Engineering solvent resistance in semiconducting polymer films through UV-induced polydiacetylene crosslinking

Abstract

Semiconducting polymers have emerged as versatile, tunable materials for next-generation optoelectronic devices, offering advantages over traditional inorganic semiconductors in applications from energy harvesting to bioelectronics. Particularly, their compatibility with scalable manufacturing techniques, including solution-based deposition and printing methods, positions them favorably for commercial adoption. Among the recent strategies used to enhance the mechanical, thermal, and electronic properties of these polymers, crosslinking—through covalent or non-covalent interactions—has been shown to be especially efficient for improving their stability, robustness, and functionality. Notably, crosslinking can also confer solvent resistance to these materials, a crucial feature for multilayer device fabrication that can help to maintain layer integrity during sequential printing processes. In this work, we synthesized a diketopyrrolopyrrole–carbazole conjugated copolymer functionalized with 1,3-butadiyne groups on the carbazole side chains, enabling covalent crosslinking via UV-induced topochemical polymerization into polydiacetylene (PDA) networks. Raman spectroscopy confirmed PDA crosslink formation, while atomic force microscopy and grazing incidence wide-angle X-ray scattering were used to demonstrate the preservation of polymer film morphology post-crosslinking. Quantitative nanomechanical mapping revealed significant enhancements in mechanical properties upon PDA formation. Additionally, sequential deposition and crosslinking cycles demonstrated the robust solvent resistance of crosslinked films, confirmed by UV-vis spectroscopy. These results highlight topochemical polymerization of diacetylenes as an effective strategy for engineering mechanically robust, solvent-resistant conjugated polymer films suitable for advanced multilayer organic electronics.