A Photopatternable Conjugated Polymer with Thermal‐Annealing‐Promoted Interchain Stacking for Highly Stable Anti‐Counterfeiting Materials

Abstract Photoresponsive polymers can be conveniently used to fabricate anti‐counterfeiting materials through photopatterning. However, an unsolved problem is that ambient light and heat can damage anti‐counterfeiting patterns on photoresponsive polymers. Herein, photo‐ and thermostable anti‐counterfeiting materials are developed by photopatterning and thermal annealing of a photoresponsive conjugated polymer (MC‐Azo). MC‐Azo contains alternating azobenzene and fluorene units in the polymer backbone. To prepare an anti‐counterfeiting material, an MC‐Azo film is irradiated with polarized blue light through a photomask, and then thermally annealed under the pressure of a photonic stamp. This strategy generates a highly secure anti‐counterfeiting material with dual patterns, which is stable to sunlight and heat over 200 °C. A key for the stability is that thermal annealing promotes interchain stacking, which converts photoresponsive MC‐Azo to a photostable material. Another key for the stability is that the conjugated structure endows MC‐Azo with desirable thermal properties. This study shows that the design of photopatternable conjugated polymers with thermal‐annealing‐promoted interchain stacking provides a new strategy for the development of highly stable and secure anti‐counterfeiting materials.