We report the synthesis, morphology, and properties of poly(3-hexylthiophene)-block-poly(butyl acrylate) (P3HT-b-PBA) for stretchable electronics applications, which are consisted of semiconducting P3HT and low glass transistion temperature (T-g) PBA blocks. The P3HT-b-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 (GIRD). 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-b-PBA(12k). The field effect transistor (FET) using P3HT-b-PBA as the active layer exhibited a high p-type mobility over 10(-2) cm(2) indicating its good charge transporting ability. Furthermore, the P3HT-b-PBA(6k) based FET under 100% strain had a high mobility of 2.5 X 10(-2) cm(2) V-1 s(-1) with an on/off ratio of 7.2 X 10(6), and it maintained over 10(-2) cm(2) 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.