Influence of π–π stacking on the self-assembly and coiling of multi-chromophoric polymers based on perylenebis(dicarboximides): an AFM study

The assembly behavior at surfaces of very stiff polyisocyanopeptides (PICs) functionalized with semiconducting perylenebis(dicarboximide) (PDI) side chains has been investigated by atomic force microscopy. These multi-chromophoric arrays are unique as they combine an ultra-stiff central polymer main-chain scaffold upon which the PDI chromophores can self-organize through π–π stacking, making them interesting and versatile building blocks for nanoelectronics. In this paper we compare three PIC derivatives featuring different side groups: M1—no chromophores, M2—chromophores capable of π–π stacking, and M3—chromophores where the stacking is hindered by the presence of bulky substituents in the bay area of the PDI. The effect of the different side functionalizations on the macromolecule assembly at surfaces was compared by studying the morphology and aggregation tendency of all three polymers when adsorbed on silicon, mica and graphite substrates. Making use of nano-manipulation of these functional rods with the AFM tip gave insight into the polymer structure and its coiling behaviour.