Showing papers on "Miscibility published in 2021"

Like dissolves like: A first-principles theory for predicting liquid miscibility and mixture dielectric constant

Abstract: Liquid mixtures are ubiquitous Miscibility and dielectric constant are fundamental properties that govern the applications of liquid mixtures However, despite their importance, miscibility is usually predicted qualitatively based on the vaguely defined polarity of the liquids, and the dielectric constant of the mixture is modeled by introducing mixing rules Here, we develop a first-principles theory for polar liquid mixtures using a statistical field approach, without resorting to mixing rules With this theory, we obtain simple expressions for the mixture’s dielectric constant and free energy of mixing The dielectric constant predicted by this theory agrees well with measured data for simple binary mixtures On the basis of the derived free energy of mixing, we can construct a miscibility map in the parameter space of the dielectric constant and molar volume for each liquid The predicted miscibility shows remarkable agreement with known data, thus providing a quantitative basis for the empirical “like-dissolves-like” rule

Calculation aided miscibility manipulation enables highly efficient polythiophene:nonfullerene photovoltaic cells

Abstract: Polythiophenes, with merits of low cost and high scalability of synthesis, have received growing interest in organic solar cells. To date, the best-performing polythiophene:nonfullerene solar cells exhibit typical power conversion efficiencies (PCEs) of 10%–12%, which is much lower than those employing PM6- and D18-type polymers. This inferior performance is mostly limited by the improper miscibility between polythiophene and acceptors. Efforts on engineering the molecular structure to systematically tune the miscibility are required. With the aid of group contribution calculations, the miscibility of polythiophene:nonfullerene blend system was finely tuned by varying the ratios of siloxane-terminated chains and alkyl chains in ester-substituted polythiophenes through random copolymerization. Based on a series of the polythiophene and nonfullerene acceptors, the detailed analysis of blend miscibility and performance reveals a surprising anticorrelation between the Flory-Huggins interaction parameter ( χ aa) and the optimal time of solvent vapor annealing for device performance across these systems. Primarily due to the slightly higher χ aa, the blend of PDCBT-Cl-Si5 and ITIC-Th1 results in a record-high PCE of 12.85% in polythiophene:nonfullerene solar cells. The results not only provide a calculation-guided approach for molecular design but also prove that precise control of the miscibility is an effective way to design high-performance polythiophene:nonfullerene blends and beyond.

Efficient n-Doping of Polymeric Semiconductors through Controlling the Dynamics of Solution-State Polymer Aggregates.

Abstract: Doping of polymeric semiconductors is often limited by the miscibility issue between polymers and dopants. Although significant efforts have been devoted to enhancing the miscibility via chemical modification, the electrical conductivities of n-doped polymeric semiconductors are usually below 10 S cm -1 . Here, we report a different approach to overcome the miscibility issue by modulating the solution-state aggregates of conjugated polymers. We found that the solution-state aggregates of conjugated polymers not only change with solvent and temperature but also change with solution aging time. Modulating the solution-state polymer aggregates can directly influence their solid-state microstructures and miscibility with dopants. As a result, both high doping efficiency and high charge carrier mobility were simultaneously obtained. The n-doped electrical conductivity of P(PzDPP-CT2) can be tuned up to 32.1 S cm -1 after exploring the dynamics of the polymer aggregates. This method can also be used to improve the doping efficiency of other polymer systems (e.g. N2200) with different aggregation tendencies and behaviors. Our results highlight the importance of understanding the dynamics of the polymer aggregates and the influence on the solid-state microstructures and doping efficiency.

Measurement and modeling of minimum miscibility pressure: A state-of-the-art review

Abstract: This paper gives a critical review of miscibility-measurement techniques published in the open literature along with recommendations and lessons learned. Many of these published methods violate the inherent assumptions for multicontact miscibility (MCM). The confusion often arises from a failure to distinguish between first-contact miscibility (FCM), in which two fluids can be mixed in all proportions without forming two phases, and MCM, in which fluid compositions that arise during the flow of two phases in a porous medium approach a specific critical point within the constraints of the MCM definition. There are many analytical, numerical, correlational, and experimental methods available to estimate the minimum miscibility pressure (MMP) for MCM flow. The numerous available methods, some of which are quite inexpensive, have caused significant misunderstandings in the literature and in practice regarding their ability to estimate MMP. Our experience has shown that the best methods are those that honor the multicontact process (MCM), in which flow interacts with phase behavior in a prescribed way. Good methods that achieve this are slimtube experiments, detailed slimtube simulations, multiple-mixing-cell calculation methods, and the method of characteristics (MOC). Techniques such as the rising-bubble-apparatus (RBA) and vanishing-interfacial-tension (IFT) (VIT) experiments are subject to significant uncertainties, although they can still provide useful information. Numerous MMP correlations have been developed. They should be used with caution for systems similar to those used to develop the correlation. Use for other fluid systems can lead to significant errors. We discuss the advantages and disadvantages of most current methods and show that various combinations of methods can reduce uncertainty.

Blend Miscibility of Poly(ethylene terephthalate) and Aromatic Polyesters from Salicylic Acid.

Abstract: Poly(ethylene terephthalate) (PET) is one of the most prevalent polymers in the world due to its combined thermal, mechanical, and gas barrier attributes. Blending PET with other polymers is an appealing strategy to further tailor properties to meet the needs of an even more diverse range of applications. Most blends with PET are macrophase-separated; only a few miscible systems have been reported. Here, the miscibility of the aromatic polyesters poly(salicylic glycolide) (PSG) and poly(salicylic methyl glycolide) (PSMG) with PET is described. Both PSG and PSMG have similar chemical structures to PET but are derived from sustainable resources and readily degradable. This study suggests that they are fully miscible with PET over the entire composition range, which is attributed to favorable interactions with PET. Negative polymer-polymer interaction parameters (χ) were determined using Flory-Huggins theory to describe melting temperature variations in the blends. In addition, the PET blends showed mechanical properties that are intermediate between the two homopolymers.

Fine-Tuning Miscibility and π-π Stacking by Alkylthio Side Chains of Donor Molecules Enables High-Performance All-Small-Molecule Organic Solar Cells.

Abstract: Optimization of morphology and precise control of miscibility between donors and acceptors play an important role in improving the power conversion efficiencies (PCEs) of all-small-molecule organic solar cells (SM-OSCs). Besides device optimization, methods such as additives and thermal annealing are applied for finely tuning bulk-heterojunction morphology; strategies of molecular design are also the key to achieve efficient phase separation. Here, a series of A-D-A-type small-molecule donors (SM4, SM8, and SM12) based on benzodithiophene units were synthesized with different lengths of alkylthio side chains to regulate crystallinity, and their miscibility with the acceptor (BO-4Cl) was investigated. Consequently, SM4 with a short alkylthio substituent had a high crystallization propensity, leading to the oversized molecular domains and the poor morphology of the active layer. Meanwhile, SM12 with a longer alkylthio substituent showed weak crystallinity, causing a relatively looser π-π stacking and thus adversely affecting charge-carrier transport. The SM-OSC based on the small-molecule donor SM8 with a mid-length alkylthio substituent achieved a better PCE over 13%, which was attributed to a more harmonious blend miscibility without sacrificing carrier-charge transport. Eventually, the modulation of phase separation and miscibility via controlling the lateral side chains has proven its potential in optimizing the blend morphology to aid the development of highly efficient SM-OSCs.

Effect of the stearic acid-modified TiO2 on PLA nanocomposites: Morphological and thermal properties at the microscopic scale

Abstract: In this work, a route is developed to synthesize nanocomposites based on polylactic acid (PLA) and stearic acid-modified TiO2 nanoparticles (TiO2-SA). The nanocomposite is prepared in two steps by solution and melt methods. Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), as well as Thermogravimetric Analysis (TGA) are used to characterize the synthesized materials. Quantum chemical calculations are carried out by means of density functional theory (DFT) calculations, Blends study and AIM analysis, to investigate the role of Stearic Acid (SA) on the nanocomposite PLA/TiO2 at microscopic level. FTIR analysis confirms the functionalization of TiO2 nanoparticles by stearic acid (SA). The DSC results illustrates the overall TiO2 effect in reducing the glass transition temperature Tg (from 58° to 52 °C) and the rise in the crystallinity degree (from 0.19° to 7.18 °C) where the 5% of nanoparticle shows the optimum result. This could be attributed to the fact that TiO2-SA acts as a nucleating agent, as confirmed also by XRD patterns. TGA analysis shows that the thermal stability of PLA decreases by the addition of TiO2-SA and this effect is monothonic with TiO2 content where the 1% nanoparticle shows the most thermally stable formulation. Simulations at atomic level confirmed the dispersion of treated TiO2 in the matrix. In particular, SA plays the role of electron donor with PLA and TiO2, increasing the miscibility between them by a strong hydrogen bond. The main results obtained allow considering SA as a valid option for the functionalization of TiO2 before inclusion in PLA matrix.

Lubricant-Infused Surfaces for Low-Surface-Tension Fluids: The Extent of Lubricant Miscibility

Abstract: Lubricant-infused surfaces (LISs) and slippery liquid-infused porous surfaces (SLIPSs) have shown remarkable success in repelling low-surface-tension fluids. The atomically smooth, defect-free slippery surface leads to reduced droplet pinning and omniphobicity. However, the presence of a lubricant introduces liquid-liquid interactions with the working fluid. The commonly utilized lubricants for LISs and SLIPSs, although immiscible with water, show various degrees of miscibility with organic polar and nonpolar working fluids. Here, we rigorously investigate the extent of miscibility by considering a wide range of liquid-vapor surface tensions (12-73 mN/m) and different categories of lubricants having a range of viscosities (5-2700 cSt). Using high-fidelity analytical chemistry techniques including X-ray photoelectron spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and two-dimensional gas chromatography, we quantify lubricant miscibility to parts per billion accuracy. Furthermore, we quantify lubricant concentrations in the collected condensate obtained from prolonged condensation experiments with ethanol and hexane to delineate mixing and shear-based lubricant drainage mechanisms and to predict the lifetime of LISs and SLIPSs. Our work not only elucidates the effect of lubricant properties on miscibility with various fluids but also develops guidelines for developing stable and robust LISs and SLIPSs.

Prediction of the Miscibility of PBAT/PLA Blends.

Abstract: Designing polymer structures and polymer blends opens opportunities to improve the performance of plastics. Blending poly(butylene adipate-co-terephthalate) (PBAT) and polylactide (PLA) is a cost-effective approach to achieve a new sustainable material with complementary properties. This study aimed to predict the theoretical miscibility of PBAT/PLA blends at the molecular level. First, the basic properties and the structure of PBAT and PLA are introduced, respectively. Second, using the group contribution methods of van Krevelen and Hoy, the Hansen and Hildebrand solubility parameters of PBAT and PLA were calculated, and the effect of the molar ratio of the monomers in PBAT on the miscibility with PLA was predicted. Third, the dependence of the molecular weight on the blend miscibility was simulated using the solubility parameters and Flory–Huggins theory. Next, the glass transition temperature of miscible PBAT/PLA blends, estimated using the Fox equation, is shown graphically. According to the prediction and simulation, the blends with a number-average molecular weight of 30 kg/mol for each component were thermodynamically miscible at 296 K and 463 K with the possibility of spinodal decomposition at 296 K and 30% volume fraction of PBAT. This study contributes to the strategic synthesis of PBAT and the development of miscible PBAT/PLA blends.

Enhancement of Solar Thermal Fuel by Microphase Separation and Nanoconfinement of a Block Copolymer

Abstract: Until now, solar thermal energy storage within phase-change materials (PCMs) depends on π–π and van der Waals interactions to improve their miscibility, which often brings about finite enhancement ...

Composition and Oxidation Dependence of Glass Transition in Epoxy Asphalt

Abstract: Miscibility, and lack of it, is decisive for durable polymer-modified asphalt binders and reflects the long-term performance of asphalt materials in terms of fatigue and thermal cracking. In this w...

Stability of Film-Forming Dispersions: Affects the Morphology and Optical Properties of Polymeric Films.

Abstract: Starch-based films are promising alternatives to synthetic films in food packaging. They were widely studied in terms of mechanical and optical properties. In food packaging, optical properties are of great interest because ultra violet (UV-light) protection is strictly required. Nevertheless, the characterization of film-forming dispersions was poorly addressed, especially regarding its correlation with the film produced. In this work, we characterized film-forming dispersions at different compositions of starch and carboxymethyl cellulose (CMC) by Turbiscan. This instrument is based on multiple light scattering and gives significant information about the miscibility of polymers in the dispersed phase. Indeed, it identifies the phenomena of destabilization and phase separation before their visibility to the unaided eye. This work aimed to study whether the homogeneous/inhomogeneous morphology of films could be forecast by the analysis of profiles obtained in the dispersed phase. The films produced were investigated by optical microscopy and absorbance analysis. As the CMC fraction increased, Turbiscan showed reduced phase separation. This implies better miscibility of mixture components and higher gelification degree. The related film was more homogeneous and presented higher UV absorbance. Consequently, film-forming dispersions and optical properties of films are strictly correlated and Turbiscan-based analysis is very useful to investigate the dispersion stability and predict the film quality.

The experimental research for reducing the minimum miscibility pressure of carbon dioxide miscible flooding

Abstract: As the minimum miscibility pressure in the research area is higher than the formation fracture pressure, it is impossible to form the miscible flooding. To address this problem, the effect of two chemical reagents (citric acid isobutyl ester, citric acid isopentyl ester) on reducing the minimum miscibility pressure (MMP) of carbon dioxide and the crude oil was determined through the long slim tube displacement experiment. The experimental results show that the minimum miscibility pressure could decrease significantly with increasing the injected slug size of the chemical reagents, but the decrease became smaller and smaller. The chemical reagents had an optimal injected slug size of 0.003 PV (pore volume). At such slug size, the minimum miscibility pressure for citric acid isobutyl ester was reduced by 6.1 MPa and for citric acid isopentyl ester the reduction was 5.5 MPa. The minimum miscibility pressure was reduced by 20.61% and 18.58%. The addition of citric acid isobutyl ester slug could greatly reduce the minimum miscibility pressure, with a better effect. The recovery of the miscible flooding experiment scheme after injection of citric acid isobutyl ester slug was higher by 6.5%–11.6% than that of the scheme without citric acid isobutyl ester injection. Therefore, the citric acid isobutyl ester was recommended as the best chemical reagent to reduce the minimum miscibility pressure. The research results are of certain guiding significance for the overall realization of miscible flooding to enhance oil recovery in the research area.

Phase Behavior and Miscibility of CO2–Hydrocarbon Mixtures in Shale Nanopores

Abstract: The phase behavior of shale fluids is different from conventional reservoir fluids due to fluid adsorption and capillary pressure. The miscibility phenomenon between CO2 and oil in nanopores is als...

Plasticization of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with an Oligomeric Polyester: Miscibility and Effect of the Microstructure and Plasticizer Distribution on Thermal and Mechanical Properties.

Abstract: In the last few decades, many efforts have been made to make poly(3-hydroxybutyrate) (PHB) and its copolymers more suitable for industrial production and large-scale use. Plasticization, especially using biodegradable oligomeric plasticizers, has been one of the strategies for this purpose. However, PHB and its copolymers generally present low miscibility with plasticizers. An understanding of the plasticizer distribution between the mobile and rigid amorphous phases and how this influences thermal, mechanical, and morphological properties remains a challenge. Herein, formulations of poly(hydroxybutyrate-co-valerate) (PHBV) plasticized with an oligomeric polyester based on lactic acid, adipic acid, and 1,2-propanediol (PLAP) were prepared by melt extrusion. The effects of the PLAP content on the processability, miscibility, and microstructure of the semicrystalline PHBV and on the thermal, morphological, and mechanical properties of the formulations were investigated. The compositions of the mobile and rigid amorphous phases of the PHBV/PLAP formulations were easily estimated by combining dynamic mechanical data and the Fox equation, which showed a heterogeneous distribution of PLAP in these two phases. An increase in the PLAP mass fraction in the formulations led to progressive changes in the composition of the amorphous phases, an increase of both crystalline lamellae and interlamellar layer thickness, and a decrease in the melting and glass transition temperatures as well as the PHBV stiffness. The Flory-Huggins interaction parameter varied with the formulation composition in the range of -0.299 to -0.081. The critical PLAP mass fraction of 0.37 obtained from thermodynamic data is close to the value estimated from dynamic mechanical analysis (DMA) data and the Fox equation. The mechanical properties showed a close relationship with the distribution of PLAP in the rigid and mobile amorphous phases as well as with the microstructure of the crystalline phase of PHBV in the formulations.

A New Era in Engineering Plastics: Compatibility and Perspectives of Sustainable Alipharomatic Poly(ethylene terephthalate)/Poly(ethylene 2,5-furandicarboxylate) Blends

Abstract: The industrialisation of poly(ethylene 2,5-furandicarboxylate) for total replacement of poly(ethylene terephthalate) in the polyester market is under question. Preparation of high-performing polymer blends is a well-established strategy for tuning the properties of certain homopolymers and create tailor-made materials to meet the demands for a number of applications. In this work, the structure, thermal properties and the miscibility of a series of poly(ethylene terephthalate)/poly(ethylene 2,5-furandicarboxylate) (PET/PEF) blends have been studied. A number of thermal treatments were followed in order to examine the thermal transitions, their dynamic state and the miscibility characteristics for each blend composition. Based on their glass transition temperatures and melting behaviour the PET/PEF blends are miscible at high and low poly(ethylene terephthalate) (PET) contents, while partial miscibility was observed at intermediate compositions. The multiple melting was studied and their melting point depression was analysed with the Flory-Huggins theory. In an attempt to further improve miscibility, reactive blending was also investigated.

Investigation of structure, mechanical, and shape memory behavior of thermally activated poly(ε-caprolactone): azide-functionalized poly(vinyl chloride) binary polymer blend films

Abstract: Like alloys in metallurgy, polymers are blended to obtain new characteristics, which is important to extend their application area. In this study, three different compositions of azide-functionalized poly(vinyl chloride)-PVC-N3 and poly(e-caprolactone)-PCL were blended. Physical properties, such as mechanical and thermal behavior of the blends, were investigated through the tensile test, DSC, and TGA. Also, a blended polymer with equal participation of each constituent was trained to determine the shape memory behavior of the sample. The results showed that PVC-N3 and PCL were completely miscible; therefore, all physical properties are somewhere between the pure polymers. The blend with only 50% PCL, as an example, still kept its shape memory behavior; additionally, the blended polymers partially achieved crystalline behavior by adding PCL to the PVC-N3. The tensile test also showed that the modulus of toughness and other mechanical behavior depends on the compositional ratio of the polymers. Consequently, the miscibility of the PCL and PVC-N3 enhances the physical properties of both polymers as a function of composition.

Effect of amorphous cellulose on the deformation behavior of cellulose composites: molecular dynamics simulation

Abstract: This study was aimed at predicting and enhancing the properties of the blend, as well as exploring the mechanism, of a polylactic acid (PLA)/amorphous cellulose composite system through molecular characterization. The static properties of the amorphous cellulose/PLA blend model and the mechanical response of the material under uniaxial tension were studied by molecular dynamics simulation to establish the structure–property relationship. PLA and cellulose showed poor miscibility, the change in the compatibility of the mixture can be attributed to the hydrogen bond interaction between the cellulose and PLA functional groups. The radius of gyration, interaction and free volume of the molecular chain in the blend were analyzed. The conformational changes under tensile deformation indicated that the load-bearing role of cellulose in the system was the main reason for increasing the strength of the material. The yield process was considered to be the infiltration of free volume caused by deformation.

Impact of Sequential Fluorination of Donor and/or Acceptor Polymers on the Efficiency and Morphology of All-Polymer Solar Cells

Abstract: To fine-tune all-polymer solar cells (all-PSCs), fluorine atoms were introduced on the bithiophene of thiophene-flanked dioxo-benzodithiophene-based donor polymers (P2T-0F and P2T-2F) and/or on the...