Leveraging Non-Covalent Interactions to Control the Morphology and Electrical and Mechanical Properties of Stretchable Semiconducting Composites

Physical blending conjugated polymers (CPs) with elastomers has been established as an effective method for enhancing the stretchability of semiconductors. However, predictable control of the morphology for incompatible polymer rubber blends remains a challenge. In this work, we demonstrated the control of phase separation size of CP/elastomer composites by strategically controlling the location sites of H-bonding functional groups in CPs and elastomers, while investigating their effects on mechanical and electrical properties. We incorporated amide functional groups into a DPP-based semiconducting polymer (DPPTVT-A) and polyisobutylene-based elastomer (PIB-A) to enable inter- and intraphase hydrogen bonding (H-bonding) cross-links within CP/elastomer composites. Along with their nonamide counterparts, we fabricated four different CP/elastomer composites, DPPTVT-A/PIB-A, DPPTVT-A/PIB, DPPTVT/PIB-A, and DPPTVT/PIB, with dual-, uni-, and non-H-bonding cross-links and compared their phase behavior and electronic and mechanical properties. The location of the H-bonding greatly influenced the property of the semiconducting rubber as characterized by scattering, spectroscopy, and electrical characterization. Importantly, we found that creating a H-bonding cross-link into both domains of CP/elastomer composites can not only improve energy dissipation upon stretching but also maintain the electrical performance when applying high tensile stress. This work provides a comprehensive study of the morphology of CP/elastomer composites, offering valuable insights into the future design of stretchable CP/elastomer composites.