Degree Of Phase Separation Research Articles

Properties of thermoplastic polyurethane synthesized from bio‐based diisocyanate for FDM 3D printing

AbstractBio‐based polymeric materials have recently gained popularity due to their unique properties, including environmental friendliness, biodegradability, and sustainability. In this study, the bio‐based TPUs were successfully synthesized by one‐shot polymerization method, utilizing 100% bio‐based polytrimethylene ether glycol (PO3G) as polyols, 71% bio‐based 1,5‐pentamethylene diisocyanate (PDI) as isocyanates, and 100% bio‐based 1,4‐butanediol BDO as chain extenders. The as‐prepared TPUs, which contained up to 92% bio‐based material were investigated using a variety of analytical methods, including morphological investigations, mechanical testing, thermal analysis, rheological behavior, docking analysis, and cytotoxicity studies. For PPB 3 (1:3:2), PPB 4 (1:4:3), PPB 5 (1:5:4), and PPB 7 (1:7:6), the initial modulus values were 78, 151, 194, and 314 GPa, and the shore‐A hardness values were 92, 93, 93, and 94. Additionally, a notable variation in the degree of phase separation (DPS) of 0.575, 0.647, 0.716, and, 0.738 between hard segment (HS) and soft segment (SS) was noticed among synthesized bio‐based TPUs and an increase in DPS with higher molar ratios corresponded to a higher content of HS. Besides, the bio‐based TPU proved outstanding cell viability results, representing its potential appropriateness for various biomedical applications. Eventually, docking simulations were shown in silico to evaluate the interaction of bio‐based TPU with the DNA gyrase enzyme. Furthermore, the results of bio‐based TPUs demonstrated excellent applications in the production of 3D printing using FDM. We effectively prepared 3D printing to provide a viable answer to environmental concerns.

Scalable robust photothermal superhydrophobic coatings for efficient anti-icing and de-icing in simulated/real environments

Photothermal superhydrophobic coatings are supposed promising to prevent ice accumulation on infrastructures but often experience significant performance degradation in real icing conditions and lack mechanical robustness. Here, we report design of robust photothermal superhydrophobic coatings with three-tier hierarchical micro-/nano-/nanostructures by deposition of nanosized MOFs on natural attapulgite nanorods, fluorination, controlled phase separation of a hydrophobic adhesive and spraying assembly. Phase separation degree and adhesive content significantly influence the coatings’ properties by regulating the structural parameters and morphology. In simulated/real icing environments, the coatings simultaneously show (i) high superhydrophobicity and stable Cassie-Baxter states due to their low-surface-energy, three-tier micro-/nano-/nanostructure, (ii) excellent photothermal effect primarily due to nanosized MOFs, and (iii) good mechanical robustness by the phase-separated adhesive, reinforcement with attapulgite and the coatings’ self-similar structure. Accordingly, combined with low thermal conductivity, the coatings exhibit remarkable anti-icing/frosting (e.g., no freezing in at least 150 min and almost free of frost in 25 min) and de-icing/frosting performances (e.g., fast de-icing in 12.7 min and fast de-frosting in 16.7 min) in such environments. Furthermore, we realize large-scale preparation of the coatings at reasonable costs. The coatings have great application potential for anti-icing and de-icing in the real world by efficiently using natural sunlight.

Microalgae aggregation induced by thermoresponsive polymers

Algal biomass harvesting is one of key technical hurdles impeding the commercialization of algae-based biorefinery. The goal of this work is to develop an innovative technology for algae cell harvesting. Thermoresponsive polymers (TRPs) such as poly(N-isopropylacrylamide) (PNIPAM) and its derivatives were studied on their properties and potential applications for microalgae harvesting. Various PNIPAM was synthesized, and the effects of charge, molecular weight (MW), amine content, and polymer concentration on the polymer phase transition temperature, the degree of phase separation, and the harvesting of microalgae (Chlorella vulgaris) were investigated. The lower critical solution temperature (LCST) of PNIPAM decreased with the increase of polymer concentration, while the decline rate reduced under high MW. The amine content didn’t significantly affect the LCST of TRPs. Approx. 92 % of algae cells were harvested by PNIPAM-300 kDa. Modified TRPs showed few benefits in enhancing algae harvesting. TRPs are a promising class of polymers for microalgae harvesting.

Lattice Boltzmann Model for Rarefied Gaseous Mixture Flows in Three-Dimensional Porous Media Including Knudsen Diffusion

Numerical modeling of gas flows in rarefied regimes is crucial in understanding fluid behavior in microscale applications. Rarefied regimes are characterized by a decrease in molecular collisions, and they lead to unusual phenomena such as gas phase separation, which is not acknowledged in hydrodynamic equations. In this work, numerical investigation of miscible gaseous mixtures in the rarefied regime is performed using a modified lattice Boltzmann model. Slip boundary conditions are adapted to arbitrary geometries. A ray-tracing algorithm-based wall function is implemented to model the non-equilibrium effects in the transition flow regime. The molecular free flow defined by the Knudsen diffusion coefficient is integrated through an effective and asymmetrical binary diffusion coefficient. The numerical model is validated with mass flow measurements through microchannels of different cross-section shapes from the near-continuum to the transition regimes, and gas phase separation is studied within a staggered arrangement of spheres. The influence of porosity and mixture composition on the gas separation effect are analyzed. Numerical results highlight the increase in the degree of gas phase separation with the rarefaction rate and the molecular mass ratio. The various simulations also indicate that geometrical features in porous media have a greater impact on gaseous mixtures’ effective permeability at highly rarefied regimes. Finally, a permeability enhancement factor based on the lightest species of the gaseous mixture is derived.

Crystallization‐correlated phase separation of polypropylene random copolymers

AbstractEthylene segments are incorporated into stereoregular propylene‐propylene‐propylene (PPP) homo‐sequences to create locally disordered ethylene‐propylene (EP) segments in polypropylene random copolymer (PPR) through a phase separation process, resulting in large quantities of spherical EP rubbery particles for improving impact toughness. However, the manipulation on size and distribution of these spherical EP rubbery phases remains insufficiently understood. In this study, the phase separation of PPR and the influence of crystallization on phase separation were investigated using rheological measurements and small‐angle x‐ray scattering (SAXS) methods. Combined with the isothermal crystallization method, phase separation was differentiated by the crystallization rate. The molecular chain states corresponding to different crystallization conditions were studied to interpret the varying rubbery particle sizes resulting from phase separation. The results showed that phase separation of EP segments from PPP is highly related to crystallization. Isothermal crystallization at temperatures ranging from 110 to 130°C leads to a high degree of phase separation due to the fast crystallization rate, as evidenced by the presence of small quantities of large pores in microscopic observations. This work provides insights into the phase separation of random copolymers and establishes correlations for manipulating the low‐temperature toughness of PPR.

Fluorine substitution for aggregation transformation and exciton dissociation acceleration in non-fused electron acceptors

In order to enable low-cost manufacture of organic solar cells (OSCs), it is very important to develop non-fused electron acceptors to match with one of the cheapest polymer donors, poly(3-hexylthiophene) (P3HT). However, the lower exciton dissociation and charge transfer are still the main factors that limit the improvement of P3HT-based OSCs. Herein, we designed one class of A2-A1-D-A1-A2 type non-fused electron acceptors and synthesized BTA34 and F-BTA34 by introducing benzo[d][1,2,3] triazole as the bridged unit. The dominated H-aggregation in F-BTA34 affords high degree of crystalline and proper phase separation when blended with polymer P3HT, which ensure efficient exciton dissociation and higher charge carrier mobility. Consequently, P3HT:F-BTA34 devices demonstrate a better performance with higher short-circuit current and fill factor. The blend of P3HT:BTA34 exhibits a broader distribution of the mixing domains, resulting in relative longer-lived charge species. This work provides useful strategies to design non-fused electron acceptors to match with P3HT from the perspective of simultaneously improving exciton dissociation and suppressing charge recombination.

Research on the lubricating oil leakage characteristics in the vapor compression heat pump system under refrigerant leaking

Refrigerant leakage is a situation that often occurs in refrigeration equipment such as heat pumps. However, certain alternative refrigerants, while exhibiting superior environmental performance, possess varying levels of flammability. The leakage of flammable refrigerants into confined spaces can pose a significant risk of explosion. The amount of lubricant in the leaking refrigerant will undoubtedly affect the flammability characteristics of the refrigerant. In this paper, the content of PVE32 oil in the leaking refrigerant during the operation of a heat pump was investigated. The results showed that, under the five leakage rate scenarios set up in the experiment, the oil concentration was highest when the leakage occurred at the condenser inlet and lowest when the leakage was at the evaporator outlet. During the leakage process of the experiment, as the mass flow rate of the leakage increased, the oil content in the early stage of the leakage increased, but the oil content in the late stage of the leakage decreased. The reasons for the change in oil content were analyzed by the oil circulation rate and the degree of phase separation. The decrease of the oil circulation rate and the change of the degree of phase separation were the key factors affecting the magnitude of the oil content as the leakage proceeded. The results of the study reveal the leakage characteristics of lubricating oil with refrigerant leakage.

Soybean protein isolate-sodium alginate double network emulsion gels: Mechanism of formation and improved freeze-thaw stability

Soybean protein isolate (SPI) is widely used in the food industry. However, SPI-based emulsion gels tend to aggregate and undergo oiling-off during freeze-thawing. In this study, emulsion gels were prepared by a combination of heat treatment and ionic cross-linking using SPI and sodium alginate (SA) as raw materials. The focus was on exploring the mechanistic effects of the SPI-SA double network structure on the freeze-thaw stability of emulsion gels. The results showed that the addition of SA could form different types of network structures with SPI, due to different degrees of phase separation. In addition, SA appearing on the SPI network indicated that the addition of Ca2+ shielded the electrostatic repulsion between SPI and SA to form SPI-SA complexes. The disappearance of the characteristic peaks of SA and SPI in Fourier transform infrared spectroscopy analysis also confirmed this view. Low-field nuclear magnetic resonance data revealed that SA played a role in restricting water migration within the emulsion gels, increasing bound water content, and thereby improving the water-holding capacity of the emulsion gels. Therefore, the incorporation of SA improved the freeze-thaw stability of SPI emulsion gels. These findings offer a theoretical basis and technical support for SPI application in frozen products.

Strength Enhancement of Polyurethane Film by Solution Annealing.

Recently, polyurethane elastomer (TPU) has attracted more and more attention depending on its excellent optical, mechanical, and retreatment properties. The high strength of polyurethane has always been pursued, which can enable its application in more fields. In this work, an aliphatic polyurethane elastomer membrane (HRPU6) was successfully synthesized, and its strength was obviously improved by solvent annealing technology. The tensile strength and adhesion strength can reach 64.56 and 2.58 MPa, but 36.55 and 1.57 MPa only before solvent annealing, respectively. The impact strength of laminated glass based on HRPU has also been significantly improved after solvent annealing, confirmed through drop ball impact testing. It has been confirmed that the increase in strength of HRPU6 is attributed to the enhancement of hydrogen bonding and the improvement of the phase separation degree.

Effects of hypromellose acetate succinate on recrystallization inhibition, miscibility, and dissolution enhancement of baloxavir marboxil solid dispersions

Solid dispersions (SDs) have emerged as a promising strategy to enhance the solubility and bioavailability of poorly soluble active pharmaceutical ingredients. However, SDs tend to recrystallize unless suitable excipients are utilized. This study aimed to facilitate the rational selection of polymers and formulation design by evaluating the impact of various polymers on the miscibility, and phase behavior of SDs using baloxavir marboxil (BXM) with a high crystallization tendency as a model drug. Meanwhile, the effects of these polymers on the solubility enhancement and recrystallization inhibition were also assessed. The results indicated that the miscibility limit of BXM for HPMCAS was around 40 % drug loading (DL), whereas for PVP, PVPVA, and HPMC approximately 20 % DL. The BXM-HPC system exhibited limited miscibility with DL of 10 % or higher. BXM SDs based on various polymers exhibited varying degrees of spontaneous phase separation once DL exceeded the miscibility limit. Interestingly, a correlation was discovered between the phase separation behavior and the ability of the polymer to inhibit recrystallization. BXM-HPMCAS SDs exhibited optimal dissolution performance, compared with other systems. In conclusion, the physicochemical properties of polymers significantly influence BXM SDs performance and the BXM-HPMCAS SDs might promote an efficient and stable drug delivery system.

Effect of B2O3 and Basic Oxides on Network Structure and Chemical Stability of Borosilicate Glass

Glass properties play crucial roles in ensuring the safety and reliability of electronic packaging. However, challenges, such as thermal expansion and resistance to acid corrosion, pose long-term service difficulties. This study investigated the impact of the microstructure on acid resistance by adjusting the glass composition. A glass material with excellent acid resistance was obtained by achieving a similar coefficient of thermal expansion to tantalum; it exhibited a weight loss rate of less than 0.03% when submerged in 38% sulfuric acid at 85 °C for 200 h. Theoretically, this glass can be used to seal wet Ta electrolytic capacitors. Differential scanning calorimetry (DSC) was used to analyze the glass transition temperature and thermal stability of borosilicate glasses. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and Raman spectroscopy were used to study the microstructure of the amorphous phase of the borosilicate glass, which revealed a close relationship between the degree of network phase separation in the borosilicate glass and the degree of polymerization (isomorphic polyhedron value, IP) of the glass matrix. The IP value decreased from 3.82 to 1.98 with an increasing degree of phase separation. Boron transitions from [BO4] to [BO3] within the glass network structure with increasing boron oxide content, which diminishes the availability of free oxygen provided by alkaline oxide, resulting in a lower acid resistance. Notably, the glass exhibited optimal acid resistance at boron trioxide and mixed alkaline oxide contents of 15% and 6%, respectively. Raman experiments revealed how the distributions of various bridging oxygen atoms (Qn) affect the structural phase separation of the glass network. Additionally, Raman spectroscopy revealed the depolymerization of Q4 into Q3, thereby promoting high-temperature phase separation and highlighting the unique advantages of Raman spectroscopy for phase recognition.

Buffer choice and pH strongly influence phase separation of SARS-CoV-2 nucleocapsid with RNA.

The SARS-CoV-2 nucleocapsid (N) protein is crucial for virus replication and genome packaging. N protein forms biomolecular condensates both in vitro and in vivo in a process known as liquid-liquid phase separation (LLPS), but the exact factors regulating LLPS of N protein are not fully understood. Here, we show that pH and buffer choice have a profound impact on LLPS of N protein. The degree of phase separation is highly dependent on the pH of the solution, which is correlated with histidine protonation in N protein. Specifically, we demonstrate that protonation of H356 is essential for LLPS in phosphate buffer. Moreover, electrostatic interactions of buffer molecules with specific amino acid residues are able to alter the net charge of N protein, thus influencing its ability to undergo phase separation in the presence of RNA. Overall, these findings reveal that even subtle changes in amino acid protonation or surface charge caused by the pH and buffer system can strongly influence the LLPS behavior, and point to electrostatic interactions as the main driving forces of N protein phase separation. Further, our findings emphasize the importance of these experimental parameters when studying phase separation of biomolecules, especially in the context of viral infections where the intracellular milieu undergoes drastic changes and intracellular pH normally decreases.

Attapulgite-Based Stable Superhydrophobic Coatings for Preventing Rain Attenuation of 5G Radomes.

Superhydrophobic coatings hold immense promise for various applications. However, their practical use is currently hindered by issues such as poor stability, high costs, and complex preparation processes. Here, we present the preparation of cost-effective and stable superhydrophobic coatings through fluorination of natural attapulgite (F-ATP) nanorods and subsequent solvent-induced phase separation of a silicone-modified polyester adhesive (SMPA) with the F-ATP nanorods dispersed in it. Phase separation of the F-ATP/SMPA system forms a uniform suspension of microaggregates, which can be easily utilized for preparing superhydrophobic coatings via spray coating. The coatings have a low-surface-energy hierarchical micro/nanostructure due to phase separation of SMPA and adhesion of F-ATP to it. Moreover, the effects of the solvent composition (i.e., phase separation degree of SMPA) and the SMPA/F-ATP mass ratio on the morphology, superhydrophobicity, and stability of the coatings were investigated. After systematic optimization, the coatings exhibit excellent static and dynamic superhydrophobicity as well as high mechanical, chemical, thermal, and UV aging stability. Finally, the coatings were applied to the 5G radome surface and showed good rain attenuation prevention performance. Thus, we are confident that the superhydrophobic coatings have great application potential due to their advantages of outstanding performance, straightforward preparation procedures, cost-effectiveness, etc.

Experimental study on leakage characteristics of gas-liquid two-phase flow in a horizontal pipe

Oil and gas pipeline leakage accidents caused by aging and third-party damage have increased, resulting in polluting the ecological environment and jeopardizing life and property safety. A detailed and systematic investigation on the leak characteristics of oil and gas two-phase pipelines is significantly urgent. The leak experiments were performed on a horizontal tube with a diameter of 32 mm. There was a 3 mm round leakage hole at the bottom of the tube. The distance of the leakage hole from the pipe inlet was 4.8 m. Three inlet flow patterns, including stratified flow, slug flow, and annular flow via adjusting the gas superficial velocity (1.73 m/s ≤ USG ≤ 24.19 m/s) and liquid superficial velocity (0.017 m/s ≤ USL ≤ 0.415 m/s), were obtained. The conclusions point out that the type of leakage, whether it is mainly liquid or both gas and liquid, depends on the USG. The degree of phase separation in stratified flow is the greatest among the three inlet flow patterns, with a maximal phase separation efficiency (η) of 0.403. Slug flow has the least phase separation degree. Interestingly, the η is directly proportional to the inlet mass fraction only for slug flow. The harmonic frequency that appeared in the power spectral density curves for the pressure difference of leakage hole in slug flow, indicates that leakage is not a standard periodic event. The liquid velocity loss is primarily related to the gas leakage mechanism. These findings can provide new insights into two-phase pipeline leak detection and accident consequence prediction.

Steric repulsion introduced by loop constraints modulates the microphase separation of chromatins.

Within the confines of a densely populated cell nucleus, chromatin undergoes intricate folding, forming loops, domains, and compartments under the governance of topological constraints and phase separation. This coordinated process inevitably introduces interference between different folding strategies. In this study, we model interphase chromatins as block copolymers with hetero-hierarchical loops within a confined system. Employing dissipative particle dynamics simulations and scaling analysis, we aim to explain how the structure and distribution of loop domains modulate the microphase separation of chromatins. Our results highlight the correlation between the microphase separation of the copolymer and the length, heterogeneity, and hierarchically nested levels of the loop domains. This correlation arises from steric repulsion intrinsic to loop domains. The steric repulsion induces variations in chain stiffness (including local orientation correlations and the persistence length), thereby influencing the degree of phase separation. Through simulations of block copolymers with distinct groups of hetero-hierarchical loop anchors, we successfully reproduce changes in phase separation across diverse cell lines, under fixed interaction parameters. These findings, in qualitative alignment with Hi-C data, suggest that the variations of loop constraints alone possess the capacity to regulate higher-order structures and the gene expressions of interphase chromatins.

Study of shape memory mechanism and performance of shape memory polyurethane prepared based on tetrahydrofuran

A series of shape memory polyurethane (SMPU) substrates were fabricated utilizing polyether polyol (PPG) with varying molecular weights, 4,4′-diphenylmethane diisocyanate (MDI), and4,4′-methylene-bis-(2-chloroaniline) (MOCA) as primary raw materials. Tetrahydrofuran (THF) served as the solvent. The investigation focused on the effects of different soft segment molecular weights and additional THF content on the properties of SMPU. The study aimed to explore the impact of varying soft segment molecular weights and THF additions on the shape memory properties of polyurethane, as well as the mechanism behind THF's influence. The findings demonstrated that the introduction of THF significantly enhanced the phase separation degree and ordered hydrogen bonding of polyurethane, leading to the acquisition of shape memory properties. Compared to specimens without THF addition, when PPG had a molecular weight of 500, hydrogen bonding increased by 50 %. Furthermore, at THF addition of 9 mL, the specimen exhibited the highest shape recovery degree, with a phase separation temperature of 28.21 °C, a degree of carbonyl-ordered hydrogen bonding of 49.08 %, a bending strength of 43.81 MPa, and an impact toughness of 38.19 KJ/m2. The shape memory performance of the specimens was evaluated at various temperatures, revealing that the models both achieved 100 % shape fixation at different temperatures. Additionally, the degree and rate of retraction increase with the increase in temperature. The shape memory performance of the prepared specimens was shown to be good by the DMA shape memory cycling test.

Preparation of tough and stiff ionogels via phase separation.

Ionogels have the advantages of thermal stability, non-volatility, ionic conductivity and environmental friendliness, and they can be used in the field of flexible electronics and soft robotics. However, their poor mechanical strength and complex preparation methods limit their practical application. Herein, we propose a simple strategy to improve the performance of ionogels by adjusting their phase separation behavior. In a polymer-ionic liquid (IL) binary system with an upper critical solution temperature (UCST) and Berghmans' point, the phase separation behavior will be frozen below the temperature corresponding to the Berghmans' point, and thus, the degree of phase separation can be adjusted by controlling the cooling rate. We found that a polyacrylamide (PAM)-IL binary system possessed a UCST and Berghmans' point and the resulting ionogels had excellent mechanical properties. Their tensile strength, tensile modulus, compressive strength and compressive modulus reached 31.1 MPa, 319.8 MPa, 122 MPa and 1.7 GPa, respectively, while these properties of the other ionogels were generally less than 10 MPa. Furthermore, they were highly transparent, stretchable, stable and multifunctional.

Over 18.7% efficiency for bulk heterojunction and pseudo-planar heterojunction organic solar cells achieved by regulating intermolecular compatibility

Inferior compatibility between PM6 and BTP-eC9 will optimize the phase separation degree between the two molecules.

A tunable fluorescence waterborne polyurethane-based Ln3+ (Ln=Eu,Tb) complex with antibacterial activity

Tunable fluorescent luminescent materials have attracted much attention in many fields of application. Herein, Tb(PABA)3Phen with red fluorescence and Eu(PABA)3Phen with green fluorescence were synthesized by using p-aminobenzoic acid (PABA) and o-phenanthroline (Phen) as the first and second ligands and Tb3+ and Eu3+ as the central ions. Then, Ln3+ (Ln = Eu, Tb) was bonded to the polyurethane chains as chain extenders to prepare waterborne polyurethane complexes with tunable fluorescence and antibacterial activity (WPU-TbxEu1-x). The bonding of Tb(PABA)3Phen and Eu(PABA)3Phen on polyurethane chains significantly improved the compatibility of soft and rigid polyurethane segments and reduced the degree of phase separation. WPU-TbxEu1-x had good thermal stability and above 220 °C decomposition temperature. Notably, WPU-TbxEu1-x achieves adjustable fluorescence from red to green by adjusting Tb(PABA)3Phen and Eu(PABA)3Phen into the polyurethane chains. Compared with Tb(PABA)3Phen and Eu(PABA)3Phen, the fluorescence lifetimes of WPU-Tb1.0Eu0 and WPU-Tb0Eu1.0 are significantly longer, reaching 1.375 ms and 1.05 ms, respectively. WPU-Tb1.0Eu0 and WPU-Tb0EU1.0 have excellent antibacterial effects against Staphylococcus aureus and Escherichia coli and can be used as a WPU-Tb1.0Eu0 and WPU-Tb0Eu1.0 have fantastic antibacterial effects on S. aureus and E. coli and can be used as an environmentally friendly antibacterial material with broad application prospects. More importantly, WPU-TbxEu1-x uses water as a dispersed phase, which is particularly safe and environmentally friendly.

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.