Induced Phase Separation Research Articles

Selective localization of carbonized polymer dots in amorphous phase towards high breakdown strength and energy density of PVDF-based dielectric composites

In a general way, there is a contradictory between dielectric constant (εr) and breakdown strength (Eb) in dielectric materials, and improving the discharge energy density (Ud) of dielectric polymers has become a great challenge. The semicrystalline ferroelectric polymer polyvinylidene fluoride (PVDF) is favored for its high εr, but its relatively weak Eb in amorphous regions makes it still difficult to obtain appreciable Ud. In response to the fact that the current method of introducing rigid chain amorphous polymers into the amorphous regions of PVDF has limited capability to enhance its Eb, in this work, due to the crystallization induced phase separation, carbonated polymer dots (CPDs) as well as PMMA were introduced into the amorphous region of PVDF, and CPDs/PVDF/PMMA composites were prepared towards high Eb and Ud. It is confirmed that, CPDs significantly increase the entanglement density of molecular chains in amorphous regions of PVDF; in addition, CPDs rely on their inorganic carbon cores with unique electrical properties to resist carrier migration in amorphous regions of PVDF under high electric fields. In brief, CPDs are used as a reinforcing agent for the amorphous region of PVDF to further enhance its Eb and Ud. The composite loaded with 0.1 wt% CPDs exhibits the superior Ud of 12.4 J/cm3 at the Eb of 652.0 MV/m. This work provides new understanding on the dielectric response of ultrasmall-sized CPDs on polymer dielectrics, which could help us design new dielectric polymer composites with suppressed segmental motions for high breakdown strength and high energy density applications.

FABRICATION AND CHARACTERIZATION OF POLYETHERSULFONE (PES) MEMBRANES BY BLENDING POLYMERS FOR REMOVAL OF ORGANIC COMPOUNDS IN AIR

The PES membrane was modified using a polymer blending method to improve the performance and characteristics of the membrane. This research aims to see the effect of adding biosilica additives on the performance characteristics of PES membranes and determine the optimal composition of additives and solvents for making membranes. The membrane was made using the Non-solvent Induced Phase Separation (NIPS) method with a composition consisting of 18% PES, with the addition of varying concentrations of silica (1%, 2%, 3%, and 4%) and the membrane using the solvent N-Methyl- 2 Pyrrolidone (NMP) and Dimethyl Sulfoxide (DMSO). Membrane characterization was carried out by observing membrane morphology using Scanning Electron Microscopy (SEM), membrane surface functional group analysis test using Fourier Tranform Infrared (FTIR), membrane porosity test using the dry-wet weight procedure method, the highest porosity value was found on membrane B2 using a solvent DMSO with 2% silica is 16.88%. Membrane performance was carried out by pure water flux testing, the highest pure water flux value was found in membrane B2 with 2% silica, namely 64.14 L/m2.h. The antifouling test uses flux ratio recovery, the highest antifouling value is found on the A3 membrane with 3% silica, namely 91.3%. As well as rejection of the humic acid solution as a Natural Organic Matter (NOM) sample model using the ultrafiltration (UF) module with a dead end filtration flow system, the highest rejection value was found on the B2 membrane with 2% silica, namely 64.4%.

Engineering Water‐Stiffening Polymers via PEG‐Sidechain‐Mediated Microphase Separation

AbstractStiffness‐variable polymers have found their enormous potential in practical applications that require automatic adaptation and modulation. However, prevailing materials are often constrained by specific operational triggers, limited mechanical responsiveness, and inadequate universality. In this study, drawing inspiration from the mechanism of non‐solvent induced phase separation (NIPS), a novel series of polymers exhibiting reversible water‐triggered stiffening is designed and synthesized by covalently incorporating poly(ethylene glycol) (PEG) as a non‐solvent mediator onto the hydrophobic poly(meth)acrylates backbones. Owing to the hydrophilicity difference between PEG sidechains and backbones, these polymers display swift and substantial alterations in stiffness, with large‐scale and regulable changes (from several‐fold to exceeding 200‐fold) upon water penetration, resulting from water‐induced microphase separation. Meanwhile, the polymers also possess intrinsic dual‐responsive shape‐memory properties. Due to the excellent commercial availability, versatility, and designability of these polymers, the work provides novel perspectives for the advancement of water‐triggered stiffening materials and opens avenues for their prospective applications in various domains.

2-Methylpyrazine: A Greener Solvent for Nonsolvent Induced Phase Separation (NIPS) Membrane Fabrication

2-Methylpyrazine: A Greener Solvent for Nonsolvent Induced Phase Separation (NIPS) Membrane Fabrication

Additive manufacturing of porous ceramic structures by indirect powder bed fusion with laser beam using a novel polyamide/alumina-based feedstock

Porous alumina structures were developed by indirect Powder Bed Fusion with Laser Beam (PBF-LB), employing a novel feedstock (composite granules) based on alumina (Al2O3), bio-renewable polyamide 612 (PA612), and micron-sized graphite (MG) using a commercial PBF-LB machine that operates with a low-power visible light diode laser. Regular and slightly rounded composite granules were prepared via the thermally induced phase separation (TIPS) process in dimethyl sulfoxide (DMSO) using 0.05 vol% of PA612, 40/60 vol% of Al2O3/PA612 and 6.25 wt% of MG, and then characterized via density measurements, Hausner's ratio, SEM-EDS, particle size distribution, Raman spectroscopy, DSC, and TGA. Experimental conditions to be used in the PBF-LB process were determined in order to obtain high-quality green porous structures with a controlled geometry. After the heating treatments, sintered components with good structural integrity, a high open porosity associated with interconnected pores in the struts, and a ceramic matrix with microsized-equiaxial grains were obtained. The evaluation of the mechanical properties was performed by diametral compression testing. In order to improve these properties, a vacuum infiltration process involving a low-concentration alumina-ethanol suspension was used on pre-sintered discs. As a consequence of the infiltration process, the discs showed improved mechanical properties after sintering without the porosity having been significantly affected.

A novel, green, and environmentally friendly PBS/nano-CaCO3 hybrid membrane

Biodegradable membrane materials can be degraded into small molecules under natural conditions, which can effectively alleviate the environmental pollution caused by the waste of traditional organic membrane materials. In this work, biodegradable poly (butylene succinate) (PBS)/nano-CaCO3 hybrid membranes has been prepared via non-solvent induced phase separation method by blending environmentally friendly nano-CaCO3 particles with PBS. The incorporation of nano-CaCO3 particles into the membrane leads to a notable enhancement in mechanical strength, from 1.03±0.05 MPa to 1.42±0.13 MPa, resulting in a substantial increase of approximately 37 %. Additionally, the introduction of these particles also contributes to a reduction in contact angle, from 63° to 56°. Consequently, the issue of inadequate mechanical strength and limited hydrophilicity of PBS membrane is effectively addressed. Moreover, the pure water permeance of membrane increases from 8.5 L·m−2·h−1·bar−1 to 89.3 L·m−2·h−1·bar−1, and the permeability is greatly improved. The permeance recovery rate of the membrane increases from 78 % to 95 %, and the anti-fouling performance is improved. In addition, PBS can be degraded after the service of PBS/nano-CaCO3 hybrid membrane, and CaCO3 particles are environmentally friendly. Therefore, the PBS/nano-CaCO3 hybrid membrane hybrid membrane prepared in this study is a green and environmentally friendly membrane material.

Interconnected porous BT-VTS/PVDF-HFP nanocomposites with enhanced electroactive β-phase and crystallinity fabricated via thermally induced phase separation

Interconnected porous BT-VTS/PVDF-HFP nanocomposites with enhanced electroactive β-phase and crystallinity fabricated via thermally induced phase separation

Thermally induced phase separation of UHMWPE mixture with dioctyl adipate: Competition of liquid–liquid phase separation and polymer crystallization

The thermal behavior of ultra-high molecular weight polyethylene (UHMWPE) with dioctyl adipate (DOA) was investigated by the differential scanning calorimetry (DSC) method. Capillary-porous bodies were obtained via thermally induced phase separation of DOA mixtures with polyethylenes of different molecular weight at different cooling rates. Analysis of the morphology of the prepared porous bodies together with DSC data and results of cloud point estimation revealed an unexpected effect of a cooling rate on the type of phase separation occurring in the mixture during its cooling from homogeneous state. Particularly it was shown that increase in the cooling rate reduces the probability of realization of liquid – liquid phase separation in the mixture. It was argued that such behavior, different from the standard semicrystalline polymers, is a result of kinetic hindrance of liquid – liquid phase separation in mixtures containing a polymer with such a high molecular weight.

Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology

Rigid polylactic acid (PLA) foams fabricated via thermally induced phase separation (TIPS) utilizing a ternary solution of PLA, Tetrahydrofuran (THF), and water. The PLA gels were stabilized mechanically by the substituting of the THF/water solvent mixture with ethanol as non-solvent and subsequently vacuum dried. A comprehensive characterization of PLA foams was achieved by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Brunauer–Emmett–Teller (BET) analyses. The BET area obtained in the PLA foam is up to 18.76 m2/g. The Response Surface Methodology (RSM) was utilized to assess the impacts of four independent variables (polymer concentration, solvent composition, quench temperature, and aging time) on the pore size and density of PLA foam. The experimental findings demonstrated that the fabrication parameters could be fine-tuned to govern the morphology of the pores, comprising their size and density. The optimal values of parameters for cell size were identified by RSM to be 8.96 (wt%), 91.60 (w/w), 5.50 °C, and 3.86 h for the optimum cell size of 37.96 µm (37.78 by Genetic Algorithm). Optimum density by RSM 88.88 mgr/cm3 (88.38 mgr/cm3 by Genetic Algorithm) was obtained at 5.00 (wt%), 89.33 (w/w), 14.40 °C and 2.65 h.

Fluorescent protein tags affect the condensation properties of a phase-separating viral protein.

Fluorescent protein (FP) tags are extensively used to visualize and characterize the properties of biomolecular condensates despite a lack of investigation into the effects of these tags on phase separation. Here, we characterized the dynamic properties of µNS, a viral protein hypothesized to undergo phase separation and the main component of mammalian orthoreovirus viral factories. Our interest in the sequence determinants and nucleation process of µNS phase separation led us to compare the size and density of condensates formed by FP::µNS to the untagged protein. We found an FP-dependent increase in droplet size and density, which suggests that FP tags can promote µNS condensation. To further assess the effect of FP tags on µNS droplet formation, we fused FP tags to µNS mutants to show that the tags could variably induce phase separation of otherwise noncondensing proteins. By comparing fluorescent constructs with untagged µNS, we identified mNeonGreen as the least artifactual FP tag that minimally perturbed µNS condensation. These results show that FP tags can promote phase separation and that some tags are more suitable for visualizing and characterizing biomolecular condensates with minimal experimental artifacts.

Traveling fronts in vibrated polar disks: At the crossroad between polar ordering and jamming.

We investigate experimentally the collective motion of polar vibrated disks in an annular geometry, varying both the packing fraction and the amplitude of the angular noise. For low enough noise and large enough density, an overall collective motion takes place along the tangential direction. The spatial organization of the flow reveals the presence of polar bands of large density, as expected from the commonly accepted picture of the transition to collective motion in systems of aligning polar active particles. However, in our case, the low density phase is also polar, consistent with what is observed when jamming takes place in a very high density flock. Interestingly, while in that case the particles in the high density bands are arrested, resulting in an upstream propagation at a constant speed, in our case the bands travel downstream with a density-dependent speed. We demonstrate from local measurements of the packing fraction, alignment, and flow speeds that the bands observed here result both from a polar ordering process and a motility induced phase separation mechanism.

High-performance PVDF/PVB blend membranes with tailored sponge-like structure and antifouling properties for beer filtration

Currently limited research reported the design of microfiltration (MF) membranes specially for handling complex food processing streams such as rough beer. This study aimed to address this knowledge gap by tailoring for the first time a new class of polyvinylidene fluoride/poly(vinyl butyral) (PVDF/PVB) blend MF membrane with highly controllable pore structure and improved anti-fouling properties, and demonstrate its potential in real rough beer filtration. Combining an unconventional nonsolvent thermally induced phase separation (NTIPS) method and a unique quinary dope solution (i.e., PVDF/PVB/PVP/DMAc/MgCl2) with lower critical solution temperature (LCST) feature, the roles of PVB content and coagulation temperature were investigated in terms of pore structure characteristics and hydrophilicity. Although both the control PVDF membrane M0 without PVB and M6 with optimal 6.0 % PVB achieved similar turbidity removal (98–100 %), M6 exhibited enhanced permeance ranging from 27 % to 12 % with increasing simulated feed complexity from containing dextran only, yeast only to yeast/dextran mixture. The contribution of fouling of these key beer components was analyzed, indicating that the co-existence of yeast and dextran significantly aggravated fouling. Combining with membrane autopsy, in real rough beer filtration M6 showed permeance of 26.7 L·m−2·h−1·bar−1 at 1 bar that was ∼70 % higher than M0. Although with ∼50 % less irreversible fouling than M0, water cleaning implemented on M6 only recovered 62.5 % of flux. The simultaneous investigations on alkaline cleaning and operating pressure found that: a reasonably low pressure seemed favorable, e.g., 63.6 L·m−2·h−1·bar−1 at 0.2 bar, achieving up to flux recovery of ∼91 % with only ∼10 % contributed by irreversible fouling. Overall this study offers a facile yet practical strategy to tailor membranes for beer filtration, serving as an inspiration for designing future membrane processes for treating complex food processing and industry waste streams.

Reduction of polyketone membranes prepared by thermally induced phase separation with solvent co-extrusion for enhanced fouling resistance

This study utilized solvent co-extrusion technology and NaBH4 reduction to fabricate polyketone (PK) hollow fiber membranes with high water permeance and fouling resistance. Variations in reduction reaction time were explored to assess their impact on chemical composition, morphology, and properties. The results showed that the reduction reaction leads to the conversion of carbonyl groups on the membrane surface to hydroxyl groups, and with prolonged reaction time, the amount of hydroxyl groups on the membrane surface increases to a certain extent. The change in membrane chemical composition enhanced the hydrophilicity, while leaving the membrane morphology, mechanical properties, and separation performance largely unaffected. Static adsorption tests with bovine serum albumin (BSA) and E. coli exhibited distinct fouling behavior. While pristine PK membranes displayed significant BSA adsorption, PK reduction significantly reduced it. Both pristine and reduced PK membranes showed minimal E. coli attachment, likely due to weak interactions. Dynamic filtration tests demonstrated excellent flux recovery for reduced PK membranes, especially after 10 min of reduction, indicating superior fouling resistance with high flux recovery and low irreversible fouling, regardless of foulant type. These findings highlight a straightforward and efficient approach for producing high-performance membranes with exceptional fouling resistance suitable for practical applications.

Formation of Polyimide Membranes via Non-Solvent Induced Phase Separation: Insight from Molecular Dynamics Simulations.

Molecular dynamics simulations were applied to investigate the formation of P84 polyimide membranes through the non-solvent induced phase separation (NIPS) process, considering two scenarios: one using a conventional organic solvent like n-methyl-2-pyrrolidone (NMP) and the other a greener alternative, γ-butyrolactone (GBL), with water serving as the non-solvent. Different compositions of polymer solutions were established along the binodal boundaries of the respective systems, derived from experimental cloud point data on the ternary phase diagram. The resulting polymer membranes were analyzed and compared in terms of their morphology. The wettability of their surfaces was notably affected by the polymer content in the initial casting solution and demonstrated a correlation with the Brunauer-Emmet-Teller (BET) specific surface area of the associated polymer nanostructures. The GBL solvent systems produced porous polymers qualitatively similar to those obtained with NMP, albeit with slightly narrower pore size distributions.

Multifunctional Nanofibrous Hollow Microspheres for Enhanced Periodontal Bone Regeneration.

Destructive periodontitis destroys alveolar bone and eventually leads to tooth loss. While guided bone regeneration, which is based on creating a physical barrier to hinder the infiltration of epithelial and connective tissues into defect sites, has been widely used for alveolar bone regeneration, its outcomes remain variable. In this work, a multifunctional nanofibrous hollow microsphere (NFHMS) is developed for enhanced alveolar bone regeneration. The NFHMS is first prepared via combining a double emulsification and a thermally induced phase separation process. Next, E7, a short peptide with high specific affinity to bone marrow-derived stem cells (BMSCs), is conjugated onto the surface of NFHMS. After that, bone forming peptide (BFP), a short peptide derived from bone morphology protein 7 isloaded in calcium phosphate (CaP) nanoparticles, which are further encapsulated in the hollow space of the NFHMS-E7 to form NFHMS-E7-CaP/BFP. The NFHMS-E7-CaP/BFP selectively promoted the adhesion of BMSCs and expelled the adhesion of fibroblasts and epithelial cells. In addition, the BFP is sustainedly released from the NFHMS-E7-CaP/BFP to enhance the osteogenesis of BMSCs. A rat challenging fenestration defect model showed that the NFHMS-E7-CaP/BFP significantly enhanced alveolar bone tissue regeneration. This work provides a novel bioengineering approach for guided bone regeneration.

Kinetic Theory of Motility Induced Phase Separation for Active Brownian Particles.

When two active Brownian particles collide, they slide along each other until they can continue their free motion. For persistence lengths much larger than the particle diameter, the directors do not change, but the collision can be modeled as producing a net displacement on the particles compared to their free motion in the absence of the encounter. With these elements, a Boltzmann-Enskog-like kinetic theory is built. A linear stability analysis of the homogeneous state predicts a density instability resulting from the effective velocity reduction of tagged particles predicted by the theory.

Formation of Microporous Poly Acrylonitrile-Co-Methyl Acrylate Membrane via Thermally Induced Phase Separation for Immiscible Oil/Water Separation.

An interconnected sponge structure and porous surface poly (acrylonitrile-co-methyl acrylate) (P(AN-MA)) microfiltration membranes (MF) were fabricated via thermally induced phase separation (TIPS) by using caprolactam (CPL), and acetamide (AC) as the mixed diluent. When the ternary system was composed of 15 wt.% P(AN-MA), 90 wt.% CPL, and 10 wt.% AC and formed in a 25 °C air bath, the membrane exhibited the highest water flux of 8107 L/m2·h. The P(AN-MA) membrane contained hydrophobic groups (-COOCH3) and hydrophilic groups (-CN), leading it to exhibit oleophobic properties underwater and hydrophobic properties in oil. The membrane demonstrates efficient separation of immiscible oil/water mixtures. The pure water flux of the petroleum ether/water mixture measured 870 L/m2·h, and the pure oil flux of the petroleum tetrachloride/water mixture measured 1230 L/m2·h under the influence of gravity. Additionally, the recovery efficiency of diluents through recrystallization was 85.3%, significantly reducing potential pollution and production costs.

Metal-Halogen Interactions Inducing Phase Separation for Self-Healing and Tough Ionogels with Tunable Thermoelectric Performance.

Ionic liquid-based thermoelectric gels become a compelling candidate for thermoelectric power generation and sensing due to their giant thermopower, good thermal stability, high flexibility, and low-cost production. However, the materials reported to date suffer from canonical trade-offs between self-healing ability, stretchability, strength, and ionic conductivity. Herein, a self-healing and tough ionogel (PEO/LiTFSI/EmimCl) with tunable thermoelectric properties by tailoring metal-halogen bonding interactions, is developed. Different affinities between polymer matrix and salts are exploited to induce phase separation, resulting in simultaneous enhancement of ionic conductivity and mechanical strength. Molecular dynamics (MD) simulations and spectroscopic analyses show that Cl- ions impair the lithium-ether oxygen coordination, leading to changes in chain conformation. The migration difference between cations and anions is thus widened and a transition from n-type to p-type thermoelectric ionogels is realized. Furthermore, the dynamic interactions of metal-ligand coordination and hydrogen bonding yield autonomously self-healing capability, large stretchability (2000%), and environment-friendly recyclability. Benefiting from these fascinating properties, the multifunctional PEO-based ionogels are applied in sensors, supercapacitors, and thermoelectric power generation modules. The strategy of tuning solvation dominance to address the trade-offs in thermoelectric ionogels and optimize their macroscopic properties offers new possibilities for the design of advanced ionogels.

Preparation and Investigation of High Surface Area Aerogels from Crosslinked Polypropylenes.

Polypropylene-based aerogels with high surface area have been developed for the first time. By chemical crosslinking of polypropylene with oligomeric capped-end amino compounds, followed by dissolution, thermally induced phase separation, and the supercritical CO2 drying process or freeze-drying method, the aerogels exhibit high specific surface areas up to 200 m2/g. Moreover, the silica-cage multi-amino compound was utilized in a similar vein for forming hybrid polypropylene aerogels. According to the SEM, the developed polypropylene-based aerogels exhibit highly porous morphology with micro-nanoscale structural features that can be controlled by processing conditions. Our simple and inexpensive synthetic strategy results in a low-cost, chemically resistant, and highly porous material that can be tailored according to end-use applications.

Diffusion mediated thermally induced phase separation for preparing poly(vinylidene fluoride) membranes with enhanced separation performances

Thermally induced phase separation (TIPS) process is an appealing method for preparing poly(vinylidene fluoride) (PVDF) membranes for separation. In this work, we developed a diffusion mediated thermally induced phase separation (d-TIPS) to prepare PVDF membranes with great molecules separation performances. We investigated the thermodynamics of ternary polymer solutions including PVDF, caprolactam (CPL), and Polyethylene glycol (PEG). We controlled liquid–liquid phase separation and the CPL diffusion by adjusting the addition of PEG and molecular weight to modulate the evolution of morphology from spherulitic to bicontinuous structure. The resulting membrane was characterized by morphology, surface chemistry, tensile strength, water contact angle, and perm-selectivity. The membrane was further stretched for enhanced strength, permeance, and rejection. This work provides a fundamental understanding of the diffusion mediated thermally induced phase separation and shows the great potential of PVDF membranes in macromolecules separation.