Conjugated Multiblock Copolymers and Microcracked Gold Electrodes Applied for the Intrinsically Stretchable Field-Effect Transistor.

The rise of flexible electronic devices has led to extensive research into conjugated polymer structural engineering. Integrating polymer channels and contact electrodes, warranting high stretchability, is still critical, and the microcracked gold technique provides a potential strategy to integrate them. Conjugated block copolymers have gained significant attention due to their high flexibility, allowing for tailored polymer structures to meet the specific requirements of different device characteristics. In this study, novel N-type multiblock copolymers (multi-BCPs) composed of rigid poly(naphthalene diimide--bithiophene) and flexible polyisobutylene segments were successfully synthesized as polymer semiconductors for the first time. The materials are named based on the weight fraction of soft segments: NDI (0 wt %), mAB73 (27 wt %), and mAB60 (40 wt %). The study explores the mechanical properties, crystallinity, and electrical performance of flexible multi-BCPs. The results show that introducing soft segments significantly enhances stretchability, with crack-onset strains beyond 100% because of their low elastic moduli of 40-50 MPa. Furthermore, the OFET device of mAB73 achieves unchanged mobility under 100% strain, outperforming mAB60 due to excessive polyisobutylene blocks. At the end of this study, an integrated stretchable device with high stretchability is fulfilled by utilizing the microcracked gold technique to combine the multi-BCP channels and contact electrodes. The integrated device can be applied to biomedical electronics without toxic or corrosive electrode materials. The influencing factors, including contact resistance, channel charge mobility, and electrode resistance, are systematically studied to investigate the integrated device's mobility-stretchability relationship. The results indicate that the contact resistance between the multi-BCP channels and contact electrodes is essential to the device's performance. Among these, mAB73, containing soft segments, exhibits more stability than NDI due to the microcracked gold electrodes with infiltrated gold nanoparticles in the rubbery channel surface. Appropriately incorporating soft segments significantly enhances mobility retention under tensile strains, highlighting the potential of multi-BCP designs in stretchable electronic applications.