Mechanochemically Induced Circularly Polarized Luminescence from Polymers.

Abstract

Achieving diversified optical signals in polymer mechanochemistry remains a significant challenge, particularly within the area of light polarization. This work pioneers the development of mechanochemically induced circularly polarized luminescence (MICPL) in polymers. We have designed crosslinked polymer networks by photopolymerizing achiral mechanophores (Diels-Alder adducts of maleimide and anthracene derivatives) with the chiral monomer L(-)-bornyl acrylate (LBA). Mechanical compression triggers the retro-Diels-Alder reaction of the mechanophores, releasing fluorophores. Crucially, the applied force simultaneously promotes the aggregation of these released fluorophores and transfers the nonreciprocal chirality inherent in the compressed chiral polymer matrix (PLBA) to these aggregates, resulting in bright, force-dependent CPL emission with a high luminescence dissymmetry factor of up to 10-2. The versatility of this strategy was demonstrated with a series of mechanophores with varying electronic structures and copolymer matrix, enabling tunable CPL colors spanning from blue-violet to green to yellow-orange, and a ternary system achieving white CPL. The MICPL property was retained in copolymer systems (e.g., copolymers with achiral monomer methyl acrylate), demonstrating its potential as a macromolecular chiral optical probe for multimodal stress reporting. These findings resolve questions about mechanical force-regulated chirality and offer a platform for on-demand CPL materials.