Quantum Coherence and Chirality-Induced Photon and Electron Spin Polarization in Donor-Acceptor Bottle-Brush Polymers

Spin-spin coupling and charge transfer are enriched in open-shell donor-acceptor (D-A) polymers due to the interplay of intrachain and interchain interactions. However, due to spin decoherence caused by the strong interchain interaction, quantum coherence and Rabi oscillations remain rarely observed in open-shell D-A polymers. Here, we report photophysical, quantum coherence, and magnetic properties in a series of bottle-brush-like polyradicals ([D^+•A^-•]_n) composed of π-conjugated narrow-band gap backbones of alternating strong electron acceptors (benzobisthiadiazole) and strong electron donors (pyrroledithiophene), from which polyesters are grafted via controllable ring-opening polymerization. The impact of the side-chain chirality on the optical and spin properties of the D-A backbones has been studied in these bottle-brush polymers. The spin-lattice and spin-spin relaxation times as well as the Rabi frequencies and the magnetic properties of the polyradicals as electron spins in the backbones of [D^+•A^-•]_n show strong dependence on the chain length and the rigidity of the polymer side chains.