Biomimetic structure of chitosan reinforced epoxy natural rubber with self-healed, recyclable and antimicrobial ability.

Inspired by biomaterials with hard and soft structures, we reported a type of self-healed, recyclable and antimicrobial elastomers material (ECTS) which exhibited both strong mechanical strength and high toughness. ECTS was designed by furfuryl amine modified epoxy natural rubber (ENR-FA) and furaldehyde modified chitosan (CTS-FUR) through Diels-Alder (D-A) reaction. The dynamic loading capacity of the chitosan skeleton, the stress ductility of the matrix and the dynamic cross-linking between the hard and soft components gave the elastomer excellent mechanical strength, toughness and self-healing ability. The tensile strength and the elongation at break could reach up to 7.55 MPa and 487%, respectively. In addition, due to the reversibility of the covalent bond between chitosan framework and rubber matrix, the crosslinking network destroyed by external force could be reestablished under high temperature stimulation. The mechanical properties of the sample could be restored to more than 90% of the original sample, whether it was complete fracture, cyclic damage or recyclable. ECTS exhibited excellent antibacterial activity against both gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Pseudomonas aeruginosa), with antibacterial efficiency more than 99%. So, ECTS might has a promising application prospect in medical materials, intelligent devices, 4D-printing, etc.

A NIR laser induced self-healing PDMS/Gold nanoparticles conductive elastomer for wearable sensor.

Self-healing conductive elastomers have been widely used in smart electronic devices, such as wearable sensors. However, nano fillers hinder the flow of polymer segments, which make the development of conductive elastomer with rapid repair and high ductility a challenge. In this work, thioctic acid (TA) was grafted onto amino-modified polysiloxane (PDMS-NH2) by dehydration condensation of amino group and carboxyl group. By introducing gold nanoparticles, a dynamic network based on S-Au interaction was constructed. The dynamic gold cross-linking could effectively dissipate the energy exerted by external force and improve the extensibility of conductive elastomer. In addition, S-Au interaction had a good optothermal effect, so that the elastomer rapidly healed under NIR irradiation, and the repair efficiency reached 92%. We further evaluated the performance of the conductive elastomer as a strain sensor. The sample could accurately monitor the bending of human joints and small muscle state changes. This kind of self-healable conductive elastomer based on dynamic S-Au interaction has great potential in the fields of interpersonal interaction and health monitoring.