Search

Four-dimensional (4D) printing, combining three-dimensional (3D) printing with time-dependent stimuli-responsive shape transformation, eliminates the limitations of the conventional 3D printing technique for the fabrication of complex hollow constructs. However, existing 4D printing techniques have limitations in terms of the shapes that can be created using a single shape-changing object. In this paper, we report an advanced 4D fabrication approach for vascular junctions, particularly T-junctions, using the 4D printing technique based on coordinated sequential folding of two or more specially designed shape-changing elements. In our approach, the T-junction is split into two components, and each component is 4D printed using different synthesized shape memory polyurethanes and their nanohybrids, which have been synthesized with varying hard segment contents and by incorporating different weight percentages of photo-responsive copper sulfide-polyvinyl pyrrolidone nanoparticles. The formation of a T-junction is demonstrated by assigning different shape memory behaviors to each component of the T-junction. A cell culture study with human umbilical vein endothelial cells reveals that the cells proliferate over time, and almost 90% of cells remain viable on day 7. Finally, the formation of the T-junction in the presence of near-infrared light has been demonstrated after seeding the endothelial cells on the programmed flat surface of the two components and fluorescence microscopy at day 3 and 7 reveals that the cells adhered well and continue to proliferate over time. Hence, the proposed alternative approach has huge potential and can be used to fabricate vascular junctions in the future. [ABSTRACT FROM AUTHOR]

With ongoing miniaturization and weight reduction of portable electronic devices, effective heat dissipation is essential to inhibit malfunctions and premature failure. The application of fillers in a polymer matrix enhances the thermal conductivity of lightweight materials but impedes recyclability. All-polyethylene (all-PE) materials represent a sustainable and easy-to-recycle single-material alternative, whereby high and tunable thermal conductivity is provided by process-induced hierarchical PE nanostructures. Essential for this type of composite-free high-performance material is the specific PE composition containing high amounts of ultra-high molecular weight PE that form ultrastrong extended-chain nanostructures induced by shear and elongational flow during processing. This results in self-reinforcing fibre-like shish-kebab nanostructures with a high thermal conductivity parallel to the extended PE chains. Extrusion-based 3D printing enables tuning the orientation of the PE nanostructure to tailor the orientation and magnitude of the thermal conductivity. Thus, this material class highlights the possibility of combining digitally programmable heat management in 3D printed materials with sustainable material concepts. [ABSTRACT FROM AUTHOR]

Liquid crystalline materials found numerous applications in modern technologies due to their ability to respond to external fields. In this context, ferronematic liquid crystals are fascinating because they offer a response to weak magnetic fields in addition to electrical fields. Nevertheless, the synthesis of stable ferronematic liquid crystals represents a challenge for colloidal and synthetic chemists. In this work, we present a straight-forward strategy for directly incorporating presynthesized magnetic nanoparticles into every other interlayer of synthetic 2 : 1 layered silicates, which subsequently can be swollen to nematic phases simply by immersion into water, offering almost infinite stability. The resulting ferronematic suspension shows a sensitive response to magnetic fields. Moreover, the synthetic strategy is highly modular, enabling for variations of the magnetic nanosheets that allow for tuning the interaction between nanosheets and blocking temperature. [ABSTRACT FROM AUTHOR]

Polyethyleneimine aids the gas diffusion precipitation of nano-structured basic cobalt carbonate sheets at the air/solution interface. Upon drying, these mineral films undergo self-rolling into 3D coiled structures. Exploring this principle for the design of self-supported functional materials, porous Co3O4 spirals composed of interconnected nanoparticles are obtained by thermal conversion. [ABSTRACT FROM AUTHOR]

Polycarbonate diblock copolymers with a biobased poly(limonene carbonate) (PLimC) and a poly(cyclohexene carbonate) (PCHC) block were prepared viaβ-diiminate zinc catalysed living ring-opening copolymerization (ROCOP) of CO2 and trans-limonene oxide and cyclohexene oxide, respectively. trans-Limonene oxide can be readily obtained from limonene, a renewable non-food source, that can be found in the peel of many citrus fruits and is the main component of orange oil. The block formation was realised by sequential addition of the epoxide monomers. The composition of the resulting amorphous poly(limonene carbonate)-block-poly(cyclohexene carbonate) (PLimC-b-PCHC) diblock copolymers was analysed by 1H NMR spectroscopy. The self-assembly of the diblock copolymers into well-defined bulk morphologies was studied by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Depending on the composition and molecular weight the formation of cylindrical, lamellar, and hexagonally perforated lamellar morphologies was observed. [ABSTRACT FROM AUTHOR]

Coating metal nanocrystals with responsive polymers provides a model case of smart, functional materials, where the optical properties can be modulated by external stimuli. However the optical response is highly sensitive to the polymer shell morphology, thickness and dielectric contrast. In this paper we study the nature of cross-linked, thermoresponsive polymer shells for the first time using four different scattering approaches to elucidate the density profile of the shells. Each scattering method provides unique information about the temperature-induced changes of shell thickness in terms of hydrodynamic radius and radius of gyration, the pair-distance distribution functions of the shells as well as the dynamic network fluctuations. Only a combination of these different scattering techniques allows to develop a morphological model of the core-shell particles. We further demonstrate control of the cross-linker distribution in core-shell synthesis by semi-batch precipitation copolymerization. Conducting the polymerization in three steps, we show for the first time that the polymer shell thickness can be successively increased without affecting the shell morphology and response behavior. [ABSTRACT FROM AUTHOR]

We present an investigation of β-lactoglobulin adsorption onto spherical polyelectrolyte brushes (SPBs) by small angle X-ray scattering (SAXS). The SPB consists of a polystyrene core onto which long chains of poly(styrene sulfonate) are grafted. The amount and the distribution of proteins adsorbed in the brush layer at low ionic strength can be derived from SAXS. The analysis of the SAXS data reveals additionally that some of the protein molecules form aggregates of about six monomers in the adsorbed state. Furthermore, the position and the amount of slightly bound protein can be detected by the combination of the SAXS results and the SPB loading after extensive ultrafiltration. The total amount of adsorbed protein is compared to data derived from isothermal titration calorimetry. The comparison of both sets of data demonstrates that the protein molecules in the inner layers of the spherical polyelectrolyte brush are firmly bound. Proteins located in the outer layers are only weakly bound and can be washed out by prolonged ultrafiltration. [ABSTRACT FROM AUTHOR]

Spinel cobalt(ii,iii) oxide (Co 3 O 4 ) represents a p-type semiconductor exhibiting promising functional properties in view of applications in a broad range of technological fields including magnetic materials and gas sensors as well as sustainable energy conversion systems based on photo- and electrocatalytic water splitting. Due to their high specific surface area, nanoparticle-based structures appear particularly promising for such applications. However, precise control over the diameter and the particle size distribution is required to achieve reproducible size-dependent properties. We herein introduce a synthetic strategy based on the decomposition of hydroxide precursors for the size-controlled preparation of purified Co 3 O 4 nanoparticles with narrow size distributions adjustable in the range between 3-13 nm. The particles exhibit excellent colloidal stability. Their dispersibility in diverse organic solvents further facilitates processing ( i.e. ligand exchange) and opens exciting perspectives for controlled self-assembly of the largely isometric primary particles into mesoscale structures. In view of potential applications, functional properties including absorption characteristics and electrocatalytic activity were probed by UV-Vis spectroscopy and cyclic voltammetry, respectively. In these experiments, low amounts of dispersed Co 3 O 4 particles demonstrate strong light absorbance across the entire visible range and immobilized nanoparticles exhibit a comparably low overpotential towards the oxygen evolution reaction in electrocatalytic water splitting., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Triblock terpolymers exhibit a rich self-organization behavior including the formation of fascinating cylindrical core-shell structures with a phase separated corona. After crystallization-induced self-assembly of polystyrene-block-polyethylene-block-poly(methyl methacrylate) triblock terpolymers (abbreviated as SEMs = Styrene-Ethylene-Methacrylates) from solution, worm-like core-shell micelles with a patchy corona of polystyrene and poly(methyl methacrylate) were observed by transmission electron microscopy. However, the solution structure is still a matter of debate. Here, we present a method to distinguish in situ between a Janus-type (two faced) and a patchy (multiple compartments) configuration of the corona. To discriminate between both models the scattering intensity must be determined mainly by one corona compartment. Contrast variation in small-angle neutron scattering enables us to focus on one compartment of the worm-like micelles. The results validate the existence of the patchy structure also in solution.