Twin matrix composites (TMC) are novel composite architectures where reinforcing composite elements are embedded in a secondary resin to address various mechanical functions suited for diverse engineering applications such as morphing wings. Here, for the first time, a recyclable twin matrix composite using micro-pultruded rods as reinforcements will be manufactured. Within the scope of the work, the design of the TMC mould which allows 0°/90°/0° reinforced layup will be discussed and created through additive manufacturing. Recycling and remanufacturing TMC will be conducted up to 4 times, and surface characteristics of the rods will be examined to monitor the effect of recycling. Interlaminar shear strength of TMC made from fresh and recycled rods will be investigated comparatively.

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Over the past 30 years, the polymer composite industry has flourished, producing advanced structural materials for the aviation, energy, and transportation sectors. However, the use of crosslinked thermoset matrices has been linked to significant end-of-life challenges, presenting a critical issue for the industry. Moreover, the industry is characterized by numerous labor-intensive processes. In alignment with Industry 4.0 principles, two major routes have been identified to enhance sustainability: the utilization of high-performance thermoplastic matrices and the integration of artificial intelligence in manufacturing. Nevertheless, there are substantial concerns regarding the life cycle assessment of these technologies, which are not accounted for in the initial calculations, including the environmental footprint of polymer synthesis and energy requirements for training AI. This perspective aims to address potential and significant CO₂ emissions from chemical feedstocks and the high computing requirements of these new technologies.

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Utilization of sustainable feedstocks to fabricate renewable thermosetting epoxy resins has been of great interest recently; however, their translation into composite structures and benchmark comparisons are poorly understood. Phloroglucinol is a phenolic molecule obtained from brown algae, and its epoxidized form is a high viscosity, high reactivity monomer. In this study, the potential of epoxidized phloroglucinol as a laminating resin was examined in comparison with a bisphenol A diglycidyl ether (BADGE) epoxy monomer employing the Epikure 04908 linear amine hardener system. Utilization of a reactive diluent for PHTE resin was necessary for room temperature laminating applications to reduce viscosity, and the thermomechanical properties of PHTE-based resins and composites are superior to those of BADGE systems.@en

Metal-free graphitic carbon nitrides are on the rise as polymer photocatalysts under visible light illumination, taking shares in a range of promising photocatalytic reactions, including water splitting. Their simple synthesis and facile structural modification afford them exceptional tunability, enabling the creation of photocatalysts with distinct properties. While their metal-free nature marks a significant step towards environmental sustainability, the high energy consumption required to produce carbon nitride photocatalysts remains a substantial barrier to their widespread adoption. Furthermore, the process of condensation at approximately 550 °C typically results in solid yields of less than 15 %, significantly challenging their economic viability. Here, we report on lowering manufacturing conditions of carbon nitride photocatalysts whilst enhancing photocatalytic activity by introducing binaphthyl diamine as a structural mediator. At 450 °C in 2 hours, carbon nitride photocatalyst shows a lower bandgap and enables visible light induced hydrogen evolution (194 μmol h⁻¹) comparable to benchmark carbon nitride photocatalysts.

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In this work, we pioneered the preparation of diamond-containing flexible electrodes using 3D printing technology. The herein developed procedure involves a unique integration of boron-doped diamond (BDD) microparticles and multi-walled carbon nanotubes (CNTs) within a flexible polymer, thermoplastic polyurethane (TPU). Initially, the process for the preparation of homogeneous filaments with optimal printability was addressed, leading to the development of two TPU/CNT/BDD composite electrodes with different CNT:BDD weight ratios (1:1 and 1:2), which were benchmarked against a TPU/CNT electrode. Scanning electron microscopy revealed a uniform distribution of conductive fillers within the composite materials with no signs of clustering or aggregation. Notably, increasing the proportion of BDD particles led to a 10-fold improvement in conductivity, from 0.12 S m^-1 for TPU/CNT to 1.2 S m^-1 for TPU/CNT/BDD (1:2). Cyclic voltammetry of the inorganic redox markers, [Ru(NH₃)₆]^3+/2+ and [Fe(CN)₆]^3-/4-, also revealed a reduction in peak-to-peak separation (ΔE_p) with a higher BDD content, indicating enhanced electron transfer kinetics. This was further confirmed by the highest apparent heterogeneous electron transfer rate constants (k⁰_app) of 1 × 10^-3 cm s^-1 obtained for both markers for the TPU/CNT/BDD (1:2) electrode. Additionally, the functionality of the flexible TPU/CNT/BDD electrodes was successfully validated by the electrochemical detection of dopamine, a complex organic molecule, at millimolar concentrations by using differential pulse voltammetry. This proof-of-concept may accelerate development of highly desirable diamond-based flexible devices with customizable geometries and dimensions and pave the way for various applications where flexibility is mandated, such as neuroscience, biomedical fields, health, and food monitoring.

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Developing high-performance carbonaceous anode materials for sodium-ion batteries (SIBs) is still a grand quest for a more sustainable future of energy storage. Introducing sulfur within a carbon framework is one of the most promising attempts toward the development of highly efficient anode materials. Herein, a microporous sulfur-rich carbon anode obtained from a liquid sulfur-containing oligomer is introduced. The sodium storage mechanism shifts from surface-controlled to diffusion-controlled at higher synthesis temperatures. The different storage mechanisms and electrode performances are found to be independent of the bare electrode material's interplanar spacing. Therefore, these differences are attributed to an increased microporosity and a thiophene-rich chemical environment. The combination of these properties enables extending the plateau region to higher potential and achieving reversible overpotential sodium storage. Moreover, in-operando small-angle X-ray scattering (SAXS) reveals reversible electron density variations within the pore structure, in good agreement with the pore-filling sodium storage mechanism occurring in hard carbons (HCs). Eventually, the depicted framework will enable the design of high-performance anode materials for sodium-ion batteries with competitive energy density.

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The present study describes the development of cure kinetics and chemo-rheological models for an epoxy vitrimer based on polyimine exchange to elucidate the potential in terms of processing and accurate process selection. Reaction kinetics is investigated using differential scanning calorimetry. A good agreement between the model and data can be demonstrated for different stoichiometries by selecting a parallel reaction approach consisting of an nth-order and an autocatalytic approach. The suggested chemo-rheological model captures the intrinsically high viscosity of the resin over a broad temperature and curing range, even after the gelation point. The Di-Benedetto equation represents the glass transition temperature advancement with cure while combining the rheological Winter-Chambon criterion and the kinetic model determines the degree of cure at the gelation. These results give important advice for improved process modeling of vitrimeric resins, facilitate accurate process selection, and pave the way towards the development of composites based on the matrix system investigated in this work.

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The development of epoxy resin formulations from renewable feedstocks has been thoroughly explored in the chemical literature. A simple one-pot chemical reaction involving sustainable phenolic molecules and epichlorohydrin results in the production of renewable epoxy monomers. These monomers can be cured with amines or anhydrides to yield cross-linked thermosetting resins. Although a wide variety of recipes exist, there is a notable gap in the application of these sustainable resin formulations to engineering contexts. This gap is primarily due to the lack of comprehensive, standardized analyses of these resin recipes, which impede their potential use in advanced composite applications. In this study, we reveal a high-performance resin formulation utilizing epoxidized phloroglucinol derived from brown algae in combination with an aerospace-grade amine hardener. The resin processing and thermomechanical properties are investigated using ASTM standard tests including tensile strength, flexural strength, fracture toughness, and interlaminar shear strength. Given the detailed comparative analysis, the partially renewable resin recipe outperforms petroleum derived analogues.

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Two-dimensional (2D) materials have great potential in macromolecular synthesis, yet there are some areas that still need to be explored, such as anionic polymerization. In this study, we present the first example of photoinduced anionic polymerization of ethyl-2-cyanoacrylate (ECA) using 2D graphitic carbon nitride (g-C₃N₄) as an active photocatalyst responsive to visible light. Our results demonstrate that particularly the mesoporous structure of g-C₃N₄ can initiate polymerization through the generation of electron-hole pairs upon exposure to visible light. To have a better insight into mechanistic pathways, several experiments, including control experiments, are conducted. The obtained polymers and the synthesized g-C₃N₄ materials are characterized comprehensively by chromatographic, thermal, and spectroscopic techniques. Accordingly, this study demonstrates an innovative process that can offer several advantages over traditional polymerization methods, including the ability to initiate polymerization at ambient temperatures and achieve high polymerization rates.

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Epoxy resins have been used as composite matrix materials for over half a century, enabling lightweight materials for a variety of applications. Their properties including high strength, chemical resistance, and ease of processing feature them as prime candidates for composite applications. Currently, high performance epoxy monomers are derived from non-renewable feedstocks, which presents a problem for future generations and technologies regarding sustainability. Many bio-based alternatives have been investigated, but properties fall short of high-performance industry standards due to a lack of appropriate chemical groups. Herein 3 bio-based epoxy monomers, with potential to replace high-performance standards, are compared against 3 petroleum derived industry standards. Industrial high performance aromatic diamine crystalline hardener is used to synthesise resin systems. Tensile, flexural and fracture toughness properties are investigated following ASTM standards. Beyond a practical investigation of the physical properties of these resins a comparison of chemical structure to mechanical properties is made. Free volume investigations using positron annihilation lifetime spectroscopy (PALS) were performed, and can be used to explain to some degree the observed properties of the resin systems. @en

The aerospace industry has been benefiting from the utilization of polymer materials since fiber-reinforced polymer composites (FRPC) offer high performances at low densities compared to metals. FRPC facilitated the design of lightweight materials, which is extensively used in aviation today. Since their first integration into structural parts, FRPC has experienced exponential growth over the years and has received a special interest from manufacturing engineering. While FRPC today is a major focus in engineering, the design of polymer matrix relies on polymer chemistry. However, aircraft materials are facing a pressing issue related to sustainability, since their environmental footprint is at an alarming level. In this review, commercial thermosetting polymer composites employed in aircraft structures are exhibited from a chemistry perspective by depicting starting products and curing reactions. The potential of chemistry to help design next-generation sustainable FRPC for structural parts by means of utilization of sustainable feedstock, energy-efficient processing, and recycling, is disseminated.

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From the synthesis of small biomolecules to complex macromolecular structures, click chemistry is one of the most promising and straightforward methodologies owing to its easy accessibility and high efficiency. A dual-heterogeneous photocatalyst with the capability of engendering light emission in upconversion materials combined with graphitic carbon nitride (g-CN) could present a powerful tool in electron transfer reactions, specifically in copper-catalyzed azide-alkyne cycloaddition (CuAAC) click reactions. We herein describe a “geared photochemistry” approach for producing an electron from g-CN by in-source lightening in the near-infrared region using upconversion glass that produces copper(i) to initiate the click reaction. Using this approach, the photocatalytic activation of g-CN has been achieved by using Tm³⁺ and Yb³⁺ ion-doped zinc-tellurite glass which absorbs laser irradiation at 975 nm and is capable of emitting blue light at 475 nm. The efficiency of this system has been investigated for various CuAAC reactions ranging from small molecule synthesis to the macromolecular scale including modification strategies of polymers.

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Polymerization of multifunctional thiol-ene molecules is attractive as a proof of concept in photopolymerization, yet the formation of a bead structure is highly restricted. This manuscript will show graphitic carbon nitride based liquid–liquid printing and subsequent photopolymerization to form thiol-ene polymer beads with extreme simplicity and potential scalability.@en

Solar irradiation provides critical energy to conduct chemical reactions. Many light-sensitive materials, such as semiconductors, guide photoredox-induced chemical pathways to tailor favored chemical conversions. Polymer synthesis by light is popular, however mainly addressed by conducting radical-based polymerization strategies. Oxidative photopolymerization is an advanced method to form functional polymers that are otherwise formed through complicated reactions. Herein, infant-stage oxidative photopolymerization will be introduced with examples in the field.

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The utilization of sunlight to conduct chemistry has been on a stark rise in the era of sustainability. A similar trend is observed in polymer science, mainly to initiate polymerization and modify polymer materials, but mostly relying on the utilization of soluble initiator/activator molecules. Semiconductors, on the other hand, grant a platform for "photoredox"induced chemical pathways, so that reductive and oxidative reactions (as well as radical formation) can be tailored according to band positions. Despite their utilization as dispersed or dissolved phases, immobilization of semiconductors on macroscale solid surfaces is attractive to entail scale-up options. In this Review, semiconductors incorporated in cross-linked porous polymer networks will be summarized both from synthesis and application perspectives.

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Controlled radical polymerization corresponds to variety of synthetic strategies that aim the generation of precise macromolecular architectures. Iodine transfer polymerization (ITP) is one of the oldest methods to conduct controlled radical polymerization; however, it seems to have lost visibility compared to other popular techniques. It relies on utilization of iodine species in reversible deactivation kinetics, and it has some significant advantages compared to other methods. Its simplicity, minimized toxicity, metal-free nature, no coloring on final product, and ease of purification provide widespread applicability, even in industry. In this perspective, the basics of ITP are re-introduced, and emerging technologies (heterophase polymerization, photoinitiation, and sustainability) in ITP are discussed.

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