An Ultrastrong and Highly Stretchable Polyurethane Elastomer Enabled by a Zipper‐Like Ring‐Sliding Effect

Abstract

Elastomers with excellent mechanical properties are in substantial demand for various applications, but there is always a tradeoff between their mechanical strength and stretchability. For example, partially replacing strong covalent crosslinking by weak sacrificial bonds can enhance the stretchability but also usually decreases the mechanical strength. To surmount this inherent tradeoff, a supramolecular strategy of introducing a zipper‐like sliding‐ring mechanism in a hydrogen‐bond‐crosslinked polyurethane network is proposed. A very small amount (0.5 mol%) of an external additive (pseudo[2]rotaxane crosslinker) can dramatically increase both the mechanical strength and elongation of this polyurethane network by nearly one order of magnitude. Based on the investigation of the relationship between molecular structure and mechanical properties, this enhancement is attributable to a unique molecular‐level zipper‐like ring‐sliding motion, which efficiently dissipates mechanical work in the solvent‐free network. This research not only provides a distinct and general strategy for the construction of high‐performance elastomers but also paves the way for the practical application of artificial molecular machines toward solvent‐free polyurethane networks.

Healable, Recyclable, and Mechanically Tough Polyurethane Elastomers with Exceptional Damage Tolerance

“…The strengthening and toughening of the PU-BPY 0.5 -Zn elastomers were further characterized by cyclic tensile tests with increasing strains but no delay time (Figure 4a). [37,50,51] The hysteresis areas for each loading-unloading cycle of the elastomers are plotted as a function of the strain in Figure 4b. The hysteresis areas for the elastomers are small when the strain is lower than 400%, meaning that the elastomers mainly undergo elastic deformation with the rupture of an extremely small amount of hydrogen and coordination bonds.…”

“…[3,34,35] In contrast, elastomers conferred with good damage tolerance can effectively prohibit the propagation of physical damage such as cuts and cracks to retain most of their mechanical properties. [31,36,37] Therefore, elastomers integrated with damage tolerance and healability are more effective than those solely integrated with healability in extending service life and enhancing reliability. The damage tolerance of elastomers or other kinds of polymer materials requires efficiently dissipating energy concentrated in the damaged regions.…”

Supramolecular adhesive materials from small‐molecule self‐assembly

“…have been developed by the self-assembly of building blocks. Diverse noncovalent interactions include hydrogen-bonding, 12,13 π-π stacking, 14,15 van der Waals interactions, 16,17 electrostatic interactions, 18 hydrophobic effects, 19,20 host-guest interactions 21,22 and dynamic covalent bonds. [23][24][25] Precisely tuned precursor molecules organize into desired ensembles with distinct physicochemical properties via the "bottom-up" approaches.…”

Self-Healing Thermoplastic Polyurethane Linked via Host-Guest Interactions

“…Unfortunately, their rupture stress just reached the kPa scale meaning that they cannot be classified as tough materials. Thermoplastic polyurethane (TPU) [ 51 , 52 , 53 ] as a thermoprocessable elastomer has recently attracted attention in the preparation of tough materials, due to its chemical structure, which can be finely tuned to generate the desired transparency and mechanical properties. TPU usually has a multiphase microstructure, in which the hard domains act as reinforcing filler, and they are connected by thermally reversible crosslinks and embedded in the soft matrix.…”