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.
In this article, chlorotrifluoroethylene (CTFE)-based fluorocarbon composite latexes and their coatings are successfully fabricated by an environmentally friendly preparation method based on a new multifunctional waterborne polyurethane (MFWPU) dispersion. It is worth noting that the MFWPU acts as the sole system stabilizer as well as microreactor and simultaneously endows the composite coating with excellent double self-healing performance and adhesion. Moreover, the introduction of a dynamic disulfide bond in the polyurethane dispersion entrusts the coating with excellent scratch self-healing performance. Simultaneously, carbon–carbon double bonds in the polyurethane dispersion increase the compatibility between the core polymer and shell polymer. The fluorine-containing chain segments can be distributed in the coating evenly during the self-assembly film-forming process of composite particles so that the original element composition of the worn coating surface can restore the original element composition after heating, and the coating presents a regeneration ability, which further and verifies the usefulness of the double self-healing model of the coating. Afterward, efficient recovery and durability, which are two contradictory properties of scratch self-healing polymers, are optimized to obtain a composite coating with excellent comprehensive performance. The research results regarding the composite system may provide a valuable reference for the structural design and application of waterborne fluorocarbon functional coatings in the future.
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