Nonfluorinated, transparent, and spontaneous self-healing superhydrophobic coatings enabled by supramolecular polymers

Transparent self-healing superhydrophobic coatings have important applications on lenses, solar cells, helmet visors, and windshields et al. However, their applications at the present stage are limited by hazardous fluorinated materials, low transmittance, and heating treatment for healing. In this study, nonfluorinated, transparent, and superhydrophobic coatings with spontaneous self-healing ability are successfully fabricated via spray coating an ethanol solution of polydimethylsiloxane (PDMS)-based supramolecular polymer cross-linked via N-coordinated boroxines (N-Boroxine-PDMS) and SiO2 nanoparticles. Benefiting from the use of spray-coating technique, the transparent self-healing superhydrophobic coatings can be readily applied to various substrates such as plastic spectacle lens, wood, metal, and paper, greatly expanding the scope of applications. The obtained coatings possess good transparency with a transmittance at 550 nm of 90.1% and excellent superhydrophobicity with a contact angle of 160.9° and a sliding angle of 1°, which can be attributed to the use of N-Boroxine-PDMS that is inherently transparent and hydrophobic. The N-Boroxine-PDMS/SiO2 coatings can withstand water impact, UV irradiation, and heating at elevated temperatures due to the use of N-Boroxine-PDMS. More importantly, the coatings are capable of repetitively and spontaneously healing the chemical damage caused by exposure to hydrogen peroxide or O2 plasma at room temperature because the reversibility of N-coordinated boroxines allows the oligomers of N-Boroxine-PDMS readily migrate to the damaged surface. Our finds show evidence that the use of properly designed supramolecular polymers as coating materials provides a simple and effective way to simultaneously integrate good transparency, stability, and spontaneous room-temperature self-healing ability in superhydrophobic coatings.