Improving the bending resistance of double-layer printed flexible OLEDs with PEDOT: PSS-PEO composite HIL films

Flexible organic light-emitting diodes (OLEDs) are expected to have excellent device performance and mechanical robustness in many areas, such as wearable electronics and display devices. For the traditional materials of OLED anode, ITO is undoubtedly the most mature transparent conductive electrode available. However, the brittle and rigid nature of ITO severely limit the development of flexible OLED. In this work, a solution blending film consisting of poly (3,4 ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) and poly (ethylene oxide) (PEO) was used as a hybrid hole injection layer, where PEO polymer in the composite films can greatly improve the bending resistance of device. The printed flexible OLEDs doped with PEO exhibit impressive mechanical durability, maintaining 80.4% of its maximum external quantum efficiency after 1000 bends at a radius of curvature of 10 mm, compared to 46.3% for the counterpart without PEO doping.

Polylactic acid/multi walled carbon nanotubes (PLA/MWCNT) nanocomposite for 3D printing of medical devices

In recent years, the composite nanomaterials area has had a great development impact in health sciences. Biomaterials depict as one of the most promising since they are compatible with additive manufacturing (AM) techniques. It is also possible to use them to mold specific medical parts. Composite nanomaterials have shown good biocompatibility and low toxicity to have benefits equal to or greater than metals (i.e., Co-Cr alloy). The purpose of this study is to develop a nanocomposite biomaterial (PLA/MWCNTf) from Polylactic Acid (PLA) and functionalized Multi Walled Carbon Nanotubes (MWCNTf) to evidence its potential application in 3D printing of orthopedic fixation devices. PLA/MWCNTf nanocomposite was prepared by solution blending technique, incorporating a proportion of 0.5 wt% of MWCNTf to the PLA matrix. TGA analysis of the PLA/MWCNTf was used to determine the thermal stability, a slight increase was found compared to the PLA. FTIR spectroscopy confirmed the presence of carboxylic acid groups in the MWCNTf which improves good incorporation of the nanotubes in the PLA matrix. Additionally, Raman spectroscopy, SEM, and AFM micrographs were used to verify MWCNTf reached the PLA surface homogeneously. Additive manufacturing preparation was done by extrusion molding of PLA/MWCNTf as well as its 3D printing.

The Effect of WS2 Nanosheets on the Non-Isothermal Cold- and Melt-Crystallization Kinetics of Poly(l-lactic acid) Nanocomposites

In the present work, hybrid nanocomposite materials were obtained by a solution blending of poly(l-lactic acid) (PLLA) and layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) as a filler, varying its content between 0 and 1 wt%. The non-isothermal cold- and melt-crystallization and melting behavior of PLLA/2D-WS2 were investigated. The overall crystallization rate, final crystallinity, and subsequent melting behavior of PLLA were controlled by both the incorporation of 2D-WS2 and variation of the cooling/heating rates. In particular, the analysis of the cold-crystallization behavior of the PLLA matrix showed that the crystallization rate of PLLA was reduced after nanosheet incorporation. Unexpectedly for polymer nanocomposites, a drastic change from retardation to promotion of crystallization was observed with increasing the nanosheet content, while the melt-crystallization mechanism of PLLA remained unchanged. On the other hand, the double-melting peaks, mainly derived from melting–recrystallization–melting processes upon heating, and their dynamic behavior were coherent with the effect of 2D-WS2 involved in the crystallization of PLLA. Therefore, the results of the present study offer a new perspective for the potential of PLLA/hybrid nanocomposites in targeted applications.

Understanding thermal and rheological behaviors of bimodal polymethyl methacrylate (BPMMA) fabricated via solution blending

In this work, a series of bimodal polymethyl methacrylate (BPMMA) was fabricated via solution-blending two neat PMMA resins. Rheology, DMTA, thermal infrared imager measurements were used in an attempt to probe the internal structure of the as-prepared BPMMA. It was demonstrated that the thermorheological behavior of the BPMMA was heavily dependent on shear rate, temperature as well as blending ratio. In addition, a typical “V-shaped” response, namely, a dip in storage modulus (G′) followed by an upturn in the plot of G′ versus measuring temperature for D4 (with lower weight-average molecular weight) was observed, characteristic of occurrence of thermorheological complexity. Our experimental results of physical–mechanical testings suggested that the BPMMA had better comprehensive properties than those of their neat PMMA counterparts.

Experimental Investigation on the Effect of Graphene Oxide Additive on the Steady-State and Dynamic Shear Properties of PDMS-Based Magnetorheological Elastomer

Isotropic polydimethylsiloxane (PDMS)-based magnetorheological elastomers (MREs) filled with various contents of graphene oxide (GO) additive were fabricated by the solution blending-casting method in this work. The morphologies of the produced MREs were characterized, and the results indicate that the uniform distribution of GO sheets and carbonyl iron particles (CIPs) becomes difficult with the increase of GO content. The steady-state and dynamic shear properties of the MREs under different magnetic field strengths were evaluated using parallel plate rheometer. It was found that the physical stiffness effect of GO sheets leads to the increase of the zero-field shear modulus with increasing GO content under both the steady-state and dynamic shear loads. The chemical crosslinking density of PDMS matrix decreases with the GO content due to the strong physical crosslinking between GO and the PDMS matrix. Thus, the MREs filled with higher GO content exhibit more fluid-like behavior. Under the dynamic shear load, the absolute MR effect increases with the GO content due to the increased flexibility of the PDMS matrix and the dynamic self-stiffening effect occurring in the physical crosslinking interfaces around GO sheets. The highest relative MR effect was achieved by the MREs filled with 0.1 wt.% GO sheets. Then, the relative MR effect decreases with the further increase of GO content due to the improved zero-field modulus and the increased agglomerations of GO and CIPs. This study shows that the addition of GO sheets is a possible way to prepare new MREs with high MR effect, while simultaneously possessing high zero-field stiffness and load bearing capability.

Percolation Effects in MCNT-filled Polystyrene: Rheological,Optical, Adhesion and Conductive Investigations

This work is devoted to the preparation and characterization of some polystyrene/multiwall carbon nanotubes (PS/MCNT) systems. The dispersion of the reinforcement agent within the PS medium was done via sonication and the resulting nanocomposites containing 0-40 wt% MCNTs were achieved by solution blending procedure. Shear flow and viscoelastic properties were tested by means of rheology, revealing some changes in the sample microstructure. Dispersion curves of the matrix and low filled nanocomposite were registered at variable temperatures. The theoretical refractive index and corresponding dielectric constant at optical frequencies were analyzed as a function of the system composition. Heat transport in the reinforced materials was examined by computer modeling, which enabled calculation of thermal conductivity. Electrical transport features were assessed using a theoretical approach relying on the physical properties of each phase. The surface adhesion of the samples with various materials was determined to check the suitability for applications in technical or bio-related fields.

Phase Structure and Properties of Ternary Polylactide/Poly(methyl methacrylate)/Polysilsesquioxane Blends

Ternary blends of polylactide (PLA, 90 wt.%) and poly(methyl methacrylate) (PMMA, 10 wt.%) with functionalized polysilsesquioxanes (LPSQ-R) were obtained by solution blending. R groups in LPSQ containing hydroxyethyl (LPSQ-OH), methylglycolic (LPSQ-COOMe) and pentafluorophenyl (LPSQ-F5) moieties of different chemical properties were designed to modify PLA blends with PMMA. The effect of the type of LPSQ-R and their content, 1–3 wt.%, on the structure of the blends was studied with scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (SEM-EDS), dynamic mechanical thermal analysis (DMTA) and Raman spectroscopy. Differential scanning calorimetry (DSC) and tensile tests also showed various effects of LPSQ-R on the thermal and mechanical properties of the blends. Depth-sensing indentation was used to resolve spatially the micro- and nano-scale mechanical properties (hardness and elastic behaviour) of the blends. The results showed clearly that LPSQ-R modulate the structure and properties of the blends.