Mechanically Tough and Durable Poly(siloxane imide) Network Elastomer for Stretchable Electronic Applications

Abstract

In the development of organic electronics, polyimide (PI)-based materials have drawn significant research attention due to their remarkable features, including a simple synthesis, solution processability, outstanding thermal stability, and respectable mechanical strength. Despite the good electronic performance of PI-based materials, a high elastic modulus over 1 GPa and a modest elongation at break of the conventional PIs have restricted their applications in stretchable electronics. To address this issue, poly(siloxane imide) (PSI) with a soft siloxane chain has been proposed to achieve a significantly reduced modulus and an increased stretchability. However, previous works revealed the weak mechanical strength of PSI, in which the latest reported stretchable device comprising PSI thin film could only sustain a tensile strain below 40%. Herein, in the present study, we developed a thermally stable and mechanically durable PSI network through the polyaddition–condensation reaction between 4,4′-oxidiphthalic anhydride, aminopropyl-terminated polydimethylsiloxane, and varied amounts of 1,3,5-triaminophenoxybenzene (TAB) as a cross-linker. An optimal PSI network with 11.1% TAB exhibited a high decomposition temperature at 426 °C, a softening temperature over 200 °C, an elongation at break over 400%, a superior toughness at 13.29 MJ m–3, and low strain hysteresis. Owing to the improved solubility of PSI, the polymer elastomer can be processed as a substrate material or thin-film active layer with good mechanical properties. Finally, all-solution-processed, stretchable, and durable electronic devices including resistive memory and organic field-effect transistors were fabricated using the designed PSI with an affordable and feasible solution process. This work underlines the importance of network design on soft polymers to create mechanically tough and durable elastomers for next-generation stretchable electronics.