Electrosynthesis of Biocompatible Free-Standing PEDOT Thin Filmsat a Polarized Liquid|Liquid Interface br

Conducting polymers (CPs)find applications in energy conversion and storage, sensors, and biomedical technologiesonce processed into thinfilms. Hydrophobic CPs, like poly(3,4-ethylenedioxythiophene) (PEDOT), typically require surfactantadditives, such as poly(styrenesulfonate) (PSS), to aid their aqueous processability as thinfilms. However, excess PSS diminishes CPelectrochemical performance, biocompatibility, and device stability. Here, we report the electrosynthesis of PEDOT thinfilms at apolarized liquid|liquid interface, a method nonreliant on conductive solid substrates that produces free-standing, additive-free,biocompatible, easily transferrable, and scalable 2D PEDOT thinfilms of any shape or size in a single step at ambient conditions.Electrochemical control of thinfilm nucleation and growth at the polarized liquid|liquid interface allows control over themorphology, transitioning from 2D (flat on both sides with a thickness of <50 nm) to"Janus"3D (withflat and rough sides, eachshowing distinct physical properties, and a thickness of >850 nm)films. The PEDOT thinfilms werep-doped (approaching thetheoretical limit), showed high pi-pi conjugation, were processed directly as thinfilms without insulating PSS and were thus highlyconductive without post-processing. This work demonstrates that interfacial electrosynthesis directly produces PEDOT thinfilmswith distinctive molecular architectures inaccessible in bulk solution or at solid electrode-electrolyte interfaces and emergentproperties that facilitate technological advances. In this regard, we demonstrate the PEDOT thinfilm's superior biocompatibility asscaffolds for cellular growth, opening immediate applications in organic electrochemical transistor (OECT) devices for monitoringcell behavior over extended time periods, bioscaffolds, and medical devices, without needing physiologically unstable and poorlybiocompatible PSS.