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Phosphonium-based polythiophene conjugated polyelectrolytes (CPEs) with three different counterions (dodecylsulfate, octylsulfate and perfluorooctane sulfonate) are synthesized to determine how the nature of the counterion affects the thermal properties, the self-assembly in thin films and the performance as the cathode interfacial layer in polymer solar cells (PSCs). The counterion has a significant effect on the thermal properties of the CPEs, affecting both their glass transition and crystalline behaviour. Grazing-incidence wide-angle X-ray scattering studies also indicate that changing the nature of the counterion influences the microstructural organization in thin films (face-onversusedge-on orientation). The affinity of the CPEs with the underlying photoactive layer in PSCs is highly correlated with the counterion species. Finally, in addition to an increase of the power conversion efficiency ofca15% when using these CPEs as cathode interfacial layers in PSCs, a higher device stability is noted, compared to a reference device with a calcium interlayer. (c) 2020 Society of Industrial Chemistry This work was supported by the CNRS and the Universite de Montpellier. This work was also supported in part by the Science Foundation Ireland under grant no. 12/IP/1608. Research in Mons is supported by FNRS-FRFC (2Dto3D project - EOS programme) and Region Wallonne (OPTI2MAT excellence programme). The University of Mons and Hasselt University co-authors are grateful for financial support by the Science Policy Office of the Belgian Federal Government (BELSPO; PAI/IAP 7/05). JK is a postdoctoral fellow of the Research Foundation - Flanders (FWO Vlaanderen). NVdB thanks the Vrije Universiteit Brussel for a post-doctoral grant. The HINT COST action MP1202 and French-Irish programme 'Hubert Curien Ulysses' (31998ZF) are also acknowledged for support. This research has also been supported by the European Commission under the 7th Framework Programme through the 'Research Infrastructures' action of the 'Capacities' programme (contract no. CP-CSA_INFRA-2008-1.1.1 Number 226507-NM13). We further thank the Diamond Light Source for beamtime at the I07 beamline (experiment SI13868) and TA Instruments for the RHC equipment. Clement, S (corresponding author), Univ Montpellier, ENSCM, CNRS, ICGM, Montpellier, France. sebastien.clement1@umontpellier.fr

Conjugated polyelectrolyte (CPE) interfacial layers present a powerful way to boost the I-V characteristics of organic photovoltaics. Nevertheless, clear guidelines with respect to the structure of high-performance interlayers are still lacking. In this work, impedance spectroscopy is applied to probe the dielectric permittivity of a series of polythiophene-based CPEs. The presence of ionic pendant groups grants the formation of a capacitive double layer, boosting the charge extraction and device efficiency. A counteracting effect is the diminishing affinity with the underlying photoactive layer. To balance these two effects, we found copolymer structures containing nonionic side chains to be beneficial. Funding Agencies|IAP project Functional Supramolecular Systems [7/05]; Science Policy Office of the Belgian Federal Government (BELSPO); Research Program of the Research Foundation Flanders (FWO) [G.0415.14N]; Foundation for Fundamental Research on Matter (FOM) from The Netherlands Organization for Scientific Research (NWO) [V0714M-13MV60]; Swedish Research Council Linnaeus LiLi-NFM at Linkoping University; Vrije Universiteit Brussel (VUB); University of Montpellier; CNRS; University of Mons

Self-healing polymers render their life cycle more sustainable by recovering their properties upon healing. Intrinsic self-healing polymers can be recycled, which further reduces waste production. Yet, despite these intrinsic benefits, several sustainability issues remain largely neglected, including the use of fossil-derived materials, hazardous chemicals, and the material management at the end of its life. Herein we report a series of castor oil-based self-healing elastomers that account for these challenges and show improved mechanical and self-healing capabilities compared to the other bio-based self-healing materials. Castor oil was functionalized using a simple, one-pot, solventless synthesis from renewable resources and crosslinked by Diels-Alder cycloaddition. They can be reprocessed and recycled, or hydrolytically degraded at the end of their service life. The mechanical properties of the materials can be tuned (Young’s modulus 0.5-20 MPa), with a fracture strain of up to 487%. A fracture strain of 100% could already be recovered after just 60 seconds at room temperature, and 75% of the mechanical properties after just 24 h. By taking advantage of these properties, a soft pneumatic gripper has been developed, capable of healing autonomously which is fully recyclable and degradable. Hence, we provide a sustainable alternative for soft-robotics applications and for self-healing elastomers in general.

The variability in the shapes and sizes of objects presents a significant challenge for two-finger robotic grippers when it comes to manipulating them. Based on the chemistry of vitrimers (a new class of polymer materials that have dynamic covalent bonds, which allow them to reversibly change their mechanical properties under specific conditions), we present two designs as 3D-printed shape memory polymer-based shape-adaptive fingertips (SMP-SAF). The fingertips have two main properties needed for an effective grasping. First, the ability to adapt their shape to different objects. Second, exhibiting variable rigidity, to lock and retain this new shape without the need for any continuous external triggering system. Our two design strategies are: 1) A curved part, which is suitable for grasping delicate and fragile objects. In this mode and prior to gripping, the SMP-SAFs are straightened by the force of the parallel gripper and are adapted to the object by shape memory activation. 2) A straight part that takes on the form of the objects by contact force with them. This mode is better suited for gripping hard bodies and provides a more straightforward shape programming process. The SMP-SAFs can be programmed by heating them up above glass transition temperature (54°C) via Joule-effect of the integrated electrically conductive wire or by using a heat gun, followed by reshaping by the external forces (without human intervention), and subsequently fixing the new shape upon cooling. As the shape programming process is time-consuming, this technique suits adaptive sorting lines where the variety of objects is not changed from grasp to grasp, but from batch to batch.

The high-temperature transformations and crystallization of K-based inorganic polymers made from FeO-SiO2 and FeO-SiO2-Al2O3 iron-rich model slags were investigated, with particular focus on the effect of the Al/K and Si/K molar ratios. Upon firing to 1100 °C, the main crystalline phases were hematite and (iron) leucite. Addition of corundum decreases the crystallization rate of leucite. Increasing the Al/K molar ratio increased the thermal stability due to the substitution of Al3+ for Fe3+ in leucite. The Si/K molar ratio impacted the crystallization of leucite. Upon firing to 1100 °C and 1350 °C there was a linear correlation between the amount of leucite and the Si/K molar ratio. Higher Si/K molar ratio resulted in ceramics with higher glass content and lower thermal stability. Thus, the phase assemblage can be adjusted by changing the amount of activator.

Peptide-based hydrogels represent promising systems for the sustained release of different types of drugs, ranging from small molecules to biologicals. Aiming at subcutaneous injection, which is a desirable parenteral administration route, especially for biologicals, we herein focus on physically crosslinked systems possessing thixotropic behaviour. The purpose of this study was to evaluate the in vitro and in vivo properties of hydrogels based on the amphipathic hexapeptide H-FQFQFK-NH2, which served as the lead sequence. Upon doubling the length of this peptide, the dodecapeptide H-FQFQFKFQFQFK-NH2 gave a significant improvement in terms of hydrogel’s in vivo stability post-injection, as monitored by nuclear SPECT/CT imaging. This increased hydrogel stability also led to a more prolonged in vivo release of encapsulated peptide cargoes. Even though no direct link with the mechanical properties of the hydrogels before injection can be made, an important effect of the subcutaneous medium was noticed in post invivo injection measurements. The results were validated for a therapeutically relevant analgesic peptide using the hot-plate test as an acute pain model. Gratifyingly, it was confirmed that elongation of the hydrogelator sequence induced more extended antinociceptive effects. Altogether, this simple structural modification of the hydrogelating peptide could provide a basis for reaching longer durations of action upon use of these soft biomaterials.

The molecular dynamics of the reversible network 4F230-2M230 were studied systematically by dielectric relaxation spectroscopy (DRS) at frequencies between 10–1 and 107 Hz under both isothermal and non-isothermal conditions, focusing on the cooperative segmental dynamics as sensed by the dielectric α-relaxation. This reversible network is based on the furan–maleimide Diels–Alder reaction of a 4-functional furan-functionalized Jeffamine coupled with a 2-functional maleimide. Different strategies for extracting a “dielectric” glass transition temperature (Tg) were employed and compared. First, relaxation times τα were derived by conventional Havriliak–Negami fits of dielectric spectra and then fitted to the Vogel–Fulcher–Tammann (VFT) equation, which yields the dynamic Tg of partially cured samples (approach I). Alternatively, the thermal glass transition temperature was derived from the dielectric spectra ε′(f, T) using a fine structure analysis by bivariate differential sampling. Both the dynamic and thermal Tgs revealed an excellent agreement, confirming the stability of the VFT fits as well as the equivalence of both quantities as usually expected for bulk glass-forming materials. Two attempts were made to find a unique set of VFT parameters based on a global fit considering DRS spectra from partially cured samples during heating from −120 to 100 °C. Via a first procedure (approach II), a unique set of VFT parameters EV and τ∞ was obtained that well describes the relaxation times during non-isothermal cure at temperatures where the effects of ongoing cure kinetics can be neglected. To overcome this restriction, a refined approach III was developed that includes the earlier reported kinetic model for the DA reaction and allows accurate predictions for the relaxation time evolution during both isothermal and non-isothermal cure experiments. Based on this unique description, a new technique for continuous cure monitoring was proposed and tested. This technique allows us to compute in real-time dynamic Tg from the relaxation time τα at any stage of the isothermal or non-isothermal cure process using two unique VFT parameters from the global fit procedure. This approach might stimulate new applications of DRS-based cure monitoring.

water uptake in organic coatings. To this aim, we start from a physical model, where not only Fickian diffusion of water is taken into account but also the adsorption/desorption reaction of water on the polymer matrix. Starting from a number of important coating properties and crucial model parameters, derived from gravimetric and Fourier transform infrared (FTIR) measurements as the model input, the local water concentration over the coating thickness as a function of time is modelled for a polyethylene glycol diacrylate (PEGDA) coating. The modelled water concentration is then used to calculate virtual capacitance values which are evaluated against experimental capacitance values extracted from impedance measurements. The constraints of the FEM model and ORPEIS experiments and the discrepancies between them are critically discussed in order to carry out a meaningful model validation, eventually leading to model improvements.

Self-healing soft robots show enormous potential to recover functional performance after healing the damages. However, healing in these systems is limited by the recontact of the fracture surfaces. This paper presents for the first time a shape memory alloy (SMA) wire-reinforced soft bending actuator made out of a castor oil-based self-healing polymer, with the incorporated ability to recover from large incisions via shape memory assisted healing. The integrated SMA wires serve three major purposes; (i) Large incisions are closed by contraction of the current-activated SMA wires that are integrated into the chamber. These pull the fracture surfaces into contact, enabling the healing. (ii) The heat generated during the activation of the SMA wires is synergistically exploited for accelerating the healing. (iii) Lastly, during pneumatic actuation, the wires constrain radial expansion and one-side longitudinal extension of the soft chamber, effectuating the desired actuator bending motion. This novel approach of healing is studied via mechanical and ultrasound tests on the specimen level, as well as via bending characterization of the pneumatic robot in multiple damage healing cycles. This technology allows soft robots to become more independent in terms of their self-healing capabilities from human intervention.

The thermophysical properties, mechanical behavior, and healing performance of Diels–Alder-based polymer networks can be tuned widely by changing the molar mass, functionality, and stoichiometric ratio of the multifunctional diene (e.g., furan) and dienophile (e.g., maleimide) monomers. Blending furan-functionalized monomers with a high and low molar mass opens a new dimension in tuning the properties of the resulting reversible polymer network blends (RPNBs), containing different ratios of elastomeric and thermoset phases, with low and high crosslink densities and glass transitions below and above room temperature, respectively. Increasing the thermoset content up to 20 wt % raises the gel transition temperature (Tgel), relaxation time (τ), rubbery plateau modulus, ultimate stress, and Young’s modulus of the stiffened elastomers, while the strain at fracture and self-healing efficiency remained mostly unchanged. Conversely, the addition of up to 20 wt % of the elastomer phase drastically toughens the thermosets because of stress dissipation, which can suppress the stress concentration in the phase-separated network blends. The blends showed higher stress and strain at break while retaining similar Young’s moduli. The toughness increases up to an order of magnitude at 50 wt %, compared to the pure thermoset. The phase-separated morphologies were evidenced by the presence of the Tg’s of the pure networks in DSC and DMA.

The combination of different polymers in the form of blended plastics has been used in the plastic industry for a long time. Nevertheless, analyses of microplastics (MPs) have been mainly limited to the study of particles made of single-type polymers. Accordingly, two members of the Polyolefins (POs) family, i.e., Polypropylene (PP) and Low-density Polyethylene (LDPE) are blended and extensively studied in this work due to their applications in industry as well as abundance in the environment. It is shown that 2-D Raman mapping only provides information about the surface of blended MPs (B-MPs). While complimentary 3-D volume analysis is needed to fully understand the presence of various polymers in such complex samples. Therefore, 3-D Raman mapping is applied to visualize the morphology of the distribution of polymers within the B-MPs together with the quantitative estimation of their concentrations. A parameter defined as the concentration estimate error (CEE) evaluates the precision of the quantitative analysis. Furthermore, the impact of four excitation wavelengths 405, 532, 633, and 785 nm is investigated on the obtained results. Finally, the application of a line-shaped laser beam profile (line-focus) is introduced for reducing the measurement time from 56 to 2 h.

Fungi-mediated self-healing concrete is a novel approach that promotes the precipitation of calcium carbonate (CaCO3) on fungal hyphae to heal the cracks in concrete. In this study, we set out to explore the potential of fungal species isolated from a limestone cave by investigating their ability to precipitate CaCO3 and to survive and grow in conditions relevant to concrete. Isolated strains belonging to the genera Botryotrichum sp., Trichoderma sp. and Mortierella sp. proved to be promising candidates for fungi-mediated self-healing concrete attributed to their growth properties and CaCO3 precipitation capabilities in the presence of cement.

Funding Information: This work was supported by the European Union Horizon 2020 research programme under MSCA COFUND grant agreement 101034352 with co-funding from the VUB-Industrial Research Fund: X-ray tomography was also supported by the Academy of Finland via RAMI infrastructure project (#293109). Publisher Copyright: © 2023 by the authors. As we know, 3DPC is printed layer by layer compared with mold-casting conventional concrete. Pore structure and layer-to-layer interface are two main aspects of the internal structure for 3DPC, which decide 3DPC’s mechanical performance. The layer-to-layer interface caused by printing is specific to 3DPC. The emphasis of this study lies in the layer-to-layer interfaces of 3DPC. The first aim of this study is to quantify the characteristics of the layer-to-layer interface and therefore characterize different aspects of the interfaces. The second aim of this study is to explore how the internal structure of printed concrete influences the mechanical performance of 3DPC. This research set out to design a series of experimental comparisons between 3DPC and casted concrete with the same compositions. Mechanical tests, i.e., compressive stress, ultrasonic Pulse Velocity test, flexural tension, and tension splitting, as well as the Ultrasonic Pulse Velocity test, were performed to check the mechanical performance of3DPC. Contrary to what has often been expected, the mechanical test results showed the printed concrete has a quality not worse than casted concrete with the same recipe. Meanwhile, the X-ray computed tomography (X-CT) is used to characterize the internal structure, pore shapes, and interfaces of 3DPC. First, the investigation revealed that the lower total porosity and fewer big voids could be the fundamental causes meaning 3DPC has a better mechanical performance than casted concrete. Second, the statistics based on aspect ratio show that the distribution curves follow similar trends, regardless of the printed or casted concrete. Third, this study quantified the depth of the different interfaces for 3DPC. The results suggest that the porosity in an interface varies in a range. The author’s pioneer work has contributed to our present understanding of the interfaces of 3DPC.

The statistics analysis shows that the distribution curves of pore shapes follow similar trends, regardless of the printed concrete or casted concrete. The bigger voids with an equivalent diameter of more than 80 μm for casted concrete are more “equant” compared to printed concrete

In the field of soft robotics, knowledge of material science is becoming more and more important. However, many researchers have a background in only one of both domains. To aid the understanding of the other domain, this tutorial describes the complete process from polymer synthesis over fabrication to testing of a soft finger. Enough background is provided during the tutorial such that researchers from both fields can understand and sharpen their knowledge. Self-healing polymers are used in this tutorial, showing that these polymers that were once a specialty, have become accessible for broader use. The use of self-healing polymers allows soft robots to recover from fatal damage, as shown in this tutorial, which increases their lifespan significantly.

Discrete spacers allow to transversally connect planar textiles and to transform them into pseudo-3D architectures. These 3D textiles can provide the optimal reinforcement in cement composites as the concrete casting process is enhanced and the textile placement within the mould is well-controlled. This research investigated the effect of discrete spacer connections on the flexural properties and cracking behaviour of TRCs and performed a comparison with equivalent 2D TRC systems (same in-plane textiles but without connections) and with knitted 3D textiles. Additional investigated parameters were the material of the reinforcement (glass, carbon) and the density of the textile (fibre volume fraction of the composite). A four-point bending experimental campaign was conducted on four different textile configurations containing (i) no connections (ref), (ii) four spacer connections distributed over the shear zone, (iii) nine spacer connections distributed over the entire length between the supports (both shear and constant moment zone) and (iv) 3D knitted connections. The spacer connections resulted in a pronounced post-cracking stiffness increase and a positive influence on the crack formation of the TRC. Their influence was however dependent on the fibre volume fraction (Vf) of the in-plane reinforcement; configurations with a higher Vf required a higher degree of connections to showing a post-cracking stiffness increase.

The valorization of Fe-rich fayalite slag (FS) as a precursor for alkali-activated materials (AAMs) is hampered by its low reactivity at ambient temperature. Here, FS was blended with waste-based reactive co-binders such as ladle slag (LS) and blast furnace slag (BFS) to improve the fresh and hardened state properties of the AAMs for potential construction applications. The results showed that the incorporation of LS and BFS as an additional source of Ca and Al accelerated the reaction kinetics and influenced the binder gel type and formation mechanism. In all the mixes, Fe, Si and Na are present in the evolving binder gel. In addition to these elements, the binder gel of the blended formulations is also rich in higher quantities of Ca and Al and showed possible formation of C-A-S-H and C-(N)-A-S-H together with the development of andradite, a calcium ferrosilicate hydrate phase formed from chemical interaction between FS and co-binders; it indicates that both FS and co-binder participated in the binder gel formation. Furthermore, the nucleating and filling effects of co-binders improved the workability, ultrasonic pulse velocity and mechanical properties; this also densified the structure and lowered the water absorption and permeable porosity of the blended mortars. The compressive strength of blended mortars was above 20 MPa, thus satisfying the strength requirements of building materials according to ASTM C62. The results of this study emphasize the reuse potential of FS with other waste streams in producing eco-friendly AAMs, which can have a wide range of construction applications.

Reversible poly(methacrylate) networks are synthesized with tunable thermomechanical and self-healing properties. The focus is on high-modulus networks (guide value around 500 MPa at 25 °C) in combination with fast self-healing for applications as coatings at ambient temperature. In case of a broad temperature window for outdoor applications, mechanical robustness up to 120 °C is aimed for. Methacrylate-functionalized Diels-Alder prepolymers containing furan-maleimide reversible covalent bonds are first synthesized at 25 °C. The prepolymers act as reversible crosslinkers in the subsequent UV-polymerization at 60 °C. Reaction-induced phase-separation is achieved by changing the balance between soft and hard blocks, leading to homogeneous and (partially) phase-separated, fully reversible poly(methacrylate) networks. The incorporation of urethane bonds introduces hydrogen bonding capacity. For comparison, irreversible poly(methacrylate) networks, i.e. without reversible Diels-Alder bonds, are synthesized via UV-polymerization of irreversible methacrylate-functionalized prepolymers. A tunable self-healing behavior is demonstrated. The single-dynamic high-modulus poly(methacrylate) networks, i.e. purely based on reversible Diels-Alder bonds, show slowest self-healing, e.g. 7 days in ambient conditions. The dual-dynamic high-modulus poly(methacrylate) networks, i.e. based on covalent Diels-Alder bonding and supramolecular hydrogen bonding, show fastest self-healing, e.g. 10 min in ambient conditions, if hydrogen bonding is combined with intrinsic local network mobility in case of a (partially) phase-separated network morphology.

The development of bio-based polymers displaying promising end-of-life opportunities would have an immense impact on the polymer industry but has remained largely unexplored. Therefore, in this work, self-healing bio-aromatic networks with lignin contents up to 29 wt % were designed based on the thermoreversible Diels−Alder reaction. The networks were developed by reacting a furan-functionalized solvent-extracted lignin and a furan-bearing polyether (F5000) with a bismaleimide (DPBM). The obtained networks were nanophase-separated between a flexible F5000-rich phase and a rigid lignin-rich phase, which was evidenced by (modulated temperature) differential scanning calorimetry and small angle X-ray scattering. Partially due to the phase-separation, improved mechanical properties were obtained, including a higher Young’s modulus and improved toughness. In addition, the thermal stability of the networks significantly increased due to the addition of lignin. Besides the thermomechanical improvement, the networks showed promising stress-relaxation, creep resistance, healing, and reprocessability. A macroscopic healing efficiency of 62% of the toughness was obtained. Moreover, the networks were completely resoluble, which allows for promising recycling possibilities.

Recent advances in soft continuum robots revealed the need for accurate models, required to develop advanced control strategies. In this paper a general methodology is presented that allows to create an accurate inverse kinematic control based on hyperelastic models, fitted on mechanical material properties. This methodology is based on finite element analysis (FEA) and links the mechanical properties of the material to the simulated behaviour of a Pneunet actuator. This procedure is valid for any sort of hyperelastic material used in soft robotics, however, as a case study, a specific material with a self-healing ability is considered. This elastomeric polymer can recover from macroscopic damages without losing its mechanical performances, after undergoing a heat treatment. In this article, an accurate characterisation of the mechanical behaviour of this material is provided, involving mechanical testing, both in tensile and compression. On this experimental characterisation data constitutive laws are fitted, using a FEA simulator. The robustness of this material modelling is shown, re-fitting the curve for material samples that were exposed to multiple damage-healing cycles. With this obtained constitutive model, a FEA simulation of a bending soft pneumatic actuator is developed. The simulation results are experimentally validated with a dedicated test bench consisting of a pressure control unit and a motion tracking camera. Using this validated model, an inverse kinematic control is developed, including the FEA simulation in the control scheme.

Kaolin and halloysite are aluminosilicate materials widely available in Cameroon. The present study aims at investigating the fresh and hardened properties of consolidated metakaolin- meta-halloysite blends geopolymer binders cured at room temperature (23 ± 3 ◦C). To produce the geopolymers, metakaolin was used as the main solid precursor and was replaced by meta-halloysite up to 50 wt%. The raw materials and synthesized products were characterized using BET, FX, XRD, FTIR, SEM/EDS, leachability, setting time, mechanical properties, water absorption, porosity and bulk density. The results revealed that both initial and final settings decreased with the rise of the meta-halloysite content. Such behaviour is related to the higher reactivity of meta-halloysite which led to a higher geopolymerization rate resulting in shorter setting and hardening times of the MK-based binder. Incorporating meta-halloysite increased the rate of release of aluminosilicate oligomers in the alkaline solution favourable for the development of a dense and strong matrix explaining the high mechanical performances. The compressive strength and bulk density increased from 30.3 to 65.2 MPa and 1.75 to 2.12 g.cm− 3, respectively. The highest performance was attained on sample GP50, which contained 50 wt% metakaolin and meta-halloysite (65.2 MPa) and also had a decreased porosity (13.02%) and water absorption (6.72%).

In this work, the separate diffusion of water and ions through a polyethylene glycol diacrylate (PEGDA) coating was characterized using an integrated spectro-electrochemical technique. The ions ingress front position profile along the thickness of the coating was derived from fitting odd random phase electrochemical impedance spectroscopy (ORP-EIS) data using a physically relevant electrochemical equivalent circuit (EEC). The arrival time of the ions at the coating/metal oxide buried interface obtained from EEC and rapid uptake of water was verified using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements in Kretschmann geometry integrated in the ORP-EIS set-up.

Although concrete is a prominent building material in nearly all construction applications, it is also known for its reinforcement corrosion and thus material degradation due to crack formation. These severe durability issues ignited the use of microorganisms to self-heal concrete cracks in a biological way by promoting the precipitation of CaCO3 on their cell walls. Filamentous fungi have recently emerged as high-potential self-healing agents because of their ability to grow in large mycelial networks providing abundant nucleation sites for CaCO3 precipitation. Based on the extensive research already conducted on bacteria-based self-healing concrete, protection of the microbial spores in the concrete mix is key to the survival of the microorganism. This research therefore applied a natural encapsulation technique derived from bacteria-based literature on fungal spores. The fungus Trichoderma reesei, already known in the field of self-healing concrete, was used to prepare the capsules. First results showed that the fungus was able to withstand the encapsulation process, yet could not survive when embedded in cement due to its harsh conditions. The possibilities to optimize the procedure are however discussed in the paper and give rise to a broad range of research opportunities.

Point defects play important and crucial roles in the design of high performance photocatalysts. We report on the electrochemical fabrication of black Ti−Mo-Ni−O nanotubes as a promising electrode material for solar-assisted water splitting. The ternary Ti−Mo-Ni−O catalyst was annealed in hydrogen atmosphere to induce point defects in the material to enhance its conductivity, charge carriers density, and performance. The effect of annealing duration on the performance of ternary Ti−Mo-Ni−O nanotube films was investigated. The hydrogen-annealed nanotubes showed enhanced optical characteristics in the visible spectrum, which can be related to the formation of defect states upon hydrogen annealing. The 10 h-annealed sample showed an exceptionally enhanced photocurrent density of ∼10 mA/cm2 with a remarkable open-circuit voltage of ∼−1.0 VAg/AgCl under AM 1.5G illumination. This improved photocurrent is in agreement with the obtained 75 % incident-photon-to-current-conversion-efficiency (IPCE), confirming the improved photoactivity of the hydrogen-treated mixed oxide nanotubes.

Diels–Alder (DA) cycloadditions in reversible polymer networks are important for designing sustainable materials with self-healing properties. In this study, the DA kinetics of hydroxyl-substituted bis- and tetrafunctional furans with bis- and tris-functional maleimides, both containing ether-functionalized spacers, is investigated by modelling two equilibria representing the endo and exo cycloadduct formation. Concretely, the potential catalysis of the DA reaction through hydrogen bonding between hydroxyl of the furans and carbonyl of the maleimides or ether of the spacers is experimentally and theoretically scrutinized. Initial reaction rates and forward DA rate constants are determined by microcalorimetry at 20 °C for a model series of reversible networks, extended with (i) a hydroxyl-free network and hydroxyl-free linear or branched systems, and (ii) polypropylene glycol additives, increasing the hydroxyl concentration. A computational density-functional theory study is carried out on the endo and exo cycloadditions of furan and maleimide derivatives, representative for the experimental ones, in the absence and presence of ethylene glycol as additive. Additionally, an ester-substituted furan was investigated as a hydroxyl-free system for comparison. Experiment and theory indicate that the catalytic effect of H-bonding is absent or very limited. While increased concentration of H-bonding could in theory catalyze the DA reaction, the experimental results rule out this supposition.

Alkali-activated materials (AAMs) provide an opportunity to up-cycle several residues into added-value materials. Although generally praised for their performance under thermal loads, the thermal behavior of AAMs is dictated by a multitude of factors and the performance of CaO-FeOx-rich systems may differ from geopolymers. Therefore, this work ascertains the high‑temperature resistance of CaO‑FeOx-Al2O3-SiO2-rich AAMs. Mortars were exposed to different heating rates (≤10 °C/min) and temperatures (≤1100 °C), and volume and mass loss, apparent density, compressive strength (CS), mineralogical composition, and morphology were evaluated. At low heating rates, the main effects noted were densification and a gradual lightening of color as the temperature rose. CS underwent an abrupt decline at 750 °C and recovered at higher temperatures, reaching a maximum value of 184 ± 13 MPa at 1100 °C. With an increased heating rate to 10 °C/min, the strength loss at 750 °C persisted, but maximum CS was halved when firing at 900 °C. At 1100 °C, a significant reduction of CS was observed, but all samples maintained their integrity. Except for 1100 °C at 10 °C/min, all sintered-AAMs presented residual CS above 40 MPa. These results demonstrate that CaO-FeOx-Al2O3-SiO2-rich AAMs present interesting thermal behavior and can be potentially used to produce glass-ceramics or refractory materials from secondary resources.

Incorporation of compact spectroscopic near-infrared (NIR) light detectors into various wearable and handheld devices opens up new applications, such as on-the-spot medical diagnostics. To extend beyond the detection window of silicon, i.e., past 1000 nm, organic semiconductors are highly attractive because of their tunable absorption. In particular, organic NIR wavelength-selective detectors have been realized by incorporating donor:acceptor thin films, exhibiting weak intermolecular charge-transfer (CT) absorption, into an optical microcavity architecture. In this work, the alkyl side chains of the well-known PBTTT donor polymer are replaced by alkoxy substituents, hereby redshifting the CT absorption of the polymer:PC61BM blend. It is shown that the unique fullerene intercalation features of the PBTTT polymer are retained when half of the side chains are altered, hereby maximizing the polymer:fullerene interfacial area and thus the CT absorption strength. This is exploited to extend the detection range of organic narrow-band photodetectors with a full-width-at-half-maximum of 30–38 nm to wavelengths between 840 and 1340 nm, yielding detectivities in the range of 5 × 1011 to 1.75 × 1010 Jones, despite the low CT state energy of 0.98 eV. The broad wavelength tuning range achieved using a single polymer:fullerene blend renders this system an ideal candidate for miniature NIR spectrophotometers.

Because of their intriguing properties for optoelectronic applications, research on organic semiconducting polymers has steadily progressed over the past decades, yielding increasingly fine-tuned (hetero)aromatic polymer backbones. In this work, the push-pull copolymer PDTPQx is synthesized, both via Stille poly-condensation and direct arylation polymerization (DArP), permitting comparison of the two procedures. Near-infrared organic photodetectors (OPDs) are constructed based on these different polymer batches in combination with PC 61 BM, and their performance was investigated. From the current-voltage characteristics, it is clear that the DArP polymer-based devices outperform those prepared from the Stille polymers, both in terms of dark current density and external quantum efficiency (EQE), and therefore in terms of specific detectivity as well. The relatively high highest occupied molecular orbital energy level of PDTPQx, in combination with the clear charge-transfer absorption band observed for the DArP-based device, is beneficial for application in organic resonant cavity photodetectors. Such OPDs are prepared for the DArP PDTPQx:PC 61 BM (1:4) blends with 180 and 210 nm thick bulk heterojunction active layers. EQEs of 2.5% at 1016 nm and 1% at 1140 nm are achieved, with full-width-at-half-maximum peak responses of 44 and 45 nm, respectively, and detectivities of 2.24 × 10 10 and 1.06 × 10 10 Jones. The authors thank Huguette Penxten for CV analysis, Christel Willems for the TEM sample preparation, and Brent Fripont for the graphical abstract artwork. We also thank the Research Foundation – Flanders (FWO Vlaanderen) for continuing financial support (projects G0D0118 N, G0B2718 N, 1S50820 N, 11D2618 N), as well as the European Research Council (ERC, grant agreement 864625). Dr. Q. Liu acknowledges financial support from the European Union’s Horizon 2020 research and innovation program under the Marie-Curie grant agreement no. 88279.

Sensory receptors in biological systems are an essential part of natural organisms to perceive, understand and adapt to their environment and evaluate their internal state. They are interlinked with the senses of living organisms and are an important tool for the survival and evolution of species. Researchers have implemented the biomimetic receptor approach into the development of artificial sensors, in an attempt to mimic the sensory transduction of organisms, like self-healing ability and flexibility. However, aspects of biological transduction like selectivity and multi-sensing are still underdeveloped in the field of soft self-healing sensors (SSHS). The multi-sensing aspect is discussed in this review paper, focusing on resistive-based SSHS for detecting different stimuli, like strain, pressure, tactile, temperature, chemical species and structural damage. The inspiration from sensory transduction of biological systems will be a key factor for the further development of SSHS and their application in soft robotics, electronic skin, smart wearables and haptic devices.

Self-healing polymers can address the damage susceptibility in soft robotics. However, in most cases, their healing requires a heat stimulus, provided by an external device. This paper presents a self-healing soft actuator with an integrated healable flexible heater, functioning as the stimuli-providing system. The actuator is constructed out of thermoreversible elastomers that are crosslinked by the Diels-Alder (DA) reaction, which provides the healing ability. The heater is manufactured from a DA-based composite network filled with 20 wt% carbon black to provide electrically conductive properties for resistive Joule heating. The flexibility of the heater does not compromise the actuator performance upon integration and the self-healing properties of both heater and actuator allow for damage repair. This includes very large damages, as both heater and actuator can recover (near 100%) from being cut completely in two pieces, using Joule heating at 90 °C with a bias voltage of about 30 V. The embedded heater, avoids the need for external intervention in the healing process, and provides healing quality assessment and a healing on-demand mechanism, paving the way for an optimum healing solution of damage resilient soft robots that require heat as a healing stimulus.

A comprehensive study was undertaken to obtain a more fundamental understanding of the phase behavior of the p-DTS(FBTTh2)2:PC71BM system, used in small molecule organic solar cells, with a strong focus on the amorphous phase and its influence on crystallinity. Three dedicated thermal protocols were used in combination with advanced thermal analysis, solid-state NMR, and wide-angle X-ray diffraction. Rapid cooling, to avoid structure formation and gain insight in the amorphous phase, and slow cooling, to promote structure formation, were used as limiting cases to explain the intermediate behavior after device processing from solution. A complete state diagram was developed, and the glass transition (Tg)–composition relationship was determined. In the case of slow cooling and the procedure used for device processing, the rapid crystallization of p-DTS(FBTTh2)2 leads to an enrichment of the amorphous phase in PC71BM, increasing its Tg and causing vitrification of the mixed amorphous phase before crystallizationwhen the total amount of PC71BM exceeds 70 wt %. The common processing additive 1,8-diiodooctane (DIO) was found to lead to a lower p-DTS(FBTTh2)2 crystallinity and smaller average crystal size. More importantly, it acts as a strong plasticizer, lowering Tg significantly and thus reducing the morphological stability of the p-DTS(FBTTh2)2:PC71BM mixtures.

The controlled polymerization of a new biobased monomer, 4-oxocyclopent-2-en-1-yl acrylate (4CPA), was established via reversible addition-fragmentation chain transfer (RAFT) (co)polymerization to yield polymers bearing pendent cyclopentenone units. 4CPA contains two reactive functionalities, namely, a vinyl group and an internal double bond, and is an unsymmetrical monomer. Therefore, competition between the internal double bond and the vinyl group eventually leads to gel formation. With RAFT polymerization, when aiming for a degree of polymerization (DP) of 100, maximum 4CPA conversions of the vinyl group between 19.0 and 45.2% were obtained without gel formation or extensive broadening of the dispersity. When the same conditions were applied in the copolymerization of 4CPA with lauryl acrylate (LA), methyl acrylate (MA), and isobornyl acrylate, 4CPA conversions of the vinyl group between 63 and 95% were reached. The additional functionality of 4CPA in copolymers was demonstrated by model studies with 4-oxocyclopent-2-en-1-yl acetate (1), which readily dimerized under UV light via [2 + 2] photocyclodimerization. First-principles quantum mechanical simulations supported the experimental observations made in NMR Based on the calculated energetics and chemical shifts, a mixture of head-to-head and head-to-tail dimers of (1) were identified. Using the dimerization mechanism, solvent-cast LA and MA copolymers containing 30 mol % 4CPA were cross-linked under UV light to obtain thin films. The cross-linked films were characterized by dynamic scanning calorimetry, dynamic mechanical analysis, IR, and swelling experiments. This is the first case where 4CPA is described as a monomer for functional biobased polymers that can undergo additional UV curing via photodimerization. J.S., D.E.P.V., and K.V.B. acknowledge the project D-NL-HIT carried out in the framework of INTERREG-Program Deutschland-Nederland, which is co-financed by the European Union; the MVVIDE NRW; the Ministerie van Economische Zaken en Klimaat; and the provinces of Limburg, Gelderland, NoordBrabant, and Overijssel. The computational resources and services used in this work were provided by the VSC (Flemisch Supercomputer Center), funded by the Research Foundation Flanders (FWO) and the Flemisch Government department EWI. Bernaerts, KV (reprint author), Maastricht Univ, Fac Sci & Engn, AMIBM, NL-6167 RD Geleen, Netherlands. katrien.bernaerts@maastrichtuniversity.nl

The reliability of printed circuit boards (PCB) is at risk due to continuous miniaturization. As a result, PCBs are more susceptible to external factors such as humidity, temperature, contamination, etc., which affect their general performance, leading to failure of electronic devices. Therefore, protection of the devices against these factors is gaining greatly in importance. Plasma polymerization is used as a method to form a protective barrier by applying plasma polymer films on PCBs. However, the humidity robustness of such plasma coatings on the PCB surface is unknown. In this work, several methods were used to characterize two types of plasma-coated PCBs based on 1H,1H,2H-perfluorodecyl acrylate precursor (single-layer and stacked coatings) upon exposure to humidity, temperature, and bias voltage. Modulated-temperature differential scanning calorimetry enabled thermal analysis of the plasma coatings. Electrochemical impedance spectroscopy in combination with the gravimetric moisture vapor sorption technique were used to study the interaction of these coatings with moisture and quantify the water uptake. The results revealed an only 2% increase of the capacitance of the coatings due to water uptake. Direct-current (DC) leakage current measurements were used to study the influence of a bias voltage applied between the electrodes on the coated PCBs upon exposure to cyclic climatic conditions. Electrical DC testing revealed the protective character of the stacked coating, which did not fail under the given stress conditions, in contrast to the single-layer plasma coatings.

A significant number of organic electronic devices rely on blends of electron-donating and electron-accepting molecules. In bulk heterojunction organic photovoltaics, the nanoscopic phase behavior of the two individual components within the photoactive layer has a major impact on the charge separation and charge transport properties. For polymer:fullerene solar cells, it has been hypothesized that an increased accessibility of the electron-deficient monomer unit in push-pull type low bandgap polymers allows for fullerene ‘docking’. The close proximity of electron donor and acceptor molecules enables more efficient charge transfer, which is beneficial for the device efficiency. With this in mind, we synthesized a series of PBDTTPD [poly(benzodithiophene-thienopyrroledione)] low bandgap copolymers with varying side chains. Solar cells were fabricated for all polymers and the device characteristics were compared. The combination of proton wideline solid-state NMR (ssNMR) relaxometry and sensitive external quantum efficiency (sEQE) measurements was shown to provide essential information on donor-acceptor interactions and phase separation in bulk heterojunction organic photovoltaics. The reduced charge transfer state absorption and the observed phase separation of crystalline PC71BM domains for the polymers containing the most accessible methyl-TPD unit indicate a diminished contact between donor and acceptor, leading to a loss in performance.

Concrete is the most used construction material worldwide due to its abundant availability and inherent ease of manufacturing and application. However, the material bears several drawbacks such as the high susceptibility for crack formation, leading to reinforcement corrosion and structural degradation. Extensive research has therefore been performed on the use of microorganisms for biologically mediated self-healing of concrete by means of CaCO3 precipitation. Recently, filamentous fungi have been recognized as high-potential microorganisms for this application as their hyphae grow in an interwoven three-dimensional network which serves as nucleation site for CaCO3 precipitation to heal the crack. This potential is corroborated by the current state of the art on fungi-mediated self-healing concrete, which is not yet extensive but valuable to direct further research. In this review, we aim to broaden the perspectives on the use of fungi for concrete self-healing applications by first summarizing the major progress made in the field of microbial self-healing of concrete and then discussing pioneering work that has been done with fungi. Starting from insights and hypotheses on the types and principles of biomineralization that occur during microbial self-healing, novel potentially promising candidate species are proposed based on their abilities to promote CaCO3 formation or to survive in extreme conditions that are relevant for concrete. Additionally, an overview will be provided on the challenges, knowledge gaps and future perspectives in the field of fungi-mediated self-healing concrete.

Bitumen is a complex mixture whose composition–structure-property relationships are not well-understood. Therefore, it is essential to understand which components may develop microstructures, how and when these features appear, and if they are initiated or influenced by other components. Many studies have reported so- called bee structures as well as other phases on bitumen surfaces. A large number of observations point to-wards the crystallinity of waxy compounds as an explanation for the bees. However, doubt remains about the origin of the other phases and the possibility of other bitumen components as promoters of the bee formation. In this study, bee structures were investigated using two microscopy techniques: atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). By using model wax compounds, especially blends of waxes differing in melting points and chain lengths, bee structures and surrounding islands were created on featureless bitumen surfaces. Structures very similar to what is observed on a paraffinic bitumen were obtained. This in-dicates that bees and the surrounding areas both consist of crystallisable components. Moreover, bee structures were also generated on other surfaces, such as mineral oil and a maltene fraction. Bee formation is not limited to bituminous materials and bitumen components are not needed as promotors. Furthermore, CLSM offers possi-bilities to scan through transparent layers and to investigate surfaces under glass, for example. In contact with such a solid substrate, as well as after water submersion, no microstructural features were observed. Adding a combination of n-alkanes, to transparent oil, induced bee structures at the oil-air interface. The transparency of the oil allowed the visualization of wax crystallization in the bulk, where the added waxes crystallize as small particles. These small crystals are expected to influence the mechanical properties, such as low-temperature stiffening effects, which have been reported for paraffinic bitumen.

Copper slag (CS) remains a challenging industrial by-product with a relatively small utilization fraction. The present study investigated the development of one-part alkali-activated cements based on CS, ground granulated blast furnace slag (GGBS) and a mixture of the two as a precursor. We investigated 5 to 15 wt% solid sodium metasilicate (Na2SiO3) and disilicate (Na2Si2O5) as alkaline reagents. Isothermal calorimetry showed that the reactivity of the system was higher for the metasilicate based samples, with early reaction and higher cumulative heat released. Metasilicate based samples also presented a more densified microstructure, lower porosity and higher strength. Better performances were observed with 10 wt% metasilicate/disilicate with respect to the 5 and 15 wt%. The 28-day compressive strength and elastic modulus of 10 wt% metasilicate samples reached 75 MPa and 25 GPa, respectively, and, for paste samples, ranged from 100 wt% GGBS to 50/50 wt% CS/GGBS. The microstructure and calorimetry of the pastes showed that GGBS actively participated in the binding process, whereas CS played a smaller role and acted as a filler and catalyst. The substitution of commercial GGBS by CS up to 50 wt% did not affect the overall performance, thus, bringing CS forward as an economically interesting precursor.

Self-healing materials can prolong the lifetime of structures and products by enabling the repairing of damage. However, detecting the damage and the progress of the healing process remains an important issue. In this study, self-healing, piezoresistive strain sensor fibers (ShSFs) are used for detecting strain deformation and damage in a self-healing elastomeric matrix. The ShSFs were embedded in the self-healing matrix for the development of self-healing sensor fiber composites (ShSFC) with elongation at break values of up to 100%. A quadruple hydrogen-bonded supramolecular elastomer was used as a matrix material. The ShSFCs exhibited a reproducible and monotonic response. The ShSFCs were investigated for use as sensorized electronic skin on 3D-printed soft robotic modules, such as bending actuators. Depending on the bending actuator module, the electronic skin was loaded under either compression (pneumatic-based module) or tension (tendon-based module). In both configurations, the ShSFs could be successfully used as deformation sensors, and in addition, detect the presence of damage based on the sensor signal drift. The sensor under tension showed better recovery of the signal after healing, and smaller signal relaxation. Even with the complete severing of the fiber, the piezoresistive properties returned after the healing, but in that case, thermal heat treatment was required. With their resilient response and self-healing properties, the supramolecular fiber composites can be used for the next generation of soft robotic modules.

In this work, a new methodology is developed to study the initial behaviour of model organic coatings shortly after coming into contact with an aqueous solution, using odd random phase electrochemical impedance spectroscopy (ORP-EIS). The impedance results are resolved over time via the calculation of the instantaneous impedance and fitted with a physically meaningful equivalent circuit. Many physical parameters could be obtained, such as the rapid water uptake, the resistivity of the coatings and the penetration depth of ions in the coatings. The fitting results were verified using differential scanning calorimetry (DSC) and gravimetry.

Intrinsic self-healing polymer networks were developed based on dynamic covalent bonding by means of thermoreversible Diels-Alder (DA) cycloadditions. The DA bonds are preferentially broken in case of damage, but also reversibly reform, leading to a repeatable healing cycle and an increased lifetime for many applications, such as sustainable coatings [1], [2]. However, thermo-mechanical robustness is requiring a network in the (partially) vitrified state, with a sufficient-ly high Tg. This work focuses on the effect of vitrification on DA reaction kinetics, using fully reversible model systems of furan and maleimide compounds. In bulk, using (MT)DSC, vitrification is followed through (non-)isothermal heat capacity meas-urements, while non-isothermal microcalorimetry provides heat flow information. These results are used to optimize the parameters of a kinetic model, consid-ering the DA endo−exo stereochemistry. In addition, dynamic rheometry allows the construction of time-temperature-transformation (TTT) and continuous-heating-transformation (CHT) diagrams for both reversible elastomers and thermo-sets [3]. A double asymptotic behavior of the isoconversion lines is revealed, and also two subsequent gelation/degelation events can occur during non-isothermal curing. This bulk study was extended towards thin films through AC chip calorime-try, yielding preliminary results to compare vitrification in bulk and thin layers. This work is the first systematic study of diffusion-controlled reversible DA network formation. The DA reaction was proven to proceed in diffusion-controlled conditions, allowing self-healing in mobility-restricted applications [2], [4].

International audience; The intrinsic compliance of soft robots provides safety, a natural adaptation to its environment, allows to absorb shocks, and protects them against mechanical impacts. However, a literature study shows that the soft polymers used for their construction are susceptible to various types of damage, including fatigue, overloads, interfacial debonding and cuts, tears and perforations by sharp objects. An economic and ecological solution is to construct future soft robotic systems out of self-healing polymers, incorporating the ability to heal damage. This review paper proposes criteria to evaluate the potential of a self-healing polymer to be used in soft robotic applications. Based on these soft robotics requirements and on defined performance parameters of the materials, linked to the mechanical and healing properties, the different types of selfhealing polymers already available in literature are critically assessed and compared. In addition to a description of the state of the art on self-healing soft robotics, the paper discusses the driving forces and limitations to spur the interdisciplinary combination between self-healing polymer science and soft robotics.

Selective Laser Sintering (SLS) is a well-known additive manufacturing technique that builds 3D complex structures by sintering powder particles together upon laser irradiation. In the polymer field, thermoset resins are a popular choice for a plethora of applications due to their great mechanical properties and thermochemical stability. However, due to their irreversible crosslinked nature, they are hard to be processed using SLS. Herein, a covalently crosslinked polymer thermoset based on thermally reversible Diels-Alder (DA) bonds has been printed using SLS. The thermoreversible network exhibits a glassy behavior due to its high crosslinked density and glass transition temperature and was successfully milled into a suitable particle size, morphology and flow for SLS applications. At low temperatures, the DA equilibrium shifts towards the formation of the DA crosslinks, while at high temperatures the DA adducts gradually dissociate, allowing flow and reprocessability at temperatures above 131˚C. Furthermore, the printed parts exhibit healing ability when heated above their glass transition temperature, reaching a fracture stress and Young’s Modulus of 25.4 MPa and 1416 MPa, respectively. Thus, the dynamic nature of the network extends the build lifetime upon damage and also brings the opportunity of recycling or reprocessing, enhancing circularity compared to classic thermosets.

This study focused on the development and characterization of biodegradable films based on gelatin capsule residue crosslinked with the natural agent genipin extracted from genipap (Genipa americana L.). Their potential on maintaining the quality attributes (level of peroxides, conjugated dienes and trienes and color) of extra‐virgin olive oil under accelerated storage conditions was investigated. Results showed that the genipin‐crosslinked films had a dark blue appearance. Their total soluble matter, water vapor permeability, tensile strength, ultraviolet and visible light barriers and thermal properties were improved in relation to the uncrosslinked film, whereas their moisture content and microstructure were not affected. In general, films presented comparable properties to those of glutaraldehyde‐crosslinked films. The developed films successfully protected the packed oil from primary and secondary oxidation and maintained the color over the storage period. Therefore, this study demonstrated the effectiveness of genipin on improving the properties of gelatin‐based films and the promising application of films as food packaging.

An important and integral effort toward understanding the formation and reorganization of mesoscale structures in functional organic thin films, being of fundamental importance to the development o...

This work focused on the development of edible films based on gelatin capsule residue by ohmic heating. The effect of the electric field strength (9.5 V cm−1 and 19 V cm−1) on the mechanical, thermal, physicochemical and morphological properties of films was investigated and compared to films produced by the conventional heating method. Results demonstrated that the application of 9.5 V cm−1 during ohmic heating was able to improve tensile strength from 2.66 MPa to 6.62 MPa in comparison to the conventional method, whereas the film developed using 19 V cm−1 reached a value of 3.26 MPa. Young's Modulus was also significantly increased, while an opposite effect was observed for elongation at break. Modulated differential scanning calorimetry analysis revealed that all samples had two transition temperatures. Electrically treated film (9.5 V cm−1) presented increased crystallinity and thermal stability. Thickness, morphology and water-related properties were not affected by the application of electric field. Films produced by ohmic heating, especially when 9.5 V cm−1 was applied, presented improved mechanical and thermal properties, with increased crystallinity.

A novel functional 2,6-substituted donor-acceptor anthracene derivative, bearing a long alkyl spacer and a polymerizable end-group, is synthesized from readily available compounds. This monomer possesses conjugated electron donor and acceptor moieties to achieve UV absorption and anthracene dimerization at higher wavelengths and under milder conditions, than anthracene and other reported anthracene derivatives. The compound was shown to absorb at higher wavelengths and dimerize much faster compared to most 9-substituted anthracenes. The fast photochemical and relatively slow thermal scission of the dimers were studied and related to the chemical structure, i.e. the 2,6-substitution.

The lifetime of soft robots is limited by their susceptibility to damage. Recent breakthroughs in healable soft robots have overcome this issue by manufacturing systems from self-healing polymers. However, to operate and recover autonomously, compatible sensors need to be embedded. We show that innovative healable soft sensors to measure strain, force, and damage, based on a self-healing conductive elastomeric composite, were developed and integrated with near-perfect interfacial strength in a healable soft gripper. The paper details the complete development of the gripper, including the selection of the conductive composite based on carbon black and nanoclay, sensor and actuator characterization, and its manufacturing. The gripper with embedded sensors recovers its actuation, sensor function, and damage detection after being severely damaged, and this multiple times.

The chemical structure and location of substituents on anthracene derivatives influence the electron balance of the aromatic system, thus determining the wavelengths at which light is absorbed, which results in the photochemically induced dimerization or monomerization. Here, the thermal dissociation kinetics of 7 photodimers of 9-substituted anthracene derivatives are studied using a combination of spectroscopic and calorimetric techniques in the condensed state and compared to scarce literature data on thermal dissociation of other anthracene derivatives. The length and chemical structure of the substituent chains have a clear impact on the melting temperatures of the anthracene derivatives and corresponding photodimers. The crystallinity of the photodimers and monomers in turn influences the thermal dissociation kinetics. The thermal dissociation behaviour and previously published photochemistry data are related to the electronic effects of the substituents by means of the Hammett parameters. Stronger electron-withdrawing effects result in larger red shifts of the maximum wavelength λmax for the photodimerization of the anthracene derivatives. It is also shown that for the studied substitutions on the 9-position of anthracene, the higher the magnitude of the electronic effect - both electron-donating and electron-withdrawing - the faster the thermal dissociation kinetics and thus the lower the thermal stability. The strong electronic effects of the substituents on the thermal and photochemical reactivity of the anthracene derivatives and their photodimers allow tuning of the thermal or photochemical responsiveness, e.g. for polymer networks.

Time-temperature-transformation (TTT), temperature-conversion-transformation (TxT), and continuous-heating-transformation (CHT) diagrams are studied for a set of reversible elastomeric and thermosetting covalent networks, based on Diels–Alder (DA) furan–maleimide cycloaddition reactions using different concentrations of furan and maleimide functional groups. Microcalorimetry, modulated temperature differential scanning calorimetry, and dynamic rheometry are used as experimental tools in combination with kinetic modeling. The DA kinetics, based on two parallel equilibrium reactions for endo and exo cycloadducts, are optimized for the set of reversible networks cured between 20 and 90 °C. Each simulated isoconversion line in TTT and CHT, in contrast with irreversible networks, shows a totally different shape with a horizontal asymptotic limit at the high-temperature side, Tcure, corresponding to the DA equilibrium conversion xeq at Tcure. It is also proven that all gelation lines are isoconversion lines and that each gel conversion can be predicted by the Flory–Stockmayer equation. Moreover, the slight differences in the endo–exo kinetics and equilibrium constants lead to a predicted superposition and a double asymptotic behavior of the isoconversion lines in TTT and CHT. As a consequence, two subsequent gelation/degelation events can occur during nonisothermal curing, as shown in the CHT diagram. These phenomena are experimentally confirmed for one of the reversible covalent networks.