Self-healing Polyurethane Elastomer Research Articles

Self-Healing Polyurethane Elastomers with Superior Tensile Strength and Elastic Recovery Based on Dynamic Oxime-Carbamate and Hydrogen Bond Interactions.

The preparation of self-healing polyurethane elastomers (PUEs) incorporating dynamic bonds is of considerable practical significance. However, developing a PUE with outstanding mechanical properties and high self-healing efficiency poses a significant challenge. Herein, this work has successfully developed a series of self-healing PUEs with various outstanding properties through rational molecular design. These PUEs incorporate m-xylylene diisocyanate and reversible dimethylglyoxime as hard segment, along with polytetramethylene ether glycol as soft segment. A significant amount of dynamic oxime-carbamate and hydrogen bonds are formed in hard segment. The microphase separated structure of the PUEs enables them to be colorless with a transparency of >90%. Owing to the chemical composition and multiple dynamic interactions, the PUEs are endowed with ultra-high tensile strength of 34.5MPa, satisfactory toughness of 53.9MJ m-3, and great elastic recovery both at low and high strains. The movement of polymer molecular chains and the dynamic reversible interactions render a self-healing efficiency of 101% at 70°C. In addition, this self-healing polyurethane could still maintain high mechanical properties after recycling. This study provides a design strategy for the preparation of a comprehensive polyurethane with superior overall performance, which holds wide application prospects in the fields of flexible displays and solar cells.

A super strong polyurethane elastomer with efficient self-healing performance enabled by partially mixing reversible hard domains

The reversible chain extender Diels-Alder-diol (DA-diol) containing thermally dissociable Diels-Alder adducts (DA adducts) was synthesized and combined with 1,4-butanediol (BDO) as composite chain extenders used for preparing a transparent polyurethane elastomer (DAPU) with high mechanical strength and efficient self-healing ability by partially mixing reversible hard domains. The optimal DAPU occupies a desired high tensile strength of 65 MPa, and its elongation at break and toughness are of 1050 % and 216 MJ·m−3, respectively. Meanwhile, the DAPU-0.2 elastomer heals at 110 °C for 2 h with a healing efficiency of 95%. The desirable mechanical strength and efficient self-healing ability are attributing to the BDO chain extended hard segments ensure the high strength at room temperature, while DA-diol chain extended hard segments endow the as-prepared DAPUs with self-healing ability at an elevated temperature. This work overall points to a strategy in designing self-healing polyurethane elastomers with markedly improved mechanical strength by partially mixing reversible hard domains.

Self-healing polyurethane elastomer with ultra-high mechanical strength and enhanced thermal mechanical properties

Polyurethane (PU) materials are widely used due to their excellent comprehensive properties including high strength, good wear resistance and weather resistance. To further improve the service life and safety of polyurethane materials, self-healing polyurethane materials have been developed. However, self-healing polyurethane generally suffers from low mechanical strength and poor thermal mechanical properties. Here, we have constructed a strong dual network by introducing benzene-1,4-diboronic acid (PDBA) into poly(urethane-urea) (PUU). On one hand, PDBA can form coordination bonds with nitrogen atoms in PUU, leading to the formation of a dual network consisting of boron-nitrogen coordination and hydrogen bonding. This dual network imparts PUU with a maximum tensile strength of 84.2 MPa. On the other hand, boron-nitrogen coordination is more stable than hydrogen bonding at high temperature, thereby significantly enhancing the thermal mechanical properties of PUU (the mechanical strength of PUU-PDBA-50 % and PUU-PDBA-100 % increased by 1.8 times and 2.4 times, respectively, compared to PUU at 100 °C). Meanwhile, the dynamic nature of the dual network endows the material with self-healing ability.

Room-temperature self-healing polyurethane elastomers with high strength and superior self-healing efficiency based on aromatic disulfide-induced

Polymers are inevitably subject to mechanical damages during molding, processing, and application. Self-healing of internal and surface damage in polymers can be achieved by endowing the materials with room-temperature self-healing functions. This improvement significantly eliminates safety risks caused by material damage, enhances the safety, stability, and service life of polymer materials, facilitates the realization of sustainable resource development, and aligns with the concept of "low carbon". Room-temperature self-healing materials mainly rely on motility of molecular chain segments and dynamical equilibration of forces acting within the system. However, there have been few reports of polyurethane elastomers with high strength and high self-healing efficiency. In this paper, PUIPBD polyurethane elastomers were prepared by the chemical reacting of polytetrahydrofurandiol PTMEG-2000, isophorone diisocyanate IPDI, 1,4-butanediol (BDO) with 4,4′-dihydroxydiphenyl disulfide (DHDDS) as monomers. It was found that the self-healing efficiency of the synthesized polyurethane elastomer series was very high after 48 h of self-healing at 25 °C, all of which exceeded 79 %, and the tensile strength, elongation and fracture toughness of best performing elastomer PU90/10 could reach 89.8 %, 99.9 %, and 95.6 %, respectively after 48 h of self-heal at room temperature, showing good simultaneous room temperature self-healing efficiency.

Realization of dual crosslinked network robust, high toughness self-healing polyurethane elastomers for electronics applications

Currently, research into self-healing polyurethane materials has progressed significantly; however, ensuring that the materials exhibit excellent mechanical properties and good healing efficiency is an urgent problem. In this study, a self-healing polyurethane elastomer exhibiting the synergistic enhancement effect of a double-crosslinked network is prepared by introducing a hydrogen-bond functional monomer and the Diels-Alder reaction. Consequently, the resulting elastomer shows a high fracture strength of 72.5 MPa, an elongation at break of 1241.0 %, an ultrahigh toughness of 235.7 MJ/m3, and a fracture energy of 219.4 KJ/m2. Dynamic covalent crosslinking and reversible hydrogen bonding dual networks endow the elastomers with good self-healing properties and multiple repair capabilities, thus allowing them to achieve up to 86 % self-healing efficiency. In addition, we prepare self-healing capacitive electronic devices using a liquid metal blended and compounded with a dual dynamic bonded polymer system, which exhibit stable electrochemical properties, excellent mechanical properties, excellent self-healing properties, and two-component recyclable properties after mechanical training. The self-repairing device can be reused, thus significantly reducing material waste and pollution, and benefits environmental and resource conservation.

An antibacterial, highly stretched and self-healing polyurethane elastomer for flexible electronic devices

Broadening the range of practical applications of self-healing materials has become a research hotspot for the development of durable and smart materials. This study the development of a hydrogen bond-rich of self-healing elastomer, formed by the combination of disulfide and diazolidinyl urea (DU) cross-linked polyurethane polymers (PDD). The prepared polyurethane elastomer material possessed extremely high mechanical properties (including a stress of 25 MPa and high toughness of 306 MJ/m3). Besides, PDD exhibited an excellent self-healing performance. Even if it is subjected to long-term tensile deformation or extreme strain, it could recover almost completely to its initial state within 12 h in a 60 °C environment. In addition, the synergistic effect of diazolidinylurea and element S on the polymer film gave the material excellent antimicrobial properties. Finally, we added carbon nanotubes into the polyurethane system and assembled them into smart sensors for applications in flexible electronic devices. The versatility of this sensor has been demonstrated in human motion applications.

A stretch hardening self-assembly strategy inspired by natural rubber for degradable, recyclable and self-repairing polyurethane elastomers

How to develop polyurethane elastomer with excellent mechanical properties and quick repair ability under mild conditions still needs to be overcome and improved. The transformation from static amorphous structure to dynamic crystalline state is an important factor for natural rubber to obtain high elasticity and mechanical properties. Therefore, with the aim of strengthening the dynamic crystalline phase of polycarbonate, a kind of high-strength and fast self-healing polyurethane elastomer with dual-phase transformation function was prepared by molecular conformation design. After testing, the mechanical strength of the elastomer is about 47 MPa, and the fracture energy is about 216 J/m2. Under mild conditions, rapid self-repair can be achieved within 1000 minutes, and the repair efficiency is as high as 95%, which is far higher than that of previously reported high toughness materials. Through the microstructure test, it is found that ultimate tensile hardening strategy of elastomers is the key to obtain high mechanical properties. Loose amorphous structure endows the elastomer with excellent dynamic properties, which is conducive to the rearrangement of disulfide bonds in the structure, so that the elastomer can quickly self-repair in a short time. In addition, the elastomer is easy to recycle and biodegrade (the degradation rate is 30.4% at 35 days), which provides an excellent strategy for the design of a new generation of electronic skin carriers.

Self-healing polyurethane elastomer with wider damping temperature range by synergistic interaction of suspended chains and dynamic disulfide bonds

In order to overcome the sharp damping peak that limits the application of polyurethane elastomers (PUE) and the cut that affects its service life as functional floor coating, a self-healing PUE with broader damping temperature range and high self-healing efficiency was prepared by incorporation of prepolymer synthesized from polycaprolactone diol and isophorone diisocyanate and chain extenders including 4,4′-diaminodiphenyl disulphide (DAPS) and double-hydroxyl suspended chains synthesized from IPDI, polyethylene glycol monomethyl ether and 2-amino-1,3-propanediol. The effects of different functionalities were carefully investigated at the fixed dosage of 30%. DAPS with dynamic disulfide bonds were revealed of higher efficiency in improving the damping properties and self-healing rate. The synergistic effects of the two functionalities were studied by varying the usage of DAPS from 10% to 50% when the suspension chain amount fixed at 30%. The effective damping (tan δ > 0.3) domain presents a range of 131.57 °C with 100% increase of tan δ compared with the base sample, and the self-healing efficiency reaches 95% when the usage of DAPS and suspension chain were 30% and 50%, respectively. The modified material achieved prominent improvement in damping properties and cut self-healing ability, showing potential application in aerospace and acoustic coatings for vibration and noise reduction.

Vat photopolymerization 3D printing of transparent, mechanically robust, and self-healing polyurethane elastomers for tailored wearable sensors

As flexible sensors are soft and prone to damage in practical applications, stretchable conductors with self-healing capacity can extend their service life. However, existing vat photopolymerization (VP) 3D-printed self-healing elastomers generally have a tensile strength of less than 1 MPa, which limits the load-bearing capacity and application range of the flexible sensors. Herein, a photocurable oligomer comprising dynamic hindered urea bonds (HUBs) was synthesized to prepare self-healing elastomers. By using a surface-functionalized spherical nano-silica (Nano-SiO2) for reinforcement modification, the tensile strength and elongation at break of the 3D-printed elastomer were enhanced by 73.7% and 111.3%, respectively, without compromising the transparency and photopolymerization rate. The fractured elastomer exhibited a high tensile strength of 5.44 MPa and a stretchability of 372% after self-healing. Subsequently, a stretchable ionic conductive elastomer (SICE) with high transparency and self-healing properties was developed by incorporating ionic liquids into the 3D-printed elastomer. The high resolution of VP-based 3D printing allowed the construction of pyramid-Kelvin lattice microstructures in the pressure sensor, which enhanced the pressure sensitivity of the sensor several times compared to the pyramid structure. In addition, combining Voronoi tessellation and kirigami art to fabricate tailored wearable sensors with smart structures, broadens the application range and improves the wearing comfort of the sensors.

A high strength, high toughness and transparent room-temperature self-healing elastomer based on the synergy effect of quadruple dynamic bonding structure

As a functional material, the transparent elastomers have been rapidly developed and applied in different fields, such as electroluminescence devices, sensors, medical and communication equipment. However, it is a huge challenge to prepare the transparent elastomers with excellent room-temperature self-healing performance and high mechanical performance. Herein, based on the synergy effect of quadruple dynamic reversible interaction, we proposed a new strategy to synthesize a room-temperature self-healing polyurethane elastomer with high strength of 15.3 MPa, high elongation at break of 1232% and high transparency. First, the polyurethane elastomer exhibited high elongation and toughness based on mechanical energy consumption from reversible fracture and reformation of sacrifice bonds, including hydrogen bonds and coordinate bonds. Moreover, the rapid reversible reaction of boronic ester bonds, oxime bonds and especially hydrogen bonds endowed the elastomer excellent self-healing performance. After introducing coordinate bonds, the elastomer exhibited high strength based on increased hard segment microdomains and the microphase separation. To further probe the mechanisms of room-temperature self-healing process and high mechanical performance, the molecular chain mobility was studied. The relationship among molecular chain mobility, molecule chain entanglement, microphase separation and aggregation structure were revealed, indicating molecular chain mobility was the key factor to self-healing performance in polyurethane elastomer.

Self-Healing Polyurethane Elastomers with High Mechanical Properties Based on Synergistically Thermo-Reversible and Quadruple Hydrogen Bonds

It is still challenging and attractive to prepare polyurethane (PU) materials with excellent self-healing ability while improving their mechanical properties and high ductility. Here, a multifunctional linear PU supramolecular elastomer was successfully prepared by introducing a cross-linking network of quadruple hydrogen bonds and thermo-reversible Diels–Alder bonds and rigid ring structure to the linear backbone. The results exhibited that the obtained PU elastomer displayed a high tensile strength (6.30 MPa), elongation (1957.84%), toughness (84.48 MJ/m3), and excellent repair efficiency (93.33%). The quadruple hydrogen bonds from 5-(2-hydroxyethyl)-6-methyl-2-aminouracil and thermo-reversible Diels–Alder bonds from the conjugated reaction of 4,4′-bismaleimide diphenylmethane with furfuryl alcohol, due to its synergetic dual reversible bonds, formed the PU elastomer that possessed excellent mechanical, self-healing, shape recovery, and reprocessing properties. The prepared multifunctional PU can be used as a substrate for flexible conductive materials or as conductive composite material with conductive materials, which can self-repair many times when the surface is damaged, can be recycled, and greatly improve the service life of the material. Therefore, the prepared multifunctional high-performance self-healing PU materials have potential applications in several fields.

Tough self-healing polyurethane elastomers based on interpenetrating networks containing multiple hydrogen bond networks, flexible blocks, metal coordination and covalent cross-linking

Currently, it is a challenge to prepare elastomers with high mechanical properties and high self-healing efficiency. In the present work, by mixing a polyurethane (PU) prepolymer with a PU elastomer containing 2-ureido-4[1H]-pyrimidinone (UPy) groups, we obtained a new PU elastomer based on interpenetrating networks. In this condition, four different structures coexist in the interpenetrating polymer networks: covalent cross-linking network, metal-ion coordination network, multiple hydrogen bond network and flexible blocks. The experimental results demonstrated that the presence of metal-ion coordination network, multiple hydrogen bond network and flexible blocks is beneficial for the improvement in healing efficiency, while the coexistence of covalent cross-linking network, metal-ion coordination network and multiple hydrogen bond network benefits to improve the mechanical properties.

Sustainable metal-free polyurethane elastomers from bile acids: self-healing properties and biocompatibility

Currently, self-healing polymers with superior elasticity have made great progress in healthcare devices and flexible electronics. Benefiting from rigid skeletons and hydroxyl groups of bile acids, herein sustainable self-healing polyurethanes have been developed via an alternative metal-free strategy in which bile acid units and oligo(ethylene glycol)s serve as hard and soft segments, respectively. The bile acid based polyurethane could achieve a similar mechanical performance (7.96 MPa of Young's modulus) to certain soft tissues and maximum self-healing efficiency of 90% in tensile strength for 3 h. Multiple hydrogen bonds originated from hydroxyl groups of bile acids and urethane bonds synergistically attribute to self-healing ability, which represents the first example that quadruple hydrogen bonds of sustainable molecules driven elastomers have been reported. Moreover, taking into account the desirable biocompatibility both in vitro and in vivo, it is highly anticipated that these sustainable metal-free self-healing polyurethane elastomers would be explored for practical applications, such as soft tissue repairing.

Dual-hard phase structures make mechanically tough and autonomous self-healable polyurethane elastomers

It is a key challenge to combine high mechanical strength and excellent autonomous self-healing properties in one elastomer to match the requirements of commercial applications. Chemical cross-linking or ordered crystalline domains can afford high mechanical strength but are often based on the cost of losing autonomous self-healing performance. To address this dilemma, a strategy involving dual hard-phase structures was developed to reinforce self-healing polyurethane elastomers, by introducing plant oil-derived aliphatic chains into the hard segments. The dangling fatty acids not only allow segmental motion of the hard domains but also suppress the crystallization within polyurethane soft segments. The tailored dual-hard phase structure and dynamic chain motion are responsible for outstanding mechanical properties (tensile strength to 21.8 MPa and toughness of 131.6 MJ m−3) and autonomous self-healing ability (∼100 % healing efficiency). Furthermore, a versatile mechanical robust flexible conductor is conveniently constructed with an auto-repair capability at ambient conditions. This work represents a molecular design paradigm of simultaneously integrating balanced mechanical strength, durability, and self-healing ability for high-performance elastomers that can find applications such as skin-inspired wearable devices.

High strength, self-healing polyurethane elastomer based on synergistic multiple dynamic interactions in multiphase

Inspired by some biological phenomena, self-healing materials has been made great progress over the past decades. However, it is challenging to establish an adaptable strategy to achieve a good tradeoff between mechanical strength and self-healing ability. Herein, we reported a self-healing polyurethane elastomer (PPG-UPy-SS) with desirable mechanical performance and wonderful self-healing capacity via incorporating synergistic multiple dynamic interactions in multiphase. The 2-amino-5-(2-hydroxyethyl)-6-methylpyrimidin-4-ol (UPy) motif was introduced into the PPG segment to keep the mechanical performance profiting from the regular arrangement of hydrogen-bonding array and microphase separation benefited from π-π stacking of UPy dimers. 4-aminophenyl disulfide (APDS) was embedded into the loosely stacked amorphous region to increase the mobility of the chain segment to improve self-healing performance. The optimized sample PPG-UPy50%-SS50% possesses high tensile strength and fracture toughness of 18.2 MPa and 57.3 MJ m−3, and satisfactory self-healing efficiency of 99% and 96% (10 h at 80 °C), respectively.

Self-assembly strategy based on multiple hydrogen bonds for super tough, self-healing polyurethane elastomers

Focusing on the self-assembly strategy of polymer chain structure, designing and synthesizing intelligent, tough and healable polymer materials is an effective way to meet the high-end applications of materials. Inspired by spider silk, we designed a preparation scheme for a repairable polyurethane-polyurea elastomer (IPAD-6.4) with an unprecedented mechanical toughness of 625.10 MJ/m3 and elongation at break of 3756.56%. After repeated cyclic stretching, the elastic body can recover 92.85% of the dissipated energy in only 2 h. These results are achieved by the hierarchical hydrogen bonds formed by different groups and the reasonable covalent cross-linking network. Additionally, the elastomer shows excellent healing ability (repair efficiency ∼102.77%). A flexible conductive composite film is prepared by simple physical assembly. The sensor can not only accurately detect the bending motion of human joints, but also has excellent antibacterial properties, which gives the material application potential in medical and engineering fields.

Photo-responsive rapid self-healing polyurethane elastomer with anticorrosion and antibacterial functions

In this paper, polyurethane (PU) with polyethylene glycol as a soft segment and isophorone diisocyanate as a hard segment were designed and synthesized. Copper complex (Cu(HD)2) was synthesized in PU preparation, bringing excellent self-healing, photothermal and antibacterial properties. The content of Cu2+ accounted for less than 2wt% of PU elastomer. Cu(HD)2 acted as a chain extender and provided coordination bonds for elastomer to promote the self-healing process. Experiments showed that Cu(HD)2 exhibited excellent photothermal properties in PU. The maximum temperature of the samples after 5 min irradiation under a sunlight simulator could reach 120 °C. The results of the self-healing experiment showed that mechanical properties of PU could be recovered by nearly 90%, and electrochemical protection performance could be recovered by nearly 100%. Antibacterial experiments proved that PU could release Cu2+, forming an antibacterial ring around PU. PU has excellent application in the field of anticorrosion and antibacterial coatings.

Self-healing polyurethane elastomer based on 2-ureido-4[1H]-pyrimidinone

Unlike the organisms in nature, the synthetic materials are difficult to repair the damage via self-regulation. Even the self-healing materials generally require the external stimuli (e.g., temperature, pressure, light, etc) to repair themselves. In this paper, self-healing polyurethane elastomer was designed and prepared based on 2-ureido-4[1H]-pyrimidinone compound by the simple physical blending method. The tensile strength and the elongation at break of the self-healing polyurethane elastomer were 0.65 MPa and 623.1%, respectively. The healing performance was measured by cut-off experiment, showing that the fracture of the self-healing polyurethane elastomer was healed at room temperature without external stimuli and kept excellent mechanic properties. The healing efficiencies of the tensile strength and the elongation at break were achieved to 87.7% (0.57 MPa) and 71.7% (446.7%) after healing at room temperature with 30 h, respectively. When the temperature was up to 80 °C, the healing time curtailed at 1 h. And the tensile strength and the elongation at break were recovered to 0.59 MPa and 532.1%, respectively. These promising results provide a strategy that allows increasing the life cycle of materials, adapting them to a circular economy model, thus reducing the generation of waste.

Self-healing polyurethane with high strength and toughness based on a dynamic chemical strategy

Menthane diamine promotes the strength and toughness of H-bonding and disulfide bonding-based self-healing polyurethane elastomers and simultaneously improves the elasticity and self-healing performance.

A room-temperature self-healing elastomer with ultra-high strength and toughness fabricated via optimized hierarchical hydrogen-bonding interactions

A room-temperature self-healing polyurethane elastomer synthesised via optimized hierarchical H-bonding interactions ultimately exhibited a synchronous self-healing efficiency of more than 83% with tensile strength, elongation, and toughness.