Fabrication and characterization of hierarchical microcapsules with multi-storage cells for repeatable self-healing

Repeatable Self-Healing of a Protective Coating Based on Vegetable-Oil-Loaded Microcapsules

Generally, microcapsule-based self-healing materials have the limitation of single local self-healing. A few studies have reported repeatable self-healing in these microcapsular materials, but there is a challenge to develop multi-cycle self-healing materials that have the advantages of easier preparation and a more efficient operation. In this work, a mixture of two vegetable oils, soybean and olive oil, was used as a healing agent. The atmospheric oxygen-induced reaction behavior (in the presence of a catalyst) was investigated for various compositions of the vegetable oil mixtures; infrared spectroscopy, recovery testing, and viscoelasticity measurement were performed to find an optimum composition of the healing agent. Microcapsules loaded with soybean oil and catalyst-containing olive oil were separately prepared and used to prepare a dual-capsule self-healing coating. It was demonstrated through optical and scanning electron microscopy that, upon scribing the self-healing coating, the vegetable oils flowed out from microcapsules to self-heal the damaged area. When the healed area of the self-healing coating was re-scribed, self-healing was repeated, which was confirmed by scanning electron microscopy (SEM) and anticorrosion and electrochemical testing. Our new repeatable self-healing coating provides the merits of easy preparation, no need for external intervention such as light irradiation, and an environmentally-friendly nature.

Preparation of Poly(thiol-urethane) Covalent Adaptable Networks Based on Multiple-Types Dynamic Motifs

To solve the issue of polymeric materials recycling, developing intrinsic self-healing materials containing dynamic bonds has attracted many researchers' highly concerning. However, the tradeoff between their mechanical strength and stretchability always does not avoid. Herein, to surmount the above tradeoff, metal-ligand (Cu²⁺ -S) interactions are introduced into the cross-linking polythiourethane covalent adaptable networks (PTU CANs) with three kinds of dynamic motifs (thiourethane, disulfide, and hydrogen bonds). When the molar ratio of Cu²⁺ to S is 6.37%, the break strength (9.41 ± 0.34 MPa) and Young's modulus (26.02 ± 0.55 MPa) of the metal-ligand coordination complex PTU (Cu²⁺ -PTU-3) dramatically increase, whereas the peak strain almost does not decline (454.44 ± 3.95%). To conduct the repairing, Cu²⁺ -PTU-3 is further confirmed excellent repairing capability. Therefore, these new PTU CANs have significant potential for the new self-healing materials.