Biomimetic Water-Responsive Self-Healing Epoxy with Tunable Properties.
As dynamic cross-linking networks are intrinsically weaker than permanent covalent networks, it is a big challenge to obtain a stiff self-healing polymer using reversible networks. Inspired by the self-healable and mechanically adaptive nature of sea cucumber, we design a water-responsive self-healing polymer system with reversible and permanent covalent networks by cross-linking poly(propylene glycol) with boroxine and epoxy. This double cross-linked structure is self-healing due to the boroxine reversible network as well as showing a room-temperature tensile modulus of 1059 MPa and a tensile stress of 37 MPa, on a par with classic thermosets. The dynamic boroxine bonds provide the self-healing response and enable up to 80% recovery in modulus and tensile strength upon water contact. The system shows superior adhesion to metal substrates by comparison with the commercial epoxy-based structural adhesive. Besides, this system can change modulus from a stiff thermoset to soft rubber (by a factor of 150) upon water stimulus, enabling potential applications of either direct or transform printing for micro/nanofabrication. Moreover, by incorporating conductive nanofillers, it becomes feasible to fabricate self-healing and versatile strain/stress sensors based on a single thermoset, with potential applications in wearable electronics for human healthcare.
['Yuan|Dian|D|http://orcid.org/0000-0002-8699-4127', 'Delpierre|Sébastien|S|', 'Ke|Kai|K|http://orcid.org/0000-0002-6283-0689', 'Raquez|Jean-Marie|JM|http://orcid.org/0000-0003-1940-7129', 'Dubois|Philippe|P|', 'Manas-Zloczower|Ica|I|']
water-responsive self-healing epoxy boroxine strain sensors