag adsorption. This study verified structural changes resulted from silver ions adsorption and confirmed the potential for thermosensitive chitosan hydrogels to applied as an adsorbent for water treatment applications.

Preparation of high-performance antibacterial/antifungal citric acid–starch adhesives based on physical entanglement and chemical crosslinking

Starch-based wood adhesives are widely used as environmentally friendly and formaldehyde-free alternatives in the manufacturing of wood products. However, their poor water resistance and inability to inhibit bacterial/fungal growth limit their practicality. To address this issue, a physicochemical double-crosslinked network structure between citric acid, starch, and wood was prepared in this study by physically entangling the wood structure and chemically crosslinking the starch molecules, with citric acid preventing the activity of various enzymes and denatured proteins within microbial cells, thereby inhibiting bacterial and fungal growth. In water resistance cycling tests, the resulting esterified starch plywood demonstrated a 47.6 % and 13.2 % increase in water resistance compared with starch plywood and commercially available phenolic resin plywood, respectively. In addition, the tighter intermolecular bonding in the crosslinked structure results in a 31 % increase in heat resistance. The physical “nailing” and chemical crosslinking between the adhesive and the wood improved considerably the bonding strength to 98.36 %. The dual role of the physicochemical crosslinking of starch adhesives provides a straightforward strategy for the preparation of inexpensive, water-resistant, and fungal/bacterial-resistant starch adhesives, thus contributing to the promotion of starch adhesives.

Ag-S coordination strategy for high recovery driving stress in recyclable shape memory polymers

To address the issue of low strength and recovery stress in recyclable shape memory polymer (SMP) materials with dynamic covalent bonds in practical applications, we propose a method based on Ag-S coordination interactions to improve dynamic covalent bonds, thereby preparing recyclable SMP with high recovery stress and large recovery strain. The introduction of in situ reduced silver nanoparticles (AgNPs) in the SMP system play multiple roles, serving as additional physical crosslinking points at the microscale and coordinating with disulfide bonds in the system to construct a multi-level dynamic network structure. This endows the material with exceptional mechanical properties (tensile strength of 25.93 MPa and fracture strain of 1466.83 %) and recovery driving stress (5.59 MPa), while maintaining more than 99 % shape recovery and fixity rate. Furthermore, due to the outstanding photothermal performance of AgNPs, the composite material has acquired remote photothermal driving capabilities. The proposed Ag-S coordination enhancement offers a new approach for SMP materials that achieve both large actuation distance and high recovery stress, holding significant potential for applications in soft robotics and actuators.

Thermosensitive Hydrogel Containing Chinese Herbal Compound Extract and Hyaluronic Acid-Chitosan Quaternary Ammonium Salt Microspheres for Topical Application: Preparation and Characterization

Allergic contact dermatitis (ACD) is a highly prevalent allergic inflammatory dermatosis with persistent severe pruritus. Zhi-Yang-Fang (ZYF), a topical Chinese herbal compound used in clinical practice for treating ACD, has certain drawbacks such as inconvenience in use and its impact on aesthetics. This research aimed to overcome these shortcomings by developing an F127/F68-based thermosensitive hydrogel containing ZYF aqueous extract and hyaluronic acid-chitosan quaternary ammonium salt (HA-HTCC) microspheres. The 19 major components of ZYF aqueous extract were preliminarily identified using ultra-high-performance liquid chromatography coupled to Quadrupole-Exactive Orbitrap mass spectrometry (UPLC-Q Exactive Orbitrap-MS) analysis. HA-HTCC microspheres and HA-HTCC microspheres containing ZYF aqueous extract were prepared using the physical cross-linking method, and the success of the preparation was confirmed through a series of characterisations. The concentration of F127 and F68 was screened. The proportions of each substance in the final hydrogel formulation were determined, prepared using the cold method, and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and a rotational rheometer. These technologies verified the successful preparation, temperature sensitivity, and stability of the hydrogel. The hydrogel developed may be considered a promising approach for the management of ACD.

CMC-Na and Laponite dual network reinforced P (AM-co-NVCL) hydrogel with pH/temperature dual sensitivity

In this paper, poly (acrylamide-co-N-vinylcaprolactam) [poly(AM-co-NVCL)] hydrogels were modified by aqueous solution polymerization using sodium carboxymethyl cellulose (CMC-Na) and Laponite. Their properties were characterized by infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), rheological testing, and scanning electron microscopy (SEM). The swelling kinetics showed that the equilibrium swelling ratio of the xerogel was influenced by the monomer ratio, crosslinking agent, and modifier content. As the Laponite and CMC-Na content increased, the compressive strength of the composite hydrogel increased, while the elongation at break decreased. The modified composite hydrogel exhibited dual sensitivity to pH and temperature. DSC and rheological tests indicated that CMC-Na functioned as a physical crosslinking agent in the system, and with the increase in CMC-Na content, the crosslinking effect was enhanced. SEM demonstrated that the addition of Laponite and CMC-Na increased the number of pores in the hydrogel and decreased the pore size.

Hydroxyl-Functionalized Polymers of Intrinsic Microporosity and Dual-Functionalized Blends for High-Performance Membrane-Based Gas Separations.

Membrane technology has shown significant growth during the past two decades in the gas separation industry due to its energy-savings, compact and modular design, continuous operation, and environmentally benign nature. Robust materials with higher permeability and selectivity are key to reduce capital and operational cost, pushing it forward to replace or debottleneck conventional energy-intensive unit operations such as distillation. Recently designed ladder polymers of intrinsic microporosity (PIM) and polyimides of intrinsic microporosity (PIM-PI) with pores <20 Å have demonstrated excellent gas permeation performance. Here, a series of plasticization-resistant PIM-based membrane materials is reported, including the first example of a hydroxyl-functionalized triptycene- and Tröger's base-derived ladder PIM and two PIM-PI homopolymers and a series of dual-functionalized polyimide blends containing hydroxyl- and carboxyl-functionalized groups. Specifically, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)-based PIM-PI blends demonstrated extremely high selectivity for a variety of industrially important applications. An optimized polyimide blend containing ─OH and ─COOH groups showed permselectivity values of 136 for CO2/CH4, 11.4 for O2/N2 and 636 for H2/CH4. Such extreme size-sieving capabilities are attributed to physical crosslinking induced by strong hydrogen bonding forming tightly structured polymer networks. The study provides a new general strategy for developing plasticization resistant, robust, and highly-selective PIM-based membrane materials.

Room temperature shape self-adjustable tough hydrogel based on multi-physical crosslinking

Room temperature shape adjustable hydrogels (rtSAH) can be (re)processed into different stable shapes at ambient conditions, making them appealing for various applications. However, elastomer-like and mechanically tough rtSAH is hard to obtain because of the elastic recovery force that prevents a deformed new shape from being fixed. Herein, we demonstrate a supramolecular elastic rtSAH having high tensile strength (2.6 MPa) and large strain at break (1770 %), whose network structure is designed to rely on a combination of strong and weak non-covalent interactions through three types of physical crosslinking: host–guest interaction, hydrogen bonding and coordination interaction. When deformed at room temperature and held in that state for sufficient time, the hydrogel adapts to a stable new shape while remaining elastic. The reconstruction of the dynamic Fe3+-carboxylate coordination interaction in the deformed hydrogel is the key to self-locking the new shape with stored elastic energy and enabling the shape memory function. Exposure the rtSAH to UV light or an acid solution disrupts the coordination crosslinking and allows the hydrogel to recover its initial shape. The demonstrated structural design represents an effective strategy to develop all-physically crosslinked shape memory hydrogels whose shapes can be reprocessed and self-locked at room-temperature.

A multi-stimulus responsive nanogel actuator with the π-π stacking interaction self-assembly and application for bioinspired smart skin with light, heat and humidity responses and superb UV resistance

The fabrication and development of assemblies of bionic smart skin with multi-stimulus response and multi-color tunable properties is a major challenge in the field of advanced materials and smart wearable devices. In this work, an amphiphilic functional nanogel switch connected by long polyether chain segments containing bis-spiropyran with the π-π stacking interactions was designed. A multi-stimulus responsive color-changing nanogel actuator (SP-PEG-NA) was constructed using ionic liquid-assisted self-assembly. A composite bionic smart skin (WPU/SP-PEG@CF) was prepared by compositing SP-PEG-NA, waterborne polyurethane (WPU) and flexible cotton fabric based on physical cross-linking. The smart skin possesses multiple color-changing properties in response to light, heat and humidity. Even under ultra-low UV intensity (0.025 mW/cm2), WPU/SP-PEG@CF also exhibits significant photochromic properties. Surprising, the smart composite constructed with the nanogels possessed extremely high UV shielding performance (UPF 628.68) and photocontrolled hydrophobic-hydrophilic transition properties. The self-assembled nanogel actuators greatly improved the stimulus–response sensitivity. The multiple supramolecular noncovalent interactions of the nanogel actuator such as hydrophilic long polyether structures hydrogen-bonding and π-π stacking interactions endowed nanogel highly self-assembly properties. They showed excellent multi-stimulus response in color-changing, versatility and reversibility. The multi-stimulus responsive and multifunctional smart composites prepared using self-assembled nanogel has potential applications in smart wearable materials, sensors and information display.

Preparation of accelerated-wound-healing lignin/dopamine-based nano-Fe3O4 hydrogels in sensing

Flexible conductive hydrogels hold great promise for applications in motion and medical detection. It is difficult to produce conductive hydrogel epidermal sensors in wearable hydrogels with dependable adhesion, sensing, and wound-healing properties. Nano-Fe3O4 was used as physical cross-linking points in the polyacrylamide/polyvinyl alcohol double network (PP) to increase the strain capacity of the hydrogel. The conductive lignin-dopamine (LD) was immobilized on the surface of Fe3O4 particles, and the LD-coated Fe3O4 was then incorporated into the double network hydrogel to create the PP/LD/Fe3O4 hydrogel. This work was done to look into the possibility of using Fe3O4 hydrogels as flexible strain sensors. The addition of LD/Fe3O4 caused the composite hydrogel to strain up to 124 %, with a modulus of elasticity of 21,308 Pa and electrical conductivity as high as 2.3 S•m−1 following the introduction of LD/Fe3O4. Moreover, the PP/LD/Fe3O4 hydrogel's adhesive qualities offered adequate antimicrobial properties and promoted wound healing. These results indicate that the developed electricity-responsive and tissue-adhesive hydrogel dressing offers a candidate to serve as a tissue sealant for wound healing.