A Heterocyclic Polyurethane with Enhanced Self-Healing Efficiency and Outstanding Recovery of Mechanical Properties

Abstract

A functional polyurethane based on the heterocyclic group was synthesized and its self-healing and mechanical properties were examined. To synthesize a heterocyclic polyurethane, a polyol and a heterocyclic compound with di-hydroxyl groups at both ends were blended and the blended solution was reacted with a crosslinker containing multiple isocyanate groups. The heterocyclic polyurethane demonstrates better self-healing efficiency than the conventional polyurethane with no heterocyclic groups. Furthermore, unlike the conventional self-healing materials, the heterocyclic polyurethane examined in this study shows an outstanding recovery of the mechanical properties after the self-healing process. These results are attributed to the unique supramolecular network resulting from the strong hydrogen bonding interaction between the urethane group and the heterocyclic group in the heterocyclic polyurethane matrix.Polymers 2020, 12, 968 2 of 11 several decades [7]. While they are more susceptible to damage caused by mechanical stress because of their low mechanical surface properties, these materials can effectively self-heal the areas damaged by the mechanical stress. In light of the critical issues mentioned above, self-healable polymeric coating materials will be preferred to hard coating materials for application in flexible displays. Therefore, endowing conventional polymeric materials with the ability to self-heal both dents and scratches is considered to be vital for the development of next-generation flexible displays [8,9].Traditionally, both extrinsic and intrinsic strategies have been employed to introduce the self-healing capability to polymeric materials. Extrinsic systems depend on embedded capsules or vascular networks [10][11][12]. When the material is damaged, the embedded container will release the contained healing agents to heal the damage by polymerization or chemical reaction. However, repeated healing at the same site is inherently difficult due to the limited amount of the healing agent inside the container, and the healing ability will disappear immediately after the healing agent is depleted [7]. By contrast, intrinsic systems utilize the reversible interaction between the components of the matrix [13][14][15][16], allowing them to repeatedly self-heal the same damaged areas. It is also noted that in contrast to intrinsic systems, it is difficult for the extrinsic systems to maintain the initial optical properties after the self-healing process because of the large difference in the color and refractive index between the intact matrix and the healed region. For these reasons, it is concluded that intrinsic systems are a more appropriate solution for applications, such as in display technologies, that require excellent optical properties.Polyurethane is a widely used intrinsic self-healing material that has been extensively studied because it can effectively recover from the dents on the surface due to its high elasticity [17][18][19][20][21]. However, while polyurethane can self-heal the dents on...

Highly Self-Healable Polymeric Coating Materials with Enhanced Mechanical Properties Based on the Charge Transfer Complex

“…It has been reported that self-healing materials usually have a trade-off relationship between self-healing ability and mechanical strength [ 19 , 20 , 23 ]. Figure 5 and Figure 6 illustrate the essential benefits of the self-healing PCMs developed in this study.…”

“…Intrinsic self-healing materials exploit reversible interactions between the components in the matrix for self-repair. Reversible interactions are classified as chemical (Diels–Alder reactions [ 10 , 11 , 12 ] and disulfide bonds [ 13 , 14 , 15 ]) or physical (host–guest interactions [ 16 , 17 ], hydrogen bonding interactions [ 18 , 19 , 20 ], ionic interactions [ 21 , 22 , 23 ], metal–ligand interactions [ 24 , 25 , 26 ], and π–π interactions [ 27 , 28 , 29 ]).…”

Investigating the Impact of Hardness on Dielectric Breakdown Characteristics of Polyurethane

“…Additionally, PU, like many other self-healing materials, faces a trade-off between mechanical strength and self-healing capacity, which can result in compromised restoration of mechanical properties after damage occurs. 17,19 However, a significant challenge lies in understanding the dielectric properties of PU. This study aimed to investigate the dielectric characteristics of PU with different levels of hardness.…”

“…PUs are composed of urethane repeating units. The synthesis of PUs involves polymerizing polyisocyanates and macropolyols and the inclusion of chain extenders. − The macropolyols, such as polyether diols or polyester diols, are the soft segments. In contrast, the isocyanates (aromatic or aliphatic) and chain extenders (small diols or diamines) are known as the hard segment.…”

Preparation and Properties of Self-Healing Waterborne Polyurethane Based on Dynamic Disulfide Bond

“…Therefore, some researchers introduced the biological self-healing characteristics and mechanisms into polymer materials and formed functional self-healing materials through bionic design. These materials can recover their original properties spontaneously after damage or under external stimulation, resulting in new intelligent/smart materials with longer lives and more reliable performances, such as shaped memory polymer [ 1 , 2 , 3 ] and self-healing polymer [ 4 , 5 ] intelligent polymer materials.…”