Decoupling particle size and charge transport in PEDOT:PSS via morphological inheritance of monomer emulsification

Abstract

The intrinsic trade-off between colloidal processability and macroscopic electrical conductivity has long hindered the advancement of poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in precision flexible electronics.While pursuing nanoscale colloidal dispersions typically leads to a proliferation of grain boundaries that drastically degrade the material's electrical properties, we demonstrate that this trade-off can be decoupled at the level of polymerization kinetics. Herein, we propose a nanoreactor strategy leveraging the "morphological inheritance" of emulsified monomers. By modulating the pre-emulsification energy from mechanical stirring to high-pressure homogenization (HPH), we achieved a controlled, cross-scale reduction in colloidal particle size from 2911 nm down to 76 nm. Notably, despite the abundance of physical grain boundaries introduced by this miniaturization, the resulting HPH films maintain an exceptional electrical conductivity of 373 S cm⁻¹, comparable to the 409 S cm⁻¹ observed in micrometer-scale systems, while achieving mirror-like surface flatness (Rq = 1.06 nm). Grazing-incidence wide-angle X-ray scattering (GIWAXS) reveals the underlying crystallization mechanism: nanoconfined templates generated by extreme cavitational shear force the PEDOT chains to overcome conformational disorder, adopting a highly extended and ordered arrangement. This confinement effect unexpectedly extends the crystal coherence length (CCL) to 12.35 Å. By enhancing charge delocalization within the crystalline domains, this microscopic ordering fundamentally compensates for the transport resistance induced by grain boundary accumulation.Furthermore, the HPH nanocolloids exhibit excellent fluid processing stability (viscosity of 12 mPa•s), and their ultrahigh specific surface area endows the films with outstanding interfacial electrochemical capacitance. Ultimately, this work establishes a paradigm in which "microscopic ordering compensates for macroscopic defects," providing crucial physicochemical criteria for the rational design of high-performance conducting polymers.