Helical Nanocavity-Driven Upconversion Circularly Polarized Luminescence with Efficient Triplet Dynamics in Poly(methyl methacrylate) Stereocomplexes

Triplet–triplet annihilation photon upconversion circularly polarized luminescence (TTA-UC-CPL) in solid-state materials remains challenging because the molecular ordering required for chirality often compromises triplet energy transfer and oxygen tolerance. Herein, we report a poly(methyl methacrylate) stereocomplex that forms a helical nanocavity coencapsulating a chiral dopant, an emitter, and a photosensitizer. X-ray diffraction, electronic circular dichroism, and vibrational circular dichroism measurements reveal cooperative confinement of the chromophores within a helical nanocavity of preferred handedness. The stereocomplex exhibits efficient UC-CPL under 532 nm excitation with a threshold intensity of 106 mW cm–2. The apparent triplet decay rate in the presence of the emitter is approximately 40 times faster than oxygen quenching, enabling efficient UC-CPL even in air containing oxygen. Furthermore, the material retains its dissymmetry factor over a wide excitation intensity range and can be processed into three-dimensional architectures while preserving UC-CPL activity. This work establishes helical polymer nanocavities as an effective platform for oxygen-tolerant solid-state chiroptical upconversion materials.