Synthesis, Morphology, and Properties of Poly(3‐hexylthiophene)‐block‐Poly(vinylphenyl oxadiazole) Donor–Acceptor Rod–Coil Block Copolymers and Their Memory Device Applications

Abstract

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.

Polythiophene-based materials for nonvolatile polymeric memory devices

“…Fang et al [61] synthesized donor-acceptor diblock copolymers of regioregular poly(3-hexylthiophene)-block-poly(2-phenyl-5-(4-vinylphenyl)21,3,4-oxadiazole) (P3HT-b-POXD) (Fig. 9a).…”

High-performance stretchable resistive memories using donor–acceptor block copolymers with fluorene rods and pendent isoindigo coils

“…3 Conjugated rod-coil copolymers have attracted extensive research interest for electronic applications because the conjugated rods typically possess strong interchain π-π interactions to facilitate conducting channels, whereas the soft coil blocks provide the degree of freedom for polymer chain movement to induce self-assembled molecular packing. 6 Polyfluorene (PF) is a well-known conjugated moiety for optoelectronics (for example, light-emitting diodes, 13 field-effect transistors, 14 and memory devices [15][16][17] owing to its good electrondonating ability, efficient hole carrier transport and outstanding thermal stability. PF-based rod-coil block copolymers have been explored for resistive memory applications.…”

“…A volatile SRAM PF-b-Poly(2-vinylpyridine) memory with tunable charge storage duration was previously reported. Moreover, an electronwithdrawing [6,6]-phenyl-C 61 -butyric acid methyl ester was added to associate the donor-acceptor (D-A) charge transfer interaction, converting the memory from volatile SRAM to nonvolatile WORM behavior. 16 Such a D-A effect, however, must be generated using a polymer composite (that is, adding an extra functional molecule), which may face the bottlenecks of thin-film uniformity and device reproducibility.…”

“…1-3 Such memories can be switched between high and low resistance states (that is, OFF and ON states) by applying an external electric field. [4][5][6][7][8][9][10][11][12] Electrical memory characteristics can generally be divided into two categories, namely nonvolatile (for example, WORM (writeonce-read-many-times) and flash) and volatile memory (for example, dynamic random access memory and SRAM (static random access memory)), which show different tendencies for the stored charges to dispel. The volatility of these digital information storage devices can be controlled by (1) the charge transfer or charge trapping ability of the active materials and (2) the morphological packing structures in the memory layers.…”

Multilevel nonvolatile transistor memories using a star-shaped poly((4-diphenylamino)benzyl methacrylate) gate electret

“…[1][2][3][4][5][6][7][8][9][10][11][12] Resistor-and transistor-based memory devices are popular architectural approaches for operating the memories. Data storage with resistor memories employs the changes in resistance in response to an applied voltage bias.…”