Organic mixed ionic-electronic conductors (OMIECs) represent the most distinctive class of materials in the field of bioelectronics, soft robotics and neuromorphics. Controlling the interplay of ionic/electronic transport enables versatile device design, overcoming current limitations related to reproducibility and long-term stability. Hence, different structure-property-performance control strategies have been historically employed including side-chains manipulation, polymer backbone design and blending with ion-conducting components. In this work, we design stable OMIECs based on blends of PEDOT:PSS and Nafion-Li+. The ionic and electronic properties of these systems can be fine-tuned through the control of the microstructure and morphology at multi-scale levels. The similar anionic properties of PSS and Nafion allow for their interchangeability as ionic transport pathways while enabling to manipulate the structure of the PEDOT domains, thus the overall electronic conduction. The control of these properties has been exploited to realize organic artificial synapses mediated by the neurotransmitter dopamine with tuneable level of memory retention, allowing for the design of a multi-memory neuromorphic pre-processor. Organic mixed ionic electronic conductors enable high performance devices by tuning ionic and electronic transport through structural design and polymer blending for improved stability and flexibility. Here, the authors design a stable PEDOT:PSS Nafion Li+ with tunable conduction enabling dopamine driven artificial synapses and memory control.