The increased use of high-voltage electronics requires higher performance dielectric materials. These electrically insulating layers need as high of a dielectric breakdown strength as possible. Herein, multiple polyelectrolyte layer-by-layer assemblies were studied as high-voltage insulators. The influences of molecular weight, polymer backbone architecture, and thermal cross-linking were investigated. It was found that increasing the molecular weight of either the polycation or polyanion increases the breakdown strength due to removal of chain ends that can act as breakdown initiating sites. It was also found that a linear polymer backbone architecture leads to higher breakdown strength when compared to branched polymer architectures. Lastly, through thermal cross-linking, the breakdown strength is increased, and the previously mentioned molecular weight and architecture effects are diminished. These 200–400 nm thick polymer multilayer films exhibit breakdown strengths of ∼300–400 kV/mm. Their simple water-based processing makes them an interesting new option for protecting various types of electronics.

Polyelectrolyte complex (PEC) thin films have demonstrated remarkable oxygen barrier properties, but the moisture sensitivity from the hydrophilic nature of polyelectrolytes is a significant drawback. In this study, various molar ratios (1:1, 1:2, and 1:3) of branched polyethyleneimine (PEI) and poly(acrylic acid) (PAA) were prepared as one‐pot coating solutions, which can be deposited via a simple dip‐coating process and cured with a citric acid buffer solution, which increases the charge density of PEI and triggers complexation. As‐prepared conformal thin films impart excellent gas barrier, high modulus, and high moisture resistance. Undetectable oxygen transmission rate (OTR), at both 0% and 90% RH, can be achieved with a PEI:PAA molar ratio of 1:1 and buffer curing at pH 3. The strong complexation from ionic crosslinking creates an unusually dense thin film that is promising for various packaging applications (food, electronics, etc.). This thin film exhibits one of the best‐ever polymer‐based oxygen barriers at high humidity.

Paper-based food packaging is lightweight, low cost, and highly flexible, but it suffers from a very high oxygen transmission rate (OTR ∼ 11,100,000 cc/(m 2 •day•atm)). Herein, two polyelectrolyte-based coacervate coatings were studied as oxygen gas barriers on kraft builder's paper. A single coating deposition of a polyethylenimine-poly(acrylic acid) coacervate, adding less than 20% to the paper's weight, reduced the OTR to 164,000 cc/(m 2 • day•atm). This work not only demonstrates a significant OTR improvement of a poor oxygen barrier material, but also provides the foundation for polyelectrolyte-based layers to be deposited on cellulosic materials at an industrial scale.