Well-Defined Block Copolymers with Triphenylamine and Isocyanate Moieties Synthesized via Living Anionic Polymerization for Polymer-Based Resistive Memory Applications: Effect of Morphological Structures on Nonvolatile Memory Performances

The anionic block copolymerization of 4,4′-vinylphenyl-<i>N</i>,<i>N</i>-bis­(4-<i>tert</i>-butylphenyl)­benzenamine (<b>A</b>) with <i>n</i>-hexyl isocyanate (<b>B</b>) was performed using potassium naphthalenide (K-Naph) in THF at −78 and −98 °C in the presence of sodium tetraphenylborate (NaBPh<sub>4</sub>) to afford the well-defined block copolymers for investigating the effect of morphological structures on electrical memory performances. The well-defined functional block copolymers (P<b>BAB</b>) with different block ratios had predictable molecular weights (<i>M</i><sub>n</sub> = 17 700–79 100 g/mol) and narrow molecular weight distributions (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> = 1.14–1.19). It was observed from transmission electron microscopy (TEM) that the block copolymers showed different morphological structures depending on block ratios. Although all memory devices fabricated from the resulting block copolymers with different block compositions equally exhibited nonvolatile resistive switching characteristics, which are governed by the trap-controlled space-charge-limited current (SCLC) conduction mechanism and filament formation, it was found that electrical memory performances of each device varied depending on morphological structures of the block copolymer films.