Strain-Responsive and Self-Healing Chiral Polymer Vitrimer Composites: Tunable Circular Dichroism and Mechanochromic Recovery in Self-Standing Films

Controlling the absorption and emission of circularly polarized light (CPL) in free-standing polymer thin films is central to next-generation chiral photonic and optoelectronic technologies. Still, it remains hindered by limited optical activity, weak mechanical robustness, and poor scalability. Here, we present vitrimer-based chiral self-standing films (P*VFs), synthesized <i>in situ</i> with a fluorene-thiophene chiral polymer additive, that combine mechanical stability, reprocessability, self-repairing properties, and tunable chiroptical responses. The vitrimer matrix confines hierarchically ordered helical domains, enhancing circular dichroism (CD) while suppressing linear anisotropy, as confirmed by CD spectroscopy and Mueller matrix ellipsometry. These films exhibit reversible strain-dependent CD switching, with ellipticity decreasing under stretching (5% strain) and recovering upon stress release across multiple cycles. In parallel, the dynamic vitrimer network enables mechanochromic self-healing, restoring both optical functionality and mechanical integrity. These materials are not simple blends; even a ∼ 1 wt % chiral polymer dopant in a hard-soft polymer/vitrimer triples the CD response, surpassing that of the pure polymer and thereby boosting the macroscopic chiral properties. This synergy of chirality, vitrimer dynamics, and hierarchical self-assembly yields multifunctional films that outperform spin-coated chiral polymers, offering a versatile platform for adaptive optics, stress-sensing devices, reconfigurable photonics, and resilient coatings in extreme environments.