A Scalable Synthetic Approach for Producing Homogeneous, Large Area 2D Highly Conductive Polymers

The development of 2D materials is rapidly advancing beyond traditional graphene and metal oxides and into new functional organic materials including conducting polymers (CPs). Synthesizing 2D-CPs, typically achieved by polymerizing within a highly confined space (e.g., between lipid bilayers), is a slow and poorly scalable process that is incapable of producing large area films. A 'tethered-dopant templating' method is used where a surface-grafted layer of dopant molecules regulates the 3D-growth of poly 3,4-ethylenedioxythiophene (PEDOT) allowing ultrathin and molecular-scale '2D' films having thicknesses of just ∼3 nm to be grown in an unconfined geometry over a large area (i.e., cm²). While the tethered-dopant template method is a simple and promising alternative to confined geometry templating, the electrochemical mechanisms of film growth and its impact on the film electrochemical properties have yet to be well understood. This investigation shows that the surface-tethered dopant regulates the polymerization reaction by actively suppressing chain termination to support the growth of longer and more conductive chains (i.e., higher charge carrier mobility). These 2D PEDOT films also become 'hyper-doped' with dopant to polymer mass fractions as high as 8:1, resulting in metal-like conductivity due to enhanced charge carrier density. Additionally, 2D PEDOT films achieve unprecedented homogeneity with little variability down to submicrometer length scales. This new understanding into the dopant regulation over electropolymerization combined with the unequaled metal-like conductivity, molecular-scale dimensions, and large area of 2D PEDOT represents a significant advance in CP materials that will drive innovation across numerous fields including transparent conductors, optoelectronics, bionics, and biosensing.