Ion-Precise Electrosynthesis and Memristors of Sequence-Controlled Conjugated Polymers

The ion-precise synthesis of polymer materials remains a challenge because of the counterion exchange during solution-processed synthesis and processing. Here, we demonstrate ion-precise electrosynthesis and memristors based on conjugated polymers, in which both backbone cations and counteranions are sequence-controlled for the first time. Inter- and intramolecular counterion exchanges are effectively blocked during surface-initiated growth of crystalline polymer monolayers, enabling us to distinguish a correlation between a library of sequence-controlled cationic conjugated polymers and their counteranions, as well as their intrinsic negative differential resistance (NDR). We find that controlled anion migration is a key factor in achieving ultralow NDR bias in redox-based memristors, dramatically reducing it from 1.75 V to a record low of 0.13 V. The peak-to-valley current ratio (PVCR) reaches 117 at 0.55 V, demonstrating a strategy that achieves a giant PVCR while simultaneously maintaining a low NDR bias. Unlike previously reported usual single or rarely double NDR peaks, we observe triple NDR peaks, which are theoretically more advantageous for multivalued logic computing. Our work represents a paradigm shift toward high-dimensional control of polymer structures within a two-dimensional molecular system for ion-precise memristors, while demonstrating advantages in tailoring intrinsic NDR beyond existing methods or materials.