聚合物的分子运动决定其宏观性质。当高分子薄膜厚度从微米级别降低到分子水平，其分子松弛行为将与本体发生偏离，如Tg下降。纳米技术的快速发展迫切希望深入了解聚合物超薄膜分子运动的相关规律。发展原位研究聚合物薄膜分子松弛行为如玻璃化转变的新方法是目前的当务之急。本项目首次提出利用液滴在聚合物薄膜表面润湿行为与其粘弹性之间的关系来研究聚合物薄膜的分子松弛。以聚苯乙烯、聚甲基丙烯酸甲酯等薄膜为研究对象，通过液滴在膜表面润湿行为中stick-slip现象所产生的跳跃角与膜温度的关系原位研究基底支撑的聚合物薄膜、超薄膜分子松弛行为如玻璃化转变，粘弹响应及力学损耗等；研究基底效应对超薄膜分子运动的影响及其影响的临界厚度等。从本质上解决液滴润湿行为中相关参数如跳跃角，与聚合物膜力学性能的关系。发展一种全新的原位研究高分子超薄膜玻璃化转变的手段。解决该方法的理论基础。前期研究已经证明本项目是完全可行的。

The macroscopic property of polymer was determined by the motion of their molecular chain. The glass transition temperature (Tg) is defined as the temperature at which the dynamics of molecules dramatically slow down and the molecular liquid falls out of equilibrium, manifested as a dramatic increase of the mechanical modulus, an increase in relaxation times, and also in the rise of viscosity by many orders of magnitude. It is a key parameter for characterizing the mobility of polymer chains and determines the temperature range for application of many materials. Because of the finite size effects, surface and interface effects and other impacts with decreasing of film thickness, the glass transition dynamics of nanometers-thick polymer films significantly deviates from that in bulk. With the recent advances in nanotechnology, increasing interest in thin film coatings and nano-devices of polymer materials exacerbate our concerns on the precise understanding of the physical properties and performances of nano-devices related to the segmental dynamics of polymers under confinement. Consequently, there is a great demand for novel techniques to characterize the thin film dynamics such as the glass transition, molecular mobility, flow dynamics, and mechanical response. In our previous work, the wetting behavior of liquid on polymer surface has found to be affected by the viscoelascity of the polymer film. Base on this background, the dynamic wetting of liquid on polymer surface was firstly developed to be a sensor investigating the chain relaxation of thin polymer films in the current proposal. In the glass transition region, the wetting of liquid on polymer surface exhibits "stick-slip" phenomenon and a quantitative parameter "jumping angle" was put forward to scale the "stick-slip" behavior. By detecting variation in the "jumping angle" as a function of film temperature, the relaxation dynamics of supported thin films such as Tg and viscoelascity can be accessed, and substrate effect can also be determined by detecting the liquid wetting on film surface. The aim of this project is to develop an original method for in situ characterizing the chain relaxation of thin polymer films and that influenced by the substrate, as well quest the theoretical foundation of this method. Our preceded results have proven this project to be feasible in both theory and experiment.