Semi-interpenetrating Network Research Articles

Preparation and Application of Responsive Nanocellulose Composites.

Cellulose nanofibrils/poly(N-Isopropylacrylamide) semi-interpenetrating networks (MMCNF-PNAs) were synthesized using an in situ fabrication (semi-IPN). The polymerization of N-isopropylacrylamide (NIPAM) (free radical) was conducted in the presence of magnetic modified cellulose nanofibrils (MMCNFs). The adsorption behaviors and surface morphology of the synthesized adsorbents were investigated systematically. The adsorption behaviors of the as-prepared MMCNF-PNA towards methylene blue (MB, as the model contaminant) dye was studied, and the optimal adsorption conditions were also studied. The adsorption processes could be well fitted using pseudo-second-order and Elovich kinetic models. Meanwhile, Langmuir and Freundlich isotherm models were used to fit the adsorption which occurred at 25, 37 and 65 °C. The corresponding results showed that the Freundlich isotherm model fitted the adsorption process better, indicating that the dye's adsorption happened via heterogeneous adsorptive energies on the prepared MMCNF-PNAs. Their desorption and reusability were also studied to verify magnetic responsivity. To sum up, MMCNF-PNAs are promising magnetic and thermal stimuli-responsive adsorbents, showing a controlled adsorption/desorption process.

Chitosan-based pH-sensitive semi-interpenetrating network nanoparticles as a sustained release matrix for anticancer drug delivery

Chitosan-based nanoparticles have demonstrated a growing potential for use in the drug delivery systems due to their remarkable versatility. To enhance the effectiveness of chitosan-based nanoparticles for stimulus-responsive anticancer drug delivery, a novel pH-sensitive semi-interpenetrating networks (semi-IPN) of chitosan-poly(1-vinyl imidazole) (CS-PVIm) and Chitosan-poly(methacrylic-acid) (CS-PMAA) nanoparticles were synthesized through free radical polymerization. The semi-IPN nanoparticles were analyzed to evaluate their suitability as drug carrier. The SEM analysis revealed that the nanoparticles were spherical and within the nanoscale size range. The average particle size measured by DLS for CS-PMAA nanoparticles was 107.9 nm without the drug and 175.2 nm after the drug encapsulation. CS-PVIm-nanoparticles had an average size of 138.32 nm, which was increased to 165.84 nm after the drug loading. ATR-FTIR confirmed the formation of CS-PVIm and CS-PMAA nanoparticles. Cytotoxicity analysis showed that the nanoparticles are biocompatible, with over 95 % of cell survival for the HeLa cell lines. Further, Doxorubicin-hydrochloride (Dox) loaded nanoparticles exhibited sustained drug release caused by the protonation and deprotonation of their functional groups based on pH change. The CS-PVIm-nanoparticles showed encapsulation efficiency (EE) of 57 %, whereas EE of CS-PMAA-nanoparticles were 52 %, respectively. This research presents a straightforward method for producing intelligent pH-responsive semi-IPN-nanoparticles tailored for anticancer drug delivery.

Acetal-thiol Click-like Reaction: Facile and Efficient Synthesis of Dynamic Dithioacetals and Recyclable Polydithioacetals.

Dithioacetals are heavily used in organic, material and medical chemistries, and exhibit huge potential to synthesize degradable or recyclable polymers. However, the current synthetic approaches of dithioacetals and polydithioacetals are overwhelmingly dependent on external catalysts and organic solvents. Herein, we disclose a catalyst- and solvent-free acetal-thiol click-like reaction for synthesizing dithioacetals and polydithioacetals. High conversion, higher than acid catalytic acetal-thiol reaction, can be achieved. High universality was confirmed by monitoring the reactions of linear and cyclic acetals (including renewable bio-sourced furan-acetal) with aliphatic and aromatic thiols, and the reaction mechanism of monomolecular nucleophilic substitution (SN1) and auto-protonation (activation) by thiol was clarified by combining experiments and density functional theory computation. Subsequently, we utilize this reaction to synthesize readily recyclable polydithioacetals. By simple heating and stirring, linear polydithioacetals with w of ~110 kDa were synthesized from acetal and dithiol, and depolymerization into macrocyclic dithioacetal and repolymerization into polydithioacetal can be achieved; through reactive extrusion, a semi-interpenetrating polymer dynamic network with excellent mechanical properties and continuous reprocessability was prepared from poly(vinyl butyral) and pentaerythritol tetrakis(3-mercaptopropionate). This green and high-efficient synthesis method for dithioacetals and polydithioacetals is beneficial to the sustainable development of chemistry.

Dual Semi-Interpenetrating Networks of Water-Soluble Macromolecules and Supramolecular Polymer-like Chains: The Role of Component Interactions

Dual networks formed by entangled polymer chains and wormlike surfactant micelles have attracted increasing interest in their application as thickeners in various fields since they combine the advantages of both polymer- and surfactant-based fluids. In particular, such polymer-surfactant mixtures are of great interest as novel hydraulic fracturing fluids with enhanced properties. In this study, we demonstrated the effect of the chemical composition of an uncharged polymer poly(vinyl alcohol) (PVA) and pH on the rheological properties and structure of its mixtures with a cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride already exploited in fracturing operations. Using a combination of several complementary techniques (rheometry, cryo-transmission electron microscopy, small-angle neutron scattering, and nuclear magnetic resonance spectroscopy), we showed that a small number of residual acetate groups (2–12.7 mol%) in PVA could significantly reduce the viscosity of the mixed system. This result was attributed to the incorporation of acetate groups in the corona of the micellar aggregates, decreasing the molecular packing parameter and thereby inducing the shortening of worm-like micelles. When these groups are removed by hydrolysis at a pH higher than 7, viscosity increases by five orders of magnitude due to the growth of worm-like micelles in length. The findings of this study create pathways for the development of dual semi-interpenetrating polymer-micellar networks, which are highly desired by the petroleum industry.

Ultra-stretchable, self-healing, bonding, and skin-inspired conductive triple network hydrogel for wearable strain sensors and friction nanogenerators

Hydrogel-based flexible sensors hold significant potential for applications in skin-like electronics, human motion detection, and human-machine interfaces. The development of strain-sensitive hydrogel with high stretchability, self-healing, and high conductivity is highly sought after. A hydrogel sensor with a strain-sensitive semi-interpenetrating network consisting of polyacrylamide (PAM), poly(vinyl alcohol) (PVA), and sodium alginate (SA). With environmentally benign KCl as a conductive filler, SA/PVA/PAM/KCl hydrogel has a high toughness (4.8 MJ m−3), high stretchability (1250 %), high tensile strength (510 kPa), excellent recoverability, and excellent self-adhesiveness toward various substrates. The hydrogel sensors present high sensitivity with good linearity in the majority of the detection range with a gauge factor (GF) over 6.78, a response time of 268 ms, and excellent durability. The ionic conductive hydrogel has shown excellent energy harvesting capability as a triboelectric nanogenerators (TENG). Multifunctional organic hydrogels provide a protocol for the design and preparation of multifunctional hydrogel for wearable electronics.

4D printed shape memory bismaleimide resin with high storage modulus and low shrinkage rate via second-stage curing

In recent years, the field of shape memory materials with active deformation capabilities has experienced rapid development. However, bismaleimide, as a widely used structural material in the aerospace industry, has been neglected in the field of shape memory. This work designed a UV-crosslinked network with 1-vinyl-2-pyrrolidone monomer, and prepared 4D printed smart structures based on shape memory bismaleimide resin through UV-assisted DIW printing. 4D printed semi-interpenetrating network polymer materials were obtained through a two-stage UV-thermal curing process, resulted in an increase in the material's glass transition temperature to a maximum of 187.4 °C. The storage modulus was improved to 5229 MPa. More important, we achieved a lowest shrinkage rate (0.21 %) of 4D printed polymer. The composite sandwich structure with electrical-driven shape memory performance was printed by double-sided printing of bismaleimide resin on conductive carbon fabric. 4D printed composite structure realizes in-situ self-blocking secondary curing, deformation process after curing. This significant progress provides a promising prospect for remote controllable and precise driving in the aerospace field.

Facile synthesis of an acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid copolymer / polyvinylpyrrolidone semi-IPN hydrogel with excellent swelling and anti-leakage properties

Water scarcity becomes an increasingly serious problem for humankind due to climate change and population growth, especially the water leakage in arid and semi-arid areas. Hydrogel polymers show increasingly important roles on water resources utilization. A novel hydrogel copolymer, acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid copolymer / polyvinylpyrrolidone (P(AA-co-AMPS)/PVP) semi-interpenetrating network (semi-IPN) hydrogel, was designed and successfully synthesized via a facile one-pot free radical copolymerization method. The main parameters during the synthesis process were optimized, including relative contents of polymer monomers, cross-linking agent, initiator and neutralization agent. Physical characterizations demonstrate that, P(AA-co-AMPS)/PVP hydrogel shows porous three-dimensional network structure, including a crosslinked network structure in P(AA-co-AMPS) copolymers and their intermolecular hydrogen bonding interactions with linear PVP. The as-synthesized P(AA-co-AMPS)/PVP hydrogel not only can deliver superior water absorbing capability (up to 1689.95 g g−1) and good reswelling performance, but also shows excellent water anti-leakage performance when being composed with red clay, demonstrating its multi-role applications in future sustainable agriculture.

A Semi-Interpenetrating Network Sorbent of Superior Efficiency for Atmospheric Water Harvesting and Solar-Regenerated Release.

Water is readily available nearly anywhere as vapor. Thus, atmospheric water harvesting (AWH) technologies are seen as a promising solution to support sustainable water production. This work reports a novel semi-interpenetrating network, which integrates poly(pyrrole) doped with a hygroscopic salt and 2D graphene-based nanosheets optimally assembled within an alginate matrix, capable of harvesting water from the atmosphere with a record intake of up to 7.15 gw/gs. Owing to the incorporated graphene nanosheets, natural sunlight was solely used to enable desorption, achieving an increase of the temperature of the developed network of up to 71 °C within 20 min, resulting in a water yield of 3.36 L/kgS in each cycle with quality well within the World Health Organization standard ranges. Notably, after 30 cycles of sorption and desorption, the composite hydrogel displayed unchanged water uptake and stability. This study demonstrates that atmospheric water vapor as a complementary source of water can be harvested sustainably and effectively at a minimal cost and without external energy input.

Semi-Interpenetrating Polyurethane Network with Fatigue Elimination and Upcycled Mechanical Performance

Semi-Interpenetrating Polyurethane Network with Fatigue Elimination and Upcycled Mechanical Performance

A semi-interpenetrating network acrylic pressure-sensitive adhesive for efficient transdermal application with high cohesion and adhesion

The application of pressure-sensitive adhesives (PSAs) in transdermal drug delivery systems (TDDSs) is limited. Insufficient cohesion in TDDS can lead to cold flow, patch displacement, dose inaccuracies, and the ‘dark ring’ phenomenon. To address these issues, we developed a semi-interpenetrating network (semi-IPN) PSA using a 2-hydroxyethylacrylate-modified acrylic copolymer as the linear polymer and poly[tri(propylene glycol) diacrylate] as the cross-linked network. Semi-IPN PSAs have better mechanical properties compared to traditional PSAs. The cohesion of the semi-IPN PSA was 31 times and 1.6 times that of commercially available DURO-TAK®87-2287 and DURO-TAK® 87–4098, respectively, and the cold flow of the semi-IPN PSA was significantly reduced. Furthermore, the semi-IPN PSA adhered to the human forearm for longer time and did not exhibit the ‘dark ring’ phenomenon after removal. When loaded with flurbiprofen, the semi-IPN PSA was found to maintain high levels of drug release and skin permeation amount, and flurbiprofen loading did not affect its superior cohesive performance. In conclusion, the innovative application of the semi-IPN PSA for TDDS showed excellent mechanical properties, effective adhesion to the skin without irritation, and highly effective drug release. These findings indicate that the use of the semi-IPN is both simple and highly effective for TDDS.

Facile fabrication of temperature/pH dual sensitive hydrogels based on cellulose and polysuccinimide through aqueous amino-succinimide reaction

A temperature/pH dual sensitive hydrogel with a semi-interpenetrating network (semi-IPN) structure was synthesized through an aqueous amino-succinimide reaction between water-soluble polysuccinimide and polyethyleneimine in the presence of thermosensitive cellulose derivatives. Single-factor experiments were carried out to optimize the preparation conditions of the semi-IPN hydrogel. The swelling behavior and cytotoxicity assay of the hydrogel were tested. Finally, taking 5- fluorouracil (5-Fu) as a model drug, the release performance of the 5-Fu-loaded hydrogel was investigated. The results indicated that the swelling ratio (SR) first decreased and then increased when the pH of the solutions ascended from 2 to 10. The SR decreased with the increase in temperature. In addition, the swelling behavior of the hydrogel was reversible and reproducible under different pH values and temperatures. The prepared hydrogels had good cytocompatibility. The release behavior of 5-Fu was most consistent with the Korsmeyer-Peppas model and followed the case II diffusion. The acidic environment was beneficial for the release of 5-Fu. The preparation process of the semi-IPN hydrogel is simple and the reaction can proceed quickly in water. The strategy introduced here has great potential for application in the preparation of drug carriers.

The synthesis and research of a novel organosilicon-modified waterborne blocked polyisocyanate crosslinker with a semi-interpenetrating network structure

The organosilicon intermediate containing hydrophilic tertiary amines was synthesized from N-Methylmonoethanolamine (MEA) and (3-glycidyloxypropyl) trimethoxy silane (GPTMS), followed by neutralization with acetic acid (Ac). Meanwhile, a polyurethane (PU) prepolymer was prepared by sequentially polymerizing hexamethylene diisocyanate trimer (HT-100) with polyethylene glycol (PEG-600) and methoxy polyethylene glycol (MPEG), and then chain extended by the intermediate. Ultimately, methyl ethyl ketone oxime (MEKO) was selected to block the remaining NCO group, forming a branched polyisocyanate crosslinker. Subsequently, a linear polyisocyanate crosslinker was prepared in the same system by polymerizing hexamethylene diisocyanate (HDI) with the intermediate. Consequently, an organosilicon-modified waterborne blocked polyisocyanate crosslinker with a semi-interpenetrating network structure was obtained and further processed through hydrolysis to obtain the corresponding crosslinker containing silanol groups. The structure and thermal properties of the crosslinkers were analyzed using 1H NMR, FT-IR, TG, and DTG. Furthermore, the comprehensive mechanical properties of the cured films were investigated. The results indicate that the crosslinker system containing silanol groups exhibits superior performance. When the films' maximum adhesion and the wiping resistance were optimized at 1.97 MPa and 72 times, respectively, the impact resistance still maintained above 85 cm.

Simultaneous Formation of Polyhydroxyurethanes and Multicomponent Semi-IPN Hydrogels.

This study introduces an efficient strategy for synthesizing polyhydroxyurethane-based multicomponent hydrogels with enhanced rheological properties. In a single-step process, 3D materials composed of Polymer 1 (PHU) and Polymer 2 (PVA or gelatin) were produced. Polymer 1, a crosslinked polyhydroxyurethane (PHU), grew within a colloidal solution of Polymer 2, forming an interconnected network. The synthesis of Polymer 1 utilized a Non-Isocyanate Polyurethane (NIPU) methodology based on the aminolysis of bis(cyclic carbonate) (bisCC) monomers derived from 1-thioglycerol and 1,2-dithioglycerol (monomers A and E, respectively). This method, applied for the first time in Semi-Interpenetrating Network (SIPN) formation, demonstrated exceptional orthogonality since the functional groups in Polymer 2 do not interfere with Polymer 1 formation. Optimizing PHU formation involved a 20-trial methodology, identifying influential variables such as polymer concentration, temperature, solvent (an aprotic and a protic solvent), and the organo-catalyst used [a thiourea derivative (TU) and 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU)]. The highest molecular weights were achieved under near-bulk polymerization conditions using TU-protic and DBU-aprotic as catalyst-solvent combinations. Monomer E-based PHU exhibited higher Mw¯ than monomer A-based PHU (34.1 kDa and 16.4 kDa, respectively). Applying the enhanced methodology to prepare 10 multicomponent hydrogels using PVA or gelatin as the polymer scaffold revealed superior rheological properties in PVA-based hydrogels, exhibiting solid-like gel behavior. Incorporating monomer E enhanced mechanical properties and elasticity (with loss tangent values of 0.09 and 0.14). SEM images unveiled distinct microstructures, including a sponge-like pattern in certain PVA-based hydrogels when monomer A was chosen, indicating the formation of highly superporous interpenetrated materials. In summary, this innovative approach presents a versatile methodology for obtaining advanced hydrogel-based systems with potential applications in various biomedical fields.

A three-dimensional co-continuous network structure polymer electrolyte with efficient ion transport channels enabling ultralong-life all solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) have emerged as one of the most promising candidates for the construction of solid-state lithium batteries due to their excellent flexibility, scalability, and interface compatibility with electrodes. Herein, a novel all-solid polymer electrolyte (PPLCE) was fabricated by the copolymer network of liquid crystalline monomers and poly(ethylene glycol) dimethacrylate (PEGDMA) acts as a structural frame, combined with poly(ethylene glycol) diglycidyl ether short chain interspersed serving as mobile ion transport entities. The preparaed PPLCEs exhibit excellent mechanical property and outstanding electrochemical performances, which is attributed to their unique three-dimensional co-continuous structure, characterized by a cross-linked semi-interpenetrating network and an ionic liquid phase, resulting in a distinctive nanostructure with short-range order and long-range disorder. Remarkably, the addition of PEGDMA is proved to be critical to the comprehensive performance of the PPLCEs, which effectively modulates the microscopic morphology of polymer networks and improves the mechanical properties as well as cycling stability of the solid electrolyte. When used in a lithium-ion symmetrical battery configuration, the 6 wt%-PPLCE exhibites super stability, sustaining operation for over 2000 h at 30 °C, with minimal and consistent overpotential of 50 mV. The resulting Li|PPLCE|LFP solid-state battery demonstrates high discharge specific capacities of 160.9 and 120.1 mA h g−1 at current densities of 0.2 and 1 C, respectively. Even after more than 300 cycles at a current density of 0.2 C, it retaines an impressive 73.5% capacity. Moreover, it displayes stable cycling for over 180 cycles at a high current density of 0.5 C. The super cycle stability may promote the application for ultralong-life all solid-state lithium metal batteries.

Semi-interpenetrating network hydrogels-based microcapsule for quorum quenching bacteria biocontainment to enhance biofouling control in membrane bioreactor

Microbial quorum quenching (QQ) has been proven to be a sustainable anti-biological fouling strategy for membrane bioreactors (MBR), but the long-term stability and practical application in MBR were uncertain. We reported a novel semi-interpenetrating network (SIPN) hydrogels-based design of QQ bacteria (Rhodococcus sp. BH4) encapsulation for both biofouling control and enhancement of organic pollutants removal in MBR. The microcapsule included the alginate core, chitosan thin intermediate compartment and SIPN (sodium alginate / polyacrylamide) shell, which exhibited near-perfect biocontainment, including preventing detectable QQ bacteria escape and improving mechanical strength. The QQ-microcapsules in the MBR demonstrated its significant anti-biofouling effect for treating synthetic wastewater (i.e., membrane fouling was delayed by 233%-280% compared to the control MBR membrane). Meanwhile, the efficiency of phosphorus removal was developed in QQ-microcapsule MBR because of the enhanced phosphorus removal triggered by the flocculation of polyacrylamide (PAM) fraction in SIPN. This promising QQ media brings the broad potential for biofouling control and long-term efficient operation in actual MBR wastewater treatment.

Modulation of the biocompatibility of collagen/polyelectrolyte semi-IPN hydrogels with Zn-bioMOFs.

In this study, we examined the impact of Zn-bioMOF structures on the physical and chemical characteristics as well as the in vitro biocompatibility of a matrix composed of semi-interpenetrating polymeric networks (semi-IPN) made from collagen and L-tyrosine-based polyelectrolytes. We hydrothermally synthesized L-1, ZIF-8H Zn-bioMOFs, and the Zn-(L-His)2 complex, utilizing L-histidine, a bioactive amino acid, as a ligand. These metal-organic compounds primarily enhance the mechanical properties of the novel composite hydrogels through physical interactions such as hydrogen bonds and dipolar interactions. They also accelerate the gelation process. Composites containing Zn-bioMOFs exhibited greater biocompatibility than the collagen/polyelectrolyte matrix alone, as evidenced by cytotoxicity assays conducted with porcine fibroblasts, human monocytes, and RAW 264.7 cells. Furthermore, the evaluated materials did not exhibit hemolysis. We investigated the influence of Zn-bioMOFs on cell signaling by measuring the levels of crucial cytokines involved in the healing process, such as MCP-1, TGF-β, IL-10, and TNF-α secreted by human monocytes. The composite with Zn(L-His)2 promoted the secretion of MCP-1, TGF-β, and IL-10, while a decrease in TNF-α secretion was observed with the composite containing ZIF-8H. Zn-bioMOFs enhanced certain aspects of the biomedical and physicochemical properties of the composite hydrogels. Although the overall performance of the tested materials did not differ significantly, it is worth noting that the presence of Zn-bioMOFs in biopolymeric hydrogels modulated the metabolic activity of cells important for healing and their cytokine signaling, leading to improved biomedical performance.

Transparent injectable sericin-honey hydrogel with antioxidant and antibacterial activities combined with feeding sericin accelerates diabetic wound healing.

Wound healing in diabetics is often impaired or delayed due to the presence of high reactive oxygen species and low antioxidant levels. Here, a sericin-honey semi-interpenetrating network hydrogel with excellent antioxidant activity was prepared. Besides, the sericin-honey hydrogel is transparent, injectable, sticky, highly porous, and has good swelling properties, antibacterial activity, and cell compatibility. Based on its good performance in vitro, sericin-honey hydrogel achieved effective in vivo treatment on a mouse diabetic wound model, significantly accelerating the wound healing process. Furthermore, the combined effect of feeding sericin solution played a positive role in strengthening the effect of diabetic wound repair.

Advancing electrodialysis with dually cross-linked PVDF-based anion exchange membranes having semi-interpenetrating networks

Electrically-driven membrane technology plays a crucial role in water treatment and purification, finding applications in various fields like saline water and wastewater desalination, saline concentration and wastewater recycling. The content of this study is based on dually cross-linking and hot-pressing on a PVDF blend, to fabricate a kind of anion exchange membranes (AEMs) having semi-interpenetrating network and thus improve the defect of the traditional heterogeneous AEMs. The research explores the impact of vinyl imidazole (VIM) and dimethylaminoethyl methacrylate (DMAEMA) monomers, primarily or dually cross-linking, and optimizes the membrane properties through a hot-pressing process. Under these optimized conditions, the resulting membranes exhibit robust mechanical properties and outstanding desalination capabilities, achieving an area resistance of 2.56 Ω cm2 (comparable to standard homogeneous membranes), a desalination rate of 97.26% (outperforming the Neosepta AMX: 76.90%), and a salt limiting concentration of 3.1 M (surpassing the heterogeneous AEM and Neosepta AMX). Notably, this synthesis method is characterized by its cheap raw material and low energy consumption. This research offers valuable insights for the advancement and large-scale implementation of anion exchange membrane desalination.

Photosynthetic live microorganism-incorporated hydrogels promote diabetic wound healing via self-powering and oxygen production

Electrical stimulation and oxygen are vital for promoting cell proliferation, migration, and differentiation to repair damaged tissues in chronic wound healing in patients with diabetes. The effective oxygen production by Chlorella has garnered attention in the medical field, but the potential of extracellular electron production in skin repair has not been explored. Inspired by this, we developed CHPS hydrogels, a composite of polyacrylamide and sodium alginate, with Chlorella loaded in a semi-interpenetrating network. This network is formed by crosslinking acrylamide initiated by free radicals, with alginate chains dispersed within the network. When applied to wounds, CHPS hydrogels effectively protect damaged tissue, provide mechanical support to Chlorella against external forces, and create an optimal artificial microenvironment to promote the proliferation of Chlorella. Our study demonstrated that CHPS hydrogels exhibit remarkable fracture elongation and adhesion properties and continuously produce oxygen and bioelectrical currents through photosynthesis. Furthermore, the sustained release of dissolved oxygen and bioelectricity by CHPS hydrogels significantly enhances cell proliferation, migration, and angiogenesis, leading to improved wound healing in diabetic mice. These findings provide compelling evidence for further exploration of CHPS hydrogels as a cost-effective, simple, and accessible strategy for enhancing the clinical treatment of chronic wounds in diabetic patients.

High stretchable and tough xylan-g-gelatin hydrogel via the synergy of chemical cross-linking and salting out for strain sensors

Stretchable and tough hydrogels have been extensively used in tissue engineering scaffolds and flexible electronics. However, it is still a significant challenge to prepare hydrogels with both tensile strength and toughness by utilizing xylan, which is abundant in nature. Herein, we present a novel hydrogel of carboxymethyl xylan(CMX) graft gelatin (G) and doped with conductive hydroxyl carbon nanotubes (OCNT). CMX and G are combined through amide bonding as well as intermolecular hydrogen bonding to form a semi-interpenetrating hydrogel network. The hydrogel was further subjected to salting-out treatment, which induced the aggregation of the CMX-g-G molecular chain and the formation of chain bundles to toughen the hydrogel, the tensile strain, tensile stress, and toughness of CMX-g-G hydrogels were 1.547 MPa, 324 %, and 2.31 MJ m−3, respectively. In addition, OCNT was used as a conductive filler to impart electrical conductivity and further improve the mechanical properties of CMX-g-G/OCNT hydrogel, and a tensile strength of 1.62 MPa was obtained. Thus, the synthesized CMX-g-G/OCNT hydrogel can be used as a reliable and sensitive strain sensor for monitoring human activity. This study opens up new horizons for the preparation of xylan-based high-performance hydrogels.