Free volume distribution at polymer-solid interfaces

聚合物-固体界面在从连接技术和有机电子到纳米复合材料的许多应用中起着至关重要的作用。然而，目前对界面区（界面相）的结构、形成和性质的理解是有限的，界面区可以延伸到几μm到体相中。该项目旨在通过深度分辨正电子湮没寿命谱研究聚合物固体界面的自由体积分布，为聚合物固体界面的结构和扩展提供新的见解。已经证明了巨大的潜力的帕尔斯技术结合一个缓慢的正电子束选定的模型系统，我们现在计划延长测量基板与金属和货车范德华相互作用和其他聚合物，包括聚丁二烯，这将允许直接比较计算机模拟和其他实验技术。测量还将扩展到通过UV交联制备的交联聚合物，以避免硬化剂效应。在方法上，除了先进的轮廓模拟，我们计划测量的玻璃化转变温度Tg在整个界面的深度配置文件。在恒定的注入能量作为温度的函数的测量将不仅产生Tg作为从衬底的距离的函数，而且还提供低于和高于Tg的热膨胀系数的曲线，因此揭示了作为深度的函数的聚合物动力学的重要信息。

Polymer-solid interfaces play a crucial role in many applications ranging from joining technology and organic electronics to nanocomposites. However, the present understanding of the structure, formation, and properties of the interfacial region (interphase), which can extend up to several μm into the bulk, is limited. The project aims at providing new insight into the structure and extension of polymer solid interfaces via investigation of the free volume distribution by means of depth resolved positron annihilation lifetime spectroscopy. Having demonstrated the great potential of the PALS technique in conjunction with a slow positron beam for selected model systems we now plan to extend the measurements to substrates with metallic and van der Waals interaction and to other polymers including polybutadiene which will allow direct comparison with computer simulations and other experimental techniques. The measurements will also be extended to crosslinked polymers prepared by UV crosslinking to avoid hardener effects. Methodologically, in addition to advanced profile simulations, we plan to measure depth profiles of the glass transition temperature Tg across the interface. Measurements at constant implantation energy as function of temperature will not only yield Tg as function of the distance from the substrate, but also provide profiles of the coefficients of thermal expansion below and above Tg and hence reveal important information on the polymer dynamics as function of depth.