The importance of the modulation of the elastomer properties on the structure and performance of conjugated polymer/elastomer blends

Physical blending with elastomers is a promising approach to improve the mechanical performance of conjugated polymers (CPs) without reducing their electrical performance, which is essential for stretchable flexible electronic devices. However, the effects of the properties of elastomers on the mechanical and electrical performance of CP/elastomer blend films remain unclear. Here, a stretchable semiconductor composite is systematically investigated, which is achieved by blending the brittle poly [4-(4,4-dihexadecyl-4H-cyclopenta [1,2-b:5,4-b′]dithiophen-2-yl)-alt-[1,2,5]thia-diazolo [3,4-c] pyridine] (PCDTPT) semiconductor with the thermosetting elastomer poly (dimethylsiloxane) (PDMS) containing different cross-linker contents. The cross-linker content affects the curing process of PDMS, thereby influencing the morphology and vertical phase separation structure of the PCDTPT/PDMS blend films and ultimately affecting their performance. By carefully modulating the properties of PDMS, a considerable phase separation structure, along with a network of small-sized nanofibers exhibiting long conjugation lengths or high backbone planarization, was obtained, resulting in blend films with electrical conductivity and crack onset strain (COS) values that are 2.7 times and 12.3 times greater than those of pure PCDTPT, respectively. Our findings demonstrate that precise control of cross-linker content serves as an effective strategy for modulating doping efficiency and achieving optimal performance of PCDTPT/PDMS blends. This work emphasizes the importance of the properties of elastomers on the performance of CP/elastomer blend films and provides valuable insights into appropriate elastomer selection for stretchable semiconducting thin films that simultaneously possess excellent mechanical and electrical properties.