Chemical Crosslinking Network Research Articles

Strong and tough conductive hydrogels via an amphiphilic macromolecular crosslinker for flexible strain sensor

The strength and toughness of hydrogel are usually achieved through the synergy of chemical cross-linking and physical cross-linking from multi-component contributions. However, there are few reports on hydrogels that rely on a single component to obtain two cross-linked structures. Herein, we successfully synthesized an amphiphilic macromolecular crosslinker (polyoxyethylene 20 oleyl ether acrylate (O20AC)), and introduced it into a system composed of acrylamide (AAm), sodium chloride (NaCl) and water to prepare the P(AAm-O20AC)/NaCl hydrogel with high strength, outstanding toughness, and excellent good conductivity. Notably, the O20AC possess both crosslinker properties, which not only provide hydrogels with a stable chemical cross-linking network, but also its long hydrophobic chain act as physical crosslinking points to give the hydrogel a new pathway of energy dissipation.Depending on the O20AC crosslinker, the P(AAm-O20AC)/NaCl hydrogels exhibit good strength (tensile stress 714.46 kPa), toughness (elongation at break 3005 %), and fatigue resistance (overlap of hysteresis curves in repeated loading–unloading cycles). Besides, the existence of sodium ions and chloride ions also provides the hydrogel with highly sensitive deformation-dependent conductivity (GF is 5.8 in the 400 %-500 % strain range). Collectively, the strategy of preparing chemical and physical double-crosslinked hydrogels by amphiphilic O20AC will provide a bran-new insights for the development of hydrogel sensing materials.

Structuring restricted amorphous molecular chains in the reinforced cellulose film by uniaxial stretching

The construction of the preferred orientation structure by stretching is an efficient strategy to fabricate high-performance cellulose film and it is still an open issue whether crystalline structure or amorphous molecular chain is the key factor in determining the enhanced mechanical performance. Herein, uniaxial stretching with constant width followed by drying in a stretching state was carried out to cellulose hydrogels with physical and chemical double cross-linking networks, achieving high-performance regenerated cellulose films (RCFs) with an impressive tensile strength of 154.5 MPa and an elastic modulus of 5.4 GPa. The hierarchical structure of RCFs during uniaxial stretching and drying was systematically characterized from micro- to nanoscale, including microscopic morphology, crystalline structure as well as relaxation behavior at a molecular level. The two-dimensional correlation spectra of dynamic mechanical analysis and Havriliak-Negami fitting results verified that the enhanced mechanical properties of RCFs were mainly attributed to the stretch-induced tight packing and restricted relaxation of amorphous molecular chains. The new insight concerning the contribution of molecular chains in the amorphous region to the enhancement of mechanical performance for RCFs is expected to provide valuable guidance for designing and fabricating high-performance eco-friendly cellulose-based films.

High mechanical strength, strong adhesion, self-healing and conductive ionic hydrogels for motion detection

The development of conductive hydrogels with outstanding mechanical properties, robust adhesion, and high sensitivity is still a major challenge. This study successfully addresses this issue by a multi-functional ionic conductive hydrogel based on a highly entangled double network (DN) structure with excellent mechanical properties, strong adhesion, high sensitivity and self-healing ability. Polyacrylic acid (PAAc)/chitosan (CS) constructed the Double Network with physical entanglement as the main effective crosslinking. The sliding entanglement points made the hydrogel show a more uniform directional network structure during stretching, and the energy dissipation was greatly reduced. Active chemically reactive polydopamine (PDA), CS, and PAAc are complexed with aluminum ions (Al3+) respectively (building appropriate chemical crosslinking networks), and Al3+ acts as a “bridge” to build a hierarchical porous networks through multiple reversible coordination bond mediated interactions, alternating rigid and elastic domains, thereby improving the comprehensive performance of hydrogels. The tensile strength of PAAc/PDA/CS (ADC) was 173.4 kPa and the elongation at break was 921.9%, both of which were improved simultaneously. Moreover, ADC composite hydrogels exhibit excellent self-healing and adhesion properties, which can be attributed to the rich reversible/irreversible interactions brought about by PDA, with an impressive adhesion strength of 85.2 kPa on pig skin, further enhancing its practicality. Additionally, the ionic hydrogel demonstrates high strain sensitivity to tension, making it an ideal material for stable sensor signal output. The sensitivity coefficient (GF) reaches an impressive 11.24, highlighting the importance of this hydrogel in ensuring consistent and precise data collection. This innovative approach expands the idea and provides data support for the molecular structure design of high-performance wearable hydrogel sensors.

Multifunctional chitosan-based lanthanide luminescent hydrogel with stretchability, adhesion, self-healing, color tunability and antibacterial ability

Lanthanide luminescent hydrogels have broad application prospects in various fields. However, most of lanthanide hydrogels possess relatively simple functions, which is not conducive to practical applications. Therefore, it is becoming increasingly urgent to develop multifunctional hydrogels. Herein, a multifunctional chitosan-based lanthanide luminescent hydrogel with ultra-stretchability, multi-adhesion, excellent self-healing, emission color tunability, and good antibacterial ability was prepared by a simple one-step free radical polymerization. In this work, our designed lanthanide complexes [Ln(4-VDPA)3] contain three reaction sites, which can be copolymerized with N-[tris(hydroxymethyl) methyl] acrylamide (THMA), acrylamide (AM), and diacryloyl poly(ethylene glycol) (DPEG) to form the first chemical crosslinking network, while hydroxypropyltrimethyl ammonium chloride chitosan (HACC) interacts with the hydroxyl and amino groups derived from the chemical crosslinking network through hydrogen bonds to form the second physical crosslinking network. The structure of the double network as well as the dynamic hydrogen bond and lanthanide coordination endow the hydrogel with excellent stretchability, adhesion and self-healing properties. Moreover, the introduction of lanthanide complexes and chitosan makes the hydrogel exhibit outstanding luminescence and antibacterial performances. This research not only realizes the simple synthesis of multifunctional luminescent hydrogels, but also provides a new idea for the fabrication of biomass-based hydrogels as intelligent and sustainable materials.

Cross-Linking Methods of the Silk Protein Hydrogel in Oral and Craniomaxillofacial Tissue Regeneration.

Craniomaxillofacial tissue defects are clinical defects involving craniomaxillofacial and oral soft and hard tissues. They are characterized by defect-shaped irregularities, bacterial and inflammatory environments, and the need for functional recovery. Conventional clinical treatments are currently unable to achieve regeneration of high-quality oral craniomaxillofacial tissue. As a natural biomaterial, silk fibroin (SF) has been widely studied in biomedicine and has broad prospects for use in tissue regeneration. Hydrogels made of SF showed excellent water retention, biocompatibility, safety and the ability to combine with other materials. To gain an in-depth understanding of the current development of SF, this article reviews the structure, preparation and application prospects in oral and craniomaxillofacial tissue regenerative medicine. It first briefly introduces the structure of SF and then summarizes the principles, advantages and disadvantages of the different cross-linking methods (physical cross-linking, chemical cross-linking and double network structure) of SF. Finally, the existing research on the use of SF in tissue engineering and the prospects of using SF with different cross-linking methods in oral and craniomaxillofacial tissue regeneration are also discussed. This review is intended to show the advantages of SF hydrogels in tissue engineering and provides theoretical support for establishing novel and viable silk protein hydrogels for regeneration.

Multifunctional sodium lignosulfonate/xanthan gum/sodium alginate/polyacrylamide ionic hydrogels composite as a high-performance wearable strain sensor

Recently, conductive hydrogels have shown great promise in flexible electronics and are ideal materials for the preparation of wearable strain sensors. However, developing a simple method to produce conductive hydrogels with excellent mechanical properties, self-adhesion, transparency, anti-freezing, and UV resistance remains a significant challenge. A novel sodium lignosulfonate/xanthan gum/sodium alginate/polyacrylamide/Zn2+/DMSO (SLS/XG/SA/PAM/Zn2+/DMSO) ionic conductive hydrogel was developed using a one-pot method. The resulting ionic conductive hydrogels have excellent mechanical properties (stress: 0.13 MPa, strain: 1629 %), high anti-fatigue properties, self-adhesion properties (iron: 7.37 kPa, pigskin: 4.74 kPa), anti-freezing (freezing point: −33.49 °C) and UV resistance by constructing a chemical and physical hybrid cross-linking network. In particular, the conductivity of G hydrogel reached 6.02 S/m at room temperature and 5.52 S/m at −20 °C. Thus, the hydrogel was assembled into a flexible sensor that could distinguish a variety of large and small scales human movements, such as joint bending, swallowing and speaking in real time with high stability and sensitivity. Moreover, the hydrogel could be used as electronic skin just like human skin and touch screen pen to write.

Self-healing polyacrylates based on dynamic disulfide and quadruple hydrogen bonds.

Herein, a self-healing polyacrylate system was successfully prepared by introducing crosslinking agents containing disulfide bonds and monomers capable of forming quadruple hydrogen bonds through free radical copolymerization. This polymer material exhibited good toughness and self-healing properties through chemical and physical dual dynamic networks while maintaining excellent mechanical properties, which expanded the development path of self-healing acrylate materials. Compared to uncrosslinked and single dynamically crosslinked polymers, its elongation at break was as high as 437%, and its tensile strength was 5.48 MPa. Due to the presence of dual reversible dynamic bonds in the copolymer system, good self-healing was also achieved at 60 °C. In addition, differential scanning calorimetry and thermogravimetric analysis measurements confirmed that the thermal stability and glass transition temperature of the material were improved owing to the presence of physical and chemical cross-linking networks.

Strain-induced crystallization behavior and tensile properties of natural rubber with different vulcanization bond types

The crosslinking network structure is a crucial factor influencing the properties of natural rubber. Therefore, investigating the impact of different vulcanization bond types on the strain-induced crystallization behavior and properties of natural rubber can provide a theoretical foundation for producing high-performance natural rubber. In this study, diverse curing systems were employed to produce vulcanized natural rubbers with varying crosslink types. The crosslinking network structures of the vulcanized rubbers were analyzed using the tube model theory. Additionally, the effects of vulcanization bonds on strain-induced crystallization behavior and tensile properties were examined through in-situ X-ray diffraction and a tensile testing machine. The results revealed that the vulcanizate with monosulfidic bonds, formed under the effective vulcanization (EV) system, primarily comprised chemical crosslinking networks, resulting in a high tensile modulus, low elongation at break, and low tensile strength. Conversely, the vulcanizate under the conventional vulcanization (CV) system exhibited a distinct entanglement network impact compared to the chemical crosslinking network, resulting in a smaller tensile modulus but the highest elongation at break and the largest tensile strength. These differences stemmed from the distinct roles of vulcanization bonds within the crosslinking network. Specifically, the relatively short monosulfidic bond quickly reached the critical degree of orientation for crystallization during stretching, leading to higher crystallinity under the same strain. However, its shorter length caused earlier fracture during stretching, resulting in network heterogeneity, reduced elongation at break, and lower tensile strength. On the other hand, the longer polysulfidic bond underwent fracture recombination during stretching, with slower orientation and delayed crystallization. Nonetheless, this recombination improved network uniformity and integrity due to stress dissipation from the initial fracture, enhancing crystallinity, elongation at break, and tensile strength. This study elucidated the influence of vulcanization crosslinking on the tensile properties of vulcanizates.

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Multifunctional films with superior mechanical performance, transparency, antibacterial properties enabled by a physical and chemical dual crosslinking network construction

Exploring sustainable and bio-degradable alternative materials based on lignin and cellulose is expected to address the serious environmental problems caused by the continuous accumulation of petroleum plastic waste. One open question is how to make a high mechanical strength lignin-cellulose material without optical haze. Herein, a multifunctional lignin-cellulose film with excellent mechanical properties and high transparency is successfully prepared based on Schiff base chemistry along with multiple hydrogen bonding interactions. Combined with the chemical and physical double cross-linking network, positively charged aminated lignin improves the compatibility with dialdehyde cellulose and also optimizes the internal structure of the material. Significantly, the obtained films (ALDC10) deliver exceptional mechanical properties (tensile strength, 164.8 MPa and Young's modulus, 12.1 GPa), which are higher than those of some commercial petroleum-based plastics. The films endow superior transparency, antimicrobial (>50 %), UV shielding, and water vapor barrier properties, making them suitable for plastics replacement in active food (apple) packaging. Additionally, the transparent films show photothermal conversion properties, which have high potential applications in food vending machine to delay spoilage of foods with reduced energy consumption. This work establishes advanced valorization of cellulose and lignin, with superior performance, which is expected to replace petroleum plastics in various applications.

Organic–inorganic interface enhancement for boosting mechanical and tribological performances of carbon fiber reinforced composites

AbstractThe limitation in the poor interface would severely affect the further development and application of carbon fiber reinforced composites (CFRP). Unique organic–inorganic hybrid architectures of MOF‐5‐NH2 and carboxymethyl cellulose (CMC) were established on the fiber/matrix interphase for promoting mechanical and tribological performances of the composites. The existence of above interfacial reinforced structure was in favor of generating abundant micromechanical interaction sites for enhancing mechanical interlocking. Meanwhile, high‐density chemical crosslinking networks played a positive role in elevating interfacial adhesion, further relieving stress concentration and hindering crack propagation. The tensile strength of CFRP‐2, CFRP‐3, CFRP‐4, and CFRP‐5 exhibited a significant rising of 27.18%, 30.64%, 27.75%, and 36.88%, respectively. The friction coefficient of MOF‐5‐NH2/CMC modified sample increased from 0.0953 to 0.1219, while the drop in the wear rate of the composites achieved 68.51%. This work provides an effective method for achieving the structure–function integrated design of composite materials according to the organic–inorganic interface enhancement of MOF‐5‐NH2/CMC.

Tailored hydrogel entrapped catalyst with highly active, controlled catalytic activity for the removal of 4-nitrophenol (4-NP)

In catalytic reactions, achieving large specific surface area immobilisation of the catalyst is an important factor affecting the catalytic effect, however, the primary challenges in utilizing hydrogels as catalyst carriers are to enhance the mechanical properties of the hydrogel to improve the activity and controllability of the catalyst. In this study, a new structure of P(AM-co-AA)/SMA/NH2-SiO2 hydrogels was synthesized via free radical polymerization, and the effects of the content of AA and NH2-SiO2 on the mechanical properties of the hydrogels were investigated. Without the use of additional cross-linking agents, both a chemical cross-linking network and a hydrophobic linkage network were established, which effectively reconstructed the structure of the hydrogels and dissipated energy. As a result, P(AM-co-AA-1.5 %)/SMA/NH2-SiO2-0.5 % hydrogel exhibited high mechanical properties, with tensile strength, elongation, and toughness reaching 1456 KPa, 4605 %, and 23.59 MJ/m3, respectively. This hydrogel can be utilized as a template for in situ and stable Ag NPs. Additionally, P(AM-co-AA)/SMA/NH2-SiO2@Ag composite hydrogels were prepared using cation exchange and in situ reduction methods for the catalytic reduction of 4-nitrophenol (4-NP). The composite hydrogel exhibited fast catalysis, high efficiency, stable cycling, recyclability and adjustable catalytic activity at 35 °C with Kapp = 0.811 min−1. Furthermore, using this composite hydrogel alleviated the need for separating metal nanoparticle catalysts from the reaction system, thereby enabling the development of robust hydrogel materials with controlled catalytic activity for the wastewater treatment industry.

A novel, robust mechanical strength, and naturally degradable double crosslinking starch-based bioplastics for practical applications

The increasing number of petroleum-based plastics has caused severe environmental pollution, which has attracted great research interest in the development of low-cost, renewable, and degradable starch-based bioplastics. However, developing starch-based bioplastics with robust mechanical strength, excellent water resistance, and thermal resistance remains a great challenge. In this study, we presented a simple and efficient method for preparing high-performance novel starch-based bioplastics with chemical and physical double crosslinking network structures filled with 2,2,6,6-tetramethylpiperidine 1-oxy-oxidized cellulose nanofibers and zinc oxide nanoparticles. Compared with pure starch-based bioplastics, the tensile strength of the novel robust strength starch-based bioplastics increased by 431.2 %. The novel starch-based bioplastics exhibited excellent mechanical properties (tensile strength up to 24.54 MPa), water resistance, thermal resistance, and biodegradability. In addition, the novel starch-based bioplastics could be reused, crushed, dissolved, and re-poured after use. After recycling, the novel starch-based bioplastics could be discarded in the soil to achieve complete degradation within six weeks. Owing to these characteristics, the novel starch-based bioplastics are good alternatives used to replace traditional petroleum-based plastics and have great development prospects.

Semi-Spontaneous Post-Crosslinking Triblock Copolymer Electrolyte for Solid-State Lithium Battery

The solid polymer electrolyte is a promising candidate for solid-state lithium battery because of favorable interfacial contact, good processability and economic availability. However, its application is limited because of low ionic conductivity and insufficient mechanical strength. In this study, the delicate molecular structural design was realized via controlled / “living” radical polymerization in order to decouple the trade-off between ionic conductivity and mechanical strength. The random and triblock copolymer electrolytes were designed and synthesized to investigate the influence of molecular structure on ionic conduction, while a chemical cross-linking network was constructed via a semi-spontaneous post-crosslinking reaction. Compared with a random counterpart, the triblock copolymer electrolyte presented stronger chain segment motion and a liquid-like mechanical response due to the independent ion-conducting block, resulting in significantly improved ionic conductivity (from 6.29 ± 1.11 × 10−5 to 9.57 ± 2.82 × 10−5 S cm−1 at 60 °C) and cell performance. When assembled with LiFePO4 and lithium metal electrodes, the cell with triblock copolymer electrolyte showed significantly improved rate performance (150 mAh g−1 at 1 C) and cycling life (200 cycles with 92.8% capacity retention at 1 C). This study demonstrates the advantages of molecular structure regulation on ionic conduction and mechanical support, which may provide new insights for the future design of solid polymer electrolytes.

Analysis of the mechanical behavior of polyurethane thermoset elastomers based on hydrogen bonding between different crosslinking point structures

To reveal the effect of polyurethane crosslinking point structures on the mechanical properties of polyurethane thermoset elastomers, using amorphous prepolymer poly (azide glycidyl ether) (GAP) as a binder, polyisocyanate cross-linker N100 and hexamethylene diisocyanate (HDI) as curing agents, trimethylolpropane (TMP) as a crosslinking agent, two GAP polyurethane thermoset elastomers that have similar chemical crosslinking network density, elastomer S0 prepared from GAP and N100 and elastomer S4 prepared from GAP and HDI/TMP, were selected to study in detail. DSC and XRD analysis indicated that two GAP polyurethane thermoset elastomers both exhibit stable amorphous aggregation structure below 80 °C. Mechanical properties test showed that thermoset elastomer S0 gives higher tensile modulus, lower tensile strength and elongation rate, while thermoset elastomer S4 gives lower tensile modulus, higher tensile strength and elongation rate. In-situ FTIR and low field nuclear magnetic resonance (LF-NMR) analysis suggested that there exists stronger urea carbonyl hydrogen bonding structure within thermoset elastomer S0, while weaker urethane carbonyl hydrogen bonding structure within thermoset elastomer S4. The different strength of the hydrogen bonding between crosslinking points imparts different segment mobility to S0 and S4. Dynamic thermodynamic analysis (DMA) indicated that, stronger urea carbonyl hydrogen bonding has suppressed segments mobility and thermoset elastomer S0 present lower loss modulus and loss factor, while thermoset elastomer S4 present higher loss modulus and loss factor because there just exist weaker urethane carbonyl hydrogen bonding interaction between crosslinking points.

Sucrose-tannin-nanosilica hybrid bio-adhesive based on dual dynamic Schiff base and disulfide bonds with enhanced toughness and cohesion

Herein, a high-performance sucrose-tannin bio-based adhesive is developed based on consisting of oxidized sucrose (OS), tannin acid (TA), SiO2 nanoparticles and 2,2′-disulfanediylbis (ethan-1-amine) (DBA) by a facile chemical cross-linking strategy. The OS-TA and OS-TA@SiO2 bio-based adhesives are characterized by XPS, FTIR, and 13C NMR, while the bonding performance is also investigated using shear strength test. Results show that the optimal formulation of OS-TA bio-based adhesive is a 2:1:1 mass ratio for OS: TA: DBA. When the mass fraction of SiO2 is 15 % and the solid content of main components is 50 %, the OS-TA@SiO2 bio-based adhesive has excellent bonding strength. Relative to OS-TA, the wet bonding strength of the OS-TA@SiO2 enhanced from 1.16 MPa to 1.85 MPa, while the dry bonding strength improved from 1.90 MPa to 2.50 MPa. The wood failure rate of the plywood fabricated by using the OS-TA@SiO2 bio-based adhesive reaches 80 %. Therefore, relying on the high flexibility of dynamic disulfide bonds, adding SiO2 nanoparticles into the adhesive system can facilitate greatly the mechanical interlocking effect and make the chemical cross-linking network more compact through the synergistic chemical interactions. This work provides new insights into producing green and renewable bio-based wood adhesives using sucrose and tannin.

Strong and flexible lignocellulosic film fabricated via a feasible molecular remodeling strategy

Biomass-derived sustainable film is a promising alternative to synthetic plastic, but hampered by strength, toughness and flexibility trade-off predicament. Here, a feasible and scalable strategy was proposed to fabricate strong and flexible lignocellulosic film through molecular reconstruction of cellulose and lignin. In this strategy, polyphenol lignin was absorbed and wrapped on the surface of cellulose fiber, forming strong interfacial adhesion and cohesion via intramolecular and intermolecular hydrogen bonding. Further, covalent ether bond was generated between the hydroxyl groups of lignocellulose to form chemical cross-linking network induced by epichlorohydrin (ECH). The synergistic effect of hydrogen bonding and stable chemical cross-linking enabled the resultant lignocellulosic film (ELCF) with outstanding mechanical strength of 132.48 MPa, the elongation at break of 9.77 %, and toughness of 9.77 MJ·m−3. Notably, the integration of polyphenol lignin synergistically improved the thermal stability, water resistance, UV-blocking performances of ELCF. Importantly, after immersion for 30 d, ELCF still possessed high wet strength of 70.38 MPa, and elongation at break of 7.70 %, suggesting excellent and durable mechanical performances. Moreover, ELCF could be biodegraded in the natural soil. Therefore, this study provides a new and versatile approach to reconstruct highly-performance lignocellulosic films coupling strength, toughness with flexibility for promising plastic replacement.

Light‐controlled switchable underwater adhesive

AbstractDespite extensive efforts in designing and preparing switchable underwater adhesives, it is not easy to regulate the underwater adhesion strength locally and remotely. Here, we design and synthesize photoreversible copolymer of poly[dopamine methacrylamide‐co‐methoxyethyl‐acrylate‐co‐7‐(2‐methacryloyloxyethoxy)‐4‐methylcoumarin]. Due to the dynamic formation and breaking of chemical crosslinking networks within the smart adhesives, the material shows widely tunable adhesion strength from ∼150 to ∼450 kPa and long‐range reversible maneuverability under orthogonal 254 and 365 nm ultraviolet light stimulation via the coumarin dimerization and cycloreversion. Moreover, the adhesive exhibits good circulation performance and stability in an acid–base environment. It also demonstrated that the bolt can be coated with the smart adhesive material for on‐demand bonding. This design principle opens the door to the development of remotely controllable high‐performance smart underwater adhesives.

Excellent strength and toughness and multifunctional protein-based adhesive produced by polyether block sulfuretted polyamidoamine-epichlorohydrin via a dual-crosslinking strategy

Developing high-temperature soy-protein meal (HSM)-based adhesives equipped with excellent bonding strength, superb toughness, and versatility is challengeable due to their inherent high hydrophilicity and agglomeration. Though conventional chemical modifications can enhance the bonding strengths of HSM-based adhesives, few strategies can achieve simultaneous enhancement and toughening. To achieve this target, the polyether block sulfuretted polyamidoamine-epichlorohydrin (SPE-PEDE) was innovatively self-prepared. The SPE-PEDE can not only form a stiff chemical bond crosslinking network through the active azetidinium groups and disulfide bonds in sulfuretted polyamidoamine-epichlorohydrin (SPE) segment, but also can provide a plasticizer phase (PEDE) which can trigger dynamic hydrogen bonding and promote stress transfer among the adhesive system. Thus, forming an efficient dual-network strengthening and toughening system inside adhesives. The improved toughness of the HSM/SPE-PEDE15% sample prepared herein achieved a 306.31% compared to the neat sample, and it bonded plywood obtained a dry bonding strength of 2.90 MPa, a wet bonding strength of 1.11 MPa, and a pre-pressing bonding strength of 760 kPa, which were 82.39%, 258.06%, and 208.94%, respectively higher than the HSM sample. Besides, the modified adhesives also exhibit high solid contents, low moisture absorption, excellent mildew resistance, and antibacterial activity, thus showing the potential to promote the industrial production of HSM-based adhesives.

Stretchable and recyclable gelatin Ionogel based ionic skin with extensive temperature tolerant, self-healing, UV-shielding, and sensing capabilities

Fabricating sustainable ionic skin with multi-functional outstanding performances using biocompatible natural polymer-based ionogel is highly desired but remains a great challenge up to now. Herein, a green and recyclable ionogel has been fabricated by in-situ cross-linking of gelatin with a green bio-based multifunctional cross-linker of Triglycidyl Naringenin in ionic liquid. Benefiting from the unique multifunctional chemical crosslinking networks along with multiple reversible non-covalent interactions, the as-prepared ionogels exhibit high stretchability (>1000 %), excellent elasticity, fast room-temperature self-healability (>98 % healing efficiency at 6 min), and good recyclability. These ionogels are also highly conductive (up to 30.7 mS/cm at 150 °C), and exhibit extensive temperature tolerance (−23 to 252 °C) and outstanding UV-shielding ability. As a result, the as-prepared ionogel can easily be applied as stretchable ionic skin for wearable sensors, which exhibits high sensitivity, fast response time (102 ms), excellent temperature tolerance, and stability over 5000 stretching-relaxing cycles. More importantly, the gelatin-based sensor can be used in signal monitor system for various human motion real-time detection. This sustainable and multifunctional ionogel provides a new idea for easy and green preparation of advanced ionic skins.