Preparation of WPU-based super-amphiphobic coatings functionalized by modified SiO particles and their anti-biofilm mechanism.

Fabrication of anti-wetting coatings with anti-biofouling and anti-biofilm properties has become a hot spot of attention in recent years. However, the anti-biofilm mechanism of anti-bacterial adhesion coatings with different wet resistance properties has not been explored in detail. In this work, SiO micro-nano particles were prepared by the Stöber method and were modified. The SiO/waterborne polyurethane (WPU) coatings were prepared by the drop coating method, and the coatings with different hydrophobic and oleophobic properties were constructed by modifying the process conditions using SiO micro-nano particles as the roughness construction factor. Taking the dominant spoilage bacteria of aquatic products, as the object, the anti-bacterial adhesion properties and anti-biofilm mechanism of the SiO/WPU coatings were investigated. The results show that, with the unmodified SiO particles increasing from 1.2% (w/V) to 4.0% (w/V), the hydrophobicity and thermal stability of the SiO/WPU coatings are significantly enhanced, but the oil repellency becomes worse due to the mesoporous structure. After SiO micro-nano particles are modified with 1,1,2,2-perfluorooctyl trichlorosilane (PFOTS), the surface energy of the SiO/WPU coatings is decreased, the liquid repellency is improved, and the surfaces are rough with the appearance of fluorocarbon compounds, but the thermal stabilities are slightly reduced. Among them, after the secondary modification of SiO micro-nano particles, the SiO/WPU coatings showed excellent oil repellency, lower surface energies and higher fluorocarbon content on the surface. Particularly, SiO/WPU coatings exhibited super-amphiphobicity after adjusting the amount of concentrated ammonia added during the secondary modification process. Meanwhile, we found that for the hydrophobic SiO/WPU coatings, the stronger the oleophobic property, the greater the anti-bacterial adhesion ability is, while the anti-bacterial adhesion ability of hydrophobic and selectively oleophobic or superhydrophobic and oleophobic SiO/WPU coatings is poor than that of amphiphilic SiO/WPU coatings. However, because the super-amphiphobic SiO/WPU coatings can be in the Cassie state with the bacterial solution for a long time, it can "capture" enough air to inhibit the irreversible adhesion of the bacteria. More importantly, the coatings can also inhibit the metabolic activity, secretion of extracellular polysaccharides, and activities of ATPase and AKP of the adherent bacteria, so it has a better anti-biofilm property. The anti-biofilm coatings can be used as food packaging materials or coated on the inner surface of packaging boxes to prevent the microbial infection.