Facile route to nature inspired hydrophobic surface modification of phosphate glass using polyhedral oligomeric silsesquioxane with improved properties

Abstract

Hydrophobic polyhedral oligomeric silsesquioxane (POSS) molecules were utilized for the surface coating to improve the hydrophobicity of the surface of phosphate glass (Pglass). To maximize the Pglass surface hydrophobicity, protrusions on the Pglass surface were successfully prepared by Pglass particles on the surface of the bulk Pglass to mimick the lotus leaf, which has a superhydrophobic surface. The results showed that the combination of hydrophobic coating by POSS and improved roughness prepared by Pglass particles with air trapped on the Pglass surface yielded significantly increased hydrophobicity close to superhydrophobicity of lotus leaf. Chemical stability tests using ethanol and acetone confirmed stability of POSS on the Pglass surface. This result was supported by the XPS data showing an increase of bridging oxygen on the Pglass surface due to the condensation reaction between the hydroxyly functional groups of the Pglass and POSS. The relatively longer hydrophobic functional group of isooctyl compared to that of the isobutyl on the POSS cages gave larger contact angles than that of conventional silane, indicating that the POSS chemicals used are able to effectively produce the so-called “umbrella effect” mechanism that covers the intrincic hydrophilic surface of the phosphate glass using bulky molecules and grafted hydrophobic POSS chemical functional groups.