James David, Higgins Anthony M, Rees Paul, Geoghegan Mark, Brown M Rowan, Chang Shion-Seng, Môn Dyfrig, Cubitt Robert, Dalgliesh Robert, Gutfreund Philipp
College of Engineering, Swansea University, Fabian Way, Crymlyn Burrows, Swansea, SA1 8EN, Wales, UK.
Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK.
Soft Matter. 2015 Dec 28;11(48):9393-403. doi: 10.1039/c5sm02008e.
Measurements have been performed on thermally equilibrated conjugated-polymer/insulating-polymer bilayers, using specular and off-specular neutron reflectivity. While specular reflectivity is only sensitive to the structure normal to the sample, off-specular measurements can probe the structure of the buried polymer/polymer interface in the plane of the sample. Systematic analysis of the scattering from a set of samples with varying insulating-polymer-thickness, using the distorted-wave Born approximation (DWBA), has allowed a robust determination of the intrinsic width at the buried polymer/polymer interface. The quantification of this width (12 Å ± 4 Å) allows us to examine aspects of the conjugated polymer conformation at the interface, by appealing to self-consistent field theory (SCFT) predictions for equilibrium polymer/polymer interfaces in the cases of flexible and semi-flexible chains. This analysis enables us to infer that mixing at this particular interface cannot be described in terms of polymer chain segments that adopt conformations similar to a random walk. Instead, a more plausible explanation is that the conjugated polymer chain segments become significantly oriented in the plane of the interface. It is important to point out that we are only able to reach this conclusion following the extensive analysis of reflectivity data, followed by comparison with SCFT predictions. It is not simply the case that conjugated polymers would be expected to adopt this kind of oriented conformation at the interface, because of their relatively high chain stiffness. It is the combination of a high stiffness and a relatively narrow intrinsic interfacial width that results in a deviation from flexible chain behaviour.
使用镜面反射和非镜面反射中子反射率对热平衡共轭聚合物/绝缘聚合物双层进行了测量。虽然镜面反射率仅对垂直于样品的结构敏感，但非镜面测量可以探测样品平面内掩埋的聚合物/聚合物界面的结构。使用扭曲波玻恩近似（DWBA）对一组具有不同绝缘聚合物厚度的样品的散射进行系统分析，从而能够可靠地确定掩埋的聚合物/聚合物界面处的固有宽度。对该宽度（12 Å ± 4 Å）的量化使我们能够通过参考自洽场理论（SCFT）对柔性链和半柔性链情况下平衡聚合物/聚合物界面的预测，来研究界面处共轭聚合物构象的各个方面。该分析使我们能够推断，在这个特定界面处的混合不能用采用类似于随机游走构象的聚合物链段来描述。相反，一个更合理的解释是共轭聚合物链段在界面平面内显著取向。需要指出的是，我们只有在对反射率数据进行广泛分析并与SCFT预测进行比较之后才能得出这个结论。并非仅仅因为共轭聚合物具有相对较高的链刚性，就预计它们会在界面处采用这种取向构象。正是高刚性和相对较窄的固有界面宽度的结合导致了与柔性链行为的偏差。
