Poly[sulfur-random-1,3-diisopropenylbenzene (DIB)] copolymers synthesized via inverse vulcanization form electrochemically active polymers used as cathodes for high-energy density Li–S batteries, capable of enhanced capacity retention (1005 mAh/g at 100 cycles) and lifetimes of over 500 cycles. In this prospective, we demonstrate how analytical electron microscopy can be employed as a powerful tool to explore the origins of the enhanced capacity retention. We analyze morphological and compositional features when the copolymers, with DIB contents up to 50% by mass, are blended with carbon nanoparticles. Replacing the elemental sulfur with the copolymers improves the compatibility and interfacial contact between active sulfur compounds and conductive carbons. There also appears to be improvements of the cathode mechanical stability that leads to less cracking but preserving porosity. This compatibilization scheme through stabilized organosulfur copolymers represents an alternative strategy to the nanoscale encapsulation schemes which are often used to improve the cycle life in high-energy density Li–S batteries.

The introduction of functional units onto semiconducting polymers either as side chains or at the α- and ω-ends of polymeric chains is the method of choice in order to impose additional functions to the final semiconducting materials when aiming specific applications. Moreover, the functionalization approach provides a route to further complex macromolecular architectures as well as the generation of hybrid materials through the covalent attachment of the semiconductor to carbon nanostructures or to inorganic nanoparticles. Via this prospective an outline over functionalized and hybrid semiconducting polymers is provided along with possible paths of future research toward functional and hybrid semiconductors.

Electronic performance in semiconducting polymers has improved dramatically in recent years owing to a host of novel materials and processing techniques. Our understanding of the factors governing charge transport in these materials has also been enhanced through advancements in both experimental and computational techniques, with disorder appearing to play a central role. In this prospective, we propose that disorder is an inextricable aspect of polymer morphology which need not be highly detrimental to charge transport if it is embraced and planned for. We discuss emerging guidelines for the synthesis of polymers which are resilient to disorder and present our vision for how future advances in processing and molecular design will provide a path toward further increases in charge-carrier mobility.

Polymer-based nanomaterials have captured increasing interest over the past decades for their promising use in a wide variety of applications including photovoltaics, catalysis, optics, and energy storage. Bottom-up assembly engineering based on the self- and directed-assembly of polymer-based building blocks has been considered a powerful means to robustly fabricate and efficiently manipulate target nanostructures. Here, we give a brief review of the recent advances in assembly and reconfigurability of polymer-based nanostructures. We also highlight the role of computer simulation in discovering the fundamental principles of assembly science and providing critical design tools for assembly engineering of complex nanostructured materials.

The chemical diversity of organic semiconductors coupled with the kinetic nature of film formation make it challenging to tune the structure of active-layer thin films in organic electronics across multiple length scales. We review techniques to tune aspects of film structure within a framework that accounts for the competition between the time available for structural development and the time required by the organic semiconductors to order, defined by a dimensionless time, τ, that describes the ratio of these two quantities. By considering these two competing time scales, we propose general guidelines to tune the film structure accordingly.

Applications of polymer thin films include functional coatings, flexible electronics, membranes and energy conversion. The physical properties of polymer films of nanoscale thicknesses typically differ from the bulk, due largely to entropic effects and to enthalpic interactions between the macromolecules and the external interfaces. Studies of the size-dependent physical properties of macromolecules have largely been devoted to linear chain polymers. In this Prospective, we review recent experiments and simulations that describe the structure and fascinating physical properties, from wetting to the glass transition, of star-shaped macromolecules. The properties of these molecules would render them more useful than their linear chain analogs, for some specific applications.

Solubilizing alkyl chains play a crucial role in the design of semiconducting polymers because they define the materials solubility and processability as well as both the crystallinity and solid-state microstructure. In this paper, we present a scarcely explored design approach by attaching the alkyl side chains on one side (cis-) or on both sides (trans-) of the conjugated backbone. We further investigate the effects of this structural modification on the solid-state properties of the polymers and on the charge-carrier mobilities in organic thin-film transistors.

Polymers with stable radical groups are promising materials for organic electronic devices due to their unique redox activity. Block copolymers with one redox active block could be used in nanostructured devices for electronic applications. We report on the synthesis and characterization of such multifunctional block copolymers in which phase separation on the 10 nm (half pitch) scale is achieved by using fluorinated blocks. Fluorination of one block increases the degree of phase separation and leads to smaller accessible domain sizes. Block copolymers with 60%, 80% and 90% of a stable radical containing block and either fluorinated or non-fluorinated second blocks were made by atom transfer radical polymerization, and their microstructure formation as a function of fluorine content is described after solvent vapor or thermal annealing. Electrical characterization of such a partly fluorinated block copolymer shows their potential for electronic devices.

Glassy organic semiconductors provide a convenient host for dispersing guest molecules, such as dopants or light-emitting chromophores. However, many glass-forming compounds will crystallize over time leading to changes in performance and stability in devices. Methods to stabilize amorphous molecular solids are therefore desirable. We demonstrate that solution-processable glasses can be formed from a mixture of 8,8′-biindeno[2,1-b]thiophenylene (BTP) atropisomers. While the trans isomer of methylated BTP, (E)-MeBTP crystallizes in spin-cast films, the addition of (Z)-MeBTP slows the growth of the spherulites. X-ray scattering and optical microscopy indicate that films containing 40% (Z)-MeBTP do not crystallize, even with the addition of nucleation agents and aging for several months.

Metamaterials are man-made designer matter that obtains its unusual effective properties by structure rather than chemistry. Building upon the success of electromagnetic and acoustic metamaterials, researchers working on mechanical metamaterials strive at obtaining extraordinary or extreme elasticity tensors and mass-density tensors to thereby mold static stress fields or the flow of longitudinal/transverse elastic vibrations in unprecedented ways. In this prospective paper, we focus on recent advances and remaining challenges in this emerging field. Examples are ultralight-weight, negative mass density, negative modulus, pentamode, anisotropic mass density, Origami, nonlinear, bistable, and reprogrammable mechanical metamaterials.

More than two decades of III-N materials research has led to the production of visible spectrum commercial light-emitting diodes (LEDs) and laser diodes (LDs). Commercial c-plane LEDs are currently limited by efficiency droop which describes the decline in efficiency with increasing input current density. Laser-based sources, however, provide peak efficiencies at much higher current densities and may circumvent efficiency droop limitations. The potential benefits of non-basal plane (NBP) orientations could accelerate the evolution of solid-state lighting from LED to LD sources. Here, we review the progress in long-wavelength (440–590 nm) NBP quantum well LD research and discuss applications in solid-state lighting, visible light communication and smart lighting.

The separation of oil–water mixtures is a widely utilized unit operation, used for handling a wide variety of mixtures from industry including: petroleum drilling and refining, fracking, waste-water treatment, mining, metal fabrication and machining, textile and leather processing, and rendering. Membrane-based methods have become increasingly attractive for the separation of oil–water mixtures because they are relatively energy-efficient, can be readily used to separate a variety of industrial feed streams, and provide consistent permeate quality. In this perspective, we discuss the design strategies for membranes with selective wettability i.e., membranes that are either selectively wet by, or prevent wetting by, the oil or water phase. The design strategies include the parameterization of two important physical characteristics: the surface porosity and the breakthrough pressure. We also discuss how they are related for membranes with a periodic geometry. On the basis of this understanding, we explore principles that allow for the systematic design of membranes with selective wettability. A review of the current literature on the separation of oil–water mixtures using membranes with differing wettabilities is also presented. Finally, we conclude by discussing the current challenges and outlook for the future of the field.

We demonstrate the fabrication by anodization of niobium oxide microcones, several microns long, from aqueous solutions of 1 wt% hydrogen fluoride (HF) with varied sodium fluoride (NaF) concentration (0–1 M). Raman spectroscopy and x-ray diffractometer analysis revealed the as-grown microcones to be crystalline Nb2O5−x with preferred (1 0 0) and (0 1 0) orientations. The overall Nb2O5−x formation rate increased with the increasing NaF concentration, and structures as tall as 20 μm were achieved in just 20 min of anodization at 1 M NaF. Rapid formation of niobia microcones was even observed in the absence of HF at this NaF concentration. Photocatalytic activity for water oxidation was highest for microcones grown under the highest NaF concentration.

Micromechanical testing of electroplated gold alloy films has been conducted using theta-like specimens. Specimens were formed by a standard combination of photolithography, electroplating, and deep reactive ion etching. Testing was performed using an instrumented indenter and the results interpreted using a finite-element model with a Ramberg–Osgood constitutive law to extract elastic and plastic material properties. The observed results were highly repeatable and appear to be sensitive to variations in both sample dimensions and material properties. These qualities suggest that the testing methodology may have significant value as a quality control technique in the fabrication of metal microelectromechanical systems.

Screen-printed organic electrochemical transistors (OECTs) were tested as glucose and lactate sensors. The intrinsic amplification of the device allowed it to detect metabolites in low molecular range and validation tests were made on real human sweat. The development of an organically modified sol–gel solid electrolyte paves the way for all printed OECT-based biosensors.

Dual-stage, constant loading-rate followed by constant-load, pyramidal indentation experiments were performed to investigate the strain-rate (10−5–10−1/s) and temperature (295–573 K) dependence of pure magnesium. The estimated total activation energy, Q (0.69–1.01 eV), and apparent activation volume, V* (17–28b3), indicate that plastic deformation is controlled by a dislocation cross-slip mechanism. The results from this work and previous studies confirm that, during pyramidal indentation of Mg, the operative deformation mechanism remains the same over a very wide strain-rate and temperature range.

First principles density functional theory calculations were conducted to investigate the structures and energetics of polyhedral oligomeric silsesquioxane (POSS) molecules with varying aluminum and alkali (sodium or potassium) concentrations. Notable trends emerge from this study namely, (1) the thermodynamic stability of the substituted POSS molecules is critically dependent on the interplay between size and composition of the POSS structures, and (2) larger POSS structures provide lower central electron density and hence better accommodate the central alkali atom. These observations, when viewed in the context of aluminosilicate based geopolymers, provide fundamental insights into the relations that describe the structure composition interplay of their underlying monomers.

The Mn-doped ZrO2/TiO2 nanostructured photocatalysts had been prepared by the simple hydrothermal method. The morphologies and structures of the as-prepared photo-catalyst were characterized by transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and electron paramagnetic resonance. The resultant nanostructured photocatalysts exhibited high photocatalytic activity under ultraviolet (UV) light irradiation, attributing to the improvement of the photo-absorption property and the separation efficiency of photo-generated electrons and holes. The hydroxyl radicals (•OH), superoxide radical (•O2−), and holes (h+) are the main active species in aqueous solution under UV light irradiation.

Epitaxial Ba2YNbO6 (BYNO) films were deposited on textured NiW substrates via pulsed laser deposition. The films have dense and smooth surface structure, and more importantly, significantly improved out-of-plane texture, compared with the NiW substrate texture. Transmission electron microscopy study confirms the c-axis tilting of BYNO film and formation of misfit dislocations at NiW/BYNO interface, suggesting that the improved texture should be attributed to the tilted epitaxy via biased dislocation mechanism. YBa2Cu3O7−δ films deposited on BYNO single-buffered NiW substrates show further texture improvement, high superconducting transition temperature of ~91 K, and critical current density of 1.8 MA/cm2 at 77 K, self-field.

We have used low-energy electron diffraction and microscopy to compare the growth of graphene on hydrogen-free Ge(111) and Ge(110) from an atomic carbon flux. Growth on Ge(110) leads to significantly better rotational alignment of graphene domains with the substrate. To explain the poor rotational alignment on Ge(111), we have investigated experimentally and theoretically how the adatom reconstructions of Ge interact with graphene. We find that the ordering transition of the Ge(111) adatom reconstruction is not significantly perturbed by graphene. Density functional theory calculations show that graphene on reconstructed Ge(110) has large-amplitude corrugations, whereas it is remarkably flat on reconstructed Ge(111). We argue that the absence of corrugations prevents graphene islands from locking into a preferred orientation.