In Situ Study of Molecular Aggregation in Conjugated Polymer/Elastomer Blends toward Stretchable Electronics
Dongle Liu, Zicheng Ding, Yin Wu, Shengzhong Liu, Yanchun Han, Kui Zhao
Abstract
Conjugated polymers exhibit potential for the development of next-generation stretchable electronics. However, an understanding of molecular aggregation during solution processing and its influence on thin-film morphology is still underexplored. Here, the influences of molecular aggregation on the film morphology, phase purity and phase separation, and mechanical and electrical properties of a partially compatible blend of conjugated polymer poly(indacenodithiophene-co-benzothiadiazole) (IDTBT) and elastomer polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) were systematically examined. When using high-boiling-point (b.p.) solvents, namely, toluene and chlorobenzene, large-scale liquid–liquid phase separation predominates IDTBT aggregation in blend films, leading to isolated IDTBT domains and, thus, poor electrical performance. In contrast, fast solvent evaporation from low-b.p. chloroform suppresses large-scale phase separation and enhances IDTBT aggregation via nanoconfinement effect. The nanoconfinement effect enables us to achieve a stretchable film with a low elastic modulus of 72 MPa, a respectable crack-onset strain of 326% (ca. 3–14 times larger than the neat IDTBT films), and a negligible loss of mobility (ca. 0.7 cm2 V–1 s–1) at 100% strain. These results provide insight into molecular aggregation and thin-film morphology in conjugated polymer/elastomer blends for high-performance stretchable electronics.