Novel donor–acceptor rod–coil diblock copolymers of regioregular poly(3‐hexylthiophene) (P3HT)‐block‐poly(2‐phenyl‐5‐(4‐vinylphenyl)‐1,3,4‐oxadiaz‐ole) (POXD) are successfully synthesized by the combination of a modified Grignard metathesis reaction (GRIM) and atom transfer radical polymerization (ATRP). The effects of the block ratios of the P3HT donor and POXD pendant acceptor blocks on the morphology, field effect transistor mobility, and memory device characteristics are explored. The TEM, SAXS, WAXS, and AFM results suggest that the coil block fraction significantly affects the chain packing of the P3HT block and depresses its crystallinity. The optical absorption spectra indicate that the intramolecular charge transfer between the main chain P3HT donor and the side chain POXD acceptor is relatively weak and the level of order of P3HT chains is reduced by the incorporation of the POXD acceptor. The field effect transistor (FET) hole mobility of the system exhibits a similar trend on the optical properties, which are also decreased with the reduced ordered P3HT crystallinity. The low‐lying highest occupied molecular orbital (HOMO) energy level (–6.08 eV) of POXD is employed as charge trap for the electrical switching memory devices. P3HT‐b‐POXD exhibits a non‐volatile bistable memory or insulator behavior depending on the P3HT/POXD block ratio and the resulting morphology. The ITO/P3HT44‐b‐POXD18/Al memory device shows a non‐volatile switching characteristic with negative differential resistance (NDR) effect due to the charge trapped POXD block. These experimental results provide the new strategies for the design of donor‐acceptor rod‐coil block copolymers for controlling morphology and physical properties as well as advanced memory device applications.

In this study, the well-defined coil-rod-coil triblock copolymer poly(4-vinyltriphenylamine)b-poly(3-hexylthiophene)-b-poly(4-vinyltriphenylamin) (PTPA-P3HT-PTPA) was used as a surfactant for P3HT/PCBM (1:1) based solar cells. The power conversion efficiency of the device was enhanced from 3.9 to 4.4% in the presence of the 0-5% PTPA-P3HT-PTPA under illumination of AM 1.5G (100 mW/cm 2 ). The morphology variation and the balance of the hole/electron mobility accounted for such enhancement. In the P3HT/PCBM/PTPA-P3HT-PTPA ternary blends, the fiber-like structure was observed for surfactant ratios of 0-5%, while a sphere-like nanostructure was observed for the surfactant ratio of 1.5%. The sphere-like nanostructure led to a smaller domain size and enhanced interfacial area for charge separation as compared to the fiber-like structure. On the other hand, the increased hole mobility in the blend with the addition of PTPA-P3HT-PTPA resulted in the balanced hole and electron mobility (μ e /μ h ∼1.7 in comparison to the ratio of 3.6 without the surfactant). The incorporated PTPA-P3HT-PTPA surfactant not only extended the lifetime of solar cells but also reduced the PCBM aggregation upon annealing, resulting in better thermal stability. The DSC result confirmed the selective miscibility of the PTPA coil segment with PCBM. These results demonstrated the superior compatibilizing effect of the rod-coil triblock copolymers for solar cell applications.

An extra electric field is introduced below the spinneret in an electro­spinning setup for producing poly(3‐hexylthiophene) (P3HT) nanofibers. The liquid jet is greatly prolonged by the additional extensional force and thinner fibers can thus be obtained. The chain conformation and orientation in fibers are probed by differential scanning calorimetry and X‐ray diffraction techniques. Under the influence of the secondary electric field, P3HT chains are extensively stretched and aligned along the fiber axis. The electrospun P3HT nanofibers are fabricated into field‐effect transistors and the charge carrier mobilities of the nanofibers with and without secondary electric field are found to be 1.54 × 10−4 and 1.62 × 10−1 cm2 V−1 s−1, respectively. The dramatic enhancement of mobility by more than 1000 times is due to the effective charge transport through the delocalization of electrons along the highly extended and oriented P3HT backbones rather than the ordinary π–π stacking. In addition to P3HT, it is found that this simple method also works for poly(3‐alkylthiophene).

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