Thermodynamically stable whilst kinetically labile coordination bonds lead to strong and tough self-healing polymers

Abstract

There is often a trade-off between mechanical properties (modulus and toughness) and dynamic self-healing. Here we report the design and synthesis of a polymer containing thermodynamically stable whilst kinetically labile coordination complex to address this conundrum. The Zn-Hbimcp (Hbimcp = 2,6-bis((imino)methyl)-4-chlorophenol) coordination bond used in this work has a relatively large association constant (2.2 × 1011) but also undergoes fast and reversible intra- and inter-molecular ligand exchange processes. The as-prepared Zn(Hbimcp)2-PDMS polymer is highly stretchable (up to 2400% strain) with a high toughness of 29.3 MJ m−3, and can autonomously self-heal at room temperature. Control experiments showed that the optimal combination of its bond strength and bond dynamics is responsible for the material’s mechanical toughness and self-healing property. This molecular design concept points out a promising direction for the preparation of self-healing polymers with excellent mechanical properties. We further show this type of polymer can be potentially used as energy absorbing material.

Engineering hydrophobically associated hydrogels with rapid self‐recovery and tunable mechanical properties using metal‐ligand interactions

“…Besides, a recent report from Bao and coworkers has indicated that the strength and dynamics of metal‐ligand coordination bonds play a critical role in dictating the mechanical properties in PDMS. [ 25 ] Hence, further work is required to optimize the potential of these interactions to obtain functional hydrogel materials. Herein, we have designed hydrogels based on copolymerization of acrylamide and the hydrophobic monomer 6‐(2,2′:6′,2‐′′ Terpyridine‐4′‐yloxy)‐hexylacrylamide ( 1 ) in the presence of metal ions (Scheme 1).…”

Fully organic compliant dry electrodes self-adhesive to skin for long-term motion-robust epidermal biopotential monitoring

“…The research works on dry contact electrodes have been focused on soft conductive polymer composites and intrinsically conductive polymers due to their adaptation to rough and even deformed skin 9,10 . The conductive polymer composites consist of elastomers and conductive nanofillers like metals 11 , nanotubes 12 , nanowires 13 , and nanosheets 14 . The conductive nanofillers are the minority in the elastomer matrix, leading to a small effective contact area between the conductive nanofillers and human skin.…”

A Self-Healing Polymer with Fast Elastic Recovery upon Stretching

“…. π stacking interactions [31][32][33], ionic interactions [34,35] and metal-ligand interactions [36][37][38][39][40][41][42][43][44], have been incorporated into various kinds of polymers as cross-linkages, leading to repeatable self-healing polymers.…”