Physical Crosslinking Research Articles

Supramolecular hydrogels based on hydrogen bonding: Impact of ionic comonomers

AbstractThe polymerization of N‐acryloyl glycineamide (NAGA) in water results in the creation of robust supramolecular hydrogels, exhibiting a network structure through inter‐chain crosslinking formed by hydrogen bonds between NAGA units. The stability of these hydrogen bonds in water is based on the aggregation of NAGA units into microdomains or clusters, thereby effectively shielding the hydrogen bonds from the surrounding aqueous medium. Beyond the inherent water absorption characteristics of these hydrogels, the unique ability for the dissociation and re‐association of their physical crosslinks imparts features such as reversible swelling and shrinking as well as self‐healing and remolding capabilities. In this study, we synthesize a series of supramolecular hydrogels through copolymerization of NAGA and ionic sodium acrylate comonomers for a dual purpose: first, to regulate water absorption levels, and second, to introduce a salt partitioning effect into the hydrogels during their swelling in salt solution. Our findings indicate that the properties of these hydrogels are intricately influenced by the volume fraction of the solid network, the concentration of ionic units, and temperature. Notably, supramolecular samples with ionic units exhibit a 16% salt rejection in a single cycle of salt partitioning during their swelling in a 1 g·L−1 sodium chloride solution.

DEVELOPMENT OF ZINC-LOADED HYDROGEL INFUSED WITH ALOE BARBADENSIS MUCILAGE FOR WOUND HEALING

This study aims to formulate and characterize zinc-loaded hydrogel infused with Aloe barbadensis mucilage for wound dressing. Five formulations containing varying proportions of carbopol, zinc, aloe and water (as vehicle) were developed via physical crosslinking using triethanolamine. All formulations had a translucent off-white colour while the control gave a transparent gel. The viscosity was highest in the control, 30000.00 ± 2.07 PaS. The pH of the formulations was between 5.7 and 5.8. Formulation 2 which is composed of 30 mg of Zinc and 1.4 mg of Aloe barbadensis incorporated into 1% w/v Carbopol Ultrez hydrogel polymer had the lowest swelling index of 79.2 ± 1.95% implying that it had the fastest drug release rate. The wounds treated with Formulation 2 had the most rapid wound healing with no sign of scars in the wound area. Histomorphometric evaluation reflected a high re-epithelisation rate of 70%, a significant percentage occupied by collagen in granulation tissue of 85%. The thickness of the tissue's central region was 10 mm. The inflammatory cells /mm2 tissue was 200 cells/mm2 while the number of microvessels in granulation tissue was 1.0 microvessels/mm2. Zinc-loaded hydrogel infused with Aloe barbadensis mucilage shows great potential as a modern wound dressing.

Solvent-free polyurethane adhesives with excellent adhesion performance at ultra-low temperature

Adhesives with excellent adhesion and high elongation at cryogenic temperatures are necessary for fields such as aerospace, transportation, superconductors, and medicine, but have difficult requirements. This study aimed to develop a solvent-free, two-component polyurethane (PU) adhesive with excellent adhesion and high elongation, especially in ultra-low temperature conditions. we incorporated bulky polydimethylsiloxane (PDMS) diol into the hard segment of the PU adhesive to enhance flexibility and improve physical cross-linking within the adhesive matrix. The resulting PDMS-based PU adhesive showed a tensile strength of 120 MPa at −170 °C and a high elongation of approximately 4 %. It showed a lap-shear strength of up to 13 MPa at −196 °C. Additionally, the adhesive was curable at 23 °C. In this study, the cryogenic applicability of the PU adhesive was evaluated at −170 °C (103 K, liquid natural gas) and −196 °C (77 K, liquid nitrogen). Future research on the polymer adhesive materials applicable to ultra-low temperatures, such as 20 K, may be necessary if storage and transportation of liquid hydrogen become feasible.

Mechanical and viscoelastic properties of novel resin-infused thermoplastic tri-block copolymer 3D glass fabric composites

The current study investigates the mechanical and viscoelastic properties of a novel acrylic resin-infused thermoplastic (Elium®) tri-block copolymer (Nanostrength®) 3D fibre-reinforced composites (FRCs). The toughened thermoplastic resins with three different concentrations of tri-block copolymer, i.e., 10 wt%, 15 wt%, and 20 wt%, were prepared and used to fabricate thermoplastic 3D-FRCs using a vacuum-assisted resin-infusion process at room temperature. The flexural, interlaminar, and viscoelastic properties and failure modes were evaluated and compared with those of pristine thermoplastic 3D-FRCs. The addition of tri-block copolymer significantly improves the flexural strength of 3D-FRC (up to 75 % and 34 % along the warp and fill directions, respectively, at 15 wt% of tri-block copolymer) and interlaminar shear strength (up to 80 % and 111 % along the warp and fill directions, respectively, at 20 wt% of tri-block copolymer). Additionally, the residual flexure and interlaminar shear strength improved up to 35 % and 109 % at 15 wt% of tri-block copolymer. Dynamic mechanical analysis (DMA) demonstrated that the glass transition temperature and storage modulus of thermoplastic 3D-FRCs were increased up to 11 °C and 24 %, respectively at 20 wt% of tri-block copolymer, which may be due to increased physical crosslinking and the agglomeration of tri-block copolymer particles. The improved mechanical and viscoelastic properties of resin-infused thermoplastic tri-block copolymer 3D-FRCs are attributed to better interface adhesion, improved matrix toughness, and crack-bridging mechanisms induced by the tri-block copolymer. The toughened thermoplastic 3D-FRCs can be utilized in the design and development of composite structures for improved damage tolerance applications.

Designed wrinkles for optical encryption and flexible integrated circuit carrier board

Patterns on polymers usually have different mechanical properties as those of the substrates, causing deformation or distortion and even detachment of the patterns from the polymer substrates. Herein, we present a wrinkling strategy, which utilizes photolithography to define the area of stress distribution by light-induced physical crosslinking of polymers and controls diffusion of residual solvent to redistribute the stress and then offers the same material for patterns as substrate by thermal polymerization, providing uniform wrinkles without worrying about force relaxation. The strategy allows the recording and hiding of up to eight switchable images in one place that can be read by the naked eye without crosstalk, applying the wrinkled polymer for optical anti-counterfeiting. The wrinkled polyimide film was also utilized to act as a substrate for the creation of fine copper circuit by a full-additive process. It generates flexible integrated circuit (IC) carrier board with copper wire density of 400% higher than that of the state-of-the-art in industry while fulfilling the standards for industrialization.

Phenol Removal through Horseradish Peroxidase Immobilization on Ultrafiltration Membranes: Comparative Analysis of Immobilization Methods and Fouling Patterns

This research investigates the removal of phenol using pure peroxidase from horseradish grade I in conjunction with a dead-end ultrafiltration membrane. Various horseradish peroxidase (HRP) immobilization techniques— physical adsorption, covalent bonding, and cross-linking with glutaraldehyde—were applied to a regenerated cellulose (RC) membrane with a surface area of 44 m2 and a molecular weight cut-off of 30 kDa. The investigation examined factors influencing phenol removal, including phenol concentration, membrane fouling, and the reusability of immobilized enzymes. Results indicated that covalent bonding was the most suitable enzyme immobilization technique, achieving a remarkable 90.1% immobilization yield. Phenol removal efficiency reached 100% at 30 min under specific conditions: phenol concentration of 1 mg/L, pH 6.0, hydrogen peroxide concentration of 0.5 mM, and operating pressure set at 3 psig, with temperature maintained at 28 ± 3 °C. Membrane fouling resulted in a decrease in flux. The performance of fouling models was found to be influenced by phenol concentration, with the Cake Formation Model (CFM) proving most effective at low concentrations, while the Complete Pore Blocking Model (CBM) emerged as more suitable at higher concentrations. The immobilized enzyme exhibited reusability for five cycles, maintaining a phenol removal efficiency exceeding 50%. These findings contribute to understanding the enzymatic phenol removal process and the use of appropriate enzyme immobilization techniques for the effective and sustainable treatment of phenol-contaminated water.

Viscoelastic Adhesive, Super-Conformable, and Semi-Flowable Liquid Metal Eutectogels for High-Fidelity Electrophysiological Monitoring.

Integrating gels with human skin through wearables provides unprecedented opportunities for health monitoring technology and artificial intelligence. However, most conductive hydrogels, organogels, and ionogels lack essential environmental stability, biocompatibility, and adhesion for reliable epidermal sensing. In this study, we have developed a liquid metal eutectogel simultaneously possessing superior viscoelasticity, semiflowability, and mechanical rigidity for low interfacial skin impedance, high skin adhesion, and durability. Liquid metal particles (LMPs) are employed to generate free radicals and gallium ions to accelerate the polymerization of acrylic acid monomers in a deep eutectic solvent (DES), obtaining highly viscoelastic polymer networks via physical cross-linking. In particular, graphene oxide (GO) is utilized to encapsulate the LMPs through a sonication-assisted electrostatic assembly to stabilize the LMPs in DES, which also enhances the mechanical toughness and regulates the rheological properties of the eutectogels. Our optimized semi-flowable eutectogel exhibits viscous fluid behavior at low shear rates, facilitating a highly conformable interface with hairy skin. Simultaneously, it demonstrates viscoelastic behavior at high shear rates, allowing for easy peel-off. These distinctive attributes enable the successful applications of on-skin adhesive strain sensing and high-fidelity human electrophysiological (EP) monitoring, showcasing the versatility of these ionically conductive liquid metal eutectogels in advanced personal health monitoring.

Tissue-adhesive, stretchable and compressible physical double-crosslinked microgel-integrated hydrogels for dynamic wound care

Integrated wound care through sequentially promoting hemostasis, sealing, and healing holds great promise in clinical practice. However, it remains challenging for regular bioadhesives to achieve integrated care of dynamic wounds due to the difficulties in adapting to dynamic mechanical and wet wound environments. Herein, we reported a type of dehydrated, physical double crosslinked microgels (DPDMs) which were capable of in situ forming highly stretchable, compressible and tissue-adhesive hydrogels for integrated care of dynamic wounds. The DPDMs were designed by the rational integration of the reversible crosslinks and double crosslinks into micronized gels. The reversible physical crosslinks enabled the DPDMs to integrate together, and the double crosslinked characteristics further strengthen the formed macroscopical networks (DPDM-Gels). We demonstrated that the DPDM-Gels simultaneously possess outstanding tensile (∼940 kJ/m3) and compressive (∼270 kJ/m3) toughness, commercial bioadhesives-comparable tissue-adhesive strength, together with stable performance under hundreds of deformations. In vivo results further revealed that the DPDM-Gels could effectively stop bleeding in various bleeding models, even in an actual dynamic environment, and enable the integrated care of dynamic skin wounds. On the basis of the remarkable mechanical and appropriate adhesive properties, together with impressive integrated care capacities, the DPDM-Gels may provide a new approach for the smart care of dynamic wounds. Statement of significanceIntegrated care of dynamic wounds holds great significance in clinical practice. However, the dynamic and wet wound environments pose great challenges for existing hydrogels to achieve it. This work developed robust adhesive hydrogels for integrated care of dynamic wounds by designing dehydrated, physical double crosslinked microgels (DPDMs). The reversible and double crosslinks enabled DPDMs to integrate into macroscopic hydrogels with high mechanical properties, appropriate adhesive strength and stable performance under hundreds of external deformations. Upon application at the injury site, DPDM-Gels efficiently stopped bleeding, even in an actual dynamic environment and showed effectiveness in integrated care of dynamic wounds. With the fascinating properties, DPDMs may become an effective tool for smart wound care.

Induction of polymer-grafted cellulose nanocrystals in hydrogel nanocomposites to increase anti-swelling, mechanical properties and conductive self-recovery for underwater strain sensing

Anti-swelling conductive hydrogels with simultaneous high tensile strength (>1 MPa) and fast self-recovery are promising candidates for underwater strain sensing, but their preparation remains challenging. Herein, novel anti-swelling conductive nanocomposite hydrogels were fabricated based on poly(acrylamide-co-acrylic acid) (P(AM-co-AA)), polymer-grafted cellulose nanocrystals (CNCs) and Fe3+ ions through a strategy combining nano-reinforcing and multiple physical crosslinking. Due to the presence of interfacial H-bonds, polymer-grafted cellulose nanocrystals played important role in endowing hydrogels with anti-swelling capacity and enhanced mechanical performance. The obtained nanocomposite hydrogels exhibited relatively low swelling ratio (2.9–3.3 g/g), high tensile strength (>1.5 MPa), fast self-recovery (86 % recovery of hysteresis within 5 min) and conductivities of 0.0534–0.0593 S/m. The combination of excellent tensile properties and conductivity endowed the hydrogel-based strain sensors with good sensitivity (GF ≈ 0.8) and reliable cycling repeatability in 0–100 % strain range. Notably, the nanocomposite hydrogels can maintain their mechanical and sensing performance after soaking in water for 14 days, making them applicable for human motion detection both in air and underwater. Hence, this work provided a facile method to construct highly robust and anti-swelling CNC-reinforced conductive hydrogels, which have potential applications in underwater strain sensing and beyond.

On the dual crosslinking for functionality enhancement of poly (acrylamide-co-acrylic acid)/chitosan-aluminum (III) ions and its characterization and sensory hydrogel fibers

In this report, we present a dual crosslinking hydrogel fiber made from polyamine saccharides chitosan (CS), synthesized through UV polymerization. This process utilizes Irgacure 2959 and N,N′-Methylenebisacrylamide (MBAA) as initiators, followed by immersion in an aluminum chloride (AlCl3) solution. The resulting hydrogel incorporates a dual crosslinking mechanism, quantitatively studied via Nuclear Magnetic Resonance (NMR) spectroscopy. This mechanism involves chemical crosslinking through radical graft polymerization of acrylamide and acrylic acid onto CS in the presence of MBAA, and physical crosslinking through hydrogen bonding interactions between P(AAm-co-AA) and a metal coordination bond. The mechanical properties of the hydrogel fiber enable it to withstand stresses up to 656 kPa and strains exceeding 300 %. Additionally, the hydrogel fiber exhibits conductivity at 1.96 Scm−1. Serving as a multifunctional material, it acts as a strain sensor and finds utility in optics. Remarkably, it demonstrates the capability to detect human motions such as finger bending and minor deformations like vibrations of the vocal cords. Furthermore, its ability to guide dynamic light makes it promising for optical applications. Consequently, this multifunctional hydrogel fiber emerges as a highly promising candidate for diverse applications in fields such as bioengineering and electronics.

Processable, reversible, and reusable 100 % bio-based pressure sensitive adhesives using nanostarch

We developed a 100 % bio-based pressure sensitive adhesive (PSA) possessing strong adhesion, as well as reusability, recyclability, and on-demand removability. The adhesive formulation is based on a colloidal mixture of starch (specifically amylopectin) nanoparticles and cellulose nanofibrils, combined with an aqueous solution of sorbitol and glycerol. Optimization of water supply and substitution of water with hygroscopic glycerol were implemented to address the challenges caused by the use of high water contents in hydrogels. By leveraging physical crosslinking through hydrogen bonding, we achieved high adhesion strength, reversibility, and reusability with 100 % bio-based materials. The optimal formulation demonstrates excellent rheological and adhesion properties, which are comparable to petrochemical-based adhesives in terms of tack, peel strength, and shear strength. While there are areas for further optimization, this work provides a foundational step towards a more sustainable adhesive industry.

Silicone‐containing polyurea elastomer possessing main‐chain boron–oxygen bonds with delayed stress relaxation and improved adhesive properties

AbstractPolyurea (PU) elastomers have attracted considerable attention in the field of protective polymeric coatings. In this work, a dithiol‐terminated boronic ester was synthesized and used to incorporate dynamic boron–oxygen (B–O) bonds in the PU main chain based on thiol isocyanate while amino‐terminated polydimethylsiloxane (PDMS) was introduced to retain good chain flexibility. The modified PU elastomer was found to have a microphase‐separated structure in which the hard blocks served as physical crosslinks. The glass transition temperature (Tg) slightly increases when dynamic B–O bonds exist while further introduction of PDMS soft segment can lower Tg to −55.63 °C. The introduction of dynamic B–O bonds and diminished hydrogen bonding led to a decrease in mechanical strength and elongation at break. Interestingly, the simultaneous incorporation of PDMS and dynamic B–O bonds is favorable for strain rate dependence and suppressing stress relaxation. The potential for bond‐exchange interactions between the dynamic B–O bonds and hydroxyl groups on metal surfaces substantially improved the adhesion of the PU elastomer to metal substrates. Therefore, our work can offer valuable insights for the structural design of functional PU coatings tailored for anti‐impact applications. © 2024 Society of Chemical Industry.

Eco-Friendly Production of Polyvinyl Alcohol/Carboxymethyl Cellulose Wound Healing Dressing Containing Sericin.

Wound dressing production represents an important segment in the biomedical healthcare field, but finding a simple and eco-friendly method that combines a natural compound and a biocompatible dressing production for biomedical application is still a challenge. Therefore, the aim of this study is to develop wound healing dressings that are environmentally friendly, low cost, and easily produced, using natural agents and a physical crosslinking technique. Hydrogel wound healing dressings were prepared from polyvinyl alcohol/carboxymethyl cellulose and sericin using the freeze-thawing method as a crosslinking method. The morphological characterization was carried out by scanning electron microscopy (SEM), whereas the mechanical analysis was carried out by dynamic mechanical analysis (DMA) to test the tensile strength and compression properties. Then, the healing property of the wound dressing material was tested by in vitro and ex vivo tests. The results show a three-dimensional microporous structure with no cytotoxicity, excellent stretchability with compressive properties similar to those of human skin, and excellent healing properties. The proposed hydrogel dressing was tested in vitro with HaCaT keratinocytes and ex vivo with epidermal tissues, demonstrating an effective advantage on wound healing acceleration. Accordingly, this study was successful in developing wound healing dressings using natural agents and a simple and green crosslinking method.

Natural multi-actives composited hydrogel patches for diabetic wound healing

Biomedical patches have garnered recognition for their efficacy in diabetic wound management. Current research efforts are focused on developing natural and efficient hydrogel patches in order to reduce inherent side effects and enhance therapeutic outcomes. In this study, we present natural multi-actives composited hydrogel patches for diabetic wound management. The novel medical patch was fabricated using freeze-dried grape peel, oligomeric proanthocyanidins (OPC) and puerarin based on spontaneous physical crosslinking. With the incorporation of OPC, the natural patch exhibited favorable photothermal antibacterial properties, effectively inhibiting S. aureus and E. coli under 808 nm near-infrared irradiation. In addition, the grape peel could induce M2 macrophage polarization and scavenge reactive oxygen species, showcasing immunomodulatory effects. Moreover, the puerarin component in the patches was discovered to promote endothelial cell proliferation and migration, thereby facilitating angiogenesis in vitro. Based on these features, we have demonstrated the antibacterial, antioxidant, anti-inflammatory, and angiogenic effects of the patches in vivo. Thus, we believe that the natural multi-actives composite patch holds significant promise for diabetic wound treatment and broader biomedical applications.

Highly Water‐Rich Robust Coating for Separating Immiscible Liquids Mixtures of Wide Range of Surface Tension Differences

AbstractDeveloping mechanically robust and chemically tolerant coatings that maintain a high water content remains an extremely challenging task to pursue to date. Here, an optimum reinforcement of a hollow nano‐clay i.e., halloysite in a dual crosslinked and interpenetrating polymeric network is introduced to yield a high (≈95 wt%) water content coating with an ability to improve toughness (9.9 ± 0.6 MJm−3 Vs. 0.5 ± 0.03 MJ m−3) of a deformable fibrous substrate. The association of covalent and physical crosslinking chemistries provides essential tolerance against exposures to diverse severe chemically complex conditions, including extremes of pH, seawater, river water, and organic solvents. High water content in the prepared hydrogel network endows a robust bio‐inspired underwater nonadhesive superoleophobicity with oil contact angle of 160.7 ± 0.2° and force of oil‐droplet adhesion of 8.7 ± 0.3 µN. This approach provides a liquid selective filtrating membrane with ultrahigh crude oil/water separation efficiency (99.7%), superior intrusion pressure (3.5 ± 0.4 kPa), relatively high separation flux (11,162 Lm−2 h−1), and the ability to perform even when the surface tension of aqueous phase is brought down to similar of oily phase. Moreover, a mixture of immiscible, non‐aqueous liquids having differences in surface tension below 2.5 mN m−1 is successfully separated.

A bioadhesive pacing lead for atraumatic cardiac monitoring and stimulation in rodent and porcine models.

Current clinically used electronic implants, including cardiac pacing leads for epicardial monitoring and stimulation of the heart, rely on surgical suturing or direct insertion of electrodes to the heart tissue. These approaches can cause tissue trauma during the implantation and retrieval of the pacing leads, with the potential for bleeding, tissue damage, and device failure. Here, we report a bioadhesive pacing lead that can directly interface with cardiac tissue through physical and covalent interactions to support minimally invasive adhesive implantation and gentle on-demand removal of the device with a detachment solution. We developed 3D-printable bioadhesive materials for customized fabrication of the device by graft-polymerizing polyacrylic acid on hydrophilic polyurethane and mixing with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to obtain electrical conductivity. The bioadhesive construct exhibited mechanical properties similar to cardiac tissue and strong tissue adhesion, supporting stable electrical interfacing. Infusion of a detachment solution to cleave physical and covalent cross-links between the adhesive interface and the tissue allowed retrieval of the bioadhesive pacing leads in rat and porcine models without apparent tissue damage. Continuous and reliable cardiac monitoring and pacing of rodent and porcine hearts were demonstrated for 2 weeks with consistent capture threshold and sensing amplitude, in contrast to a commercially available alternative. Pacing and continuous telemetric monitoring were achieved in a porcine model. These findings may offer a promising platform for adhesive bioelectronic devices for cardiac monitoring and treatment.

Highly Sensitive Flexible Capacitive Pressure Sensor Based on a Multicross-Linked Dual-Network Ionic Hydrogel for Blood Pressure Monitoring Applications.

Flexible capacitive pressure sensors based on ionic hydrogels (IHs) have garnered significant attention in the field of wearable technology. However, the vulnerability of traditional single-network hydrogels to mechanical damage and the complexity associated with preparing double-network hydrogels present challenges in developing a highly sensitive, easily prepared, and durable IH-based flexible capacitive pressure sensor. This study introduces a novel multicross-linked dual-network IH achieved through the physical and chemical cross-linking of polymers polyvinyl alcohol (PVA) and chitosan (CS), ionic solution H3PO4, and cross-linking agent gum arabic. Flexible capacitive pressure sensors, characterized by high sensitivity and a broad pressure range, are fabricated by employing mesh as templates to design cut-corner cube microstructures with high uniformity and controllability on the IHs. The sensor exhibits high sensitivity across a wide pressure range (0-290 kPa) and with excellent features such as high resolution (∼1.3 Pa), fast response-recovery time (∼11 ms), and repeatable compression stability at 25 kPa (>2000 cycles). The IHs as a dielectric layer demonstrate long-term water retention properties, enabling exposure to air for up to 100 days. Additionally, the developed sensor shows the ability to accurately measure the pulse wave within the small pressure range. By combining the pulse wave acquired by the sensor with a trained neural network model, we achieve successful blood pressure (BP) prediction, meeting the standards set by the Association for the Advancement of Medical Instrumentation and the British Hypertension Society. Ultimately, the sensor proposed in this study holds promising prospects for broad applications in high-precision wearable medical electronic devices.

Self-assembly of curdlan molecules for the formation of thermally induced gels

The differences in the self-assembly process between cold-set (CCS) and heat-set (CHS) curdlan gels were investigated using micro-differential scanning calorimetry, atomic force microscopy, and small-angle X-ray diffraction. The results indicate that the triple-helix structure of curdlan dissociated into single helices in its suspension state (C-SUS) at 65 °C. Upon cooling to around 38 °C, these single helices assembled into long, thick fibers with a height of up to 11.50 nm, contributing to the gel structure of CCS. Heating C-SUS from 65 °C to 90 °C caused the single helices to transform into triple helices due to hydrophobic interactions. Subsequent cooling to 25 °C, led to the formation of short, thick bundles with a height of up to 8.78 nm, forming the network structure of CHS gel. As a consequence, CHS gels exhibited higher hardness and elasticity but lower fatigue resistance. This is attributed to an increased degree of physical cross-linking, as evidenced by a reduction in the size (Ξ) and spacing (ξ) of high-density domains within the gel structure, and a simpler mechanism of energy dissipation through alignment of the molecular chain segment. These findings are valuable for the design and development of curdlan-based gels with tailored mechanical properties.

SYNTHESIS AND STUDY OF THE INFLUENCE OF ALKALI CONCENTRATION AND TEMPERATURE ON THE PHYSICOCHEMICAL PROPERTIES OF CRYOGELS BASED ON GELATIN AND CHITOSAN

Much of the polymer research is focused on improving existing polymers or developing new biomaterials with tunable properties. Natural polymers that have certain segments that contribute to an additional therapeutic effect are more often used as a biocompatible polymer. Polymers can be produced using a variety of methods, including covalent cross-linking, dynamic covalent cross-linking, physical cross-linking, cryopolymerization, 3D printing, electrospinning, etc. Cryopolymerization is a unique method and has several advantages over other methods. By cryofreezing it is possible to obtain a porous structure in which the size and volume of the pores can be controlled by changing the concentration of the initial monomers and temperature. The purpose of this study is to determine the effect of alkali concentration and cryopolymerization temperature on the properties of cryogels. The objects of study in this work are cryogels based on gelatin and chitosan. Methodology. The functional groups of the cryogels were determined by IR spectroscopy. The results of a study of the sorption and desorption of polymers are presented. The results of polymer degradation in phosphate-saline solution over 8 weeks are also shown. These studies were based on changes in mass, that is, they were carried out using the gravimetric method. Conclusion. The results of a study of the influence of alkali concentration and temperature on the physicochemical properties of cryogels based on gelatin and chitosan are presented. Cryogels based on gelatin and chitosan are synthesized without the use of harmful chemical cross-linking agents, which makes them attractive for tissue engineering.

Non-covalently crosslinked networks MXene-doped poly(eutectic) conductive elastomers with antimicrobial, self-healing, tunable mechanical properties, and wide temperature durability

Poly(eutectic) elastomers, as an emerging category of flexible electronic materials, have garnered growing interest for their cost-effectiveness, non-volatility, and biocompatibility. Nonetheless, they encounter challenges including limited functionalities, sensitivity, durability, and mechanical properties. This study involved synthesizing various MXene-doped poly(eutectic) elastomers using robust acrylamide and soft acrylic acid as organic monomers, minor MXene nanosheets as inorganic fillers and physical crosslinkers, and a rapid in-situ photopolymerization method within 2 min. Owing to the synergistic effect of thermodynamic self-assembly, high-density hydrogen bonding, and cation-dipole interactions in the matrix networks, the resulting non-covalently crosslinked elastomers exhibited remarkable mechanical strength (up to ∼ 16.2 MPa) and impressive tensile properties (nearly 700 %), along with rapid electrical self-healing (within 0.046 s) and the ability to withstand loads up to 2500 times their weight following self-healing without fracturing. Notably, these elastomers also demonstrated excellent microstrain (1 %–10 %) sensitivity with a gauge factor of 2.02, wide temperature tolerance (−20 °C ∼ 60 °C), outstanding harsh temperature durability (−20 °C) exceeding 22,000 cycles, and antibacterial properties. Furthermore, these elastomers-assembled strain sensors displayed real-time and rapid response in human motion detection and wireless signal transmission, presenting a promising approach for designing functionally integrated elastomeric materials.