Stretchable Conjugated Rod–Coil Poly(3-hexylthiophene)-<i>block</i>-poly(butyl acrylate) Thin Films for Field Effect Transistor Applications

We report the synthesis, morphology, and properties of poly­(3-hexylthiophene)-<i>block</i>-poly­(butyl acrylate) (P3HT-<i>b</i>-PBA) for stretchable electronics applications, which are consisted of semiconducting P3HT and low glass transistion temperature (<i>T</i>_g) PBA blocks. The P3HT-<i>b</i>-PBA thin films self-assembled into fibrillar-like nanostructures and maintained the edge-on oreientation even at a low P3HT composition, based on the results from atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD). By varying the P3HT/PBA ratio, the tensile modulus decreased as the block length of PBA increased, from 0.93 GPa for P3HT to 0.19 GPa for P3HT-<i>b</i>-PBA_12k. The field effect transistor (FET) using P3HT-<i>b</i>-PBA as the active layer exhibited a high p-type mobility over 10^–2 cm² V^–1 s^–1, indicating its good charge transporting ability. Furthermore, the P3HT-<i>b</i>-PBA_6k based FET under 100% strain had a high mobility of 2.5 × 10^–2 cm² V^–1 s^–1 with an on/off ratio of 7.2 × 10⁶, and it maintained over 10^–2 cm² V^–1 s^–1 for 1000 cycles, suggesting the promising stability and reproducbility. The result demonstrated that the newly designed conjugated rod–coil block copolymers could have potential applications in stretchable electronic devices

Isoindigo-Based Semiconducting Polymers Using Carbosilane Side Chains for High Performance Stretchable Field-Effect Transistors

Isoindigo-based conjugated polymers, PII2T-C6 and PII2T-C8, with carbosilane side chains have been designed and synthesized for stretchable electronic applications. The carbosilane side chains offerred a simple synthetic pathway to evaluate long and branched side chains in high yields and were prepared with a six or eight linear spacer plus two hexyl or octyl chains after branching. The studied polymers showed a high charge carrier mobility of 8.06 cm² V^–1 s^–1 with an on/off current ratio of 10⁶ as probed using a top-contact transistor device with organized solid state molecular packing structures, as investigated through grazing-incidance X-ray diffreaction (GIXD) and atomic force microscopy (AFM) technique systematically. The studied polymers, more attractive, exhibited superior thin film ductility with a low tensile modulus in a range of 0.27–0.43 GPa owing to the branched carbosilane side chain, and their mobility was remained higher than 1 cm² V^–1 s^–1 even under a 60% strain along parallel or perpendicular direction to the tensile strain. Such polymer films, in addition, can be simultaneously operated over 400 stretching/releasing cycles and maintained stable electrical properties, suggesting the newly designed materials possessed great potential for next-generation skin-inspired wearable electronic application with high charge carrier mobility, low tensile modulus, and stable device characteristics during stretching