Multi-energy dissipation mechanisms in supramolecular hydrogels with fast and slow relaxation modes

Subaru Konishi; Junsu Park; Osamu Urakawa; Motofumi Osaki; Hiroyasu Yamaguchi; Akira Harada; Tadashi Inoue; Go Matsuba; Yoshinori Takashima

doi:10.1039/d2sm00735e

Multi-energy dissipation mechanisms in supramolecular hydrogels with fast and slow relaxation modes

Soft Matter. 2022 Oct 5;18(38):7369-7379. doi: 10.1039/d2sm00735e.

Authors

Subaru Konishi¹, Junsu Park^{1

2}, Osamu Urakawa¹, Motofumi Osaki^{1

2}, Hiroyasu Yamaguchi^{1

2

3}, Akira Harada⁴, Tadashi Inoue^{1

2}, Go Matsuba⁵, Yoshinori Takashima^{1

2

3

6}

Affiliations

¹ Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan. takasima@chem.sci.osaka-u.ac.jp.
² Forefront Research Center, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
³ Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
⁴ SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
⁵ Graduate School of Organic Materials Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan. gmatsuba@yz.yamagata-u.ac.jp.
⁶ Institute for Advanced Co-Creation Studies, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.

PMID: 36124981
DOI: 10.1039/d2sm00735e

Abstract

Reversible cross-links by non-covalent bonds have been widely used to produce supramolecular hydrogels that are both tough and functional. While various supramolecular hydrogels with several kinds of reversible cross-links have been designed for many years, a universal design that would allow control of mechanical and functional properties remains unavailable. The physical properties of reversible cross-links are usually quantified by thermodynamics, dynamics, and bond energies. Herein, we investigated the relationship between the molecular mobility and mechanical toughness of supramolecular hydrogels consisting of two kinetically distinct reversible cross-links via host-guest interactions. The molecular mobility was quantified as the second-order average relaxation time (〈τ〉_w) of the reversible cross-links. We discovered that hydrogels combining fast (〈τ〉_w = 1.8 or 18 s) and slowly (〈τ〉_w = 6.6 × 10³ or 9.5 × 10³ s) reversible cross-links showed increased toughness compared to hydrogels with only one type of cross-link because relaxation processes in the former occurred with wide timescales.