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Vinyl esters and carbonates have recently been demonstrated to have considerably lower cytotoxicity than their more commonly used (meth)acrylate counterparts, inspiring their use in the 3D printing of biomaterials. However, the degradation rates of such synthetic photopolymers are slow, especially in the mild conditions present in many biological environments. Some applications, for example, tissue regeneration scaffolds and drug release, require considerably faster biodegradation. Furthermore, it is essential to be able to easily tune the degradation rate to fit the requirements for a range of applications. Herein we present the design and synthesis of hydrolytically degradable polyphosphazenes substituted with a vinyl carbonate functionalized amino acid. Thiolene copolymerization with vinyl esters gave cured polymers which are demonstrated to considerably accelerate the degradation rates of cured vinylester/thiolene polymer scaffolds. Graphical abstract

The aim of this contribution is to present a comprehensive approach to study the extent of hydrogen entry into a hot-dip-galvanized DP1000 steel, which is exposed to corrosive conditions. For this purpose, the Z100 coating was immersed in 5% sodium chloride solution at room temperature. The distribution of hydrogen and the spots of increased hydrogen entry were detected with scanning Kelvin probe (SKP) and scanning Kelvin probe force microscopy (SKPFM). Effects of hydrogen inserted during corrosion on the mechanical properties were determined in slow-strain rate tests (SSRT). Hydrogen quantification was achieved via thermal desorption mass spectrometry (TDMS), giving additional insights into the mobility of the inserted hydrogen within the steel by distinguishing diffusible and trapped hydrogen.

Over the last 30 years, scanning electrochemical microscopy (SECM) has become a fundamental technique in corrosion research. With its high spatial resolution and its ability to study local electrochemistry, it contributes essentially to the understanding of corrosion processes. By using selective micro- and nano-sensors, concentration profiles of different corrosion relevant species, from protons to metal ions, can be established. This review provides a comprehensive overview about SECM based techniques and discusses various types of microsensors, including materials selection and preparation techniques, and it provides extensive tables on redox-couples for specific corrosion research applications.

Co-extrusion is commonly used to produce polymer multilayer products with different materials tailoring the property profiles. Adhesion between the individual layers is crucial to the overall performance of the final structure. Layer adhesion is determined by the compatibility of the polymers at the interface and their interaction forces, causing for example the formation of adhesive or chemical bonds or an interdiffusion layer. Additionally, the processing conditions, such as temperature, residence time, cooling rate, and interfacial shear stress, have a major influence on the interactions and hence resulting layer adhesion. Influences of temperature and residence time are already quite well studied, but influence of shear load on the formation of an adhesion layer is less explored and controversially discussed in existing literature. In this work, we investigated the influence of different processing conditions causing various shear loads on layer adhesion for a two-layer co-extruded polymer sheet using a polypropylene and polypropylene talc compound system. Therefore, we varied the flow rates and the flow geometry of the die. Under specific conditions interfacial flow instabilities are triggered that form micro layers in the transition regime between the two layers causing a major increase in layer adhesion. This structure was analyzed using confocal Raman microscopy. Making use of these interfacial flow instabilities in a controlled way enables completely new opportunities and potentials for multi-layer products.

Electrocatalytic CO2-to-CO conversion represents one pathway to upgrade CO2 to a feedstock for both fuels and chemicals (CO, deployed in ensuing Fischer–Tropsch or bioupgrading). It necessitates se...

Purpose This papers aims to study the influence of water absorption on the mechanical properties of poly lactic acid (PLA) and PLA/Wood composites. Virgin PLA and PLA/Wood double-bone-shaped specimens were prepared by two methods: injection moulding and 3D printing. The results were compared to each other and showed the influence of the production method on the properties of the produced parts. Design/methodology/approach Morphology studies were done by scanning electron microscopy (SEM) from fracture surfaces of tensile and notched impact specimens of all samples. Tensile properties were analysed by the production and testing of dog-bone-shaped samples. Heat deflection temperature (HDT) was tested, as also was the crystallinity of the tested samples by differential scanning calorimetry. Findings The values for notched impact strength were higher upon water uptake in the case of injection-moulded specimens, which was not the case with 3D-printed specimens. Tensile properties of the specimens produced by both methods were reduced after water absorption tests. Values of the HDT were also lower after water absorption tests studied for both processing methods. Originality/value Morphology studies were done by SEM from fracture surfaces of tensile as well as notched impact specimens of injection-moulded and 3D-printed samples. The effect of water storage on various samples was tested. The two different production technologies were compared to each other owing to their influence of water storage. This study also dealt with NFC compounds and produced NFC composites and the influence of water storage on these samples.

Polymerization of an acrylate-based ink, filled with aluminum oxide nanoparticles, which is going to be used in PolyJet™ technology (Stratasys Ltd., Israel), was investigated. In a free-radical photopolymerization of acrylates, oxygen inhibits polymerization and results in a decreased monomer conversion. The presented research shows the influence of TODA (2-[2-(2-methoxyethoxy)ethoxy]acetic acid) on the polymerization degree and mitigation of the oxygen inhibition effect. By incorporating 20–40 vol% of TODA into the system, full polymerization of acrylate in air atmosphere can be achieved. This is due to dissociable hydrogens in the TODA structure. In addition, TODA can overcome agglomeration of the aluminum oxide nanoparticles in the ceramic-filled ink due to steric stabilization.

In this study the curing of an epoxy resin consisted of a diglycidyl ether of bisphenolA (DGEBA) resin and an aromatic Polyamine hardener was monitored combining a Raman-spectrometer and shear rheometry (Rheo-Raman). The set-up allow to carry out curing experiments at various temperatures (100, 120, 140 and 160 °C) where rheological measurements were performed using an oscillation rheometer and a plate-plate geometry while simultaneously Raman spectra were recorded. Raman-spectroscopy allows the determination of the reaction turnover and therefore the degree of cross-linking. Combined with the rheological data obtained, e.g. the gel point and the vitrification point, one can get a better insight in the processes occurring and the influence of different measurement parameters on the obtained rheological properties. Thus, the reaction turnover has been investigated at significant stages of the curing process.

Among the terrestrial Crustacea, isopods have most successfully established themselves in a large variety of terrestrial habitats. As in most Crustacea, their cuticle consists of a hierarchically organised organic phase of chitin-protein fibrils, containing calcium carbonate and some calcium phosphate. In previous studies, we examined the tergite cuticle of Tylos europaeus, which lives on seashores and burrows into moist sand. In this study, we investigate the closely related species Helleria brevicornis, which is completely terrestrial and lives in leaf litter and humus and burrows into the soil. To get deeper insights in relation between the structure of the organic and mineral phase in species living in diverse habitats, we have investigated the structure, and the chemical and crystallographic properties of the tergite cuticle using various preparation techniques, and microscopic and analytical methods. The results reveal long and short epicuticular sensilla with brushed tips on the tergite surface that do not occur in T. europaeus. As in T. europaeus a distal exocuticle, which contains a low number of organic fibres, contains calcite while the subjacent layers of the exo- and endocuticle contain amorphous calcium carbonate. The distal exocuticle contains a polygonal pattern of mineral initiation sites that correspond to interprismatic septa described for decapod crabs. The shape and position of calcite units do not follow the polygonal pattern of the septa. The results indicate that the calcite units form by crystallisation from an amorphous phase that progresses from both margins of the septa to the centres of the polygons.

Causal factors leading to epizootic shell disease (ESD) lesions in American lobster, Homarus americanus H. Milne-Edwards, 1837, are not well understood. We explore the structural and physiological bases for development of ESD from preclinical stages invisible to unaided eye to early visible stages. We present a lobster shell model, which develops structural functional vulnerability and suggests plausible routes to ESD. Medallions of carapace cuticle were obtained from carapace fixed with protocols to minimize movement of mineral and macromolecular components. Rapid processing of medallions was used to encourage large sample sizes compatible with environmental surveys. One- and two-dimensional analytic maps of polished sections of the cuticle, obtained with an electron microprobe, described the composite mineral and polymeric structures. Micro-Raman spectroscopy was used to identify bond properties of phosphates and carbonates, as well as signatures of organic structures. The frequency and properties of structures identified can be monitored through the lobster molting cycle using a high throughput application of micro-computed tomography (μCT). We observed density differences in the calcite layer, exocuticle, and endocuticle, and the frequency and structure of CaCO3 structures in the endocuticle and membranous layer of carapace cuticle during chosen stages of the molting cycle. The correlative microscopy and μCT of shell structures provides improved understanding of the lobster cuticle structure. Detailed structural differences quantified through development and under different environmental conditions can provide insight into causes and vulnerabilities associated with ESD.

The depth distribution of melamine in polyester-based coatings was investigated by XPS (X-ray photoelectron spectroscopy) as well as Raman analysis on cryo-ultra-low-angle microtome (cryo-ULAM) prepared coatings on hot dip galvanized (HDG) steel panels. Additionally, free standing films were analyzed on the air/coating and the coating/substrate interfaces: for polyester/melamine ratios ≤20 wt.% the melamine concentration was equal on both sides of free films, which is in accordance with literature. This finding could not be confirmed for the coatings applied on HDG steel panels that revealed a higher amount of melamine in the surface-near region. In addition various types of non-linear melamine concentration gradients have been detected over depth by XPS as well as Raman spectroscopy. This behavior was confirmed for all types of coatings irrespective of binder chemistry and curing temperatures in the range of 220–260°C. Whereas previous studies have mainly focused on higher melamine concentration where gradient properties are more pronounced, this work tries to fills the gap towards lower melamine contents, which are of greater relevance for industrial coatings. According to these results, a qualitative model on the melamine distribution has been established, which explains the observed non-linear gradients on the basis of transport phenomena and crosslinking kinetics within the curing process. This model is also in agreement with experimental findings from previous works.

Additive Manufacturing represents a well-known and fast growing material processing technology. Printed part is formed by adding material layer by layer until the part is finished without requiring any additional molds. Therefore, using Additive Manufacturing can save time and costs in comparison to commercial production methods particularly when manufacturing complex prototypes or small batch series. Another advantage of Additive Manufacturing is its freedom of design. This review is focused on material extrusion, a specific Additive Manufacturing technology. It begins with a short overview of the most common materials processed with this technology. Subsequently, we discuss several processes and machine parameters in material extrusion as well as their influence on the printing process and on the final properties of the printed part. Based on this knowledge, various challenges in material extrusion are also identified. These challenges must be resolved in order to improve the material extrusion process.

Biodegradable and biocompatible elastic materials for soft robotics, tissue engineering or stretchable electronics with good mechanical properties, tunability, modifiability or healing properties drive technological advance, and yet they are not durable under ambient conditions and do not combine all the attributes in a single platform. We have developed a versatile gelatin-based biogel, which is highly resilient with outstanding elastic characteristics, yet degrades fully when disposed. It self-adheres, is rapidly healable and derived entirely from natural and food-safe constituents. We merge all the favourable attributes in one material that is easy to reproduce and scalable, and has a low-cost production under ambient conditions. This biogel is a step towards durable, life-like soft robotic and electronic systems that are sustainable and closely mimic their natural antetypes.

A simple supramolecular crosslinked gel is reported with a photosensitive ruthenium bipyridine complex functioning as a crosslinker and poly(4‐vinylpyridine) (P4VP) as a macromolecular ligand. Irradiation of the organogels in H2O/MeOH with visible and NIR light (in a multiphoton process) leads to cleavage of pyridine moieties from the ruthenium complex breaking the cross‐links and causing degelation and hence solubilization of the P4VP chains. Real‐time (RT) photorheology experiments of thin films showed a rapid degelation in several seconds, whereas larger bulk samples could also be photocleaved. Furthermore, the gels could be reformed or healed by simple heating of the system and restoration of the metal–ligand crosslinks. The relatively simple dynamic system with a high sensitivity towards light in the visible and NIR region make them interesting positive photoresists for nano/micropatterning applications, as was demonstrated by writing, erasing, and rewriting of the gels by single‐ and multiphoton lithography.

Co-evaporation of Cu and Pd was used for the deposition of a relatively small gradient concentration thin film combinatorial library with Pd amounts between 4 and 14 atomic percent (at%). Screening for electrocatalytic oxidation of formaldehyde was performed by scanning droplet cell microscopy along the Cu–Pd compositional spread in alkaline solution and a best material performance for this process was identified for 7.5 at% Pd in Cu confirming results from co-sputtering studies. However, the microstructure and crystallographic analysis of Cu–Pd thin film alloys showed a compositionally induced gradual change of properties without any significant discontinuity. This indicates that the Cu–Pd atomic ratio is the main factor defining the electrocatalytic activity of the investigated alloys. This finding is also confirmed for bulk Cu–Pd alloys where the reproducibility of significant formaldehyde oxidation electrocatalytic activity when using Cu-7.5 at% Pd was demonstrated. An amperometric formaldehyde sensor was fabricated and its reproducibility, repeatability and stability were assessed. During successive anodic formaldehyde current oxidation peak observations a standard deviation value of 8% was measured. Multiple efficient successive use of the same sensor (5 to 10 times) were demonstrated and a maximum of 5% decrease in the current density was observed after 21 days of normal environment storage during a shelf-lifetime evaluation of the sensor. Overall, the study reveals inexpensive approaches for fabrication of multiple use formaldehyde sensors via thermal evaporation or bulk alloy casting, as well as the transfer of the main feature (i.e. maximum current density for formaldehyde oxidation) from a thin film combinatorial library to bulk samples.

Polymers have various interesting properties, which depend largely on their inner structure. One way to influence the macroscopic behaviour is the deformation of the polymer chains, which effects the change in microstructure. For analyzing the microstructure of non-deformed and deformed polymer materials, Raman spectroscopy as well as differential scanning calorimetry (DSC) were used. In the present study we compare the results for crystallinity measurements of deformed polymers using both methods in order to characterize the differences in micro-structure due to deformation. The study is ongoing, and we present the results of the first tests.

The most active and efficient catalysts for the electrochemical hydrogen evolution reaction (HER) rely on platinum, a fact that increases the cost of producing hydrogen and thereby limits the widespread adoption of this fuel. Here, a metal-free organic electrocatalyst that mimics the platinum surface by implementing a high work function and incorporating hydrogen-affine hydrogen bonds is introduced. These motifs, inspired from enzymology, are deployed here as selective reaction centres. It is shown that the keto-amine hydrogen-bond motif enhances the rate-determining step in proton reduction to molecular hydrogen. The keto-amine-functionalized polymers reported herein evolve hydrogen at an overpotential of 190 mV. They share certain key properties with platinum: a similar work function and excellent electrochemical stability and chemical robustness. These properties allow the demonstration of one week of continuous HER operation without notable degradation nor delamination from the carrier electrode. Scaled continuous-flow electrolysis is reported and 1 L net molecular hydrogen is produced within less than 9 h using 2.3 mg of polymer electrocatalyst.

A Co–Cu–Ni thin film material library was fabricated using a modified 3D-printed Hull cell. Rather than previous one by one attempts a combinatorial approach was here not to miss the exact optimum performance composition. An optimum activity at Co-16 at.% Cu-12 at.% Ni for the electrocatalytic glucose oxidation was found by screening along the compositional spread using flow-type scanning droplet cell microscopy (FT-SDCM). Crystallographic properties, surface microstructure and surface topography were investigated along the entire compositional spread using X-ray diffraction (XRD), scanning electron microscopy (SEM) as well as atomic force microscopy (AFM), respectively. The entire compositional spread (Co 40–76 at.%, Cu 0–19 at.% and Ni 11–60 at.%) showed suitability for being used in glucose detection, as determined by cyclic voltammetric measurements. A maximum response for glucose electrooxidation was identified at a Ni content of 12 at.% with a current density value of 21.8 mA cm−2. The performance of a glucose sensor constructed using this identified thin film alloy was evaluated by localised amperometric detection. A linear behaviour was obtained for a wide range of glucose concentrations in the electrolyte solution between 1 mM and 100 mM. Additionally, the identified thin film alloy showed high stability, good electrooxidation reproducibility and high selectivity, thus indicating its suitability for being used as catalyst in glucose detection.

The production of printable graphene flakes is not easy to scale up when produced by ultrasonication and purified by centrifugation. In this work, natural graphite flakes were exfoliated by wet ball milling in water supported by the addition of sodium deoxycholate as a surfactant and the dispersion was formulated for inkjet printing. By subsequent dilution and filtration of the milling paste, more than 45 l of a stable dispersion of nano-graphite particles in one batch process was obtained. The dispersion was characterized by thermogravimetric analysis and UV-vis spectroscopy to determine concentration, and experiments to measure long-term stability were conducted. The nano-graphite particles were analyzed by optical microscopy, scanning electron microscopy and Raman spectroscopy, revealing 300-400 nm sized particles. The dispersion was formulated into an inkjet ink and tested as interfacial hole transport layer between the anode and the photo-active bulk-heterojunction layer of an organic solar cell with inverted structure. The nano-graphite flakes are inkjet printable and conductive and therefore show potential as a low-cost alternative to polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate.

The crustacean cuticle forms skeletal elements consisting of chitin-protein fibrils reinforced by amorphous and crystalline calcium carbonate and phosphate minerals. The edges of skeletal elements are of particular interest. They are subject to repeated strain and stress because they form transitions to the arthrodial membranes connecting them. These allow for relative movements of skeletal elements. In this study, we investigate structure, chemical composition, mineral organization and local mechanical properties of the anterior and posterior edges of the tergite cuticle in the conglobating beach isopod Tylos europaeus and compare these with the protective dorsal region of the tergites. The distribution of mineral phases at the edges resembles that of dorsal regions of the tergites. At the transition with the unmineralized arthrodial membrane the calcite containing distal exocuticle is replaced by epicuticular material and the subjacent cuticular layers containing amorphous calcium carbonate become enriched with amorphous calcium phosphate. At the edges, the local elastic modulus and hardness values are significantly lower compared to dorsal regions of the tergite cuticle, for both, the calcite and the amorphous mineral containing layers. The calcite within the tergite cuticle is assembled in different texture patterns: (i) almost random co-orientation, (ii) almost single crystalline calcite, and (iii) a graded organization. Calcite organization and co-orientation strength is highly variable, not only on very few tens of micrometres, but also between regions with different skeletal functionality. Our results show that besides structure and composition, patterns of calcite organization contribute to the hierarchical architecture and functionality of biological composites.

Weak localization describes a metallic system, where due to the presence of disorder the electrical transport is governed by inelastic electron relaxation. Therefore the theory defines a threshold of spatial and of energetic disorder, at which a metal-insulator transition takes place. To achieve a metallic state in an inherently disordered system such as a conductive polymer, one has to overcome the threshold of localization. In this work we show that the effective suppression of disorder is possible in solution-processible poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate). We grow polymer films under optimized conditions allowing self-organization in solution. Interestingly, we find the requisite threshold, at which the system becomes finally metallic. We characterize the transition using a complementary morphology and magneto-electrical transport study and find coherent electron interactions, which emerge as soon as local order exceeds the macromolecular dimensions. These insights can be used for discrete improvement in the electrical performance, in particular for tailoring conductive polymers to alternative metal-like conductors.

The optimum activity for glucose electrocatalytic oxidation was found by screening along a large spread co-sputtered combinatorial copper-palladium library (2.6 at.% to 39.2 at.% Pd) in neutral media using flow-type scanning droplet cell microscopy (FT-SDCM). The elemental composition and the surface topography were characterized along the compositional spread using energy dispersive X-ray spectroscopy (EDX), as well as atomic force microscopy (AFM). The study proves that the entire range of alloys can be implemented in glucose detection. The highest catalytic effect was obtained at a Pd content of 8.2 at.% (E SHE = 0.58 V) with a current density value of 7.33 mA cm−2. The suitability for being used as quantitative and qualitative glucose sensor was demonstrated. The calibration performed in phosphate buffer solution containing different amounts of glucose revealed two linear regions with different sensitivities towards the quantitative glucose detection. The highest sensitivity was determined in the range of 0–25 mM glucose, which is indicated by an increase of 81.2 μA cm−2 mM−1, normalized to the stepwise increase of 1 mM glucose. Also, a good long-term stability, reproducibility (relative standard deviation ~ 5%), as well as the selective sensitivity to glucose oxidation were demonstrated by performing measurements in the presence of other compounds found in blood (e.g., ascorbic acid and uric acid).

Co-deposition at glancing angles is used for deposition of an Al Nb thin film library with a compositional resolution of 0.8 at.% mm−1 and a total compositional spread of 55 at.%. Atomic self-shadowing leads to nanostructure formation along the compositional gradient. The morphology of the obtained different nanowires is fundamentally studied together with their crystallinity in the cubic system and is linked to specific Al Nb nanostructured alloys. Composition and morphology of the nanowires, naturally emerging as coupled variables due to the deposition geometry, are decoupled using the deposition distance. This allows identifying conditions for reproducing a single wire for further applications. Electrical properties are mapped across the library by scanning Kelvin probe microscopy and four point resistivity measurements. Nanowires with low work function are identified at low Nb concentration. Contact angle measurements are performed along the library before and after anodic oxide formation, and these changes are mapped as a function of composition. The presented compositional mappings are relevant for alloys selection in applications where surface tuning or functionalization is paramount.

The cuticle of the cornea in Crustacea is an interesting example of a composite material compromising between two distinct functions. As part of the dioptric apparatus of the ommatidia within the complex eye it forms transparent micro-lenses that should as well maintain the mechanical stability of the head capsule. We analyzed the ultrastructure and composition of the isopod cornea cuticle of the terrestrial species Ligia oceanica and the marine Sphaeroma serratum . We used a variety of tissue preparation methods, electron microscopic techniques as well as electron microprobe analysis and Raman spectroscopic imaging. The results reveal various structural adaptations that likely increase light transmission. These are an increase in the thickness of the epicuticle, a reduction of the thickness of the outer layer of calcite, a spatial restriction of pore canals to interommatidial regions, and, for S. serratum only, an increase in calcite crystal size. In both species protein–chitin fibrils within the proximal exocuticle form a peculiar reticular structure that does not occur within the cuticle of the head capsule. In L. oceanica differential mineralization results in a spherically shaped interface between mineralized and unmineralized endocuticle, likely an adaptation to increase the refractive power of the cornea maintaining the mechanical stability of the cuticle between the ommatidia. The results show that the habitat and differences in the general structure of the animal’s cuticle affect the way in which the cornea is adapted to its optical function.

A basic understanding of thermal properties of polymers is of fundamental importance for the development of advanced polymers. However, up to now, mainly bulk properties have been investigated. To characterize local softening processes in polymers, a local thermal analysis (LTA) technique is applied as an add-on to a scanning probe microscope. The development of a new generation of heatable cantilever probes enables thermal analysis in the sub-μm range. This method is based on an appropriate temperature calibration, which provides a reliable correlation of the applied voltage heating the tip and the actual temperature at the tip-sample interface. As the presented technique is more susceptible to environmental changes than comparable macroscopic methods, different parameters that might influence its performance are evaluated like a strong dependence on sample temperature. It is shown that the measured softening temperature on a polystyrene (PS) sample decreases from 102.2 to 66.4 °C as the temperature of the substrate is increased by 50 °C. The interaction between heat from the cantilever and the substrate is the reason for local sample softening, which opens new perspectives to understand the temperature calibration process using the melting standard method. A stepwise guideline for a suitable temperature calibration is provided.

Raman spectroscopy is a powerful tool in the determination of biological and polymeric samples. However, also the use of Raman spectroscopy for inorganic applications like for the determination of different iron oxides after specific corrosion experiments or meteorite compositions is common. In this work, the method of Raman imaging has been used for surface characterisation of high temperature long-term annealed steel samples as a function of the dew point of the annealing atmosphere. The investigation revealed that at a high dew point, oxides (Al2O3, SiO2), silicates (Fe2SiO4) and spinel phases (Fe2SiO4-spinel) could be identified by Raman imaging whereas at a low dew point the reactivity of aluminium with nitrogen and oxygen was preferred and the phase of aluminium nitride (AlN) as well as some aluminium oxide (Al2O3) could be detected. The Raman imaging was supported by EDX mapping to obtain the elemental composition of the surface and by XPS measurements to get an insight into the bonding states of the elements which both confirmed the results obtained via Raman imaging.

Poly-(lactic acid) (PLA) is one of the most popular thermoplastics for fused layer modelling (FLM). Due to its semi-crystalline nature, the influences of printing parameters on the properties of the printed part are more complicated than with amorphous thermoplastics like acrylonitrile-butadiene-styrene (ABS). In present study, the influence of the process parameters, such as temperature of the plate as well as printing angle used for the three-dimensional printing process was studied in the case of virgin PLA. In addition, PLA was mixed with an amorphous polyhydroxyalkanoate (PHA) copolymer with the aim to improve its impact properties. Mechanical performance of virgin PLA and its PLA/PHA blend prepared by 3D printing method was compared with the mechanical performance of the parts produced by injection moulding. Small and wide angle X-ray measurements were performed in order to study the influence of the crystal morphology on the mechanics of PLA and PLA/PHA 3D printed as well as injection moulded parts. The PLA/PHA parts produced by 3D printing showed higher impact strength and notched impact strength values than injection moulded parts.

Concerning polymeric monolithic materials utilized in separation science, the structural and mechanical characteristics from the nanoscopic to the macroscopic scale remain of great interest. Suitable analytical tools are urgently required to understand the polymer monolith's constituent structure, particularly in the case of nanoscale polymer properties that tend to develop gel porosity in contact with a mobile phase ultimately affecting the chromatographic performance. Herein described are our first findings from a characterization of commercially available analytical polymer monoliths based on styrene/divinylbenzene and methacrylate chemistries utilizing confocal Raman spectroscopy imaging and atomic force microscopy (AFM). Confocal Raman spectroscopy can be used to generate a three-dimensional representation of monoliths in both dry state and in contact with solvent. AFM force-indentation measurements on individual cross-sectioned globular features permit detailed assessment of mechanical properties of the stationary phase. This approach allowed so far unprecedented insight and identification of a heterogeneous cross-link density distribution of polymer material within individual globular features on a submicrometer scale.

A strategy for bonding water-rich hydrogels to diverse materials for electronic skins, energy storage, and soft optics is reported., Introducing methods for instant tough bonding between hydrogels and antagonistic materials—from soft to hard—allows us to demonstrate elastic yet tough biomimetic devices and machines with a high level of complexity. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone, and metals, reaching unprecedented interfacial toughness exceeding 2000 J/m2. Healing of severed ionic hydrogel conductors becomes feasible and restores function instantly. Soft, transparent multilayered hybrids of elastomers and ionic hydrogels endure biaxial strain with more than 2000% increase in area, facilitating soft transducers, generators, and adaptive lenses. We demonstrate soft electronic devices, from stretchable batteries, self-powered compliant circuits, and autonomous electronic skin for triggered drug delivery. Our approach is applicable in rapid prototyping and in delicate environments inaccessible for extended curing and cross-linking.

The crustacean cuticle is a composite material that covers the whole animal and forms the continuous exoskeleton. Nano-fibers composed of chitin and protein molecules form most of the organic matrix of the cuticle that, at the macroscale, is organized in up to eight hierarchical levels. At least two of them, the exo- and endocuticle, contain a mineral phase of mainly Mg-calcite, amorphous calcium carbonate and phosphate. The high number of hierarchical levels and the compositional diversity provide a high degree of freedom for varying the physical, in particular mechanical, properties of the material. This makes the cuticle a versatile material ideally suited to form a variety of skeletal elements that are adapted to different functions and the eco-physiological strains of individual species. This review presents our recent analytical, experimental and theoretical studies on the cuticle, summarising at which hierarchical levels structure and composition are modified to achieve the required physical properties. We describe our multi-scale hierarchical modeling approach based on the results from these studies, aiming at systematically predicting the structure-composition-property relations of cuticle composites from the molecular level to the macro-scale. This modeling approach provides a tool to facilitate the development of optimized biomimetic materials within a knowledge-based design approach.

The exoskeleton of crustaceans is formed by the cuticle, a chitin-protein-based nano-composite with hierarchical organization over at least eight levels. On the molecular level, it consists of chitin associated with proteins forming fibres, which are organized in the form of twisted plywood. On the higher levels, the twisted plywood organization is modified and forms skeletal elements with elaborate functions. The load-bearing parts of crustacean cuticle are reinforced with both crystalline and amorphous biominerals. During evolution, all parts of the exoskeleton were optimized to fulfill different functions according to different ecophysiological strains faced by the animals. This is achieved by modifications in microstructure and chemical composition. In order to understand the relationship between structure, composition, mechanical properties and function we structurally characterized cuticle from the dorsal carapace of the edible crab Cancer pagurus using light and scanning electron microscopy (SEM). The local chemical composition was investigated using energy dispersive X-ray spectroscopy (EDX) and confocal m-Raman spectroscopy. Nanoindentation tests were performed to study the resulting local mechanical properties. The results show local differences in structure on several levels of the structural hierarchy in combination with a very heterogeneous mineralization. The distal exocuticle is mineralized with calcite, followed by a layer containing a magnesium, phosphate and carbonate rich phase and ACC in the proximal part. The endocuticle contains magnesian calcite and ACC in special regions below the exocuticle. Structure and mineral phase are reflected in the local stiffness and hardness of the respective cuticle regions. The heterogeneity of structural organization and mechanical properties suggests remarkable consequences for the mechanical behaviour of the bulk material.

The crustacean cuticle is a bio-composite consisting of hierarchically organized chitin-protein fibres, reinforced with calcite, amorphous calcium carbonate and phosphates. Comparative studies revealed that the structure and composition of tergite cuticle of terrestrial isopods is adapted to the habitat of the animals, and to their behavioural patterns to avoid predation. In this contribution we use FE-SEM, polarized SCμ-RSI and EBSD to investigate micro- and nano-patterns of mineral phase distribution and crystal orientation within the tergite cuticle of the two terrestrial isopod speciesArmadillidium vulgareandPorcellio scaber. The results show that the proximal regions of the exocuticle contain both calcite and ACC, with ACC located within the pore canals. Calcite forms hierarchically organised mesocrystalline aggregates of similar crystallographic orientation. Surprisingly,c-axis orientation preference is horizontal in regard to the local cuticle surface for both species, in contrast to mollusc and brachiopod shell structures in which thec-axis is always perpendicular to the shell surface. The overall sharpness of calcite crystal orientation is weak compared to that of mollusc shells. However, there are considerable differences in texture sharpness between the two isopod species. In the thick cuticle of the slow-walkingA. vulgarecalcite is more randomly oriented resulting in more isotropic mechanical properties of the cuticle. In contrast, the rather thin and more flexible cuticle of the fast- runningP. scabertexture sharpness is stronger with a preference ofc-axis orientation being parallel to the bilateral symmetry-plane of the animal, leading to more anisotropic mechanical properties of the cuticle. These differences may represent adaptations to different external and/or internal mechanical loads the cuticle has to resist during predatory attempts.

Like most terrestrial isopods, Porcellio scaber stores cuticular calcium in sternal deposits before moulting. The deposits consist of spherules that are formed within a confined ecdysial space containing a fluid of known cationic composition. The spherules are composed of granular particles containing mainly amorphous calcium carbonate (ACC), little amorphous calcium phosphate, and an organic matrix. We precipitated calcium carbonate using near physiological, but phosphate-free salines and matrix proteins extracted from native deposits, and analyzed structure, mineral phase, and composition of the precipitates. Within the test solutions, the total soluble fraction leads to precipitation of ACC granules. Agglomerations of ACC granules and the dried soluble fraction of the organic matrix are virtually devoid of organic phosphates. The agglomerations mimic several aspects in the architecture of native sternal deposits and were stable for at least one month. The saline alone has no effect on the crystal phase...

The crustacean cuticle is a hierarchically organised material composed of an organic matrix and mineral. It is subdivided into skeletal elements whose physical properties are adapted to their function and the eco-physiological strains of the animal. Using a variety of ultrastructural and analytical techniques we studied the organisation of the tergite cuticle of the sand burrowing beach isopod Tylos europaeus. The surface of the tergites bear epicuticular scales, sensilla and micro-tubercles. A distal layer of the exocuticle is characterised by a low density of organic fibres and the presence of magnesium-calcite. Surprisingly, the mineral forms regions containing polyhedral structures alternating with smooth areas. Between sub-domains within the distal exocuticle calcite varies in its crystallographic orientation. Proximal layers of the exocuticle and the endocuticle are devoid of calcite and the mineral occurs in the form of amorphous calcium carbonate (ACC). Using thin sections of mineralised cuticle we describe for the first time that ACC forms tubes around single protein-chitin fibrils.

The time dependent crystallization of a low isotactic polypropylene with statistically incorporated stereoerrors was investigated by the combination of differential scanning calorimetry (DSC), wideangle X-ray scattering (WAXS) and scanning force microscopy (SFM). Owing to Scanning force microscopy (SFM) and WAXS experiments the crystallization of the sample in mixed α/γ-form aggregates can be proposed. The nucleation and growth processes of crystallization in thin polypropylene films in real time were visualized with nanometer resolution by using SFM at variable temperature. During the isothermal crystallization from the melt initially crystals of the α-form were developed. These lamellae act as nuclei for the further crystallization of γ- and mixed α/γ-lamellae, which can be observed at longer crystallization times. Time dependent SFM and WAXS experiments showed that due to the low amount of crystallizable, regular sequences and its statistical distribution only slow crystallization rates can be observed. These results form the basis for a better understanding of the crystallization of low crystallinity polypropylenes. The investigations clearly show that the distribution of the regular isotactic segments influences the crystallization properties of propene based TEP's. This opens the possibility to tailor not only the mechanical but also the thermal properties of elastomeric polypropylenes by changing the polymer microstructure.

The influence of the cocatalyst nature on the distribution of the stereoerrors along the polymer chain has been studied using either MAO or [(C 6 H 5 ) 3 C + ] [(C 6 F 5 ) 4 B-] to activate a C 1 -symmetric (Flu-Ind) complex in propene polymerization experiments. The in situ activation with borate indicated the chain back-skip as the decisive mechanism responsible for stereoerror formation. When MAO is used for activation, additionally the reversible chain transfer to aluminum occurs, which can be called into account as a second mechanism for stereoerror formation. By the combination of 13 C NMR, DSC, WAXS and SFM, it was shown that the differences in polymerization mechanisms result in variations of stereoerror formation. Due to this, the isotactic block length n iso as well as their distribution along the chain changes. Using MAO activation, polypropenes with crystallizable blocks consisting of 23-32 monomers in isotactic sequences were generated, which co-crystallized in α- and γ-phase lamellae. When the reversible chain transfer was occluded (in situ borate activation) the bimodal distribution of crystalline lamellae strongly referred to a homogeneous random distribution of stereoerrors. In this case, two crystalline populations were present. The prevailing one, which crystallized in the orthorhombic γ-modification, contained 23 consecutive isotactic blocks. Additionally, small amounts of α-phase lamellae were present consisting of longer isotactic blocks (n iso > 35). The different crystalline modifications resulted in different polymer morphologies. These changes caused in turn variations in the mechanical properties, such as elasticity and mechanical strength. This clearly shows that, by using different cocatalysts for activating C 1 -symmetric complexes, the properties of poly(propylenes) with statistically distributed stereoerrors can be tailored.

The combination of an atomic force microscope (AFM) with a Confocal Raman Microscope (CRM) has been used to study the composition of various thin films of polymer blends. The high spatial resolution of the AFM enables the morphological characterization of the polymer blends on the nanometer scale. Furthermore, when operating the AFM in Digital Pulsed Force Mode (DPFM), topographic information and local stiffness can be simultaneously recorded. This allows the material-sensitive characterization of heterogeneous materials. Thin films where PMMA (at room temperature a glassy polymer) is blended with two different styrenebutadiene rubbers are investigated. The presence of PMMA in both phase-separated thin films allows the comparison of the mechanical properties of the two different rubber phases using DPFM-AFM. When PMMA is blended with PET due to their similar mechanical properties (both are in the glassy state at room temperature) the assignment of the two phases to the corresponding polymers by AFM is rather difficult. Here, Raman spectroscopy provides additional information on the chemical composition of materials. In combination with a confocal microscope, the spatial distribution of the various phases can be determined with a resolution down to 200 nm. Therefore, the topographically different structures observed in AFM images can be associated to the chemical composition by using the Confocal Raman Microscope (CRM).

The novel asymmetric ansa-complexes [1-(9-η 5 -fluorenyl)-2-(2,5,7-trimethyl-indenyl)ethane]hafnium dichloride (7a) and [1-(9-η 5 -fluorenyl)-2-(2,4,6-trimethyl-indenyl)ethane]hafnium dichloride (7b) were prepared and used as catalysts for propylene homopolymerization reactions after in situ activation. The synthetic route allows to separate the 4,6- and 5,7-substituted ligand isomers before the complexation step. The orientation of the methyl groups to the front (4,6) or to the back (5,7) of the tetrahedral hafnocene dichloride species influences their performances in polymerization reactions. Whereas hafnocene (7b) which bears trimethyl substitution at 2,4,6-positions of the indenyl moiety exhibits only moderate activity, the 2,5,7-trimethyl substituted structure (7a) produces isotactic poly(propyl-ene)s with high molecular weights (up to M w =9.0× 10 5 g mol -1 ) and high activities [up to 3.2 x 10 5 kg of PP (mol Hf x h) -1 ]. A comparative analysis of polymerization data and mechanical behavior of 7a, and previously reported 6,7-indenyl substituted complex 6b are reported.