Bulk-Processed Plasmonic Plastic Nanocomposite Materials for Optical Hydrogen Detection.

ConspectusSensors are ubiquitous, and their importance is only going to increase across many areas of modern technology. In this respect, hydrogen gas (H2) sensors are no exception since they allow mitigation of the inherent safety risks associated with mixtures of H2 and air. The deployment of H2 technologies is rapidly accelerating in emerging energy, transport, and green steel-making sectors, where not only safety but also process monitoring sensors are in high demand. To meet this demand, cost-effective and scalable routes for mass production of sensing materials are required. Here, the state-of-the-art often resorts to processes derived from the microelectronics industry where surface-based micro- and nanofabrication are the methods of choice and where (H2) sensor manufacturing is no exception.In this Account, we discuss how our recent efforts to develop sensors based on plasmonic plastics may complement the current state-of-the-art. We explore a new H2 sensor paradigm, established through a series of recent publications, that combines (i) the plasmonic optical H2 detection principle and (ii) bulk-processed nanocomposite materials. In particular, plasmonic plastic nanocomposite sensing materials are described that comprise plasmonic H2-sensitive colloidally synthesized nanoparticles dispersed in a polymer matrix and enable the additive manufacturing of H2 sensors in a cost-effective and scalable way. We first discuss the concept of plasmonic plastic nanocomposite materials for the additive manufacturing of an active plasmonic sensing material on the basis of the three key components that require individual and concerted optimization: (i) the plasmonic sensing metal nanoparticles, (ii) the surfactant/stabilizer molecules on the nanoparticle surface from colloidal synthesis, and (iii) the polymer matrix. We then introduce the working principle of plasmonic H2 detection, which relies on the selective absorption of H species into hydride-forming metal nanoparticles that, in turn, induces distinct changes in their optical plasmonic signature in proportion to the H2 concentration in the local atmosphere. Subsequently, we assess the roles of the key components of a plasmonic plastic for H2 sensing, where we have established that (i) alloying Pd with Au and Cu eliminates hysteresis and introduces intrinsic deactivation resistance at ambient conditions, (ii) surfactant/stabilizer molecules can significantly accelerate and decelerate H2 sorption and thus sensor response, and (iii) polymer coatings accelerate sensor response, reduce the limit of detection (LoD), and enable molecular filtering for sensor operation in chemically challenging environments. Based on these insights, we discuss the rational development and detailed characterization of bulk-processed plasmonic plastics based on glassy and fluorinated matrix polymers and on tailored flow-chemistry-based synthesis of Pd and PdAu alloy colloidal nanoparticles with optimized stabilizer molecules. In their champion implementation, they enable highly stable H2 sensors with response times in the 2 s range and an LoD of few 10 ppm of H2. To put plasmonic plastics in a wider perspective, we also report their implementation using different polymer matrix materials that can be used for 3D printing and (an)isotropic Au nanoparticles that enable the manufacturing of macroscopic plasmonic objects with, if required, dichroic optical properties and in amounts that can be readily upscaled. We advertise that melt processing of plasmonic plastic nanocomposites is a viable route toward the realization of plasmonic objects and sensors, produced by scalable colloidal synthesis and additive manufacturing techniques.

Side chains affect the melt processing and stretchability of arabinoxylan biomass-based thermoplastic films.

Hydrophobization of hemicellulose causes melt processing and makes them stretchable thermoplastics. Understanding how native and/or appended side chains in various hemicelluloses after chemical modification affect melt processing and material properties can help in the development of products for film packaging and substrates for stretchable electronics applications. Herein, we describe a one-step and two-step strategy for the fabrication of flexible and stretchable thermoplastics prepared by compression molding of two structurally different arabinoxylans (AX). For one-step synthesis, the n-butyl glycidyl ether epoxide ring was opened to the hydroxyl group, resulting in the introduction of alkoxide side chains. The first step in the two-step synthesis was periodate oxidation. Because the melt processability for AXs having low arabinose to xylose ratio (araf/xylp<0.5) have been limited, two structurally distinct AXs extracted from wheat bran (AXWB, araf/xylp = 3/4) and barley husk (AXBH, araf/xylp = 1/4) were used to investigate the effect of araf/xylp and hydrophobization on the melt processability and properties of the final material. Melt compression processability was achieved in AXBH derived samples. DSC and DMA confirmed that the thermoplastics derived from AXWB and AXBH had dual and single glass transition (Tg) characteristics, respectively, but the thermoplastics derived from AXBH had lower stretchability (maximum 160%) compared to the AXWB samples (maximum 300%). Higher araf/xylp values, and thus longer alkoxide side chains in AXWB-derived thermoplastics, explain the stretchability differences.

Electrically Conducting Elastomeric Fibers with High Stretchability and Stability.

Stretchable conducting materials are appealing for the design of unobtrusive wearable electronic devices. Conjugated polymers with oligoethylene glycol side chains are excellent candidate materials owing to their low elastic modulus and good compatibility with polar stretchable polymers. Here, electrically conducting elastomeric blend fibers with high stretchability, wet spun from a blend of a doped polar polythiophene with tetraethylene glycol side chains and a polyurethane are reported. The wet-spinning process is versatile, reproducible, scalable, and produces continuous filaments with a diameter ranging from 30 to 70 µm. The fibers are stretchable up to 480% even after chemical doping with iron(III) p-toluenesulfonate hexahydrate and exhibit an electrical conductivity of up to 7.4 S cm-1 , which represents a record combination of properties for conjugated polymer-based fibers. The fibers remain conductive during elongation until fiber fracture and display excellent long-term stability at ambient conditions. Cyclic stretching up to 50% strain for at least 400 strain cycles reveals that the doped fibers exhibit high cyclic stability and retain their electrical conductivity. Finally, a directional strain sensing device, which makes use of the linear increase in resistance of the fibers up to 120% strain is demonstrated.

Tuning of the elastic modulus of a soft polythiophene through molecular doping.

Molecular doping of a polythiophene with oligoethylene glycol side chains is found to strongly modulate not only the electrical but also the mechanical properties of the polymer. An oxidation level of up to 18% results in an electrical conductivity of more than 52 S cm-1 and at the same time significantly enhances the elastic modulus from 8 to more than 200 MPa and toughness from 0.5 to 5.1 MJ m-3. These changes arise because molecular doping strongly influences the glass transition temperature Tg and the degree of π-stacking of the polymer, as indicated by both X-ray diffraction and molecular dynamics simulations. Surprisingly, a comparison of doped materials containing mono- or dianions reveals that - for a comparable oxidation level - the presence of multivalent counterions has little effect on the stiffness. Evidently, molecular doping is a powerful tool that can be used for the design of mechanically robust conducting materials, which may find use within the field of flexible and stretchable electronics.

Conducting materials as building blocks for electronic textiles.

ABSTRACT: To realize the full gamut of functions that are envisaged for electronic textiles (e-textiles) a range of semiconducting, conducting and electrochemically active materials are needed. This article will discuss how metals, conducting polymers, carbon nanotubes, and two-dimensional (2D) materials, including graphene and MXenes, can be used in concert to create e-textile materials, from fibers and yarns to patterned fabrics. Many of the most promising architectures utilize several classes of materials (e.g., elastic fibers composed of a conducting material and a stretchable polymer, or textile devices constructed with conducting polymers or 2D materials and metal electrodes). While an increasing number of materials and devices display a promising degree of wash and wear resistance, sustainability aspects of e-textiles will require greater attention.

A population-based study of seasonal variation in children's fractures.

INTRODUCTION Few Scandinavian studies have studied seasonal variations in paediatric fractures, and the studies that have focused on individual fracture sites. Furthermore, their findings do not coincide as they have described peaks in different seasons. Therefore, we described seasonal variation in the incidence rate (IR) of all paediatric fractures in the 1996-2019 period within a Danish population. METHODS We extracted data from the existing emergency room register at Odense University Hospital and included all fractures sustained by children aged 0-14 years and living in Odense Municipality. Seasonal and monthly IR were calculated using population counts stratified by age, gender and fracture site. RESULTS We recorded a significant increase in IR in spring and summer, except for a drop in July. For boys, the IR ranged from 206 in December to 404 per 10,000 person-years in June. For girls, the incidence ranged from 156 in December to 317 in May. Fractures were more frequent in the upper extremities and were up to six-fold more frequent in the epiphysis and metaphysis than in the shafts. All fracture sites showed a peak in spring and summer, suggesting that all fracture sites are subject to seasonal variation, especially the ones near the epiphysis. CONCLUSIONS The fracture peak observed in spring and summer corresponds to an increase in physical activity. The low incidence registered in July corresponds to a low level of sport activities during the summer vacations and families going on vacation in the countryside or travelling abroad. This study gives useful information for coordinating the right resources at hospitals. FUNDING none TRIAL REGISTRATION not relevant.

Hydrophobization of arabinoxylan with n-butyl glycidyl ether yields stretchable thermoplastic materials.

Hemicelluloses are regarded as one of the first candidates for the development of value-added materials due to their renewability, abundance, and functionality. However, because most hemicelluloses are brittle, they can only be processed as a solution and cannot be processed using industrial melt-based polymer processing techniques. In this study, arabinoxylan (AX) was hydrophobized by incorporating butyl glycidyl ether (BuGE) into the hydroxyl groups through the opening of the BuGE epoxide ring, yielding alkoxy alcohols with terminal ethers. The formed BuGE derivatives were melt processable and can be manufactured into stretchable thermoplastic films through compression molding, which has never been done before with hemicellulose modified in a single step. The structural and thermomechanical properties of the one-step synthesis approach were compared to those of a two-step synthesis with a pre-activation step to demonstrate its robustness. The strain at break for the one-step synthesized AX thermoplastic with 3 mol of BuGE is ≈200%. These findings suggest that thermoplastic polymers can be composited with hemicelluloses or that thermoplastic polymers made entirely of hemicelluloses can be designed as packaging and stretchable electronics supports.

Repurposing Poly(3-hexylthiophene) as a Conductivity-Reducing Additive for Polyethylene-Based High-Voltage Insulation.

Poly(3-hexylthiophene) (P3HT) is found to be a highly effective conductivity-reducing additive for low-density polyethylene (LDPE), which introduces a new application area to the field of conjugated polymers. Additives that reduce the direct-current (DC) electrical conductivity of an insulation material at high electric fields have gained a lot of research interest because they may facilitate the design of more efficient high-voltage direct-current power cables. An ultralow concentration of regio-regular P3HT of 0.0005 wt% is found to reduce the DC conductivity of LDPE threefold, which translates into the highest efficiency reported for any conductivity-reducing additive to date. The here-established approach, i.e., the use of a conjugated polymer as a mere additive, may boost demand in absolute terms beyond the quantities needed for thin-film electronics, which would turn organic semiconductors from a niche product into commodity chemicals.

Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments.

Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temperature and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The molecular design is contrary to that of other semiconductor-insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymerization of polar polythiophenes and urethane segments results in a ductile material that can be used as a free-standing solid. The copolymer displays a storage modulus of 25 MPa at room temperature, elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chemical doping and electrochemical oxidation reveal that the introduction of urethane segments does not unduly reduce the hole charge-carrier mobility and ability to take up charge. Further, stable operation is observed when the copolymer is used as the active layer of organic electrochemical transistors.

Oxidation Level and Glycidyl Ether Structure Determine Thermal Processability and Thermomechanical Properties of Arabinoxylan-Derived Thermoplastics.

Developing flexible, stretchable, and thermally processable materials for packaging and stretchable electronic applications from polysaccharide-based polymers contributes to the smooth transition of the fossil-based economy to the circular bioeconomy. We present arabinoxylan (AX)-based thermoplastics obtained by ring-opening oxidation and subsequent reduction (dA-AX) combined with hydrophobization with three different glycidyl ethers [n-butyl (BuGE), isopropyl (iPrGE), and 2-ethyl hexyl (EtHGE) glycidyl ether]. We also investigate the relationship between structural composition, thermal processing, and thermomechanical properties. BuGE- and iPrGE-etherified dA-AXs showed glass-transition temperatures (Tg) far below their degradation temperatures and gave thermoplastic materials when compression-molded at 140 °C. The BuGE (3 mol)-etherified dA-AX films at 19 and 31% oxidation levels show 244% (±42) and 267% (±72) elongation, respectively. In contrast, iPrGE-dA-AX samples with shorter and branched terminals in the side chains had a maximum of 60% (±19) elongation. No studies have reported such superior elongation of AX thermoplastic films and its relationship with molar substitution and Tg. These findings have implications on the strategic development of chemical modification routes using commercial polymer processing technologies and on fine-tuning structures and properties when specific polysaccharide-based polymers are used to engineer bio-based products for film, packaging, and substrates for stretchable electronic applications.