Abstract
A photopolymerizable thiol-ene composition was prepared as a mixture of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT), with 1 wt. % of 2,2-dimethoxy-2-phenylacetophenone (DMPA) photoinitiator. A systematic analytical analysis that investigated the crosslinked PETMP-TTT polymer coatings employed Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, differential scanning calorimetry, thermogravimetric analysis, pencil hardness, thermo-mechanical cyclic tensile, scratch testing, and atomic force microscopy. These coatings exhibited high optical transparency and shape-memory that assisted scratch-healing properties. Scratches produced on the PETMP-TTT polymer coatings with different constant loadings (1.2 N, 1.5 N, and 2.7 N) were completely healed after the external stimulus was applied. The strain recovery ratio and total strain recovery ratio for PETMP-TTT polymer were found to be better than 94 ± 1% and 97 ± 1%, respectively. The crosslinked PETMP-TTT polymer network was also capable of initiating scratch recovery at ambient temperature conditions.
Highlights
Transparent polymer films are widely used as protective coatings in flat panel displays, touch screens, photovoltaic cells, and other devices
The absorption peak of the S–H stretching band vSH is located at 2570 cm−1 [36]
After 30 s, there was a significant decrease of vSH (Figure 1b), indicating that thiol consumption proceeds very quickly
Summary
Transparent polymer films are widely used as protective coatings in flat panel displays, touch screens, photovoltaic cells, and other devices. Extrinsic self-healing polymers require inclusion of the specific healing agents that are loaded into microcapsules or vascular networks within a polymeric matrix. In this case, self-healing is triggered by the rupture of healant loaded vessels [3,4,5]. Fabrication of the highly transparent extrinsic self-healing coatings are complicated, as various inclusions strongly scatter visible light and decrease optical transparency of the films [6]. Intrinsic self-healing polymers are able to recover their properties due to the inherent physical interactions, such as molecular interdiffusion or reversible chemical bonds [4]. Reversible chemical bonding includes covalent bonds (i.e., dynamic bond exchange, Diels–Alder reactions, reversible C-ON bonds, photo-reversible reshuffling, and disulfide interchange), non-covalent interatomic bonds (metallic and ionic) and intermolecular forces
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