A high‐performance self‐healing polyurea material based on exchangeable aromatic disulfide

Abstract

High-performance polyurea materials demonstrate promising applications in the field of aerospace, military, etc. During processing and use, however, the formation of cracks may cause serious degradation of material properties. Selfhealing polyurea should be an effective way to address this issue. Here, an innovative polyurea material, which exhibited excellent mechanical properties and self-healing abilities, was synthesized from the commercially available poly(propylene glycol) bis(2-aminopropyl ether), isophorone diisocyanate, and 2-Aminophenyl disulfide (APD). The rigid benzene ring in APD is beneficial to the mechanical properties of polyureas, simultaneously the irregular structure of APD prevents the hard segments from stacking tightly, which facilitates the exchange of disulfide bonds to achieve the self-healing function. Furthermore, the microstructure, mechanical properties and self-healing ability of the polyureas are highly dependent on the amount of APD. The obtained SPU-4 exhibits robust mechanical strength (tensile stress of 21.2 MPa), outstanding stretchability (strain of 1006%), high rigidity (Young's modulus of 248.1 MPa), and excellent energy absorption (toughness of 139.7 MJÁm À3 ), besides, with heat stimulation, the self-healing efficiencies based on strength and elongation could reach 92.7% and 74.5%, respectively. The excellent properties allow the material to show broad potential in the practical applications such as protection, energy absorption, etc.

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications

“…For dynamic covalent self-healing, covalent bonds such as disulfide bonds, Diels–Alder reactions, and imine bonds are used [ 114 , 115 ]. Dynamic chemical crosslinks based on exchangeable disulfide bonds were produced by reacting diamine chain extenders containing disulfide bonds with di- or triisocyanates [ 116 , 117 ]. The presence of disulfide bonds causes a decrease in the strength of hydrogen bonds, which can facilitate their dissociation and, in turn, promote topological network rearrangement.…”

“…The presence of disulfide bonds causes a decrease in the strength of hydrogen bonds, which can facilitate their dissociation and, in turn, promote topological network rearrangement. Furthermore, the use of aromatic disulfides can allow modification of the hard-to-soft-segments ratio, leading to enhanced mechanical properties and self-healing characteristics [ 116 ].…”

The development of high‐strength, anticorrosive, and strongly adhesive polyaspartate polyurea coating suitable for pipeline spray repairs

“…Polyurea elastomer is composed of alternating flexible soft segments and rigid hard segments. [14][15][16][17] Due to the significant polarity difference and thermodynamic incompatibility between its soft and hard segments, polyurea elastomers exhibit a unique microphase-separated structure, contributing to their numerous excellent physical and mechanical properties. 18,19 Therefore, the ratio of hard and soft segments is a key factor influencing the mechanical properties and applications of polyurea, and has received widespread attention in recent years.…”

Mechanically Robust and Self-Healable Polyureas Based on Multiple Dynamic Bonds

“…According to Wool’s theory, a healing process goes through five stages: (i) surface rearrangement, (ii) surface approach, (iii) wetting, (iv) diffusion, and (v) randomization, during which diffusion stage is the most important stage controlling crack healing and the development of mechanical properties . The chain mobility that dominates the diffusion stage plays an important role in the healing process . The introduction of weak dynamic bonds into the polymer network facilitates better chain segment mobility and obtains a higher healing efficiency, but this is usually at the expense of mechanical properties.…”

“…13 The chain mobility that dominates the diffusion stage plays an important role in the healing process. 14 The introduction of weak dynamic bonds into the polymer network facilitates better chain segment mobility and obtains a higher healing efficiency, but this is usually at the expense of mechanical properties. Strong dynamic bonds and covalent cross-links are often used to improve mechanical strength, but the stretchability and self-healing properties of the material are also diminished.…”