正确理解纳米尺度下聚合物分子运动是纳米材料科学与技术发展的基础。尽管在20多年的时间里对受限聚合物体系分子运动进行了大量的研究，但存在许多无法统一的实验现象。如SiO2支撑的PS薄膜其Tg与扩散系数均随厚度的下降而下降；聚合物薄膜Tg偏离本体是否与分子量有关取决于化学结构等等。本项目是申请者在高分子表面与界面、受限体系分子运动的长期研究积累基础上提出，认为可能原因是自由表面、聚合物/基底界面层分子运动在受限聚合物体系中占主导的地位，决定了其整体的分子运动。而表面与界面具有特殊的物理化学性质，有着本体不同的分子运动规律。本项目将利用分子标记、表面敏感SFG等技术手段研究聚合物自由表面、界面不同尺度的分子运动及其与聚合物结构的关系。研究不同结构聚合物自由表面效应、基底效应的传递深度。关联聚合物自由表面、界面的分子运动与受限体系整体分子运动尺寸依赖性的关系。揭示纳米受限聚合物分子运动的本质。

With the development of nanomaterial and nanotechnology, dynamics of nanoconfined polymer continue to be the subject of significantly theoretical and practical interests in recent two decades. Although the dynamics of polymer chain in nanoscale have been extensively investigated, there are lots of confused even inconsistent experimental results. For example, a long-standing question concerns the inconsistent thickness dependences demonstrated by the Tg and coefficient of self-diffusion or diffusivity D of polystyrene films supported by silica (PS/SiOx). Based on our previous researches, we here propose that the chain dynamics near free surface or polymer/substrate interface is an important breakthrough to understand polymer properties in nanoconfinement, due to the specific physicochemical properties and chain dynamics at free surface or polymer/substrate interface. When the scale of polymer materials decrease to tens of nanometer, the volume fraction of free surface or interface increase dramatically, and the properties of polymer nanomaterial will be dominated by free surface and interface. In this project, fluorinated tracer-labeled technology and surface/interface sensitive Sum Frequency Generation (SFG) will be utilized to investigate different length scales polymer dynamics at free surface/interface and their relationships to polymer structure. The utmost distance of polymer dynamics perturbation caused by free surface and interface at different structure polymer systems will be probed. And the relationship between polymer dynamics at free surface/interface and the size-dependent dynamics of polymer film will be also explored. The aim of the study is to elucidate the characteristics and the nature of polymer dynamics in nanoscopic confinement. These studies would be helpful in reconciling the controversies of results reported by various researcher groups, as well provide theoretical basis to design and modulate the physical properties of polymer nanomaterials.