The relaxation behavior of poly(methyl methacrylate) (PMMA), spin-coated on a silicon wafer, at the water interface was examined by lateral force microscopy as a function of temperature and scanning rate. Even in water, the lateral force peak which was assigned to the segmental motion of PMMA plasticized by water molecules was clearly observed in the temperature domain. The apparent activation energy for the plasticized αa- relaxation process was much smaller than those for the original αa-relaxation processes at the intact surface and in the bulk. The depth profile of the glass transition temperature (Tg) of the PMMA film in water was obtained, showing that Tg decreases with proximity to the water phase. The Tg depression observed here was best explained in terms of the water content of the film, rather than a confinement effect.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry