Surface segregation behavior of octaalkoxy-substituted cage octasilsesquioxanes in poly(methyl methacrylate)

Octaalkoxy-substituted polyhedral oligomeric silsesquioxane (8RO-POSS), which has reactive alkoxy silyl groups at its eight vertices, is an attractive starting material for the production of silicone resins. Herein, we studied the surface segregation behavior of octaethoxy-substituted POSS (1a) and octaisopropoxy-substituted POSS (1b) on the surface of a poly(methyl methacrylate) (PMMA) film by casting their chloroform and tetrahydrofuran (THF) solutions onto glass substrates. Higher water contact angles were observed for the PMMA films containing 1b than for those containing 1a. No significant difference between the THF and chloroform solutions was observed for the PMMA films containing 1a. In contrast, higher water contact angles were observed for the PMMA film containing 1b in chloroform than in THF. The X-ray photoelectron spectroscopy Si–O peak intensity was higher in 1b than in 1a, confirming that 1b is more segregated on the PMMA surface. The PMMA film containing 3 wt% 1b from chloroform was exposed to 1 M HCl vapor or 1 M NH3 aqueous solutions at 90 °C for 5 h. Although no change in the water contact angle was observed for the film exposed to 1 M HCl, the water contact angles decreased to 77.8° when exposed to 1 M NH3, suggesting that hydrolysis proceeded.