Organic and printed electronics technologies require conductors with a work function that is sufficiently low to facilitate the transport of electrons in and out of various optoelectronic devices. We show that surface modifiers based on polymers containing simple aliphatic amine groups substantially reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene. The reduction arises from physisorption of the neutral polymer, which turns the modified conductors into efficient electron-selective electrodes in organic optoelectronic devices. These polymer surface modifiers are processed in air from solution, providing an appealing alternative to chemically reactive low-work function metals. Their use can pave the way to simplified manufacturing of low-cost and large-area organic electronic technologies.
Formation, adhesion, and accumulation of ice, snow, frost, glaze, rime, or their mixtures can cause severe problems for solar panels, wind turbines, aircrafts, heat pumps, power lines, telecommunication equipment, and submarines. These problems can decrease efficiency in power generation, increase energy consumption, result in mechanical and/or electrical failure, and generate safety hazards. To address these issues, the fundamentals of interfaces between liquids and surfaces at low temperatures have been extensively studied. This has lead to development of so called "icephobic" surfaces, which possess a number of overlapping, yet distinctive, characteristics from superhydrophobic surfaces. Less attention has been given to distinguishing differences between formation and adhesion of ice, snow, glaze, rime, and frost or to developing a clear definition for icephobic, or more correctly pagophobic, surfaces. In this review, we strive to clarify these differences and distinctions, while providing a comprehensive definition of icephobicity. We classify different canonical families of icephobic (pagophobic) surfaces providing a review of those with potential for scalable and robust development.
Low cost, controlled crystallinity, chemical, and mechanical stability enable application of polymers in energy, water, electronics, and biomedical industries. Recent studies have shown that tailoring surface properties of polymers impacts their durability and functionality in these applications. However, the functionality and performance of polymer‐based devices and systems are greatly affected by the modification method and the process parameters, highlighting the need for understanding these methods and their mechanisms of operation in detail. The selection of the modification method invariably decides the properties enhanced in the polymer. In this review, various polymer surface modification treatments are discussed. These methods are categorized into physical, chemical, thermal, and optical ways, while illustrating their advantages and disadvantages. This review also explores the surface modification of polymers by patterning which encompasses one or more surface treatment methods. An application‐oriented study is presented discussing the relative importance of a method pertaining to a specific field of end‐application.
Nanoporous stamps enable flexographic printing with uniform nanoscale thickness and micrometer-scale lateral resolution.
CVD graphene has been n-and p-doped using redox-active, solutionprocessed metal-organic complexes. Electrical measurements, photoemission spectroscopies, and Raman spectroscopy were used to characterise the doped films and give insights into the changes.The work function decreased by as much as 1.3 eV with the n-dopant, with contributions from electron transfer and surface dipole, and the conductivity significantly increased.
Thin films of bilayer poly(divinyl benzene) p(DVB)/poly(perfluorodecylacrylate) (p-PFDA) are synthesized via iCVD on steel and silicon substrates. Nanomechanical measurements reveal that the elastic modulus and hardness of the films are enhanced through the bilayer structure and that the adhesion of the films to the substrate is improved via in situ grafting mechanism. The strength of ice adhesion to the treated surfaces is reduced more than six-fold when the substrates are coated with these bilayer polymer networks. 9 Icing can decrease efficiency in power production, result in mechanical and/or electrical failure, impact monitoring and control, and generate safety hazards.2,3,5,7 Active deicing methods that are employed to melt and break previously formed ice layers necessitate increased design complexity, may have detrimental environmental consequences, and require substantial power input for operation.10,11 Passive methods have recently been employed to protect exposed surfaces using icephobic coatings with characteristics designed to retard the formation of ice and facilitate the removal of ice deposits.3,9,12-22 Such coatings have been developed using solgel systems containing uorinated compounds and low surface energy rubbers, 20 lubricant-impregnated textured surfaces, 4 via hydrothermal reaction method, 23 low-pressure plasma polymerization, 24 and phase-separation methods. 7 However, a need remains for deposition methods that produce durable and mechanically-robust coatings over the large areas with enhanced adhesion to textured/rough surfaces that are commonly encountered in real world applications.In the present work, we have designed and synthesized for the rst time a mechanically-robust bilayer consisting of a thick and dense polymer base layer that is highly cross-linked and then capped with a covalently-attached thin icephobic uorine-rich top layer. We believe that the presence of a highly cross-linked polymer layer underneath a very thin u-oropolymer cap acts as a steric barrier resisting local surface reorganization, forcing the uorinated groups to remain on the surface even under wet conditions (Fig. S1, ESI †). In addition, the mechanical properties (for example the elastic modulus and hardness) of these customized bilayer polymer networks can be signicantly enhanced. Conceptual insightsIce formation and accumulation on surfaces can result in severe problems for solar photovoltaics, offshore oil platforms, wind turbines, and aircra. Practical adoption of icephobic surfaces requires mechanical robustness and stability under the harsh real-world environments. Here we design an icephobic surface using a bilayer strategy, optimizing the base layer for mechanical properties, while the top layer provides the desired high receding water contact angle (WCA). Both layers are formed sequentially by initiated chemical vapor deposition (iCVD) in the same reaction chamber. The iCVD polymerization of divinyl benzene (DVB) yields a cross-linked hydrocarbon base layer which is capped with an ultrathi...
Chemical vapor deposition (CVD) polymerization directly synthesizes organic thin films on a substrate from vapor phase reactants. Dielectric, semiconducting, electrically conducting, and ionically conducting CVD polymers have all been readily integrated into devices. The absence of solvent in the CVD process enables the growth of high-purity layers and avoids the potential of dewetting phenomena, which lead to pinhole defects. By limiting contaminants and defects, ultrathin (<10 nm) CVD polymeric device layers have been fabricated in multiple laboratories. The CVD method is particularly suitable for synthesizing insoluble conductive polymers, layers with high densities of organic functional groups, and robust crosslinked networks. Additionally, CVD polymers are prized for the ability to conformally cover rough surfaces, like those of paper and textile substrates, as well as the complex geometries of micro- and nanostructured devices. By employing low processing temperatures, CVD polymerization avoids damaging substrates and underlying device layers. This report discusses the mechanisms of the major CVD polymerization techniques and the recent progress of their applications in devices and device fabrication, with emphasis on initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization.
Blends of 75 wt. % amorphous polylactide (PLA) with 25 wt. % poly[(butylene succinate)-co-adipate] (PBSA) and poly[(butylene adipate)-co-terephthalate] were separately prepared using an internal batch mixer. The morphology and viscoelastic properties of these two blends were analyzed and compared. Annealing did not cause any pronounced morphology changes nor a subsequent modification of the viscoelastic behavior for both blends. However, applying a shear for 20 min at a rate of 0.05 s−1 induced significant droplet coalescence in both blends, although the changes in the viscoelastic response were more prominent in the PLA/PBSA blend. It was also shown that applying a shear for 10 and 20 min at a rate of 0.2 s−1 caused a slight droplet coalescence and minor changes in the viscoelastic behavior of both blends. Moreover, the Palierne model was used to calculate the interfacial tensions between the blend components. It was also utilized to estimate the droplet size after applying annealing and shearing.
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