What musical notes can a molecule play? Carbyne is a chain of atoms that vibrates similar to an elastic string. Like the tuning of a guitar string, this vibration can be predicted based on length and tension. Using atomistic simulation, we determine the vibrational response of carbyne. We further produce audible notes, enabling specific musical composition with prescribed molecular conditions (pre-strain and length) and combine single chains into multi-chain systems to form molecular chords. Since the tension of a molecular chain is relatively low (<nN), such “strings” can potentially be developed for signaling and detection with high resolution.

Conjugated polymers (CPs) are widely investigated because of their intriguing optical and semiconducting properties in various optoelectronic device applications. Because of the one-dimensional p-orbital overlap along the main chain, CPs exhibit strong anisotropy in optoelectronic characteristics. Therefore, macroscopic assembly and alignment of CPs are essential to fully utilize their potential properties in real device applications. Here we review various processing strategies and material design principles for efficient CP alignment that result in highly anisotropic optical and electronic characteristics. Furthermore, we thoroughly review the incorporation of aligned CPs layers in organic light-emitting diodes, organic thin film transistors, and organic photovoltaic devices. The achieved macroscopic CP alignment has increased the optoelectronic properties and greatly improved device performance.

Plasmonic waveguides can transport light while still confining it beyond the diffraction limit. Recently, crossing plasmonic waveguides have been suggested for the implementation of higher-density optical networks. However, suppressing undesirable scattering at their crossing point is still a challenging task because waveguides in these structures are physically connected. Here, we present an experimental demonstration of surface plasmon propagation on an overcrossing metallic waveguide fabricated by a pick-and-place method. By spatially separating the waveguides, the undesirable interaction at the interconnection can be suppressed. Our approach could be a powerful platform to achieve high-density integration of optical waveguides.

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.

Thin films of the conjugated polymer poly(3-hexylthiophene) (P3HT) of different morphological structures were fabricated using both conventional spin-casting and the matrix-assisted pulsed laser evaporation (MAPLE). Films deposited by MAPLE exhibit inhomogeneous morphologies comprised globular subfeatures with dimensions of the order of 100 nm. We show that whereas the in-plane carrier mobilities of MAPLE-deposited films (8.3 × 10−3 cm2/V/s) are comparable with those of spin-cast analogs (5.5 × 10−3 cm2/V/s), the out-of-plane mobilities are an order of magnitude lower (4.1 × 10−4 cm2/V/s versus 2.7 × 10−3 cm2/V/s). Both in- and out-of-plane carrier transport characteristics of MAPLE-deposited films indicate a broad density of states and high carrier trap concentration. Optical absorbance spectroscopy not only corroborates a high degree of energetic disorder in MAPLE-deposited films, but also suggests that the P3HT chains possess average conjugation lengths comparable with spin-cast counterparts. Our findings, rationalized in terms of the Gaussian Disorder Model, describing carrier transport in an environment characterized by both positional and energetic disorder, provide important perspectives on the extent to which disorder impacts mechanisms of charge transport in conjugated polymers.

An ecofriendly synthesis is established to obtain ultra-small SnO2 nanoparticles (NPs) doped with metals by a hydrothermal method using only tin tetrachloride, urea, and water as reagents. This synthesis was done in a short period time at low temperature and without surfactants. Microscopy analysis revealed the formation of doped tin oxide NPs with a diameter smaller than 2.8 nm. Un-doped and doped tin oxides were obtained with a tetragonal type rutile structure with an average surface area of 348 m2/g.

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.

Depolymerizable polymers are stimuli-responsive materials triggered to depolymerize rapidly and completely into their constituent monomers on command. Applications include triggerable vehicles for controlled release, restructurable materials, disappearing or sacrificial composites, and lithographic resists. Owing to their widespread utility, significant efforts have aimed to prepare and explore depolymerizable polymers and their corresponding triggers. This “Prospective” highlights advances since their discovery over a half-century ago, discusses methods in their preparation, and presents recent developments in triggered depolymerization. It also surveys applications that harness these polymers’ unique properties, while offering insights into research directions that may contribute to progress in this dynamic field.

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.

We demonstrate the gravure printing of a high-performance indacenodithiophene (IDT) copolymer, indacenodithiophene–benzothiadiazole (C16IDT–BT), onto self-aligned organic field-effect transistor architectures on flexible plastic substrates. We observed that the combination of a gravure-printed dielectric with gravure-printed semiconductor yielded devices with higher mean-effective mobility than devices manufactured using photolithographically patterned dielectric. Peak mobilities of μ = 0.1 cm2 V−1 s−1 were measured, and exceed previous reports for non-printed C16IDT-BT on non-flexible silicon substrates.

Fullerite derivatives synthesized with a catalytic polymerization reaction at a relatively low-pressure range of 0.5–4 GPa show unique mechanical properties: elastic recovery is 98% and hardness possibly approaches 100 GPa. Structure of the samples is also unique: one composes from fragments of C60 molecules linked by the covalent bonds. To obtain the homogeneous crack-free samples, we synthesized B4C–fullerite derivatives composite which show a 550 MPa flexural stress, a 2250 MPa compressive strength, and a 28 GPa hardness and have density of 2.2 g/cm3.

The thermal history of amorphous polymers near the glass-transition temperature determines the extent to which macromolecules structurally relax, and ultimately their properties. Here, we report the correlation between physical aging, dielectric breakdown, and capacitive energy storage of polystyrene, poly(methyl-methacrylate), and associated silica nanocomposites. Guided by enthalphic recovery rates, dielectric breakdown strength increased from 20% to 40% when aged at Tg−10 °C before use. The generality of improvement and connection to enthalpic recovery afford a means to design pre-service processing of new polymers and additive manufacturing techniques to reduce excess volume within the glass; and thereby reduce initiation and inhibit propagation of electronic failure.

Metal oxide-based transistors can be fabricated by low-cost, large-area solution processing methods, but involve a trade-off between low processing temperature, facile charge transport and high-capacitance/low-voltage transistor gates. We achieve these simultaneously by fabricating zinc oxide and sodium-incorporated alumina (SA) thin films with temperature not exceeding 200 to 250 °C using aqueous and combustion precursors, respectively. X-ray reflectivity shows a compositionally distinct SA boundary layer forming near the substrate and that a portion of the SA is chemically removed during the subsequent semiconductor deposition. Improved etch resistance and reduced dielectric leakage was obtained when (3-glycidoxypropyl) trimethoxysilane was included in the SA precursor.

In this study, Vickers indentation was used to investigate the two-way shape-memory effect (TWSME) in an austenitic Ti-50.9 at.% Ni alloy, exposed to different heat treatments. Three aging treatments were used to manipulate the size of Ti3Ni4 precipitates. All samples were Vickers indented, and the indent depth was investigated as function of thermal cycling. The TWSME was found only in the material aged at 400 °C, which contained coherent precipitates. Thermal cycling shows stable TWSME, however, heating well above the austenite finish temperature lead to permanent austenitic protrusions. The results indicate that stabilized martensite plays a critical role in creating TWSME surfaces.

Material research and development is increasingly focusing on achieving specialized functionality in materials. For example, the ability to “self-heal (SH)”, or naturally repair accrued damage, is attractive because it extends the lifetime of the material by increasing resistance to damaging conditions and prolonging preservation of material properties. Additionally, shape memory (SM) materials, including SM polymers, are actively considered for their ability to change shape one or more times upon application of an external stimulus. Here, we present a polymer composite, composed of poly(vinyl acetate) (PVAc) and poly(ε-caprolactone) (PCL), exhibiting both SH and SM functionalities. In fact, the SM assists in the SH ability in a process developed by our group termed, shape memory-assisted self-healing (SMASH). The advantage of the SH composite presented here is its simple fabrication. Dual-electrospinning is used to simultaneously electrospin PVAc and PCL, achieving an interwoven polymeric composite of otherwise immiscible polymers. The dual-electrospinning method facilitates precise control of the relative weight fractions of the components, and thus allows for tuning of the material properties. Upon thermal activation, damaged PVAc–PCL composites exhibited SH under a variety of testing conditions. Furthermore, the composites exhibited impressive dual and triple SM capabilities in the dry and hydrated states, respectively. Together, the commercial availability of the components and the simplicity of preparation translate to a SMASH system that could be mass produced and used as a SH coating or alone, as a packaging material.

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.

Regarding the significance of cement paste in construction materials, the present paper aims to use nanoindentation to measure and map mechanical properties of hardened cement pastes. The mechanical properties of involved phases were extracted from grid nanoindentation on the cement paste. The results suggested that nanoindentation can be used as a tool to measure and map mechanical properties of hardened cement pastes, and can identify the phases, including outer product, inner product, calcium hydroxide (or interface of residual cement clinker), and residual cement clinker.

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.

In this work, we showcased a visible-light-assisted reduction of graphene oxide (GO) using N-doped TiO2 photocatalysts. Bench scale capacitive deionization (CDI) experiments determine the optimum working voltage for TiO2–reduced graphene oxide (RGO) nanocomposites as CDI electrodes at 1.8 V. Furthermore, the coupled TiO2 nanoparticles within the as-prepared composite also exhibited photocatalytic ability by removing the humic acid model pollutant. This property is expected to be beneficial as it could relieve the degree of fouling on the electrosorptive surface caused by dissolved organic compounds. In the end, we have demonstrated their potential as a viable desalination water treatment technology in a pilot scale CDI unit.

We report on the ability to switch an optical material composed of a polymer stabilized cholesteric liquid crystal (polymer stabilized cholesteric texture, PSCT) between stable transparent (reflective) and scattering modes. The degree of scattering is controllable with the strength of the applied electric field. The mechanism for bistable switching of the PSCT is distinguished from prior examinations by employing electromechanical displacement of a stabilizing polymer network. The stable transparent (reflective) or scattering modes are induced with a variety of driving schemes employing both alternating and direct current fields. The relative degree of scattering can be varied to allow for grayscale control potentially useful in smart window and display applications.