Tough, Photoluminescent, Self-Healing Waterborne Polyurethane Elastomers Resulting from Synergistic Action of Multiple Dynamic Bonds

Polymers that integrate multiple functions into one system broaden the application range of materials, but it remains a great challenge to obtain polymer materials with simultaneously high strength, high toughness, and high self-healing rate. In this work, we prepared waterborne polyurethane (WPU) elastomers using Schiff bases containing disulfide and acylhydrazone bonds (PD) as chain extenders. Acylhydrazone forming a hydrogen bond not only acts as a physical cross-linking point, which promotes the microphase separation of polyurethane to increase the thermal stability, tensile strength, and toughness of the elastomer, but also serves as a "clip" to integrate various dynamic bonds together to synergistically reduce the activation energy of the polymer chain movement and endow the molecular chain with faster fluidity. Therefore, WPU-PD exhibits excellent mechanical properties at room temperature, such as a tensile strength and a fracture energy of 25.91 MPa and 121.66 kJ m^-2, respectively, and a high self-healing efficiency of 93.7% in a short time under moderate heating conditions. In addition, the photoluminescence property of WPU-PD enables us to track its self-healing process by monitoring change of the fluorescence intensity at the cracks, which helps to avoid the accumulation of cracks and improve the reliability of the elastomer. This self-healing polyurethane has a great potential application value in optical anticounterfeiting, flexible electronics devices, functional automobile protective films, and so on.

Effects of Europium Complex on Thermal and Photoluminescence Properties of Polyurethane-Europium Materials

A europium complex with double bonds was synthesized with crotonic acid as the ligand and a europium ion as the center ion. Then, the obtained europium complex was added to synthesized poly(urethane-acrylate) macromonomers to prepare the bonded polyurethane-europium materials by the polymerization of the double bonds in the complex and the poly(urethane-acrylate) macromonomers. The prepared polyurethane-europium materials had high transparency, good thermal stability and good fluorescence. The storage moduli of polyurethane-europium materials are obviously higher than those of pure polyurethane. Polyurethane-europium materials exhibit bright red light with good monochromaticity. The light transmittance of the material decreases slightly with increases in the europium complex content, but the luminescence intensity gradually increases. In particular, polyurethane-europium materials possess a long luminescence lifetime, which has potential applications for optical display instruments.

Synthesis, crystal structures, and luminescent properties of Zn(ii), Cd(ii), Eu(iii) complexes and detection of Fe(iii) ions based on a diacylhydrazone Schiff base

Acylhydrazone Schiff bases are rich in N and O atoms to coordinate with metal ions to form multidentate complexes.