Microwave-Assisted Synthesis of Nanoscale VO2 Structures

Nanoscaled VO2 structures were made using a fast microwave-assisted synthesis method in acetophenone as solvent, starting from vanadium pentoxide V2O5. Insights in the reaction and purification process were elaborated by attenuated total reflection infrared and nuclear magnetic resonance spectroscopy, which validated the choice of oleyl amine as ligand and acetophenone as solvent. A straightforward heat treatment in inert atmosphere was used to convert the mixture of VOx (M) and VOOH phases to thermochromically active monoclinic VO2 (M) nanomaterials. This conversion process was monitored via in-situ X-ray diffraction and gave insight in the influence of ethanol and tert-butyl hydroperoxide on the crystal structure and morphology, monitored via bright-field transmission electron microscopy. The thermochromic switching was investigated with differential scanning calorimetry showing a latent heat up to 43.34 ​J/g

CRYSTALLINITY PREDICTION OF SHORT CARBON FIBRE REINFORCED POLYAMIDE 6 COMPOSITES MANUFACTURED BY FUSED FILAMENT FABRICATION

Polymer additive manufacturing has transformed itself from a technology that is mainly focused on rapid prototyping to a widely received manufacturing technique for highly customised products. In fused filament fabrication (FFF), due to the fast heating and cooling of the polymer, the printed part's crystallinity and mechanical properties are inevitably affected. This research proposes a numerical approach to predict the final crystallinity for FFF printed polyamide 6/short carbon fibre composite. To do so, samples were built with the FFF technique with their temperature history recorded by infrared camera measurements. Differential scanning calorimetry (DSC) was conducted on the FFF filament to calibrate the numerical model. Temperature history was used as input for the model and the printed part’s final crystallinity is predicted. Tensile tests were carried out to examine the influence of crystallinity on the printed part’s mechanical performance

Poly(alkylene terephthalate)s : from current developments in synthetic strategies towards applications

Poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT) and poly(butylene terephthalate) (PBT) are widely known and the mostly studied polymers belonging to the poly(alkylene terephthalate) (PAT) family, but there are many other polymers in this family of which the full potential has not yet been disclosed. Herein, we provide an overview of the state-of-the-art of this specific polyester type. In a first part, the various synthesis methods including melt polycondensation, solution polycondensation and ring-opening polymerisation together with their advantages and disadvantages are discussed. Next, an overview of the polymer properties and a comparison of their thermal and mechanical behaviour are provided. Due to the increasing interest in sustainability (e.g. production of PATs from bio-based monomers) and recycling aspects (e.g. depolymerisation), recent progress on PATs in these particular fields is also highlighted. Currently, PET, PTT and PBT are exploited in many applications while research is striving to broaden their application field

Single‐particle electrophoresis for studying the adsorption of cationic polymers onto anionic particles

Understanding the adsorption of polymers onto particles is crucial for many technological and biomedical applications. Even though polymer adsorption on particles is a dynamic process, most experimental techniques can only study the adsorption indirectly, in equilibrium and on the ensemble level. New analysis methods are required to overcome these limitations. We investigated the use of single-particle electrophoresis to study the adsorption kinetics of cationic polymers onto anionic particles and compared the resulting data to a theoretical model. In this approach, the electrophoretic mobility of single polystyrene (PS) particles, exposed to different concentrations of poly(2-guanidinoethyl methacrylate), was measured as a function of time. The polymer adsorption leads to an electrophoretic mobility change of the PS particle over time, from the initial negative value to a positive value at equilibrium. By fitting the kinetics data to the Langmuir model, the adsorption rate, desorption rate and equilibrium constant were determined. Finally, the adsorption kinetics of several other polymers was investigated. This showed that the presented technique enables direct analysis and comparison of the kinetics of polymer adsorption on the single-particle level.Understanding the adsorption of polymers onto particles is crucial for many technological and biomedical applications. Even though polymer adsorption on particles is a dynamic process, most experimental techniques can only study the adsorption indirectly, in equilibrium and on the ensemble level. New analysis methods are required to overcome these limitations. We investigated the use of single-particle electrophoresis to study the adsorption kinetics of cationic polymers onto anionic particles and compared the resulting data to a theoretical model. In this approach, the electrophoretic mobility of single polystyrene (PS) particles, exposed to different concentrations of poly(2-guanidinoethyl methacrylate), was measured as a function of time. The polymer adsorption leads to an electrophoretic mobility change of the PS particle over time, from the initial negative value to a positive value at equilibrium. By fitting the kinetics data to the Langmuir model, the adsorption rate, desorption rate and equilibrium constant were determined. Finally, the adsorption kinetics of several other polymers was investigated. This showed that the presented technique enables direct analysis and comparison of the kinetics of polymer adsorption on the single-particle level.A

3D-printed shape memory poly(alkylene terephthalate) scaffolds as cardiovascular stents revealing enhanced endothelialization

Cardiovascular diseases are the leading cause of death and current treatments such as stents still suffer from disadvantages. Balloon expansion causes damage to the arterial wall and limited and delayed endothelialization gives rise to restenosis and thrombosis. New more performing materials that circumvent these disadvantages are required to improve the success rate of interventions. To this end, the use of a novel polymer, poly(hexamethylene terephthalate), is investigated for this application. The synthesis to obtain polymers with high molar masses up to 126.5 kg mol-1 is optimized and a thorough chemical and thermal analysis is performed. The polymers are 3D-printed into personalized cardiovascular stents using the state-of-the-art solvent-cast direct-writing technique, the potential of these stents to expand using their shape memory behavior is established, and it is shown that the stents are more resistant to compression than the poly(l-lactide) benchmark. Furthermore, the polymer's hydrolytic stability is demonstrated in an accelerated degradation study of 6 months. Finally, the stents are subjected to an in vitro biological evaluation, revealing that the polymer is non-hemolytic and supports significant endothelialization after only 7 days, demonstrating the enormous potential of these polymers to serve cardiovascular applications. Solvent-cast direct-writing enables the additive manufacturing of personalized cardiovascular stents based on poly(hexamethylene terephthalate) with a high molar mass. These stents are hydrolytically stable, not hemolytic, and enable self-expansion due to their shape memory behavior. Significant and rapid endothelialization is achieved after 7 days of incubation with endothelial cells, demonstrating the enormous potential of these polymers to serve cardiovascular applications. imag