Synthesis, properties, and electrical memory characteristics of new diblock copolymers of polystyrene-block-poly(styrene-pyrene)

摘要

In this study, we report the synthesis, properties, and electrical memory characteristics of new diblock copolymers, polystyrene-block-poly(styrene-pyrene) (PS-b-P(St-Py)), prepared by combining atom transfer radical polymerization and Suzuki coupling reaction. The effects of the St-Py block chain length on the electronic energy level, photophysical properties, and memory characteristics were explored. The PS_(42)-b-P(St-Py)108 and PS_(66)-b-P(St-Py)_(67) devices exhibited a dynamic random access memory characteristics with different turn-on threshold voltages of —2.7 and —3.1 V, respectively. Moreover, these memory devices showed a high ON/OFF current ratio of 10~9 and were electrically stable for at least 10~4 s in both ON and OFF states. However, the PS_(113)-b-P(St-Py)_(45)-based device displayed an insulating state in a low current variation of 10~(-12) to 10~(-14) A, which had a short St-Py block length. The mechanism of the switching behavior was explained by the charge hopping conduction between the pyrene units with coexisting charge-trapping environment. The volatility of the memory effect was depended on the ability of charge trapping/back transferring of trapped charge. The present study suggested that the electrical memory characteristics could be efficiently tuned through the block ratio between insulating segment and pendant-conjugated segment of the diblock polymers.