The translational diffusion of molecules dispersed into polymer matrices slows down tremendously when approaching a nonrepulsive interface. To unravel the origin of this phenomenon, we investigated the diffusion of molecular probes in the direction normal to an adsorbing wall. Using adsorbed polymer layers as matrices, we were able to decouple interfacial and finite size effects and determined the relation between the diffusion time and the area available at the polymer/solid interface. Based on the results of our investigation, we present a physical picture, suggesting that the reduction in diffusion rate is correlated to the degree of chain adsorption onto the substrate, that is, the density of surface obstacles encountered by tracer molecules.

中文翻译：

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障碍物的密度影响吸附聚合物层中的扩散

当接近非排斥界面时，分散到聚合物基质中的分子的平移扩散会大大减慢。为了揭示这种现象的起源，我们研究了分子探针在垂直于吸附壁的方向上的扩散。使用吸附的聚合物层作为基质，我们能够解耦界面和有限尺寸效应，并确定扩散时间与聚合物/固体界面处可用面积之间的关系。根据我们的调查结果，我们展示了一幅物理图片，表明扩散速率的降低与链吸附到基板上的程度相关，即示踪分子遇到的表面障碍物的密度。