Functional materials with self-healing properties: a review.

Self-healing materials (SHMs) have been a research hot topic in recent years owing to their greatly improved longevity and safety in practical applications. Recently, research on SHMs has gradually expanded from structural materials to functional materials. Functional materials with self-healing properties (FMSH) require simultaneous repairing not only of the mechanical properties but of the functionalities from damaged cracks or wounds. It is more challenging to introduce both self-healing properties and a particular functionality to materials owing to the difficulties of preparing the materials and their more complex healing mechanism. Herein, we summarize the recent progress that has been made in FMSH, put forward insights from the perspectives of material preparation and healing mechanisms and highlight future developments for FMSH.

Electromagnetic Wave Absorption Coating Material with Self-Healing Properties.

Electromagnetic wave absorption coatings can effectively minimize electromagnetic radiation and are widely used in the military and civil field. However, even small scratches on the coating can lead to a large decline of absorption ability and bring serious consequences. To enhance the lifetime of electromagnetic wave absorbing coating, a kind of self-healing electromagnetic wave absorbing coating is developed by introducing host-guest interactions between the absorbing fillers and polymer matrix. After being damaged, the cracks on this coating can be healed completely with the aid of small amounts of water. Simultaneously, the electromagnetic absorbing ability of the coating is restored along with the self-healing process.

Super Tough, Ultrastretchable Hydrogel with Multistimuli Responsiveness.

The research of hydrogels has been increasingly focused on designing an effective energy dissipation structure in recent years. Here, we report a kind of novel supramolecular cross-linker, which was formed by self-assembling amphiphilic block copolymers with guest groups at the end and vinyl-functionalized cyclodextrin (CD) through host-guest interaction. These cross-linkers could dissipate energy effectively since they combined multiple sacrificial mechanisms across multiscales through physical interactions. The resulted hydrogel shows distinguishing mechanical properties (fracture toughness of 2.68 ± 0.69 MJ/m3, tension strength of up to 475 kPa, uniaxial stretch over 2100%), remarkable fatigue resistance, and thermal- and light-responsive behaviors.

Effective Formaldehyde Capture by Green Cyclodextrin-Based Metal-Organic Framework.

A kind of metal-organic framework made from γ-cyclodextrin (γ-CD) and potassium ions were explored as excellent formaldehyde (HCHO) absorbents. The adsorption capacity and speed of γ-CD-MOF-K are both about 9 times higher than those of activated carbon, which are attributed to the porous structure and synergistic effect of hydrogen bonding and host-guest interactions.

Reusable Xerogel Containing Quantum Dots with High Fluorescence Retention.

Although various analytical methods have been established based on quantum dots (QDs), most were conducted in solution, which is inadequate for storage/transportation and rapid analysis. Moreover, the potential environmental problems caused by abandoned QDs cannot be ignored. In this paper, a reusable xerogel containing CdTe with strong emission is established by introducing host⁻guest interactions between QDs and polymer matrix. This xerogel shows high QDs loading capacity without decrease or redshift in fluorescence (the maximum of loading is 50 wt % of the final xerogel), which benefits from the steric hindrance of ß-cyclodextrin (ßCD) molecules. Host⁻guest interactions immobilize QDs firmly, resulting in the excellent fluorescence retention of the xerogel. The good detecting performance and reusability mean this xerogel could be employed as a versatile analysis platform (for quantitative and qualitative analyses). In addition, the xerogel can be self-healed by the aid of water.

6-TIPS-ß-Cyclodextrin-Modified Fe3 O4 for Facile Enantioseparation of 1-(1-Naphthyl)ethylamine.

A new type of chiral magnetic nanoparticle was prepared from covalently linked magnetic nanoparticles (Fe3 O4 ) and heptakis-(6-O-triisopropylsilyl)-ß-cyclodextrin (6-TIPS-ß-CD). The resulting selectors (TIPS-ß-CD-MNPs) combined the good magnetic properties Fe3 O4 and efficient chiral recognition ability of 6-TIPS-ß-CD. The enantioselectivity of TIPS-ß-CD-MNPs towards 1-(1-naphthyl)ethylamine was six times higher than that of the parent ß-CD modified Fe3 O4 particles.