Department of Applied Chemistry, Kyushu University, Fukuoka 819-0395, Japan.
J Phys Chem B. 2010 Mar 18;114(10):3457-60. doi: 10.1021/jp909373g.
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 alpha(a)-relaxation process was much smaller than those for the original alpha(a)-relaxation processes at the intact surface and in the bulk. The depth profile of the glass transition temperature (T(g)) of the PMMA film in water was obtained, showing that T(g) decreases with proximity to the water phase. The T(g) depression observed here was best explained in terms of the water content of the film, rather than a confinement effect.
通过横向力显微镜研究了聚甲基丙烯酸甲酯（PMMA）在硅片上的旋涂膜在水界面处的松弛行为，考察了温度和扫描速率的影响。即使在水中，也可以在温度范围内清楚地观察到归因于 PMMA 被水分子塑化的分子链段运动的横向力峰。被水分子塑化的α(a)松弛过程的表观活化能明显小于完整表面和本体中的原始α(a)松弛过程的表观活化能。得到了 PMMA 膜在水中的玻璃化转变温度（T(g)）的深度分布，表明 T(g)随接近水相而降低。这里观察到的 T(g)降低可以很好地用膜中的含水量来解释，而不是限制效应。
