Researchers at Osaka University have designed "bifacial" ladder polymers - rigid, double-stranded polymer backbones with two deliberately different molecular faces - that show chirality-induced spin selectivity (CISS) exceeding ±90%, among the highest spin-polarization values reported for an organic chiral material.
The team's key innovation is a chirality-assisted synthesis: a C2-chiral bifacial monomer, built with two different substituents in a syn arrangement, is polymerized so the resulting ladder polymer keeps a uniform facial orientation along the entire chain. That regioselective, "one-handed" backbone is what earlier bifacial polymer designs struggled to control. Thin films of the resulting homochiral polymer self-assemble into one-handed supramolecular helices, with circular dichroism signals over 100 times stronger than non-ladder or monomeric references, and the chiral structure survives brief exposure to 300°C.
In spin-dependent transport measurements, the two enantiomers produced essentially mirror-image results: +90 ± 5% spin polarization for one (LP-(S,S)-1) and −88 ± 5% for the other (LP-(R,R)-1), with roughly an order-of-magnitude difference in current between the preferred and disfavored spin channels. That surpasses the group's own earlier chiral bifacial indacenodithiophene-based polymers, which topped out around 70% polarization, and puts this ladder-polymer platform near the top of reported CISS performance for organic materials - without requiring any magnetic materials or applied magnetic field to generate spin-polarized current.
The authors frame the result as a materials-design advance rather than a near-term device: scaling the films, integrating reliable electrodes, and confirming reproducibility and long-term stability are still open questions. But the combination of strong, controllable chirality and high spin selectivity makes bifacial ladder polymers a promising platform for organic spintronic components such as spin-selective sensors and spin-based information-processing elements.