Sacrificial Bonds Research Articles

Mechanically strong, healable, and reprocessable conductive carbon black/silicone elastomer nanocomposites based on dynamic imine bonds and sacrificial coordination bonds

Commercial conductive polysiloxane composites are usually unrecyclable and suffer from inherent poor mechanical properties. Herein, mechanically strong, healable, and reprocessable conductive carbon black (CB)/polysiloxane nanocomposites were prepared through incorporating dual crosslinks of imine bonds and Zn(II)-amino coordination bonds in elastomer networks. Following the energy-dissipating mechanisms of sacrificial bonds, the integration of coordination bonds led to the remarkable improvement of strength, stretchability, and toughness without compromising the self-healing ability or reprocessability. Furthermore, the sacrificial and reversible manner of coordination bonds in nanocomposites was studied in detail. In addition to enhancing the electrical conductivity of nanocomposites (i.e., 6.48 S/m at CB content of 12 wt%), the incorporation of CB could promote the rupture of sacrificial bonds and improve the energy-dissipating efficiency significantly.

A highly stretchable and room temperature autonomous self-healing supramolecular organosilicon elastomer with hyperbranched structure

Preparing of polymer materials similar to biological muscle properties with highly stretchable and autonomous self-healing at room temperature is a challenge. Herein, hyperbranched organosilicon polymers (HPSi) with multiple hydrogen bonds and dynamic disulfide bonds were synthesized by amino-modified poly(dimethylsiloxane) (PDMS-NH2), dithiodianiline (DTDA) and thioctic acid (TA). The “free” part of hydrogen bond promoted the dynamic interaction with related complementary parts, which effectively improved the repair efficiency. As the degree of hyperbranching increased, the supramolecular branching units brought more reversible bonds to polymers. Therefore, the heal efficiency of HPSi at room temperature showed an upward trend and it could reach to 96.9%. As the sacrificial bonds, multiple reversible hydrogen bonds effectively dissipated the energy generated by external forces with the help of disulfide bonds. Thus, the stretchability of the elastomer was strengthened. And the elongation at break of elastomer was up to 3463%. This muscle-like self-healable hyperbranched elastomer with excellent mechanical properties has great application potential in the fields of soft robots, electronic devices and coatings.

Improving the strength and toughness of macroscale double networks by exploiting Poisson\u2019s ratio mismatch

We propose a new concept that utilizes the difference in Poisson's ratio between component materials as a strengthening mechanism that increases the effectiveness of the sacrificial bond toughening mechanism in macroscale double-network (Macro-DN) materials. These Macro-DN composites consist of a macroscopic skeleton imbedded within a soft elastic matrix. We varied the Poisson's ratio of the reinforcing skeleton by introducing auxetic or honeycomb functional structures that results in Poisson’s ratio mismatch between the skeleton and matrix. During uniaxial tensile experiments, high strength and toughness were achieved due to two events: (1) multiple internal bond fractures of the skeleton (like sacrificial bonds in classic DN gels) and (2) significant, biaxial deformation of the matrix imposed by the functional skeleton. The Macro-DN composite with auxetic skeleton exhibits up to 4.2 times higher stiffness and 4.4 times higher yield force than the sum of the component materials. The significant improvement in mechanical performance is correlated to the large mismatch in Poisson's ratio between component materials, and the enhancement is especially noticeable in the low-stretch regime. The strengthening mechanism reported here based on Poisson's ratio mismatch can be widely used for soft materials regardless of chemical composition and will improve the mechanical properties of elastomer and hydrogel systems.

High performance and multifunctional protein-based adhesive produced via phenol-amine chemistry and mineral reinforcement strategy inspired by arthropod cuticles

Arthropod cuticles are extraordinarily stiff and strong due to phenol-amine chemistry and mineral reinforcement. Nevertheless, these cuticles require costly dopamine (phenol provider), acid-unstable minerals, enzymes that can be deactivated, making them difficult to imitate in artificial materials. Herein, the arthropod cuticle was mimicked by introducing a low-cost phenolic polymer (DP) and acid-stable montmorillonite into an amino-rich soy protein matrix (SPI) to develop a bio-based adhesive. Fe3+ was chosen as the oxidizing agent to trigger the oxidation of DP without using enzyme, while activating cross-linking between oxidized DP and SPI to cure the adhesive. This covalent cross-linking and mineral reinforcement strategy endowed the adhesive with a bonding strength (1.04 MPa) comparable to industrial-use adhesives, whereas its volatile organic compounds emission was about 10-fold lower than the industrial-use adhesives. The sacrificial bonds and microphase-separated structure formed from the adhesive resulted in a high toughness. Furthermore, this adhesive featured an outstanding stiffness (40.38 GPa), exceeding ten times that of normal plastics. Notably, this adhesive exhibited excellent mold resistance (288 h shelf life) and flame retardancy (level B1 in GB 8624-2012). This efficient, eco-friendly, and low-cost bionic design strategy can advance the enhancement and functionalized modification of underwater adhesives, hydrogel, and composite materials.

Toughening epoxy resin by constructing π-π interaction between a tung oil-based modifier and epoxy

Thermosets of the diglycidyl ether of bisphenol A (DGEBA) are normally brittle owing to its rigid structure. To address this problem, a bioinspired strategy to form sacrificial bonds in a curing system, which may enhance the flexibility of epoxy thermosets and maintain a favorable strength simultaneously has been proposed. A tung (Aleurites montana L.) oil diglyceride based-acid (TODGA) that may construct sacrificial bonds with the epoxy matrix in the form of π-π interactions was prepared, and was added into a DGEBA / polyetheramine curing system at varying ratios. TODGA can greatly improve the flexibility and toughness of epoxy thermosets. At the addition of 7.5 wt%, the elongation at break, toughness, and impact strength are improved from 5.9 % to 86.6 %, from 2.1 to 19.0 MJ m−3, and from 4.3 to 5.9 kJ·m−2 respectively, while the tensile strength is maintained at 34.8 MPa. In comparison, the toughening effect of TODGA outperforms that of commercial epoxidized soybean (Glycine max (L.) Merr.) oil. Although TODGA is a flexible modifier, it does not significantly decrease glass transition temperature and thermal stability. These results demonstrate that fabricating sacrificial bonds is a practical way to toughen epoxy thermosets, and TODGA can be potentially utilized as a commercial toughening agent.

Tough hydrogels with rapid self-reinforcement.

Most tough hydrogels are reinforced by introducing sacrificial structures that can dissipate input energy. However, because the sacrificial damage cannot rapidly recover, the toughness of these gels drops substantially during consecutive cyclic loadings. We propose a damageless reinforcement strategy for hydrogels using strain-induced crystallization. For slide-ring gels in which polyethylene glycol chains are highly oriented and mutually exposed under large deformation, crystallinity forms and melts with elongation and retraction, resulting both in almost 100% rapid recovery of extension energy and excellent toughness of 6.6 to 22 megajoules per cubic meter, which is one order of magnitude larger than the toughness of covalently cross-linked homogeneous gels of polyethylene glycol.

Tougher when stressed

Hydrogels Hydrogels are typically weak materials because they contain only a small fraction of polymeric material highly swollen with water. Strength can be increased by adding extra cross-linking or interpenetrating networks with some sacrificial bonds to enhance toughness; however, these properties deteriorate upon stretching and may be slow to recover after relaxation. Liu et al. developed polyethylene glycol hydrogels cross-linked with moderate fractions of polymers that form sliding rings. These allow the chain to orient in parallel when stretched, leading to rapid and reversible strain-induced crystallization and thus much tougher hydrogels. Science , aaz6694, this issue p. [1078][1] [1]: /lookup/doi/10.1126/science.aaz6694

Temperature-dependent anharmonic effects on shear deformability of Bi2Te3 semiconductor

For performance stability and wearable application of Bi2Te3 thermoelectric (TE) semiconductors, it is necessary to enhance its deformability at the operating temperature. Given Van der Waals sacrificial bond (SB) behavior in Bi2Te3 crystals, temperature-dependent anharmonic effects on the structural evolution and mechanical performance during shearing is studied through molecular dynamics simulations. With increasing temperature, in addition to larger difference of initial bond strength, the synergy between SB and defect during slipping tends to be suppressed, resulting in strain localization with less crystal deformability. The temperature-induced change of nanocrystal deformation modes is clearly identified by the growth trend difference of deformation heterogeneity parameter (F) that is defined according to configurational energy distribution. This simulation work provides new insights into the role of sacrificial bonds and substructures on synergistically deformability tuning, likely improving defect engineering strategy for designing advanced multi-scale hierarchical TE semiconductors.

Healable and Recyclable Elastomers with Record-High Mechanical Robustness, Unprecedented Crack Tolerance, and Superhigh Elastic Restorability.

Spider silk is one of the most robust natural materials, which has extremely high strength in combination with great toughness and good elasticity. Inspired by spider silk but beyond it, a healable and recyclable supramolecular elastomer, possessing superhigh true stress at break (1.21GPa) and ultrahigh toughness (390.2MJ m-3 ), which are, respectively, comparable to and ≈2.4 times higher than those of typical spider silk, is developed. The elastomer has the highest tensile strength (ultimate engineering stress, 75.6MPa) ever recorded for polymeric elastomers, rendering it the strongest and toughest healable elastomer thus far. The hyper-robust elastomer exhibits superb crack tolerance with unprecedentedly high fracture energy (215.2kJ m-2 ) that even exceeds that of metals and alloys, and superhigh elastic restorability allowing dimensional recovery from elongation over 12 times. These extraordinary mechanical performances mainly originate from the meticulously engineered hydrogen-bonding segments, consisting of multiple acylsemicarbazide and urethane moieties linked with flexible alicyclic hexatomic spacers. Such hydrogen-bonding segments, incorporated between extensible polymer chains, aggregate to form geometrically confined hydrogen-bond arrays resembling those in spider silk. The hydrogen-bond arrays act as firm but reversible crosslinks and sacrificial bonds for enormous energy dissipation, conferring exceptional mechanical robustness, healability, and recyclability on the elastomer.

A multifunctional nanocellulose-based hydrogel for strain sensing and self-powering applications

Ionic conductive hydrogel with multifunctional properties have shown promising application potential in various fields, including electronic skin, wearable devices and sensors. Herein, a highly stretchable (up to 2800% strain), tough, adhesive ionic conductive hydrogel are prepared using cationic nanocellulose (CCNC) to disperse/stabilize graphitic carbon nitride (g-C3N4), forming CCNC-g-C3N4 complexes and in situ radical polymerization process. The ionic interactions between CNCC and g-C3N4 acted as sacrificial bonds enabled highly stretchability of the hydrogel. The hydrogel showed high sensitivity (gauge factor≈5.6, 0–1.6% strain), enabling the detection of human body motion, speech and exhalation. Furthermore, the hydrogel based self-powered device can charge 2.2 μF capacitor up to 15 V from human motion. This multifunctional hydrogel presents potential applications in self-powered wearable electronics.

Biomimetic high performance artificial muscle built on sacrificial coordination network and mechanical training process

Artificial muscle materials promise incredible applications in actuators, robotics and medical apparatus, yet the ability to mimic the full characteristics of skeletal muscles into synthetic materials remains a huge challenge. Herein, inspired by the dynamic sacrificial bonds in biomaterials and the self-strengthening of skeletal muscles by physical exercise, high performance artificial muscle material is prepared by rearrangement of sacrificial coordination bonds in the polyolefin elastomer via a repetitive mechanical training process. Biomass lignin is incorporated as a green reinforcer for the construction of interfacial coordination bonds. The prepared artificial muscle material exhibits high actuation strain (>40%), high actuation stress (1.5 MPa) which can lift more than 10,000 times its own weight with 30% strain, characteristics of excellent self-strengthening by mechanical training, strain-adaptive stiffening, and heat/electric programmable actuation performance. In this work, we show a facile strategy for the fabrication of intelligent materials using easily available raw materials.

Effects of sacrificial coordination bonds on the mechanical performance of lignin-based thermoplastic elastomer composites

In this work, the coordination-based energy sacrificial bonds have been constructed in the interphase between lignin and polyolefin elastomer to prepare high performance lignin-based thermoplastic elastomers (TPEs). The strength and toughness of lignin-based TPEs can be adjusted by choosing different nitrogen heterocyclic compounds as reactive assistants and Fe3+ or Zn2+ as metal coordination centers. It was demonstrated that 3-Amino-1,2,4-triazole with three nitrogen atoms in the heterocyclic ring and one nitrogen branch chain could form the most efficient coordination bond system and generate the best mechanical performance. The system with ferric iron as coordination center exhibited better enhancement effect than divalent zinc. By adjusting the nitrogen-containing reactive additives or metal salts as coordination centers, the mechanical performance of the lignin-based TPE can be regulated, which provides a method for making green bio-composites with good strength and toughness, and also promotes the high value utilization of lignin in polymer materials.

Bioinspired hyperbranched protein adhesive based on boronic acid-functionalized cellulose nanofibril and water-soluble polyester

The development of high-performance and sustainable bio-adhesive materials has attracted significant research attention in recent years. However, producing high-performance biopolymer materials with desirable mechanical and antibacterial properties remains a challenge. Herein, a mussel-mimetic strategy is reported to fabricate a soy protein (SP)-based composite film via aqueous co-assembly of 3-aminophenylboronic acid-functionalized cellulose nanofibril (AB@CNF) and hyperbranched polyester (HPE). The water-soluble HPE with numerous hydroxyl end groups was synthesized by using a facile and green method. Through enhanced dynamic covalent interactions and intermolecular sacrificial hydrogen bonds, the incorporated AB@CNF hybrids with conjugated cis-diols strongly interact and entangle with biopolymer chains in the hyperbranched network. As a result of multiple synergistic cross-linking, the toughness and strength of the SP/HPE/AB@CNF film increase by 574% and 346% to 10.05 MJ/m3 and 14.23 MPa, respectively. Additionally, the film offers excellent antibacterial activity, flame retardance, and thermal stability. This sustainable approach should open new avenues for the design and development of biomimetic plant-derived functional materials in biomass adhesive and active packaging.

Solvent-Free UV Polymerization of n-Octadecyl Acrylate in Butyl Rubber: A Simple Way to Produce Tough and Smart Polymeric Materials at Ambient Temperature.

One of the most fascinating challenges in recent years has been to produce mechanically robust and tough polymers with smart functions such as self-healing and shape-memory behavior. Here, we report a simple and versatile strategy for the preparation of a highly tough and highly stretchable interconnected interpenetrating polymer network (c-IPN) based on butyl rubber (IIR) and poly(n-octadecyl acrylate) (PC18A) with thermally induced healing and shape-memory functions. Solvent-free UV polymerization of n-octadecyl acrylate (C18A) at 30 ± 2 °C in the presence of IIR leads to IIR/PC18A c-IPNs with sea-island or co-continuous morphologies depending on their IIR contents. The lamellar crystals with a melting temperature Tm of 51-52 °C formed by side-by-side packed octadecyl (C18) side chains are responsible for more than 99% of effective cross-links in c-IPNs, the rest being hydrophobic associations and chemical cross-links. The c-IPNs exhibit varying stiffness (9-34 MPa), stretchability (72-740%), and a significantly higher toughness (1.9-12 MJ·m-3) than their components, which can be tuned by changing the IIR/PC18A weight ratio. The properties of c-IPNs could also be tuned by incorporating a second, noncrystallizable hydrophobic monomer, namely, lauryl methacrylate (C12M), in the melt mixture. We show that the lamellar clusters acting as sacrificial bonds break at the yield point by dissipation of energy, while the ductile amorphous continuous phase keeps the structure together, leading to the toughness improvement of c-IPNs. They exhibit a two-step healing process with >90% healing efficiency with respect to the modulus and a complete shape-recovery ratio induced by heating above Tm of alkyl crystals. The temperature-induced healing occurs via a quick step where C18 bridges form between the damaged surfaces followed by a slow step controlled by the interdiffusion of C18A segments in the bulk. We also show that the strategy developed here is suitable for a variety of rubbers and n-alkyl (meth)acrylates of various side-chain lengths.

Bioinspired Polyurethane Using Multifunctional Block Modules with Synergistic Dynamic Bonds.

Nature embraces an intriguing strategy to create high-performance biomaterials, such as spider silk which presents an unparalleled combination of stiffness, tensile strength, and toughness via hierarchical structures. However, to fabricate synthetic polymers with such excellent properties remains a challenging task. Inspired by the integration of multiblock backbone and densely H-bonding assemblies in spider silk as well as the delicate iron-catecholate complexes in mussel byssus, we proposed a novel molecular design with multifunctional block modules to obtain polymer materials that exhibit excellent mechanical property, self-healing ability, and reprocessability. It was achieved by introducing reversible iron-catechol (DOPA-Fe3+) cross-links and quadruple H-bonds bearing 2-ureido-4-[1H]-pyrimidinone (UPy) dimers as multifunctional blocks into a segmented polyurethane backbone with urethane blocks and semicrystalline polycaprolactone (PCL) blocks. These two types of dynamic cross-linking knots served as the sacrificial bonds to dissipate energy efficiently under external stress burden, endowing the dual physical cross-linked networks with increased toughness and breaking elongation. Moreover, the DOPA-Fe3+ complexes could increase the crystallization of PCL, leading to remarkably enhanced Young's modulus and tensile strength. Solid-state NMR revealed the formation of quadruple H-bonds in UPy dimers and the presence of DOPA-Fe3+ complexes, which restricted the mobility of the mobile phase and enhanced the crystallinity of the PCL domain. This work provides a feasible way to develop bioinspired materials with self-healable and reprocessable features, in addition to balanced enhancement of both stiffness and toughness.

Fabrication and evaluation of biodegradable multi-cross-linked mulch film based on waste gelatin

Microplastics from wasted traditional nondegradable plastic mulching films pose a great threat to both the ecological environment as well as human health. Currently, eco-friendly and cost-effective biodegradable films are considered the most promising substitutes for nondegradable plastic mulching films. In this study, we demonstrate a simple and eco-friendly strategy to utilize the gelatin extracted from scrap skin in leather processing and prepare novel biodegradable mulch films. The gelatin chains were covalently cross-linked with tetrakis(hydroxymethyl)phosphonium chloride to reduce the hygroscopicity of gelatin. Then, polyvinyl alcohol (PVOH) was introduced into the gelatin network. The hydrogen bonds between the gelatin and PVOH and several PVOH crystalline domains acted as sacrificial bonds for energy dissipation. Thus, the multi-cross-linked gelatin matrix (GP) films showed high fracture stress (12.03–31.99 MPa) and fracture strain (211.99%–379.73%). Such high mechanical performance is comparable to that of traditional low-density polyethylene mulch films and conforms to the GB/T 35,795 regulatory standards. In addition to their excellent mechanical properties, the mulch films exhibited good water resistance, excellent light transmittance, and good biodegradability in soil. All properties of the GP films are tunable, and their eco-friendliness, low cost, and excellent properties endow them with great application potential as eco-friendly mulch films for agriculture.

الأحکام الفقهية المتعلقة بصکوک الأضاحي دراسة فقهية مقارنة

الأحکام الفقهية المتعلقة بصکوک الأضاحي دراسة فقهية مقارنة أحمد خيري أحمد عبد الحفيظ قسم الفقه، کلية الشريعة والقانون، جامعة الأزهر، القاهرة، جمهورية مصر العربية. البريد الإلکتروني: ahmedkhairy@azhar.edu.e. ملخص: يهدف البحث إلى إلقاء الضوء على صکوک الأضاحي، بداية بالتعريف بها، وأسباب ظهورها ونشأتها، والأحکام الفقهية المتعلقة بها. وقد اتبعت في کتابته المنهج التحليلي، والمنهج المقارن. وقد خلص البحث إلى نتائج، منها: أن صکوک الأضاحي نوع من النيابة أو الوکالة، وأن هناک ضوابط لا بد من توفرها في مشتري الصک، والجهة المصدرة له، وأنه يجوز شراء الأضحية عبر التسوق الإلکتروني، وأن شراء الأضاحي وذبحها خارج بلد مصدر الصک ومشتريه جائز شرعا، وأنه لا يجوز للجمعية الخيرية أن تعلن عن نشاطها في إصدار صکوک الأضاحي إلا إذا تيقنت أو غلب على ظنها وجود منفعة من هذا الإعلان، وأنه يجوز تصرف الجمعيات والمؤسسات المصدرة للصکوک في جلود الأضاحي الخاصة بالصکوک، وأنه يجوز للجهة المصدرة لصک الأضحية استبدال لحوم زائدة بلحوم الأضاحي للمصلحة، وأنه لا ضمان على الهيئات المصدرة لصکوک الأضاحي في ما يحدث لقيمة تلک الصکوک أو للأنعام التي تم شراؤها للأضحية من هلاک أو نقص أو عيب ما لم تفرط؛ لأن يدها يد أمانة. أما توصيات البحث: فإن الباحث يوصي بأن تستعين الجمعيات والمؤسسات بأهل الخبرة والمعرفة من أجل الوصول إلى الأماکن الأکثر احتياجا وإلى المساکين في دهاليز القرى والنجوع، وذلک بمشارکه الثقات من أبناء هذه المناطق الفقيرة، کما يوصي بالتزام الشفافية في الإعلان عن قيمة الصکوک التي باعتها، وعدد الأضاحي التي قامت بذبحها وتوزيعها، وعدد المستفيدين بهذه الأضاحي، وأيضا: ضرورة التزام المؤسسات المعنية بصکوک الأضاحي بالضوابط الشرعية في الشراء والذبح والتوزيع، وکذلک: وجود لجنة رقابية من الدولة، تراقب عمل الجمعيات والمؤسسات الخيرية، في أنشطتها المتعلقة بصکوک الأضاحي، وتکون أولى مهماتها تحديد حجم الأموال التي تم شراء الصکوک بها، والنفقات التي تم شراء الأضاحي بها، ومراقبة عمليات الذبح والتوزيع، وإثابة الملتزم، ومعاقبة المخالف بعقوبات رادعة. الکلمات المفتاحية: الأحکام، الأضاحي، بصکوک، الفقهية، المتعلقة. Islamic Jurisprudence Rulings Related to The Bonds of Sacrifice A Comparative Jurisprudential Study Ahmed Khairy Ahmed Abdel Hafeez Jurisprudence Department, Faculty of Sharia and Law, Al-Azhar University, Cairo, Arab Republic of Egypt. Email: ahmedkhairy@azhar.edu.e. Abstract: The research aims to shed light on the sacrificial instruments, first by introducing them, the reasons for their emergence, origin, and the sharia jurisprudential rulings related to them. This research followed the analytical method, and the comparative method. The research concluded that the sacrificial instrument is a type of prosecution or agency, and that must have rules to control the purchaser of the bond and the party issuing it, and what is permissible to buy the sacrifice through online shopping. Buying sacrificial animals and slaughtering them outside the country of the issuer of the sacrificial bond and its purchaser is legally permissible, and that a charitable association may not announce its activity in issuing sacrificial bonds unless it is certain or most likely that there is a benefit from this announcement, and that associations and institutions issuing sacrificial bond may be disposed of in the skin of sacrificial animals for bonding . The party issuing the sacrificial bond may replace the excess meat with the meat of the sacrificial animal for the benefit, and that there is no guarantee for the bodies issuing the sacrificial bonds regarding what happens to the value of those bonds or the livestock that were purchased for the sacrifice from loss, shortage, or defect, unless it is excessive. Because his hand is a hand of trust. Keywords: provisions, sacrifices, bonds, jurisprudence, related.

Tough Double Network Hydrogel and Its Biomedical Applications.

Soft and wet hydrogels have many similarities to biological tissues, though their mechanical fragility had been one of the biggest obstacles in biomedical applications. Studies and developments in double network (DN) hydrogels have elucidated how to create tough gels universally based on sacrificial bond principles and opened a path for biomedical application of hydrogels in regenerative medicine and artificial soft connective tissues, such as cartilage, tendon, and ligament, which endure high tension and compression. This review explores a universal toughening mechanism for and biomedical studies of DN hydrogels. Moreover, because the term sacrificial bonds has been mentioned often in studies of bone tissues, consisting of biomacromolecules and biominerals, recent studies of gel-biomineral composites to understand early-stage osteogenesis and to simulate bony sacrificial bonds are also summarized.

Toward Largely Enhanced Toughness and Balanced Strength in PA1012/EPDM Blends via Synergistic Effect of Sacrificial Bonds and Network Structure

AbstractHere, zinc‐neutralized ethylene propylene diene monomer (EPDM) ionomers with different neutralization levels are prepared through melt blending, and are then incorporated with polyamide 1012 (PA1012) to fabricate PA1012/EPDM ionomer blends. Interestingly, complex crosslinking networks are formed in the blends due to the construction of sacrificial bonds (Zn2+‐carboxyl, Zn2+‐amide). The as‐formed network structure and sacrificial bond endow the PA/EPDM blends with largely enhanced toughness (16 times higher than that of neat PA), as well as balanced strength and stiffness. Meanwhile, the rheological behaviors of PA1012/EPDM ionomer blends indicate their relative low melting viscosity, which can avoid the processing shortcomings of plastics toughened with rubber. Moreover, PA1012/EPDM ionomer blends show obvious gelation behavior, and a maximum notched Izod impact strength exhibited at the gel point, in which unique double network structure can be observed obviously, indicating that there is a corresponding correlation between the rheological and mechanical parameters. Furthermore, the supper‐toughening mechanism of PA1012/EPDM ionomer blends at gel point is explored, which origins from the large deformation and cavitation of rubber particles and the destruction of special double network morphologies. This study provides a novel and effective strategy to fabricate PA materials with outstanding toughness and excellent strength simultaneously.

High-Temperature-Aging Induced Sequential Recovery of Shape Memory Nitrile Butadiene Rubber Composites.

The sacrificial bonds in natural materials have inspired the preparation of shape memory polymer (SMP), which can be prepared through the construction of dual cross-linking networks in a polymer matrix. With the rise of 4D printing technology, fine control over the shape recovery of SMPs, especially control over the recovery time, is urgently needed. In this study, the high-temperature aging method is adopted to tune the shape recovery time of dual cross-linked SMPs. Shape memory acrylonitrile butadiene rubber composite (i.e., NBR-C) is prepared by introducing Zn2+-C≡N coordination bonding and sulfur covalent cross-linking networks into the rubber matrix and then thermal aging at 180 °C for various time frames. Aging increases the covalent cross-linking density, ruptures rubber chains, and generates imine structures. Moreover, the composition of the coordination bonding network becomes diversified because of the formation of coordination bonds between imines and Zn2+ ions. The mechanical "tough-brittle" transition of aged NBR-C is observed, and its glassy temperature increases with aging time, which in turn changes the shape recovery time at the same recovery temperature. On the basis of these findings, the special shape memory rubber components with sequential recovery are fabricated by partially aging the NBR-C strings. This methodology provides novel solutions for the preparation of sequential SMP products without programming heating design or using redundant chemical materials. We believe that this work will be able to help promote comprehensive research of SMPs and widen applications of SMPs in the industry.