Hydrophilic thioether-functionalized surface based on segregation of hydrophilic cage octasilsesquioxane in PMMA and its application to gold nanoparticle immobilization

We demonstrate hydrophilic sulfur functionalization on the surface of a poly(methyl methacrylate) (PMMA) film by entropy-driven surface segregation using a cage octasilsesquioxane, octa[2-(ethylthio)ethanol]-octasilsesquioxane (2a), with S-containing hydrophilic groups. Composite films were prepared by casting from solutions of 2a prepared in tetrahydrofuran (THF) and CHCl3 on a glass substrate. More effective surface segregation of 2a was achieved in the composite film casted from THF compared with that casted from CHCl3. The surface segregation behavior was strongly affected by the solubility of the compound in the casting solvent; highly soluble compounds were more likely to segregate on the surface. Gold nanoparticles (AuNPs) were immobilized on the surface of the PMMA composite film casted from THF by immersing the film in an aqueous AuNP dispersion. Using a similar protocol as for 2a, a PMMA composite film with octa[2-(ethylthio)isobutyl]-octasilsesquioxane (2c) was prepared as the control with hydrophobic sulfur-containing substituents to confirm that hydrophilic sulfur-containing substituents were required to effectively facilitate the immobilization of AuNPs on the polymer surface. Graphical Abstract We demonstrate hydrophilic sulfur functionalization on the surface of a poly(methyl methacrylate) (PMMA) film by entropy-driven surface segregation using a cage octasilsesquioxane, octa[2-(ethylthio)ethanol]-octasilsesquioxane (2a), with S-containing hydrophilic groups. Gold nanoparticles (AuNPs) were immobilized on the surface of the PMMA composite film casted from THF by immersing the film in an aqueous AuNP dispersion.