Preparation Of Hollow Porous Silica And Fabrication Of Self-healing Superhydrophobic Surfaces

Superhydrophobic surfaces have got great interest as they could be widely used in daily life. It is essential to prepare long-lived superhydrophobic surfaces as most of them are fragile or not durable. It is known that self-healing superhydrophobic surfaces could restore their superhydrophobicity after rough structures and/or low surface energy substances were damaged, which have also been widely studied. This thesis reviewed the research progress on fabrication of self-healing superhydrophobic surfaces, and presents the main research contents and results about fabrication of lasting and self-healing superhydrophobic surfaces through the use of core-shell polystyrene/Si O2 nanoparticles as coating skeleton(prepared by sol-gel method) and polydimethylsiloxane(PDMS) as hydrophobic interconnection.(1) Polystyrene(PS) particles with different sizes were prepared by emulsion polymerization method. The as-obtained PS particles were used as template, and then coated with silica by hydrolysis and condensation of tetraethoxysilane to obtain core-shell polystyrene/Si O2 particles. Then hollow porous silica particles were obtained by treating core shell particles with tetrahydrofuran(THF). The amount of the silicon source was adjusted to regulate the thickness of the hollow porous silica. Finally, hollow porous silica with best monodispersity and hollowness were obtained. Based on THF swelling and releasing PS, self-healing superhydrophobic surfaces can be successfully fabricated.(2) Core-shell polystyrene/Si O2 nanoparticles were also prepared by sol-gel method. By spraying the core/shell nanoparticles as a coating skeleton and PDMS as hydrophobic interconnection, lasting and self-healing superhydrophobic surfaces were fabricated. Transmission electron microscopy and scanning electron microscopy(SEM) were employed to observe the morphology of PS and PS/Si O2 particles. And SEM and atomic force microscope were used to observe the surface morphology of the superhydrophobic surfaces. X-ray photoelectron spectroscopy was conducted to test the element distribution of the surfaces. Optical contact angle meter was used to evaluate the wettability of surfaces. The abrasion resistance of the coating was evaluated by sand impact abrasion. The healing ability of the superhydropohobic surfaces was evaluated by air plasma etching of the substrates. The influences of spray-coating times of core-shell particles on lasting and self-healing properties of coating have been also discussed. And the effect of different healing processes on the self-healing property was studied. The mechanisms of the lasting and self-healing superhydrophobic property were also studied. Results showed that lasting and self-healing superhydrophobic surfaces could be fabricated by spraying core-shell particles and PDMS.Studies showed hollow porous silica with best monodispersity and hollowness were successfully fabricated by hard template method. The final spray-assisted superhydrophobic surfaces had a water contact angle above 160°, with sliding angle lower than 10°. Studies also showed that the spray-assisted superhydrophobic surfaces had long lasting superhydrophobicty even after several times of sand impact abrasion, and the superhydrophobicity of damaged surface from air plasma treatment could be automatically restored at ambient temperature, or repeatedly healed by THF treatment and heat healing.