Chirality transfer from molecularly dispersed versus supramolecularly assembled chiral inducers to achiral conjugated polymer semiconductors.

Abstract

Chirality transfer from chiral inducers to achiral π-conjugated polymers provides a versatile route to chiroptical semiconductors; however, how the aggregation state of the chiral inducer affects this process remains unclear. Here, we address this question using a chiral π-conjugated organogelator whose aggregation state can be controlled by the casting solvent and incorporated into the same achiral conjugated polymer host. This model system enables direct comparison of chirality transfer from molecularly dispersed and supramolecularly assembled inducer states while maintaining the molecular identities of both components. Contrary to the expectation that stronger intrinsic chiroptical activity of the chiral inducer would lead to stronger chirality transfer, supramolecular assemblies with pronounced chiroptical activity produced only a weak chiroptical response in the polymer host. In contrast, a more molecularly intermixed inducer state generated a pronounced bisignate circular dichroism response at the polymer transition, despite the negligible intrinsic circular dichroism of the inducer. Steady-state optical measurements and helicity-resolved femtosecond transient absorption spectroscopy suggest that this response arises from helicity-selective redistribution of the existing polymer oscillator strength through contact-enabled electronic-state mixing. These findings highlight the aggregation state of the chiral inducer as an important factor affecting chirality transfer in π-conjugated polymer semiconductors.

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