Mechano-responsive hydrogen-bonding array of thermoplastic polyurethane elastomer captures both strength and self-healing

Youngho Eom,Eun Seong Lee,Seon-Mi Kim,Sung Yeon Hwang,Minkyung Lee,Hyeonyeol Jeon,Dongyeop X Oh,Jeyoung Park,Jaeduk Park

doi:10.1038/s41467-021-20931-z

Abstract

Self-repairable materials strive to emulate curable and resilient biological tissue; however, their performance is currently insufficient for commercialization purposes because mending and toughening are mutually exclusive. Herein, we report a carbonate-type thermoplastic polyurethane elastomer that self-heals at 35 °C and exhibits a tensile strength of 43 MPa; this elastomer is as strong as the soles used in footwear. Distinctively, it has abundant carbonyl groups in soft-segments and is fully amorphous with negligible phase separation due to poor hard-segment stacking. It operates in dual mechano-responsive mode through a reversible disorder-to-order transition of its hydrogen-bonding array; it heals when static and toughens when dynamic. In static mode, non-crystalline hard segments promote the dynamic exchange of disordered carbonyl hydrogen-bonds for self-healing. The amorphous phase forms stiff crystals when stretched through a transition that orders inter-chain hydrogen bonding. The phase and strain fully return to the pre-stressed state after release to repeat the healing process.

Highlights

Self-repairable materials strive to emulate curable and resilient biological tissue; their performance is currently insufficient for commercialization purposes because mending and toughening are mutually exclusive
The self-healing thermoplastic polyurethane (TPU) referred to as C-IPSS was synthesized from poly(hexamethylene carbonate) diol (C, a carbonate-type aliphatic macrodiol) as the soft segment, asymmetric alicyclic isophorone diisocyanate (IP) as the hard segment, and an aromatic disulfide (SS) as the chain extender (Fig. 1a and Supplementary Fig. 1)[39,40,41,42,43,44]
The uniquely designed carbonate-type macrodiol-based TPU developed in this study exhibited a tensile strength of 43 MPa, which is as high as industrially used elastomers with strong healing abilities

Summary

Introduction

Self-repairable materials strive to emulate curable and resilient biological tissue; their performance is currently insufficient for commercialization purposes because mending and toughening are mutually exclusive. We report a carbonate-type thermoplastic polyurethane elastomer that self-heals at 35 °C and exhibits a tensile strength of 43 MPa; this elastomer is as strong as the soles used in footwear. It has abundant carbonyl groups in soft-segments and is fully amorphous with negligible phase separation due to poor hard-segment stacking. It operates in dual mechano-responsive mode through a reversible disorder-to-order transition of its hydrogen-bonding array; it heals when static and toughens when dynamic. After removal of the stress, the metastable crystal returns to the amorphous phase, with its shape and strain fully recovered, and this elastomer is immediately available for selfhealing

Methods

Results

Conclusion