Giussani Ester, Brambilla Luigi, Fazzi Daniele, Sommer Michael, Kayunkid Navaphun, Brinkmann Martin, Castiglioni Chiara
Center for NanoScience and Technology CNST, IIT@PoliMi , via Pascoli 70/3, 20133 Milano, Italy.
J Phys Chem B. 2015 Feb 5;119(5):2062-73. doi: 10.1021/jp511451s. Epub 2015 Jan 22.
Epitaxially grown highly oriented crystalline films, named form I and form II, and spin-coated films of poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}, P(NDI2OD-T2), have been investigated through infrared vibrational spectroscopy techniques (infrared absorption in double transmission at normal incidence (IRA-TR) and reflection absorption infrared spectroscopy at grazing angle incidence (RAIRS)) to get access to polymer chain orientation and structure. An analytic model to correlate the experimental intensities of the IR bands with structural parameters has been developed and applied for the three film morphologies. While spin-coated and form I films show P(NDI2OD-T2) chains lying parallel to the substrate in the face-on arrangement, form II films feature a structure with chains tilted out from the surface. The combined experimental and theoretical methodology gives insights into the local molecular orientations of naphthalene diimide (NDI2OD) and bithiophene (T2) counits. This approach can be easily extended to a variety of organic polymer semiconductors, allowing one to directly correlate molecular structure to properties such as charge transport, which is of fundamental relevance for developing quantitative models for applications in organic electronics and photovoltaics.
通过红外振动光谱技术（垂直入射双透射红外吸收（IRA-TR）和掠角入射反射吸收红外光谱（RAIRS））研究了外延生长的高度取向结晶薄膜（命名为晶型I和晶型II）以及聚{[N,N'-双(2-辛基十二烷基)-萘-1,4,5,8-双(二羧酸二亚胺)-2,6-二亚基]-alt-5,5'-(2,2'-联噻吩)}（P(NDI2OD-T2)）的旋涂薄膜，以了解聚合物链的取向和结构。已开发出一种将红外波段的实验强度与结构参数相关联的分析模型，并将其应用于这三种薄膜形态。虽然旋涂薄膜和晶型I薄膜显示P(NDI2OD-T2)链以面朝上的排列方式平行于基底，但是晶型II薄膜的特征是链从表面倾斜出来的结构。实验和理论相结合的方法深入了解了萘二亚胺（NDI2OD）和联噻吩（T2）链段的局部分子取向。这种方法可以很容易地扩展到各种有机聚合物半导体，使人们能够直接将分子结构与电荷传输等性质相关联，这对于开发有机电子学和光伏应用的定量模型具有根本意义。
