Dynamic polymer networks containing photothermal materials have been reported to demonstrate highly efficient intrinsic self-healing under irradiation. In particular, organic near-infrared-absorbing ionic salts, such as diimmonium dyes, function as transparent polymer heaters and can enhance the self-healing properties of clearcoats. In this study, we designed a self-healing automotive clearcoat with a reversible polymer network based on acryl polyol (AP) and dynamic hindered urea (HU) bonds and introduced N-butyl-substituted diimmonium borate dye (DID) as a photothermal dye. To optimize the self-healing efficiency of the clearcoat and its transparency in the visible light region, the effects of the presence or absence of dynamic HU bonds and the concentration of the photothermal dye were precisely investigated. For a polymer system containing HU with 0.1 wt % DID (AP/HU-DID_0.1), the transparent automotive clearcoat was heated to ∼70 °C under focused sunlight irradiation and exhibited excellent (∼100% healing efficiency) and fast (<30 s) scratch-healing performance compared with a commercial automotive clearcoat. In addition, this photothermal effect-based self-healing clearcoat exhibited outstanding transparency (over 95%) and has a strong advantage with respect to energy consumption because it enables faster and more localized healing compared with thermal healing processes that require heating the entire product.

Recently, self-healing materials have evolved to recover specific functions such as electronic, magnetic, acoustic, structural or hierarchical, and biological properties. In particular, the development of self-healing protection coatings that can be applied to lens components in vision systems such as augmented reality glasses, actuators, and image and time-of-flight sensors has received intensive attention from the industry. In the present study, we designed polythiourethane dynamic networks containing a photothermal N-butyl-substituted diimmonium borate dye to demonstrate their potential applications in self-healing protection coatings for the optical components of vision systems. The optimized self-healing coating exhibited a high transmittance (∼95% in the visible-light region), tunable refractive index (up to 1.6), a moderate Abbe number (∼35), and high surface hardness (>200 MPa). When subjected to near-infrared (NIR) radiation (1064 nm), the surface temperature of the coating increased to 75 °C via the photothermal effect and self-healing of the scratched coatings occurred via a dynamic thiourethane exchange reaction. The coating was applied to a lens protector, and its self-healing performance was demonstrated. The light signal distorted by the scratched surface of the coating was perfectly restored after NIR-induced self-healing. The photoinduced self-healing process can also autonomously occur under sunlight with low energy consumption.

This work describes an emulsion polymer with self-healing capability based on a dynamic covalent bonding mechanism. A latex prepolymer (LPtB) containing bulky amine units was synthesized via soap-free emulsion polymerization. Then, a one-pot crosslinkable self-healing emulsion polymer was prepared by adding a blocked isocyanurate and a catalyst into the latex prepolymer, and subsequently, a crosslinked self-healing polymer film (cLPtB) was prepared. Syntheses of self-healing polymers were confirmed by Fourier transform infrared, size exclusion chromatography, proton nuclear magnetic resonance, dynamic light scattering, and transmission electron microscopy analyses. A control latex prepolymer (LPH) was also synthesized without bulky amine functionality, and the self-healing properties of crosslinked LPH (cLPH) were compared to those of cLPtB under the same crosslinking and healing conditions. In addition, the effects of drying and crosslinking conditions at various temperatures on the film formation and crosslinking degree of polymer films were evaluated through atomic force microscopy and gel content analysis. cLPtB demonstrated a T g,DMA of 47 °C and onset dissociation of urea linkages at 120 °C, as confirmed by DMA. The cLPtB films exhibited complete restoration of mechanical properties after cutting and healing at a film formation temperature of 80 °C; they exhibited a self-healing efficiency (σSHE%) of 100%. The cLPtB coating surface also manifested a rapid healing process with 100% wound suturing at 100 °C for 5 min, as recorded by optical microscopy.