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Functional thin coatings are crucial in modern and emerging technologies, providing specified surface properties and protection, thereby influencing the performance and lifetime of materials and devices. The electrodeposition of polymer networks (EPoN) has recently been reported as a facile and potentially broadly applicable method to fabricate conformal polymeric ultrathin films on conductive substrates with arbitrary shapes and surface topography under mild solution conditions. In this work, a new generation of EPoN is introduced that utilizes a chemically reactive polymer appended by a small fraction of a electrochemical crosslinker as side groups. This EPoN iteration eliminates the need for precise end-group functionalization, enables the tuning of crosslink density and film thickness independent of polymer size, and the resulting reactive ultrathin films are amenable to post-deposition modification with desired functionalities using facile click-chemistry. To demonstrate this concept, we electrodeposit polyisoprene with small side-group fractions of the oxidative crosslinker phenol (<5%) as a thiol–ene-reactive polymer-network coating. The EPoN-derived ultrathin films are tunable and uniform with a thickness in the 100s of nanometers depending on phenol fraction and electrodeposition potential, and show a conformal morphology on complex porous electrode architectures. We further demonstrate post-EPoN functionalization of the ultrathin polyisoprene coatings with thiol–ene chemistry. 

Advances in precision coatings are critical in enhancing the functionality of porous materials and the performance of three-dimensionally (3-D) micro-architected devices in applications ranging from molecular sorption and separation to energy storage and conversion. To address this need, we report the cathodic electrodeposition of polymer networks (EPoN) that utilizes the coupling between pre-synthesized polymers with electrochemically active end groups and a complementary crosslinker to form a step-growth polymer network. The electrochemically mediated crosslinking reaction confines the network formation to the electrode surface in a passivating and self-limiting film growth, preventing uncontrolled precipitation and deposition away from the surface. The cathodic electrodeposition is compatible with a variety of conductive substrates, which is demonstrated for 3-D carbons and metals with micron-scale pores of high aspect ratio. The entire pore surface of the 3-D electrodes is enveloped by a conformal polymer thin film that is free of detectable defects and highly electronically insulating for its potential use as an ultrathin artificial electrolyte interphase or solid polymer electrolyte. Since our EPoN concept decouples the polymer functionality from its electrodeposition chemistry, we envision it to be a widely applicable method to coat various conductive non-planar and micro-architected 3-D substrates with polymers of broad functionalities. 

Functional thin films and interphases are omnipresent in modern technology and often determine the performance and life-time of devices. However, existing coating strategies are incompatible with emerging mesoscaled 3D architected and porous materials, and fail to uniformly apply functional thin films on their large and complex interior 3D surface. In this report, we introduce an approach for obtaining conformal polymeric thin films using custom-designed dual-functional monomers possessing both self-limiting electrodeposition capability and the functionality of interest in separate molecular motifs. We exemplify this approach with the monomer triethylene glycol-diphenol and demonstrate the full coating of a 3D mesoscaled battery electrode with an ultrathin lithium-ion permeable film. Our comprehensive study of the processing–structure–property relationships enables the tailorable control over the conformal thickness (7–80 nm), molecular permeability, and electronic properties. The modularity and tunability of this approach make it a promising candidate for functional polymer film deposition on arbitrary 3D structures.