Mechanically-Robust and High-Performance Thin Film Transistors with Regioregular-<i>block</i>-Regiorandom Poly(3-hexylthiophene) Copolymers

We develop mechanically-robust and high-performance organic thin film transistors (OTFTs) based on poly(3-hexylthiophene) (P3HT) regioblock copolymers (block-P3HTs). These block-P3HTs consist of regioregular (rre) and regiorandom (rra) P3HTs, where the crystalline rre block allows efficient charge transport while the amorphous rra block provides mechanical robustness and inter-domain connection. A series of block-P3HTs, having different molecular weight (M_n) of rra blocks with fixed M_n of rre blocks, are prepared and they all exhibit high hole mobility due to the formation of well-developed edge-on crystallites. In addition, mechanical robustness of block-P3HT thin films is remarkably enhanced with the longer rra block, finally leading to 30.2% of elongation at break, which is 100 times higher than rre P3HT homopolymer. In particular, the noticeable enhancement of both elongation at break and toughness is observed between the M_n of rra block, 8 and 20 kg mol^-1, indicating that the critical molecular weight of rra P3HT plays an important role in mechanical response of the block-P3HT thin films. This study provides good strategies for high-performance soft electronics to improve the mechanical properties of electroactive materials without disruption of optoelectrical properties.