Phase-separated Structure Research Articles

Phase-separated Tenmoku “Blue” glaze: Microstructure and coloring mechanism

Yohen Tenmoku, a masterpiece of Jian kiln with bright blue rendering effect under different incident light, is lack research as only three intact pieces exist in the world. Herein, this study was fortunate to work with Sun Jianxing to conduct technical characterization and material analysis of the imitation Yohen Tenmoku (Song). Black oil spots are composed of magnetite (10-25 μm) and Al doping in hematite (1-3 μm) precipitated on the glaze surface. Brilliant blue color a combination of the bright blue structural color resulting from the coherent scattering of amorphous photonic crystals composed of spherical phase separation structures of 130 nm and the coloring of iron ions produced in a weak reducing atmosphere by the addition of high iron glazes with composite alkali (CaO and MgO). Continuous refraction and reflection of the structural color between the blue glass phases gives the glaze a shiny and dazzling blue color.

Preparation and Properties of Immiscible Poly(lactic acid)/Ethyl Cellulose Bioplastic Blends with Good Transparency and Optical Control by Drawing

In this study we prepared a poly(lactic acid)/ethyl cellulose (PLA/EC) bioplastic blend film by melt pressing after solvent casting and investigated the optical, thermal, and mechanical properties in relation to the structural changes revealed by various microscopies and scattering measurements. Despite the immiscibility of PLA and EC, the blend film exhibited good optical transparency due to the close match in their refractive indices. A second run of differential scanning calorimetry during heating revealed a decrease in the glass transition temperature () and melting point () of PLA with EC although EC had the higher values. Thermomechanical analysis suggested that these decreases were due to the negative pressure generated due to the suppression of PLA shrinkage below and above during cooling. Furthermore, ductile drawing of the blend film (70/30) at an optimal temperature of 70 °C above resulted in a uniform whitening near 100% strain. Delamination at the interface between the PLA matrix and EC domain led to the formation of micrometer-sized oriented voids, which enhanced the refractive index difference in the phase-separated structure, thereby scattering light and achieving the uniform and oriented white blend film.

In-situ phase separation constructing robust hydrophobic ionogels with multifunction

Ionogels, as the promising alternative to hydrogels, have garnered great attention due to their excellent ionic conductivity, thermal stability, and non-volatility. However, the design and construction of robust hydrophobic ionogel still is a significant challenge at present, especially with a facile method. Herein, inspired by the two-phase structure of the dermis in human skin (stiff collagen fiber scaffold embedded in soft elastin matrix), a one-pot in-situ phase separation design strategy is proposed to construct the robust hydrophobic ionogel through the random copolymerization of hydrophobic monomers with the solubility difference in hydrophobic ionic liquid (IL). The resultant ionogel forms a homogeneously dual phase network containing solvent-rich soft domains and solvent-poor hard domains. The mechanical robustness can be synergistically achieved by the hard domain strong skeleton and the soft domain elastic matrix. Benefiting from multiple reversible interactions including hydrogen bonding, ion–dipole and ion-ion interactions, and physical entanglement, the ionogel shows strong IL retention, excellent self-healing, and regenerating abilities, while can adhere to different substrates. The unique phase separation structure brings temperature-dependent transparency and high-damping features. The ionogel also presents high ionic conductivity due to the abundance of movable ions. As application demonstrations, the ionogel is successfully used for dynamic pattern encryption, shock attenuation, and strain sensing. What’s more, this strategy can be also applied to improve the mechanical properties of hydrophobic ionogels based on other monomers. Hence, this work establishes an effective and general design strategy for hydrophobic ionogels demanding versatility.

Advanced composite membranes based on multifunctional fillers constructed by covalently linking phosphotungstic acid with mesoporous carbon nitride for high-performance and durable fuel cell under low humidity

Two-dimensional (2D) nanosheets possessing large specific surface area and high aspect ratio can serve as proton-conduction accelerators owing to their continuous proton transport feature. Herein, phosphotungstic acid (HPW) is chemically grafted to mesoporous carbon nitride nanosheets (CN) via a hydrothermal process to produce water-insoluble HPW/CN (PCN) nanofillers, and subsequently embedded into sulfonated poly(arylene ether sulfone) (SPAES) to develop a long-range proton transport channels for high-performance composite membranes. The loading of hydrophilic HPW enhances the dispersivity and compatibility with the SPAES polymer and improves the mechanical-dimensional-chemical stability of the composite membranes. The formed hydrogen-bonding networks and acid-base interactions between fillers and polymers could endow the SPAES/PCN membranes with favorable water-absorption ability and proton-conducting performance. Besides, the excellent interfacial interactions working as a “bridge” facilitates the formation of well-defined phase-separation structure and constructs long-range ionic/water channels at the SPAES-PCN interface. Moreover, the strong acidic HPW on surface and mesoporous structure of CN enhance effectively water-retention ability of the composite membranes, which is specially contribute to rapid proton transport at low humidity. The proton conductivity of the SPAES/PCN-7.5 membrane reaches up to 250 mS cm−1 at 90 °C, hydrous condition, and 46 mS cm−1 at 80 °C, 50 % RH, which are 42 % and 84 % higher than those of the control SPAES membrane, respectively. The SPAES/PCN-7.5 membrane achieves highest maximum power density of 404–824 mW cm−2 at 80 °C and 50%–100 % RH, exceeding that of the SPAES membrane (207–546 mW cm−2) and Nafion® 112 (359–723 mW cm−2). It still remains stable cell performance, as well as undergoes lower voltages loss and hydrogen permeation after the durability test (144 h, 80 °C/60 % RH). In addition, molecular dynamics simulation analysis is performed to offer new insight into elucidating the structure-property relationships of the composite membrane. These results indicate that the SPAES/PCN composite system is an advanced membrane for the practical applications of fuel cells.

Inverse design of polymer alloys using deep learning based on self-consistent field analysis and finite element analysis

In this study, a framework that deals with the inverse design of material structures based on macroscopic properties using deep learning models is proposed. For the framework, “polymer alloy’s phase separation structures” as material structures and “stresses” as macroscopic properties are considered. The results of self-consistent field analysis are used as structure data, in particular, the analysis result of two-dimensional phase separation structures of a diblock copolymer melt in the equilibrium state. For the stress data, the results of finite element analysis are used, in particular, the analysis results of average stresses over the system under the small-enforced-displacement condition. This framework consists of two deep learning models—one aimed at generating phase separation structures, and the other at predicting properties from structures. For the second model, we incorporate a convolutional neural network. By implementing a random search toward a model that combines these two deep learning models, we constructed the framework for the inverse design of phase separation structures that possess desired macroscopic properties. This framework is demonstrated to be able to suggest phase separation structures that realize desired stresses that are input to the framework through examples. The innovation of the method is the development of framework to propose the optimal structure of polymer alloys by using machine learning. The main novelties of this method are the construction of generative adversarial network that reproduces the phase-separation structure of polymer alloy specified by label information, realization of inverse analysis based on mechanical properties, and the simultaneous optimization of multiple mechanical properties.

The performance analysis of screw pump stator elastomers: Polyamide 6/hydrogenated nitrile blends: Mechanical, oil resistance and tribological properties

In this paper, the mechanical properties, thermal properties, oil resistance and tribology performance of hydrogenated nitrile/polyamide 6 blends were studied systematically. The inter-molecular interaction, phase separation structure, crystallinity, dynamic loss, friction morphology and other aspects of the blends were investigated. The results showed that PA6 phase had significant reinforcing effect in HNBR matrix. Due to the strong interaction between PA6 molecular chain and HNBR molecular chain, the glass transition temperature (Tg) of the blends was increased and the dynamic loss factor (tanδ) was decreased. Meanwhile, the tribology performance of the blends was significantly improved. It was due to the formation of a microball layer with PA6 particle phase as component, which effectively isolated the contact between the friction pairs.

Water-Induced Phase Separation for Anti-Swelling Hydrogel Adhesives in Underwater Soft Electronics.

The development of hydrogel-based underwater electronics has gained significant attention due to their flexibility and portability compared to conventional rigid devices. However, common hydrogels face challenges such as swelling and poor underwater adhesion, limiting their practicality in water environments. Here, a water-induced phase separation strategy to fabricate hydrogels with enhanced anti-swelling properties and underwater adhesion is presented. By leveraging the contrasting affinity of different polymer chains to water, a phase-separated structure with rich hydrophobic and dilute hydrophilic polymer phases is achieved. This dual-phase structure, meticulously characterized from the macroscopic to the nanoscale, confers the hydrogel network with augmented retractive elastic forces and facilitates efficient water drainage at the gel-substrate interface. As a result, the hydrogel exhibits remarkable swelling resistance and long-lasting adhesion to diverse substrates. Additionally, the integration of carboxylic multiwalled carbon nanotubes into the hydrogel system preserves its anti-swelling and adhesion properties while imparting superior conductivity. The conductive phase-separated hydrogel exhibited great potential in diverse underwater applications, including sensing, communication, and energy harvesting. This study elucidates a facile strategy for designing anti-swelling underwater adhesives by leveraging the ambient solvent effect, which is expected to offer some insights for the development of next-generation adhesive soft materials tailored for aqueous environments.

C-band laser emission from Er3+-doped fluorosilicate glass microspheres and its application in temperature sensing

Compared to silica glass, fluorosilicate multi-component glass has a unique phase-separated structure, which improves the stability of the glass while improving the fluorescence efficiency. In this paper, microspheres were fabricated from Er3+-doped fluorosilicate glass by adopting the traditional melt quenching and fiber heating technique. Under a 975 nm laser pumping, single and multi-mode microsphere lasers were obtained in C-band, and the lowest threshold power of about 2.0 mW is experimentally obtained at multi-mode microsphere lasers. In addition, the microsphere lasers can sense temperature with a sensitivity of 11.28 p.m./oC.

Correlating structure-mechanics relationship of multiblock copolymers: Insights from molecular dynamics simulation

Multiblock copolymers (MBCs) have garnered considerable interest in both industrial and fundamental polymer science. However, the phase structure and properties at a molecular level of MBCs remain largely unexplored. To address this, the effects of three structural factors (block number index α, interaction strength between hard segments εH−H, and hard segment stiffness kH) on the phase structure, dynamic properties and mechanical properties of MBCs have been investigated using coarse-grained molecular dynamics (CGMD) simulations. The degree of phase separation, ψ, has been quantified based on the number of neighboring beads designated to measure the phase separation structure. Results indicate that a lower α (longer block chain length), stronger εH−H, and weaker kH significantly reduce the contacts between soft and hard segments, leading to an increase in ψ. An examination of higher ψ (greater than 0.7) reveals two Tg s that converge as ψ decreases and eventually merge into one. Mechanical properties are improved with increasing α at low strains, whilst they change non-monotonically at high strains, likely due to differing contributions of soft and hard segments to the stress. Systems with stronger εH−H and kH exhibit superior mechanical properties due to their higher non-bonded energy increments and bond orientation. In general, the mode of the variation of phase separation structure, glass transition temperature and mechanical properties of MBCs at the molecular level, has been elucidated valuable insight for the design and synthesis of high-performance MBCs materials.

A review on electrically conductive polyurethane nanocomposites: From principle to application

AbstractPolyurethanes (PUs) thanks to the occurrence of phase separation and biphasic structure prevail over other polymer matrixes for impregnation of conductive fillers and production of conductive composites. A number of carbonous fillers including carbon black, carbon fiber, carbon nanotube, graphite and its derivatives, and fullerene can be loaded into the PU matrixes to impart electrical conductivity. The properties of the carbonous fillers, the filler/PU interactions, and the method of compositing determine the conductive performance of the composite. It is possible to modulate the properties of the conductive PU composites and employ them for a number of electronic applications including but not limited to the strain sensors, electromagnetic interference shielding materials, supercapacitors, and tissue engineering scaffolds. In the present review, first, the distinctive properties of PU as a matrix of conductive composites have been discussed. Then, various carbon fillers loaded into the PU matrixes and their structural and conductive properties have been debated. Thereafter, the fabrication methods of the conductive composites as well as the influential parameters on the electrical properties of the composites have been reviewed to provide an insight into how fulfill a PU composite with the desired electrical performance. And finally, a number of applications of conductive PU composites have been put forward.Highlights Polyurethanes are very capable matrixes for conductive composites. Carbonous fillers can be loaded into the PU matrixes to impart conductivity. Conductive PU composites are employed for a number of electronic applications. Herein, properties, fillers, and applications of PU composites are reviewed.

Synthesis, Characterization, and Solar Cell Applications of a Non-fused-ring Electron Acceptor Based on Vinylene-bridged Difluorobenzothiadiazole

Abstract A new non-fused-ring electron acceptor (NREA), BE4T based on vinylene-bridged difluorobenzothiadiazole (FBTzE) has been synthesized and characterized. BE4T was found to be suitable for high-performance OPVs due to its strong absorption around 600–800 nm and low-lying HOMO/LUMO energy levels. However, BE4T-based cells showed a low PCE of 1.05% owing to the formation of highly ordered edge-on and large phase separation structure in the blended films.

Surface-induced film structure for enhanced carrier transport of the conjugated/insulating polymer blends at a low semiconductor content

In this work, a donor-acceptor copolymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)- alt(3,3‴-di(2-decyltetradecyl)-2,2'; 5′,2''; 5″,2‴-quaterthiophene-5,5‴-diyl)] (PffBT4T-2DT) has been blended with the insulating polystyrene (PS) to fabricate the field-effect transistors (FETs). The blend films deposited on the SiO2 dielectric by the octadecyltrichlorosilane (OTS) modification, exhibit the FET mobility 1–2 orders of magnitude higher than those on the unmodified dielectric, as well as a 10–100 folds enhancement of mobility with decreasing the PffBT4T-2DT ratios at the concentration range of 30 wt. %-5 wt. %. Detailed microstructural characterizations reveal that the OTS modification induces the change of phase-separation structure in the blend film, in which more aggregates of the PffBT4T-2DT are enriched near the semiconductor/dielectric interface. Furthermore, the OTS modification of substrate and the addition of PS facilitate the conversion from face-on to edge-on stacking orientation so that the edge-on packing structure dominates in the films with a semiconductor content of 5–10 wt. %. Based on these results, we propose that the remarkably elevated mobility at low PffBT4T-2DT contents is attributed to the enhanced edge-on arrangement of PffBT4T-2DT as well as the favorable interconnect network of chain aggregates formed at the semiconductor/dielectric interface for efficient carrier transport pathway.

Controlling the structure of spin-coated multilayer ethylcellulose/hydroxypropylcellulose films for drug release

Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport out of pharmaceutical pellets. Water-soluble HPC leaches out and forms a porous structure that controls the drug transport. Industrially, the pellets are coated using a fluidized bed spraying device, and a layered film exhibiting varying porosity and structure after leaching is obtained. A detailed understanding of the formation of the multilayered, phase-separated structure during production is lacking. Here, we have investigated multilayered EC/HPC films produced by sequential spin-coating, which was used to mimic the industrial process. The effects of EC/HPC ratio and spin speed on the multilayer film formation and structure were investigated using advanced microscopy techniques and image analysis. Cahn-Hilliard simulations were performed to analyze the mixing behavior. A gradient with larger structures close to the substrate surface and smaller structures close to the air surface was formed due to coarsening of the layers already coated during successive deposition cycles. The porosity of the multilayer film was found to vary with both EC/HPC ratio and spin speed. Simulation of the mixing behavior and in situ characterization of the structure evolution showed that the origin of the discontinuities and multilayer structure can be explained by the non-mixing of the layers.

On-Demand Tunability of Microphase Separation Structure of 3D Printing Material by Reversible Addition/Fragmentation Chain Transfer Polymerization.

Controlling the phase-separated structure of polymer alloys is a promising method for tailoring the properties of polymers. However, controlling the morphology of phase-separated structures is challenging. Recently, phase-separated structures have been fabricated via 3D printing; however, only a few methods that enable on-demand control of phase separation have been reported. In this study, laser-scanning stereolithography, a vat photopolymerization method, is used to form a phase-separated structure via polymerization-induced microphase separation by varying the scanning speed and using macro-reversible addition/fragmentation chain transfer (macro-RAFT) agents with different average molar masses, along with multiarmed macro-RAFT agents; such structures were used to fabricate 3D-printed parts. Various phase-separated morphologies including sea-island and reverse sea-island were achieved by controlling the laser scanning speed and RAFT type. Heterogeneous structures with different material properties were also achieved by simply changing the laser scanning speed. As the deformation due to shrinkage in the process of cleaning 3D-printed parts depends on the laser scanning speed, shape correction was introduced to suppress the effect of shrinkage and obtain the desired shape.

Machine Learning for Analyzing Phase-Separated Structures of ABA Triblock Copolymer Blends in Elongation

Machine Learning for Analyzing Phase-Separated Structures of ABA Triblock Copolymer Blends in Elongation

Phase-Separated Structure of NBR/PVC Blends with Different Acrylonitrile Contents Investigated Using STEM-EDS Mapping Analysis.

We investigated the phase-separated structure of nitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) blends with different acrylonitrile (AN) contents in the NBR, using dynamic mechanical analysis measurements and scanning-transmission-electron-microscopy (STEM)-energy-dispersive-X-ray-spectroscopy (EDS) elemental analysis. Two separate sharp tan δ peaks were observed in the blend at the lower AN content of 18.0%, whereas a broad peak was observed in the blends with the higher AN contents of 29.0 and 33.5%, due to the increase in miscibility, as expected from the decrease in the solubility parameter difference with the increasing AN content. The STEM-EDS elemental analysis for the concentration distribution showed that the NBR was mixed in the large PVC domains with a diameter of several micrometers, and the excluded PVC existed around the interface of the domain-matrix phases in the blend with the lower AN content, whereas small domains with a diameter of several tens of nanometers were dispersed in the blend with the higher AN content. The concentration difference in PVC between the PVC domain and the NBR matrix became smaller with increasing miscibility as the AN content increased although the blends contained the same PVC content of 40 wt%.

Laser-induced structural modulation and superconductivity in SrTiO3

Under normal conditions, stoichiometric SrTiO3 is an excellent dielectric. It shows a structural phase transition, from cubic to tetragonal, below 105 K. In this structure, well separated domains hosting tetragonal phases with different long axes exist giving rise to the so-called X, Y, and Z domains. At very low temperatures, it becomes a quantum paraelectric in which local ferroelectric domains are found at the X, Y, and Z domain boundaries. Creation of oxygen vacancy in SrTiO3 makes it conducting with low carrier density which also undergoes an unconventional superconducting transition at sub-kelvin temperatures. We have created structural phase separation with clear domain boundaries (as in the X, Y, and Z domains) at room temperature on single crystals of SrTiO3 by irradiating the surface with high power density excimer laser pulses. We find that the domain boundaries are dominantly conducting, and the irradiated crystals undergo a superconducting phase transition below 180 mK indicating that the superconducting phase appears at the domain boundaries. This concurrence of local ferroelectricity and superconductivity in lightly doped SrTiO3 supports a ferroelectric fluctuation mediated Cooper pairing in the system. The results also point out the possibility of controlling ferroelectricity and superconductivity in functional electronic devices through surface engineering.

Quaternary ammonium-functionalized crosslinked poly(aryl ether sulfone)s anion exchange membranes with enhanced alkaline stability for water electrolysis

Quaternary ammonium-functionalized anion exchange membranes (AEMs) have important potential application value in water electrolysis. In order to further improve the ionic conductivity and stability of AEMs, a series of crosslinked AEMs based on poly (aryl ether sulfone)s (Co-PAES-QA-x-m, “x” represents the functionalized polymer segment, “m” represents the crosslinking ratio) are prepared by introducing dense quaternary ammonium cations on the side chains via Menshutkin reaction. Their polymer structures are characterized by hydrogen nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy FT-IR, and the microscopic phase separation structure of the obtained membranes is observed by atomic force microscope AFM. The ion exchange capacity (IEC) of Co-PAES-QA-x-m (x = 25%, m = 40%–100%) is between 2.03–2.48 mmol g−1, and their water uptake (WU), swelling ratio (SR) and ionic conductivity are in the range of 26.9–56.7%, 6.3–12.9% and 53.43–119.43 mS cm−1 at 80 °C, respectively. The test of chemical stability show that the ionic conductivity retention ratio of these AEMs reaches 84.7% after soaking in 2 mol L−1 NaOH solution for 480 h at 80 °C. The water electrolyzer assembled with representative Co-PAES-QA-25-60 reaches 1646.7 mA cm−2 in 2 mol L−1 NaOH solution at 2.0 V and 80 °C, and the durability test shows that its voltage only rises by 5% after 480 h at the current density of 500 mA cm−2. This work is expected to provide an effective modification method for high-performance AEMs which are used in water electrolyzer.

Silane cross-linked network and concentrated flexible sulfoalkyl groups for forming a novel C-SPAEK membrane with enhanced methanol resistance and proton conductivity for DMFC applications

In the present work, a novel poly(arylene ether ketone) with a unique molecular design that included concentrated flexible sulfoalkyl groups and a silane cross-linked network (C-SPAEK) was prepared and used as a PEM for DMFCs. The chemical structures, sulfonation degree and phase-separated morphology were characterized and identified by 1H NMR, FT-IR and SAXS. The resulting copolymers exhibited excellent thermal stability (T5%>263.8 °C) and mechanical properties (tensile strength>52.88 MPa). Additionally, the high IEC values and obvious hydrophilic/hydrophobic phase-separated structure (d > 2.71 nm) ensured that the C-SPAEK membranes possessed high proton conductivities. The C-SPAEK PEMs also displayed enhanced methanol resistance and dimensional stability, which were much better than those of a recast Nafion membrane under the same conditions. The C-SPAEK-0.4 membrane maintained a low methanol absorption of less than 48.7%, even in 4 M methanol solution. In particular, the C-SPAEK-0.6 membrane exhibited the best comprehensive performance, with a high proton conductivity (0.164 S cm−1), low methanol uptake (52.1%) and permeability (3.63 × 10−7 cm2 s−1), and maximum power density (83.2 mW cm−2), when immersed in 2 M methanol at 80 °C in a DMFC single-cell. These results suggested that the C-SPAEK membranes were sufficiently tough and had the potential to overcome the problems caused by the high methanol permeability of PEMs. The unique molecular design of C-SPAEK guaranteed a rare combination of high proton conductivity and enhanced methanol resistance, which are the key determining factors for DMFC applications.

Crystallization of Cristobalite in Sodium Borosilicate Glass in the Presence of Cr2O3.

Glass containing chromium is a promising material for use in various modern fields of application (laser technology, optoelectronic devices, and luminescent resources). Chromium oxides are well-known nucleating agents that can cause crystallization. One of the most commonly observed crystalline phases in silicate glasses is cristobalite, which lowers their mechanical strength, leading to the destruction of the material. The objective of this investigation was to study in detail the crystallization of cristobalite in sodium borosilicate glass in the presence of 2 mol% Cr2O3, depending on the thermal history of the glass. The glass was studied using XRD, SEM, EPR, FTIR-spectroscopy, XPS, and solid-state NMR. Eskolaite, α-Cr2O3, which had crystallized in this glass, stimulated the bulk crystallization of cristobalite at 550 °C after isothermally treating it for 72 h, due to the phase-separated structure of the glass with its interpenetrating phase morphology. Polytypism, resulting in the incorporation of alkalis into the cristobalite structure, was observed. Cr2O3 causes the catalytic crystallization of cristobalite at an extremely low temperature, which is at lower concentrations and temperatures than in glass containing Fe2O3 with a similar composition. The crystal growth rate and the incubation time for the crystallization of cristobalite were roughly estimated.