Cyclophane-Based π-Stacked Polymers

Abstract

This chapter focused on the synthesis and fundamental properties of π-stacked polymers, which consist of the stacked π-electron systems created by the [m.n]cyclophane, in particular [2.2]paracyclophane, in the polymer main chain. Our recent works in this field are mainly focused on due to the limited examples, and their characteristic features are summarized. Incorporation of the [2.2]paracyclophane skeleton into a π-conjugated polymer backbone leads to a π-stacked structure. Pseudo-para-, pseudo-ortho-, and pseudo-geminal-disubstituted [2.2]paracyclophanes allow the construction of various π-stacked conformations such as straight, zigzag, and fully stacked structures. Optically active π-stacked polymers comprising the planar chiral pseudo-ortho-disubstituted [2.2]paracyclophanes open a new frontier in chiral polymer chemistry. Common π-conjugated polymers have a set of HOMO (valence band) and LUMO (conduction band) energy bandgaps, whereas in the π-stacked polymers each π-electron system has its own HOMO–LUMO energy bandgap. Various aromatic groups can be incorporated into polymers; therefore, energy and charge transfer through the polymer chain can be controlled by appropriate tuning of the bandgaps and energy levels of the stacked π-electron system. We hope that this new class of π-stacked polymers can make a fundamental contribution to the field of molecular electronics in the form of single molecular wires.