单分子荧光法研究超薄膜基底界面层长程作用的分子机理及动力学性质的分布

聚合物薄膜的玻璃化转变一直是高分子物理的研究重点和难点。目前对薄膜的玻璃化转变主要采用层状模型来解释，认为基底界面层在很大程度上决定了聚合物薄膜内动力学性质的分布。由于常用实验手段都是整体平均法，难以从分子层面揭示基底界面层长程作用的机理及薄膜各层内动力学性质的分布。本项目将采用高灵敏度和高分辨率的单分子荧光散焦成像技术，基于频谱分析方法，系统地调节基底界面层聚合物的分子量、分子结构和覆盖层的厚度，研究分子间缠结作用对荧光分子转动能力的影响，揭示基底界面层长程作用的分子机理及不同分子量聚合物形成的基底界面层长程作用的范围；通过调节～10nm荧光标记层在薄膜中位置和荧光分子的尺寸，研究薄膜内不同位置局域动力学性质的差异，揭示沿膜厚方向局域动力学性质的分布及松弛运动单元尺寸。本项目将会建立薄膜体系动力学性质分布的模型，深化对受限聚合物薄膜玻璃化转变的认识，为纳米薄膜器件性能的优化提供理论指导。

The glass transition behavior of thin polymer films deviating from that of the bulk is one of the deepest unsolved problems in polymer physics. Now, layer model was widely used to explain the glass transition behavior of thin polymer films, in which the interfacial layer plays an important role in determining the distribution of dynamic properties along the depth direction. But traditional techniques are ensemble, which interrogate a large of molecules necessarily average over dynamic heterogeneity and can't reveal the molecular mechanism of the long-range effect of interfacial layer and distribution of dynamic properties in every layer of thin films from molecular level. Owing to its high sensitivity and high resolution, the defocused single molecule fluorescence will be used in the proposed research. Based on the spectral analysis method, the impact of molecular entanglement on the mobility of probes is studied by controlling the molecular weight and structure of interfacial layer and thickness of overlayer in order to reveal the molecular mechanism of the long-range effect of interfacial layer and the long-range perturbations of interfacial layer made of different molecule weight. After that, distribution of dynamic properties in every layer of the thin films and the sizes of segmental relaxation unit along the depth direction are also researched by adjusting the position of the layer (～10nm) doped with probes of different sizes. The proposed research will model the distributions of dynamic properties in thin films, further deepen our understanding of the glass transition behavior of thin polymer films and finally provide the theoretical guidance for optimizing performance of thin polymer films in industry.