In recent years, the bioelectronics field has seen the use of an increasing variety of conducting polymers because they promise to display tunable mechanical properties (flexibility) and the ability to form an intimate interface with living tissue – in strong contrast to their inorganic counterparts. Even though transduction of ionic biosignals into electronic signals is thought to be the key mechanism for successful integration of electronic devices in biological systems, little insight has so far been gained that allows understanding the interplay of electronic and ionic conductivity in the currently employed materials. Here we present a straight-forward materials science approach to this challenge that promises to control mixed ionic/electronic transport in ‘plastics’ by blending organic semiconductors with insulating commodity polymers. Blending allows inducing a more polar nature to the resulting systems and introduces the capability of controlling the interdiffusion of biological media through the final structures. More specifically, we demonstrate that electronic transport can be maintained in such multicomponent systems upon blending with the insulating matrix. Moreover, initial studies show faster switching response in large-scale organic electrochemical transistors when using blend systems compared to devices fabricated with a single-component conducting layer. This observation suggests our blend system shows efficient ionic conductivity. We tentatively relate this desirable behaviour of the semiconductor:insulator blends to the more polar nature of the latter active layers, introduced through chemical design of the insulator and the hydrophilicity of the insulating (commodity) polymer leading to the swelling of the blend in the aqueous electrolyte. We thus show that the use of conducting:insulating polymer blends has the potential to bring multifunctionality to the final material systems, including biological activity, biodegradation, topological cues, which in turn promises to enable more specific interactions with biological systems.