Phase-separated Structure Research Articles

A simple strategy for synthesis of side-chain sulfonated poly(arylene ether ketone sulfone) constructing hydrophilic/ hydrophobic phase separation structure

A simple strategy for synthesis of side-chain sulfonated poly(arylene ether ketone sulfone) constructing hydrophilic/ hydrophobic phase separation structure

Study on AEMs with Excellent Comprehensive Performance Prepared by Covalently Cross-Linked p-Triphenyl with SEBS Remotely Grafted Piperidine Cations.

A series of SEBS-C6-PIP-yPTP (y = 0-15%) AEMs with good mechanical and chemical stability were prepared by combining the strong rigidity of p-triphenyl, good toughness of SEBS, and excellent stability of PIP cations. After the introduction of a p-triphenyl polymer into the main chain, a clear hydrophilic-hydrophobic phase separation structure was constructed within the membrane, forming a continuous and interconnected ion transport channel to improve ion transport efficiency. Moreover, the molecular chains of the cross-linked AEMs change from chain-like to network-like, and the tighter binding between each molecule increases the tensile strength. The special structure of the six-membered ring makes PIP have a significant constraint effect; when nucleophilic substitution and Hoffman elimination occur at the α and β positions, the required transition state potential energy increases, making the reaction difficult to occur and improving the alkaline stability of the polymer membrane. The SEBS-C6-PIP-15%PTP membrane has the best mechanical properties (Ts = 38.79 MPa, Eb = 183.09% at 80 °C, 100% RH), the highest ion conductivity (102.02 mS. cm-1 at 80 °C), and the best alkaline stability (6.23% degradation at 80 °C in a 2 M NaOH solution for 1400 h). It can be seen that organic-organic covalent cross-linking is an effective means to improve the comprehensive performance of AEMs.

A complex network of interdomain interactions underlies the conformational ensemble of monomeric TDP-43 and modulates its phase behavior.

TAR DNA-binding protein 43 (TDP-43) is a multidomain protein involved in the regulation of RNA metabolism, and its aggregates have been observed in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Numerous studies indicate TDP-43 can undergo liquid-liquid phase separation (LLPS) in vitro and is a component of biological condensates. Homo-oligomerization via the folded N-terminal domain (aa:1-77) and the conserved helical region (aa:319-341) of the disordered, C-terminal domain is found to be an important driver of TDP-43 phase separation. However, a comprehensive molecular view of TDP-43 phase separation, particularly regarding the nature of heterodomain interactions, is lacking due to the challenges associated with its stability and purification. Here, we utilize all-atom and coarse-grained (CG) molecular dynamics (MD) simulations to uncover the network of interdomain interactions implicated in TDP-43 phase separation. All-atom simulations uncovered the presence of transient, interdomain interactions involving flexible linkers, RNA-recognition motif (RRM) domains and a charged segment of disordered C-terminal domain (CTD). CG simulations indicate these inter-domain interactions which affect the conformational landscape of TDP-43 in the dilute phase are also prevalent in the condensed phase. Finally, sequence and surface charge distribution analysis coupled with all-atom simulations (at high salt) confirmed that the transient interdomain contacts are predominantly electrostatic in nature. Overall, our findings from multiscale simulations lead to a greater appreciation of the complex interaction network underlying the structural landscape and phase separation of TDP-43.

Replicating shear-mediated self-assembly of spider silk through microfluidics

The development of artificial spider silk with properties similar to native silk has been a challenging task in materials science. In this study, we use a microfluidic device to create continuous fibers based on recombinant MaSp2 spidroin. The strategy incorporates ion-induced liquid-liquid phase separation, pH-driven fibrillation, and shear-dependent induction of β-sheet formation. We find that a threshold shear stress of approximately 72 Pa is required for fiber formation, and that β-sheet formation is dependent on the presence of polyalanine blocks in the repetitive sequence. The MaSp2 fiber formed has a β-sheet content (29.2%) comparable to that of native dragline with a shear stress requirement of 111 Pa. Interestingly, the polyalanine blocks have limited influence on the occurrence of liquid-liquid phase separation and hierarchical structure. These results offer insights into the shear-induced crystallization and sequence-structure relationship of spider silk and have significant implications for the rational design of artificially spun fibers.

Development of high-flowability melt PPS-based composites through blending with g-C3N4

Polyphenylene sulfide (PPS), commonly used as a core material for high-temperature flue gas treatment, exhibits elevated viscosity when processed even at temperature exceeding 280 °C. In this study, a novel high-flowability PPS-based composite was fabricated through the incorporation of graphitic carbon nitride (g-C3N4) via a well-established melt extrusion procedure. The enhancement of flowability in PPS was verified, and the material's texture structures and fundamental properties of composites with varying contents were determined. The composites exhibit well-dispersed g-C3N4, a significant reduction in shear viscosity (>10 %), a notable increase in melt index (>30 %), improved crystallinity, and comparable or superior performance compared to pure PPS. When the g-C3N4 was introduced into the PPS matrix, a phase-separated composite structure was formed. This structure reduces the entanglement degree between the PPS molecular chains and provides more space for free-movement of the PPS chains, and thus the improvement in flowability for the composites can be clearly demonstrated. Therefore, g-C3N4 can be used as a novel flow modifier to enhance the flowability and stability of PPS resin without compromising its fundamental properties, which offers significant prospects for improving productivity, optimizing energy usage, and managing costs for PPS-based products.

Theoretical and experimental investigation of Al3+ ion-suppressed phase-separation structures in rare-earth-doped high-phosphorus silica glasses.

Rare-earth-doped silica-based composite glasses (Re-SCGs) are widely used as high-quality laser gain media in defense, aerospace, energy, power, and medical applications. The variable regional chemical environments of Re-SCGs can induce new photoluminescence properties of rare-earth ions but can cause the selective aggregation of rare-earth ions, limiting the application of Re-SCGs in the field of high-power lasers. Here, topological engineering is proposed to adjust the degree of cross-linking of phase-separation network chains in Re-SCGs. A combination of experimental and theoretical characterization techniques suggested that the selective aggregation of rare-earth ions originates from the formation of phase-separated structures in glasses. The decomposition of nanoscale phase separation structures to the sub-nanometer scale, enabled by incorporating Al3+ ions, not only maintains the high luminescence efficiency of rare earth ions but also increases light transmittance and reduces light scattering. Furthermore, our investigation encompassed the exploration of the inhibitory mechanism of Al3+ ions on phase-separation structures, as well as their influence on the spectral characteristics of Re-SCGs. This work provides a new design concept for composite glass materials doped with rare-earth ions and could broaden their application in the field of high-power lasers.

Microphase-separation-induced polyzwitterionic ionogel with tough, highly conductive, self-healing and shape–memory properties for wearable electrical devices

A polyzwitterionic ionogel with a phase separation structure was designed to achieve a balance between mechanical robustness and ionic conductivity. This design holds immense potential for applications in wearable sensors.

Multiscale simulations reveal the driving forces of p53C phase separation accelerated by oncogenic mutations.

Liquid-Liquid phase separation (LLPS) of p53 to form liquid condensates has been implicated in cellular functions and dysfunctions. The p53 condensates may serve as amyloid fibril precursors to initiate p53 aggregation, which is associated with oncogenic gain-of-function and various human cancers. M237I and R249S mutations located in p53 core domain (p53C) have been detected respectively in glioblastomas and hepatocellular carcinoma. Interestingly, these p53C mutants can also undergo LLPS and liquid-to-solid phase transition, which are faster than wild type p53C. However, the underlying molecular basis governing the accelerated LLPS and liquid-to-solid transition of p53C remain poorly understood. Herein, we explore the M237I/R249S mutation-induced structural alterations and phase separation behavior of p53C by employing multiscale molecular dynamics simulations. All-atom simulations revealed conformational disruptions in the zinc-binding domain of the M237I mutant and in both loop3 and zinc-binding domain of the R249S mutant. The two mutations enhance hydrophobic exposure of those regions and attenuate intramolecular interactions, which may hasten the LLPS and aggregation of p53C. Martini 3 coarse-grained simulations demonstrated spontaneous phase separation of p53C and accelerated effects of M237I/R249S mutations on the phase separation of p53C. Importantly, we find that the regions with enhanced intermolecular interactions observed in coarse-grained simulations coincide with the disrupted regions with weakened intramolecular interactions observed in all-atom simulations, indicating that M237I/R249S mutation-induced local structural disruptions expedite the LLPS of p53C. This study unveils the molecular mechanisms underlying the two cancer-associated mutation-accelerated LLPS and aggregation of p53C, providing avenues for anticancer therapy by targeting the phase separation process.

Biomimetic Lipid Raft: Domain Stability and Interaction with Physiologically Active Molecules.

The cell membrane, also called the plasma membrane, is the membrane on the cytoplasmic surface that separates the extracellular from the intracellular. It is thin, about 10 nm thick when viewed with an electron microscope, and is composed of two monolayers of phospholipid membranes (lipid bilayers) containing many types of proteins. It is now known that this cell membrane not only separates the extracellular from the intracellular, but is also involved in sensory stimuli such as pain, itching, sedation, and excitement. Since the "Fluid mosaic model" was proposed for cell membranes, molecules have been thought to be homogeneously distributed on the membrane surface. Later, at the end of the twentieth century, the existence of "Phase-separated microdomain structures" consisting of ordered phases rich in saturated lipids and cholesterol was suggested, and these were termed "Lipid rafts." A model in which lipid rafts regulate cell signaling has been proposed and is the subject of active research.This chapter first outlines the physicochemical properties and thermodynamic models of membrane phase separation (lipid rafts), which play an important role in cell signaling. Next, how physiologically active molecules such as local anesthetics, cooling agents (menthol), and warming agents (capsaicin) interact with artificial cell membranes will be presented.It is undeniable that the plasma membrane contains many channels and receptors that are involved in the propagation of sensory stimuli. At the same time, however, it is important to understand that the membrane exerts a significant influence on the intensity and propagation of these stimuli.

Phase-separated structures of tunable thermoresponsive and matrix polymers for large-scale temperature monitoring coatings.

Temperature monitoring is significant and fundamental in the fields of healthcare and medicine. In surgery, ultrasonic cutting devices are used for cutting, coagulation, and hemostasis. However, surgeons are concerned about the collateral thermal damages. For example, due to the limited space during endoscopic surgery, thermal damage is caused by touching the surrounding tissues of the targeted organ with the heated shaft of the ultrasonic cutting device. The present work exhibits thermoresponsive and reversible color-change coatings for temperature-distribution imaging. The phase-separated structures of the layered conjugated and matrix polymers enable both the tuned thermoresponsivity and large-scale coating. Layered polydiacetylene (PDA) with intercalated guests exhibits reversible and thermoresponsive gradual color changes from blue to red. A matrix polymer facilitates formation of the phase-separated layered PDA and large-scale coating. Spraying the precursor solution containing the diacetylene monomer, guest molecule, and matrix polymer provides the self-organized large-scale coatings on substrates. The temperature distribution on the shaft of an ultrasonic cutting device is monitored using the coatings. The phase-separated structure of thermoresponsive and matrix polymers can be applied to tunable temperature monitoring in a variety of fields.

Doping induced mixed polytypic interfaces of MoS2 for superior electrocatalytic hydrogen evolution

Metallic 1Tphase of MoS2 is desirable for accelerating electrochemical hydrogen generation from water due to its excellent electrical conductivity. However, it is challenging to synthesize stable 1T-MoS2 on a large scale using conventional chemical or physical routes. Here in, we report highly durable Mn-doping assisted in-plane 1T/2H mixed phases of MoS2 synthesized by a simple one-step hydrothermal method. The Mn-doping not only results in a favourable electronic modification in the host lattice but also in a structural evolution from 2H (trigonal prismatic) to 1T (octahedral) phase through sulfur-plane gliding with additional defects. The 1T/2H interfaces exhibit more active sites for hydrogen evolution reaction (HER) than its bulk 2H-counterpart. The developed electrode shows relatively low overpotential of 95 mV at a current density of 10 mA/cm2 and a low Tafel slope of 72 mV/dec in 0.5 M H2SO4. In addition, Density Functional Theory based calculations also support that Mn-doping in pristine 2H-MoS2 encourages a structural phase separation. Locally hybridized d-orbitals of Mn induce the formation of 2H/1T interfaces. It results in the delocalization of electrons, and thus facilitates the hydrogen adsorption and desorption process, better than the 2H phase.

Understanding of Ionic Structure Change Under Hydration Levels by Using CSAFM

Proton exchange membranes (PEMs) are a key component of proton exchange membrane fuel cells. They work as gas separator, insulator, and proton conductor. Thus, characterization of the membrane is a crucial process for developing PEM. However, this work is not easy because its complicated phase separated morphological structure and widely varying ionic structure under hydration. Current sensing atomic force microscopy (CSAFM) measures nano current flow between a tip and the sample surface and can map the nano current flow distribution of scanned area. In this study, the ionic structure of Nafion under different hydration condition is studied by using CSAFM. Specifically, the area variation of ionic domain on the membrane surface under different relative humidity is characterized by quantitative method based on CSAFM measurement. The study is done by several steps. First, the Nafion 212 is scanned in the environmental chamber by varying 15% to 65% relative humidity. In this process, the current distribution and the morphology are simultaneously mapped at each RH. Second, the local net charge value of protons, which is connected with area of ionic domain on the membrane surface, are calculated based on current distribution. In this process, the area of ionic domain on the membrane surface under different RH is estimated. The study shows several remarkable results. First of all, the non-uniform ionic domain increasing is observed from sequentially mapped current distribution on the surface under different RH. Second, the reliable estimation method of ionic domain variation is introduced by this study.

Polyepichlorohydrin grafted poly(phenylene oxide) to construct hydrophilic and hydrophobic microphase separation anion exchange membrane

An anion exchange membrane (QAPECH-g-PPO) with polyepichlorohydrin (PECH) as the main chain and poly(phenylene oxide) (PPO) as the side chain was prepared by Williamson etherification reaction. Atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) characterization indicate that PECH grafted with PPO can effectively form a hydrophilic and hydrophobic phase separation structure. The amount of and molecular weight of PPO grafted has different effects on the membrane properties. As the amount of PPO grafted increases, the tensile strength of the membrane gradually increases. When the amount of PPO grafted exceeds 44%, the excessive hydrophobic phase prevents the formation of continuous ionic channels in the hydrophilic phase, leading to a significant decrease in ionic conductivity. When the amount of PPO is 38%, the ionic conductivity can reach 72 mS cm−1 (80 °C), while the swelling ratio is only 15%. Moreover, higher molecular weight PPO at 38% amount improves tensile strength of QAPECH-g-PPO membrane. The higher the molecular weight of PPO, the more stable the π - π stacking structure is formed, leading to more aggregation of hydrophobic phases in the anion exchange membrane and weakened constraints on ion clusters. Therefore, the water absorption and ion conductivity slightly increase.

Effect of Geometrical Confinement on Ordering of Thermoplastic Polyurethanes with Crystallizable Hard and Soft Blocks

A series of multi-block thermoplastic polyurethanes incorporating different soft block structures was synthesized. This was achieved using a poly(butylene adipate) oligomer combined with its macrodiols of both an aromatic and aliphatic nature. The composition of the hard block included 1,6-hexamethylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 1,4-butanediol. For the first time, the structural evolution and phase composition of both the hard and soft segments were analyzed during in situ thermal treatments. A combination of synchrotron small- and wide-angle X-ray scattering, differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy was used to determine the influence of the macrodiol’s nature and crystallization conditions on the polymorphic behavior of poly(butylene adipate). Using a new synthesis scheme, a relatively high degree of crystallinity for urethane blocks was achieved, which depended on the diisocyanate type in the structure of the soft segment. The hard segment domains imposed geometrical constraints on poly(butylene adipate), thereby altering its crystallization process compared to the neat oligomer. Thus, crystallization after annealing at a low temperature (80 °C) was fast, predominantly yielding a metastable β-phase. When heated to 180 °C, which was higher than the hard segment’s melting temperature, a phase-separated structure was observed. Subsequent crystallization was slower, favoring the formation of the stable α-PBA modification. The phase separation could be observed even after the hard block melting. Notably slow crystallization from an isotropic melt was documented after the disruption of phase separation at 230 °C.

Changes in the structure and physical properties of acrylic and epoxy adhesives in response to high-temperature and high-humidity environments

The strength of adhesives and adhesive joints degrade due to changes occurring in terms of environmental heat, moisture, and temperature conditions experienced during use. Adhesives with a sea-island phase separated structure consisting of hard and soft domains, are designed to improve reliability when it comes to adhesion. In this study, we investigated the changes occurring in terms of in adhesive strength and phase separated structures during the processes of repeated moisture absorption and desorption for two commercially available adhesives. We measured the adhesive strength of epoxy and acrylic adhesives containing elastomers during dry/wet cycles. The collapse of the phase-separated structures was confirmed via TEM and AFM-IR observations. The changes seen in terms of the continuous structure of the rubbery phase in the acrylic adhesive was greater than that seen in the epoxy adhesive. This caused delamination at the interface located between the adherend and the adhesive. Thus, the adhesive strength of epoxy adhesive has been deemed stable in relation to changes occurring in terms of temperature and humidity.

Comprehensive study of synergistic effects of phase separation structures and electric fields for enhancing the heat transfer performance of minichannel heat sinks

In this paper, the effects of the phase separation structure on the enhanced boiling heat transfer mechanism and bubble dynamics were investigated. Two types of phase-separation structures and one type of conventional minichannel were manufactured by ultrafast laser technology. Flow boiling experiments of a glycerol-water solution were conducted under various heat flux and electric field conditions. Entropy generation analysis was employed to comprehensively analyze and assess energy losses and irreversibility within the system. Response surface analysis method was introduced to optimize operational and design parameters for achieving optimal experimental design. Moreover, the coupling effect of the phase-separation structure and electric field was observed to have a significant impact on the enhancement of heat transfer. The visualization results indicate that, compared to conventional parallel minichannels, the countercurrent minichannel with phase-separation structure leads to a gradual decrease in the aspect ratio of confined bubbles downstream (in contrast to the increasing aspect ratio of confined bubbles downstream in general minichannels), and smaller bubbles at the upstream of adjacent minichannels gradually disappear and diminish due to the condensation effect. The experimental results demonstrate that the porous phase-separation structure plays a significant role in enhancing heat transfer performance and can reduce the increase of two-phase friction pressure drop per unit length with the increase of heat flux. Under electric field-free conditions, the porous phase separation structure exhibits a maximum increase in heat transfer efficiency of 26.2% compared to conventional structures. Furthermore, the maximum reduction in two-phase frictional pressure drop per unit length reaches 19.4%. In the presence of the synergistic effect between an electric field and the phase separation structure, the maximum heat transfer efficiency is enhanced by 65.5%. The above analysis provides an effective means for investigating the comprehensive performance of phase separation structures and the bubble dynamics of confined bubbles in heat sinks.

Effects of the heterogeneous hydration of alkaline-earth aluminosilicate glasses on phase evolution in hardened blended cement paste

Supplementary cementitious materials (SCMs) affect the hydration process and long-term properties of cementitious systems. Since a large percentage of SCMs belong to alkaline-earth aluminosilicate glasses that possess a phase-separated structure, further research into their hydration characteristics is essential. This study investigated the effects of the hydration characteristics of synthetic glasses with various phase-separated structure on the phase evolution of cementitious systems by combining simulations with experiments. The results showed that with the increasing degree of phase separation, the hydration of synthetic glass transitions from homogeneous to heterogeneous hydration. The phase evolution of hardened paste, particularly for calcium hydroxide, is influenced by the difference in hydration rates among each separated glassy phase. Compared to homogeneous hydration, the rapid hydration of the Ca-rich phase reduced the consumption of calcium hydroxide, while the rapid hydration of the Si-rich phase accelerated calcium hydroxide consumption. For glasses exhibiting phase separation characteristics, the consistency between thermodynamic simulations employing a heterogeneous hydration model and experimental results exhibits a notable enhancement.

The dynamic recruitment of LAB proteins senses meiotic chromosome axis differentiation in C. elegans.

During meiosis, cohesin and meiosis-specific proteins organize chromatin into an axis-loop architecture, coordinating homologous synapsis, recombination, and ordered chromosome segregation. However, how the meiotic chromosome axis is assembled and differentiated with meiotic progression remains elusive. Here, we explore the dynamic recruitment of two long arms of the bivalent proteins, LAB-1 and LAB-2, in Caenorhabditis elegans. LAB proteins directly interact with the axis core HORMA complexes and weak interactions contribute to their recruitment. LAB proteins phase separate in vitro, and this capacity is promoted by HORMA complexes. During early prophase, synapsis oppositely regulates the axis enrichment of LAB proteins. After the pachytene exit, LAB proteins switch from a reciprocal localization pattern to a colocalization pattern, and the normal dynamic pattern of LAB proteins is altered in meiotic mutants. We propose that LAB recruitment senses axis differentiation, and phase separation of meiotic structures helps subdomain establishment and accurate segregation of the chromosomes.

Durable poly(binaphthyl-co-p-terphenyl piperidinium)-based anion exchange membranes with dual side chains

Building well-developed ion-conductive highways is highly desirable for anion exchange membranes (AEMs). Grafting side chain is a highly effective approach for constructing a well-defined phase-separated morphological structure and forming unblocked ion pathways in AEMs for fast ion transport. Fluorination of side chains can further enhance phase separation due to the superhydrophobic nature of fluorine groups. However, their electronic effect on the alkaline stability of side chains and membranes is rarely reported. Here, fluorine-containing and fluorine-free side chains are introduced into the polyaromatic backbone in proper configuration to investigate the impact of the fluorine terminal group on the stability of the side chains and membrane properties. The poly(binaphthyl-co-p-terphenyl piperidinium) AEM (QBNpTP) has the highest molecular weight and most dimensional stability due to its favorable backbone arrangement among ortho- and meta-terphenyl based AEMs. Importantly, by introducing both a fluorinated piperidinium side chain and a hexane chain into the p-terphenyl-based backbone, the prepared AEM (QBNpTP-QFC) presents an enhanced conductivity (150.6 mS cm−1) and a constrained swelling at 80 °C. The electronic effect of fluorinated side chains is contemplated by experiments and simulations. The results demonstrate that the presence of strong electro-withdrawing fluorine groups weakens the electronic cloud of adjacent C atoms, increasing OH− attack on the C atom and improving the stability of piperidinium cations. Hence QBNpTP-QFC possesses a robust alkaline stability at 80 °C (95.3% conductivity retention after testing in 2 M NaOH for 2160 h). An excellent peak power density of 1.44 W cm−2 and a remarkable durability at 80 °C (4.5% voltage loss after 100 h) can be observed.

Comparative study on the Ru ware, Ru-type ware of Qingliangsi kiln and celadon of Zhanggongxiang kiln.

Thirty-three porcelain shards (28 Ru ware and 5 Ru-type ware) unearthed from Qinglingsi kiln and 31 celadon fragments from Zhanggongxiang kiln were studied systematically for tracing their correlation and difference in glaze and body characteristics through a variety of characterisation methods. Samples without HF corrosion were applied to achieve the microstructure and composition details by SEM and TEM. Results exhibited that there were certain similarities between Ru ware, Ru-type ware and Zhanggongxiang kiln celadon in glaze colour and thickness, body features, fracture structure; however, they showed obvious differences in body thickness, chemical composition of glaze and body, phase constituents and microstructure of glaze. Plentiful needle-like diopside were widely distributed in Zhanggongxiang kiln celadon glazes, while this type of crystals was only existed in few Ru and Ru-type ware glazes with small content. Besides, a large amount of residual quartz was present over the Ru ware glazes, which could have relation to the incorporation of agate. The liquid-liquid phase separation structure (Ca-rich droplets and Si-rich matrix) was generated within the interspaces of anorthite clusters or around the brims of anorthite needles or columns. The occurrence of phase separation was generally accompanied by Al2 O3 consumption, but suppressed in the areas far from anorthite due to the rise of Al2 O3 content, indicating that Al2 O3 was the most sensitive constituent for this glaze behaviour. The distinguished size, shape and distribution of phase-separated droplets or interconnected structures were closely associated with the scale and crowding level of anorthite crystallisation.