Blending Chiral Small Molecules to Achiral DPP-Based Conjugated Polymer to Induce Chiroptical Properties

Conjugated polymers have been developing due to their electrical and optical properties. Furthermore, the chiroptical properties with conjugated polymer have distinguished characteristics of selectivity based on handedness. There are many methods to induce chirality to conjugated polymers, but blending chiral small molecules to achiral conjugated polymers is one of promising and simple methods via supramolecular interactions. By utilizing this method, the induced chirality to conjugated polymer can be applied to optoelectronic devices for multiple signal due to differences in absorption depending on right or left circularly polarized light at the same wavelength.<br/>In this study, diketopyrrolopyrrole(DPP) based polymers with charge transport, NIR absorption property, PDVT-10 is blended with chiral small molecules, (<i>R</i>)- or (<i>S</i>)-1,1′-Binaphthyl-2,2′-diamine((<i>R</i>)- or (<i>S</i>)-BN). The chiroptical characteristics are based on the blending ratio and opposite properties between (<i>R</i>)- and (<i>S</i>)-BN with PDVT-10 in solution. In thin films, the presence of (<i>R</i>)- or (<i>S</i>)-BN affects PDVT-10, leading to the emergence of a new peak in circular dichroism on near-infrared range and a peak shift in UV-Vis spectrometer. Moreover, it is possible to invert the absorption of circular dichroism and shift UV-Vis peaks through annealing condition. The formation of helical structures through supramolecular assembly on blended films is observed on AFM images and the chiral orientation of BN is transferred to the morphology of PDVT-10 confirmed by 2D-GIWAXS analysis. Moreover, a phototransistor based on an organic field-effect transistor (OFET) demonstrates difference sensitivity to right or left circularly polarized light with a wavelength of 850 nm in the near-infrared range. In particular, the optical activity of semiconductors in the near-infrared range, combined with chirality, is significantly important due to their ability for long-range optical communication, skin penetration, and night vision. In conclusion, this blending method could be proposed as a simple and straightforward approach to induce new chiroptical properties to achiral conjugated polymers.