Stable Open-Shell Polymers via Precise Introduction of Oxygen Radicals with Quinoidal Resonance on Conjugated...

The classic donor-acceptor (D-A) conjugated polymers are highly developed in organic electronics for their potential in organic light-emitting diodes, organic field-effect transistors, and organic photovoltaics. Since 2017, we reported aggregation-induced radical (AIR) and ground-state charge transfer (GSCT), which render these materials sensitive to oxygen doping and low stability in devices. In this work, we propose a strategy to design oxygen-rich conjugated radical (ORCR) by intentionally incorporating oxygen-centered radicals into the D-A backbones. A series of D-A polymers were synthesized via atom-economical direct arylation polymerization, followed by quantitative post-synthetic dealkylation to yield the corresponding oxygen-radical polymers. The introduction of oxygen radicals showed highly lowered bandgap and highly quenched fluorescence, signaling an enhanced non-radiative relaxation pathway. Electron paramagnetic resonance confirmed their high spin concentration with high air stability. Notably, BDTO₂-BBT exhibited an extraordinary photothermal conversion temperature of 170°C under 808 nm laser irradiation for 60 s, maintaining performance over multiple cycles. This study reported robust open-shell ORCR materials but also provides a simple design paradigm for stable high-spin organic radical semiconductors.