Perylene Diimide Bearing Different Trialkyl Silyl Ethers: Impact of Asymmetric Functionalization on Self-Assembly into Nanostructures

For over a decade, a great amount of research effort has focused on controlling the size and shape of organic small molecule crystals, as these parameters impact physical and optoelectronic properties. A thorough understanding of how functionalization impacts assembly as well as guiding principles to control aggregation and self-assembly are vital to producing novel organic nanostructures for electronic applications such as organic photovoltaics (OPVs). Herein, we study the influence of unsymmetrical functionalization of perylene diimide (PDI) on self-assembly. The guiding hypothesis of this work is that the identity of the pendant functionalities will impact the size, aspect ratio, and surface properties of the resulting assemblies. Twelve asymmetrically functionalized PDI molecules are reported, in which the length of the alkyl substituents at the imide position is varied, and include alcohol and silylated alcohol functionalities at the end of the alky chain. Morphologies of these self-assembled structures were characterized by scanning and transmission electronic microscopy; crystallinity was verified by powder X-ray diffraction, and the optoelectronic and thermal properties are also reported. On the basis of the functionality of the PDI molecules, different shaped assemblies are prepared, including high aspect ratio structures with widths ranging from 0.1 to 2.5 μm and lengths 1-800 μm.