Synthesis and properties of helically-folded poly(arylenediethynylene)s

Aryl-based helical foldamers with diacetylene linkers are not only capable of providing physically large diameter cavities, but can also showcase a variety of properties, such as structural transformation, that the corresponding foldamers with simple acetylene linkers cannot achieve. Here, we have developed helical foldamers based on poly(arylene diethynylene)s (poly-ArDEs), in which each aryl group is connected by diacetylene linkers. The poly-ArDEs with naphthalene, pyrene and pyridine as a central aryl group each expressed unique properties. The foldamers incorporating naphthalene and pyrene stabilized the helical folding in a variety of solvents. In addition, the concentration-dependent emission by the pyrene polymer was completely different from that of the monomer due to its folded three-dimensional structure. The pyridine-based polymer showed unexpected solvent dependence and stimuli responsiveness, suggesting possible applications in sensing. These properties were elucidated in detail by UV–Vis absorption, fluorescence, and circular dichroism (CD) spectra, molecular dynamics calculations, and titration experiments.