The synthesis of poly[N-(3-(9H-carbazol-9-yl)propyl)methacrylamide] (PCaPMA) is presented, along with its physical, photophysical, and electrical properties, revealing its promising potential for the application in bistable memory devices. The incorporation of the carbazole heterocycle, as a functional charge carrier transporting unit attached to a saturated polymethacryalamide backbone by a flexible alkyl chain, facilitates resistive switching by the applied voltage. Thin films of the polymer, sandwiched between Al or Au and ITO electrodes, exhibit rewriteable flash memory behavior with bistable conductivity with a setting voltage ranging from 2 to 4.5 V, achieving a current ON/OFF ratio exceeding 100. The device demonstrates a remarkable lifetime and remains persistent for more than 10⁴ seconds under a static voltage of 0.5 V. The main physical mechanisms driving the resistive switching have been attributed to the electric field-induced reorientation of heterocycles, which modulates charge transport, and trapping/detrapping of charges in localized states within the bulk of the polymer. Memory persistence is strengthened by the physical crosslinking caused by hydrogen bonds between amide and carbonyl groups in the aliphatic side chains. This physical network further enhances the thermal and mechanical stability of the PCaPMA in comparison to similar polymers highlighting its potential as a suitable material for organic memory devices.

The title compound, unimer U (tpy stands for 2,2′:6′,2″-terpyridin-4′-yl end-group), by itself shows the memristor effect with a retention time of 18 h and persistence of 11 h. Its coordination copolymer with Co(II) ions, [CoU]_n, exhibits multimodal resistance changes similar to the synaptic responses observed in biological systems. More than 320 cycles of potentiation and depression measured in continuous sequence occurred without observing a significant current change, confirming the operational stability and reproducibility of the device based on the [CoU]_n polymer. The synaptic effect of a device with an indium tin oxide (ITO)/[CoU]_n/top-electrode (TE) configuration is more pronounced for the device with TE = Au compared to devices with TE = Al or Ga. However, the latter TEs provide a cost-effective approach without any significant compromise in device plasticity. The detected changes in the synaptic weight, about 12% for pair-pulse facilitation and 80% for its depression, together with a millisecond trigger and reading pulses that decay exponentially on the time scale typical of neurosynapses, justify the device’s ability to learn and memorize. These properties offer potential applications in neuromorphic computation and brain-inspired synaptic devices.

Poly[N-(3-(9H-carbazol-9-yl)propyl)methacrylamide] film sandwiched between ITO and Au electrodes is able to mimic synaptic plasticity as a fundamental behaviour of neuronal synapses.

This work combines experimental and theoretical approaches to examine how the length of an alkyl linker can be used to tune the electrochemical, optical, and device-related electrical properties of carbazolylalkyl-substituted polydithienopyrrole polymers (pCxDTP). Using a scalable four-step synthetic route, a series of monomers with systematically varied alkyl spacers was prepared and subsequently electropolymerized directly onto conductive substrates, yielding uniform polymer films suitable for device integration. The polymer band gap ranges from to 2.4 for pC3DTP to 2.0 eV for pC12DTP. This trend arises from the concurrent increase of the HOMO and lowering of the LUMO levels, with both effects depending on the alkyl chain length. Sandwich devices with an ITO | pCxDTP | Al architecture show reproducible memristive behavior, characterized by pinched hysteresis loops and pronounced frequency dependence. Longer alkyl linkers result in a more pronounced hysteresis in current-voltage already at higher sweep rates, revealing a clear relationship between molecular structure and device performance. Density functional theory and time-dependent DFT calculations are consistent with the experimental findings and indicate that alkyl linker length subtly influences frontier orbital energies, ionization potentials, and charge delocalization. Oligomer-level modeling further accounts for the observed band gap narrowing and spectral broadening through increased conjugation length and chain dispersity. Overall, these results highlight alkyl linker engineering as a practical strategy for optimizing conjugated polymers for electrochromic and memristive applications.