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Abstract Corrosion of critical metal components exacts a heavy toll in terms of maintenance and replacement costs and damage to ecosystems upon failure. Polymeric barrier coatings protect against corrosion; however, design principles for modulating polymer structure to improve corrosion inhibition remain contested and elusive. Here, we examine molecular-weight-dependent differences in the efficacy of corrosion inhibition on aluminum substrates afforded by polyetherimide (PEI) coatings. Analyses of coated substrates evidence a clear trend denoting improved corrosion inhibition for higher weighted-average molecular weight (M W) PEI. The more rigid and entangled macromolecular network of higher-M W variants exhibit stable impedance values, |Z|0.01 Hz ca. 1010 Ω/cm2, upon extended immersion in brine media, whereas lower-M W variants are readily hydrated and disentangled resulting in a significant reduction in impedance values. Results illuminate mechanistic understanding of molecular-weight-dependence in corrosion inhibition, advance a framework for considering the dynamical evolution of secondary structure, and exemplify generalizable design principles for corrosion inhibition.

Abstract Light-weighting vehicular components through adoption of light-metal structural alloys holds promise for reducing the fuel consumption of internal combustion engine vehicles and increasing the range of battery electric vehicles. However, the alloyed microstructure and surface precipitates of aluminum alloys render these materials susceptible to corrosion under modest excursions from neutral pH. Traditional chromium-based anodic passivation layers are subject to increasingly stringent environmental regulations, whereas options for sacrificial cathodic films are sparse for electropositive metals. While hybrid nanocomposite coatings have shown initial promise, mechanistic underpinnings remain poorly understood. Here, a fully imidized polyetherimide (PEI) resin is utilized as the continuous phase with inclusion of unfunctionalized exfoliated graphite (UFG). A comprehensive investigation of the mechanisms of corrosion protection reveals key fundamental design principles underpinning corrosion inhibition. First, strong interfacial adhesion, which for PEI is facilitated by binding of imide carbonyl moieties to Lewis acidic sites on Al surfaces. Second, the miscibility of ion-impervious nanoscopic UFG fillers and stabilization of a substantial interphase region at UFG/PEI boundaries that result in minimizing the free volume at the filler/polymer interface. Finally, extended tortuosity of ion diffusion pathways imbued by the below-percolation-threshold 2D fillers. These three design principles help govern and modulate ion transport from electrolyte/coating interfaces to the coating/metal interface and are crucial for the extended preservation of barrier properties. The results suggest an approach to systematically activate multiple modes of corrosion inhibition through rational design of hybrid nanocomposite coatings across hard-to-abate sectors where light metal alloys are likely to play an increasingly prominent role.

This essay analyzes a controversy involving Amelia (Mia) Rivera, a three-year old girl who was denied a life-saving kidney transplant in January 2012. As reported by Mia's mother, Chrissy, on her blog post, Mia was denied the kidney transplant because of her mental disability. Throughout the public discussion that took place over a few short weeks, we argue Mia's ineligibility was rearticulated through rhetorics of motherhood, unjust body language, and questions about medical authority. we suggest this indicates that descriptions of the body and its able-ness carry more weight in the public's understanding of health issues than does medical authority.

In this laboratory experiment, students modify a series of surfaces and explore the effects of varying surface chemistry and texture on wettability by different probe liquids. Students begin by building a simple contact angle goniometer utilizing their mobile phone cameras. Next, they contrast the wettability of planar glass substrates functionalized with alkyl silanes and fluorinated alkyl silanes and calculate surface free energies using Owens/Wendt plots. Subsequently, they synthesize ZnO tetrapods as robust textural elements and spray deposit the tetrapods onto stainless steel meshes to develop hierarchical texturation, which upon subsequent surface functionalization yields superhydrophobic and oleophobic surfaces. The series of experiments allow them to investigate the manner in which textured surfaces deviate from Young's equation and provide a vivid illustration of the thermodynamics of surface wettability. The laboratory exercise further provides a striking visual analogy for illustrating free energy landscapes and serves as a tangible means to demonstrate the role of surface chemistry with regards to the midstream oil-transportation infrastructure.