Changing the stability of polymer-based memory devices in high conductivity state via tuning the red-ox property of Hemin

Two polymer-Hemin composites, AB type block copolymer (PStCH- b -P4VP): Hemin and homopolymer of poly(4-vinylpyridine) (P4VP): Hemin, can be fabricated into sandwich memory devices. The memory device characteristics of the PStCH- b -P4VP: Hemin blends can show Flash memory behavior, while the P4VP polymer with Hemin only shows write-once-read-many-times (WORM) performance. Charge transfer and nanocomposite redox are probably responsible for the conductance-switching behavior. The results of cyclic voltammogram (CV) measurement indicate that the reversible Fe III /Fe II redox reaction is preserved well in the composite PStCH- b -P4VP: Hemin, while only polymer oxidation is observed in the P4VP: Hemin system. Due to the hindrance of StCH moiety, the coordination of pyridine and Fe II can keep the Fe II active. The P4VP has a more flexible chain that saturates the Fe II center and results in stable coordination; Fe III /Fe II redox reaction is therefore an obstacle. By tuning the coordination surroundings of the metal ion , different memory types can be obtained.