Balancing the Mechanical and Optoelectronic Properties of Light-Emitting Copolymers via Precise Control of Soft-to-Rigid Segment Ratio

Abstract

Light-emitting polymers with tunable mechanical properties are desirable for flexible optoelectronic devices. Herein, adopting the synthetic routes for polyurethanes (PU), we successfully developed a series of blue light-emitting copolymers by incorporating diarylfluorene-based trimers (rigid segments) and polydimethylsiloxane (PDMS) (soft segments) with precisely tunable mechanical properties from brittle to viscoelastic behavior. The impact of varied soft-to-rigid ratio on the balance of mechanical and optoelectronic properties were thoroughly investigated combining thermodynamic analysis, tensile testing of free-standing films and solution-processed polymer light-emitting diodes (PLED). The copolymers maintained efficient deep-blue emission regardless of segment ratio, and PLED based on the copolymers (content of PDMS < 30%) also exhibited comparable performances with a turn-on voltage of ~4 V. This study highlights the importance of achieving optimal balance between mechanical and optoelectronic properties in materials design, providing critical insights for developing flexible optoelectronic polymers.