Showing papers on "Miscibility published in 2012"
TL;DR: In this article, a mixture of polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC) was used as bio-equivalent materials for thermal analysis.
Abstract: Polymers and polymeric composites have steadily reflected their importance in our daily life. Blending poly(vinyl alcohol) (PVA) with a potentially useful natural biopolymers such as hydroxypropyl cellulose (HPC) seems to be an interesting way of preparing a polymeric blends. In the present work, blends of PVA/HPC of compositions (100/0, 90/10, 75/25, 50/50, 25/75, and 0/100 wt/wt%) were prepared to be used as bioequivalent materials. Thermal analyses [differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)], and X-ray diffraction (XRD) were employed to characterize and reveal the miscibility map and the structural properties of such blend system. The obtained results of the thermal analyses showed variations in the glass transition temperature (Tg) indicating the miscibility of the blend systems. Moreover, the changes in the melting temperature (Tm), shape and area were attributed to the different degrees of crystallinity and the existence of polymer-polymer interactions between PVA and HPC molecules. The X-ray diffraction (XRD) analysis showed broadening and sharpening of peaks at different HPC concentrations with PVA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo-polymers PVA and HPC is possible. The results showed that HPC doped in PVA film can improve the thermal stability of the film under investigation, leading to interesting technological applications.
247 citations
TL;DR: The volume fraction of polymer-rich, fullerene- rich, and polymer-fullerene mixed domains can be tuned using the miscibility leading to improvement in the charge collection efficiency and PCE in P3HS:fullerenes BHJ solar cells.
Abstract: The improvement of the power conversion efficiency (PCE) of polymer bulk heterojunction (BHJ) solar cells has generally been achieved through synthetic design to control frontier molecular orbital energies and molecular ordering of the electron-donating polymer. An alternate approach to control the PCE of a BHJ is to tune the miscibility of the fullerene and a semiconducting polymer by varying the structure of the fullerene. The miscibility of a series of 1,4-fullerene adducts in the semiconducting polymer, poly(3-hexylselenophene), P3HS, was measured by dynamic secondary ion mass spectrometry using a model bilayer structure. The microstructure of the bilayer was investigated using high-angle annular dark-field scanning transmission microscopy and linked to the polymer-fullerene miscibility. Finally, P3HS:fullerene BHJ solar cells were fabricated from each fullerene derivative, enabling the correlation of the active layer microstructure to the charge collection efficiency and resulting PCE of each system....
196 citations
TL;DR: A hydrophilicity index (HI) of ILs is proposed, in terms of the number of water molecules in the separated IL phase, which proves to be a good indicator of the phase behaviour of IL/water mixtures, as well as their phase transition temperature.
Abstract: Phase separation between ionic liquids (ILs) and molecular liquids is of interest physico-chemically, and also has industrial relevance. IL/water mixtures are of great interest in many fields. Unlike static phase separation between IL and water, dynamic shifts of IL/water mixtures between a homogeneous mixture and separate phases have a wide variety of applications. The miscibility of ILs with water generally increases upon heating, and a few ILs undergo a lower critical solution temperature (LCST)-type phase transition with water in which the separated biphases become miscible upon cooling. As the phase transition is controlled by changing the temperature by a few degrees, the LCST-type phase response of IL/water mixtures makes it possible to use ILs as solvents in various energy-saving processes. Since many hydrophilic ILs do not undergo phase separation with water, we aim to determine the necessary conditions under which hydrophobic ILs undergo the phase transition. Based on physico-chemical analysis of many hydrophobic ILs that undergo a phase separation after mixing with water, we find there is a particular range of “hydrophilicity” of these hydrophobic ILs within which the LCST-type phase transition is possible. Accordingly, a hydrophilicity index (HI) of ILs is proposed, in terms of the number of water molecules in the separated IL phase. The HI value proves to be a good indicator of the phase behaviour of IL/water mixtures, as well as their phase transition temperature. Potential application of the LCST-type phase change to the selective extraction of water-soluble proteins is also summarised.
135 citations
TL;DR: Evidence is provided for the miscibility between chitosan and cellulose in the solid state using 1-butyl-3-methylimidazolium acetate as solvent media and for the increased Ea for thermal decomposition for all the polymeric blends.
121 citations
TL;DR: In this article, X-ray diffraction, differential scanning calorimetry (DSC), and molecular simulations are used to study mixing in a variety of polymer:molecule blends by systematically varying the polymer and small molecular properties.
Abstract: While recent reports have established significant miscibility in polymer:fullerene blends used in organic solar cells, little is actually known about why polymers and fullerenes mix and how their mixing can be controlled. Here, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and molecular simulations are used to study mixing in a variety of polymer:molecule blends by systematically varying the polymer and small-molecule properties. It is found that a variety of polymer:fullerene blends mix by forming bimolecular crystals provided there is sufficient space between the polymer side chains to accommodate a fullerene. Polymer:tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) bimolecular crystals were also observed, although bimolecular crystals did not form in the other studied polymer:non-fullerene blends, including those with both conjugated and non-conjugated small molecules. DSC and molecular simulations demonstrate that strong polymer–fullerene interactions can exist, and the calculations point to van der Waals interactions as a significant driving force for molecular mixing.
105 citations
TL;DR: Electrospun GT/PCL and other similar natural-synthetic hybrid systems in constructing tissue-engineered scaffolds may offer a facile and effective approach to achieve finer and compositionally homogeneous hybrid nanofibers for effective applications.
102 citations
TL;DR: Examination of the electron mobility in amorphous blends of poly(3-hexylthiophene) and phenyl-C(61)-butyric acid methyl ester reveals that the miscibility of the components strongly affects electron transport within blends.
Abstract: Recent evidence has demonstrated that amorphous mixed phases are ubiquitous within mesostructured polythiophene-fullerene mixtures. Nevertheless, the role of mixing within nanophases on charge transport of organic semiconductor mixtures is not fully understood. To this end, we have examined the electron mobility in amorphous blends of poly(3-hexylthiophene) and phenyl-${\mathrm{C}}_{61}$-butyric acid methyl ester. Our studies reveal that the miscibility of the components strongly affects electron transport within blends. Immiscibility promotes efficient electron transport by promoting percolating pathways within organic semiconductor mixtures. As a consequence, partial miscibility may be important for efficient charge transport in polythiophene-fullerene mixtures and organic solar cell performance.
100 citations
TL;DR: The results of experiments designed to provide quantitative thermodynamic information on the miscibility, interdiffusion, and depth profile of P3HT are described, finding that the resultant thin films consist of a 'bulk' layer that is not influenced by the air or substrate surface.
Abstract: Recent work has shown that poly(3-hexylthiophene) (P3HT) and the surface-functionalized fullerene 1-(3-methyloxycarbonyl)propyl(1-phenyl[6,6])C61 (PCBM) are much more miscible than originally thought, and the evidence of this miscibility requires a return to understanding the optimal morphology and structure of organic photovoltaic active layers. This manuscript describes the results of experiments that were designed to provide quantitative thermodynamic information on the miscibility, interdiffusion, and depth profile of P3HT : PCBM thin films that are formed by thermally annealing initial bilayers. It is found that the resultant thin films consist of a ‘bulk’ layer that is not influenced by the air or substrate surface. The composition of PCBM in this ‘bulk’ layer increases with increased PCBM loading in the original bilayer until the ‘bulk’ layer contains 22 vol% PCBM. The introduction of additional PCBM into the sample does not increase the amount of PCBM dispersed in this ‘bulk’ layer. This observation is interpreted to indicate that the miscibility limit of PCBM in P3HT is 22 vol%, while the precise characterization of the depth profiles in these films shows that the PCBM selectively segregates to the silicon and near air surface. The selective segregation of the PCBM near the air surface is ascribed to an entropic driving force.
83 citations
TL;DR: Giant unilamellar vesicles are microaspirated to determine the effect of mechanical stress on the liquid/liquid miscibility temperature of a membrane composed of a ternary lipid mixture and this work validates recent theoretical predictions.
68 citations
TL;DR: In this article, the thermal and dielectric properties of the dicyanate ester of bisphenol A and diamine-based benzoxazine were investigated.
Abstract: This study discusses the miscibility, microstructure, and the thermal and dielectric properties of the reactive blends of dicyanate ester of bisphenol A and diamine-based benzoxazine. DSC and IR were applied to monitor the curing reactions of the reactive blends. Three reactions were observed in the curing reactions: the first is the cyclotrimerization of cyanate ester, producing the triazine structure; the second is the coreaction between the triazine structure and benzoxazine, forming alkyl isocyanurate and diphenyl ether linkages, followed by the further reaction of the isocyanurate linkage; and the third is the ring-opening of benzoxazine. The coreaction decomposes the polycyanurate structures and brings parts of the polycyanurate structures into the polybenzoxazine matrix. Thus, a miscible blend can be achieved in all compositions, as judged by the single composition-dependent Tg in the dynamic mechanical and thermal mechanical analyses. The experimental data also show that the dimensional stability ...
67 citations
TL;DR: In this article, the application of standard atomic force microscopy (AFM) measurements combined with nanoscale mid-infrared (mid-IR) spectroscopy was explored to evaluate miscibility in binary polymer blends.
Abstract: Determining the extent of miscibility of amorphous components is of great importance for certain pharmaceutical systems, in particular for polymer–polymer and polymer-small molecule blends. In this study, the application of standard atomic force microscopy (AFM) measurements combined with nanoscale mid-infrared (mid-IR) spectroscopy was explored to evaluate miscibility in binary polymer blends. The miscibility characteristics of a set of 50/50 (w/w) polymer blends comprising of poly(vinylpyrrolidone) (PVP) with dextran or maltodextrin (DEX) of varying molecular weights (MWs) were investigated. Standard AFM characterization results show good agreement with inferences drawn from differential scanning calorimetry (DSC) analysis in terms of forming either single or two phase systems. AFM analysis also provided insight into the microstructure of the two phase systems and how domain sizes varied as a function of polymer MWs. Nanoscale mid-IR evaluation of the blends, performed by collecting local mid-IR spectra...
TL;DR: The study explained the superior stability of INM-E PO mixtures, and demonstrated that a combination of thermal, rheological, and spectroscopic technologies can help to obtain a full picture of the drug-polymer interactions and to determine the formulation and processing conditions.
TL;DR: The aim of this work is to investigate the effect of compression on miscibility of naproxen (NAP)-PVP K25 solid dispersions, and the highly ductile nature of PVP promotes plastic deformation upon compression induced by the rotation of the PVP backbone with the transition of dihedral angles from low to high energy state.
TL;DR: It is shown that the complete miscibility with the semicrystalline polymer matrix and the improvement of thermomechanical properties in the solid state is caused by the PE-coated nanoparticles being nucleating agents for the crystallization of PE.
Abstract: A route to fully miscible polyethylene (PE) nanocomposites has been established based on polymer-brush-coated nanoparticles. These nanoparticles can be mixed with PE at any ratio, with homogeneous dispersion, and without aggregation. This allowed a first systematic study of the thermomechanical properties of PE nanocomposites without interference from aggregation effects. We observe that the storage modulus in the semicrystalline state and the softening temperature increase significantly with increasing nanoparticle content, whereas the melt viscosity is unaltered by the presence of nanoparticles. We show that the complete miscibility with the semicrystalline polymer matrix and the improvement of thermomechanical properties in the solid state is caused by the PE-coated nanoparticles being nucleating agents for the crystallization of PE. This provides a general route to fully miscibility nanocomposites with semicrystalline polymers.
TL;DR: In this paper, a series of biodegradable double crystalline poly(ethylene succinate)-b-poly(butylene succinate) (PES-b-PBS) multiblock copolymers with various PES and PBS block lengths were successfully synthesized by chain-extension reaction of dihydroxylated poly(methylene succine) (HO-PES)-OH) and poly(butane succinate), using 1,6-hexamethylene diisocyanate (HDI) as a chain extension.
TL;DR: Prepared hot-melt-extruded solid dispersions of bicalutamide (BL) using poly(ethylene oxide) (PEO) as a matrix platform using Flory-Huggins theory and FH lattice theory to confirm miscibility and reduced crystallinity of PEO, which accommodated amorphous BL at drug to polymer loadings up to 2:10.
TL;DR: In this article, the meso-dynamics of polypropylene (PP)/polyamide-11 (PA11) blends were investigated by atomistic molecular dynamics (MD) and mesoscopic dynamics simulations.
TL;DR: In this article, the influence of both bulk supercooling and cooling rate on the microstructure and phase selection during solidification of Cu-Co, CuCo-Fe, and Cu-Nb alloys exhibiting metastable liquid miscibility gaps were investigated using scanning electron microscopy, X-ray diffraction, and transmission electron microscope.
Abstract: The influence of both bulk supercooling and cooling rate on the microstructure and phase selection during solidification of Cu–Co, Cu–Co–Fe, and Cu–Nb alloys exhibiting metastable liquid miscibility gaps were investigated using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Containerless electromagnetic levitation was used to achieve large bulk supercoolings in the specimens. Supercooling of these alloys below a certain temperature resulted in metastable separation of the melt into two liquids, a Cu-lean (Co, Co + Fe, or Nb enriched) melt (L1) and a Cu-rich melt (L2). Usually, the microstructure of the phase-separated alloys consisted of spherulites corresponding to one of the phase-separated liquids embedded in a matrix corresponding to the other. The microstructure and phase selection are found to depend on factors such as: alloy composition, supercooling level, whether the material was dropped before or after recalescence, and the cooling rate during solidification. The following results were observed: (1) solidification of metastable e-Cu with enhanced Co (or Co + Fe, or Nb) solubility; (2) partitionless solidification of the L1 and L2 liquids; (3) spinodal decomposition of the supercooled liquid, and (4) secondary melt separation. The results are discussed and related to current solidification theories regarding solidification paths for the different conditions examined. The miscibility gap boundaries for the different alloys were determined and compared with those reported in the literature.
TL;DR: In this article, the authors investigated the compatibility between PHBV and PLA polymers and found that the PHV/PLA blends were immiscible due to different stereo configuration of PLA polymer and two distinct melting temperatures.
Abstract: An important strategy used in the polymer industry in recent years is blending two bio-based polymers to attain desirable properties similar to traditional thermoplastics, thus increasing the application potential for bio-based and bio-degradable polymers. Miscibility of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with poly(L-lactic acid) (PLA) were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Three different grades of commercially available PLAs and one type of PHBV were blended in different ratios of 50/50, 60/40, 70/30, and 80/20 (PHBV/PLA) using a micro-compounder at 175°C. The DSC and TGA analysis showed the blends were immiscible due to different stereo configuration of PLA polymer and two distinct melting temperatures. However, some compatibility between PHBV and PLA polymers was observed due to decreases in PLA's glass transition temperatures. Additionally, the blends do not show clear separation by SEM analysis, as observed in the thermal analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
TL;DR: In this article, phase diagrams of V-Nb, V-Ta, and Nb-Ta alloys are computed by combining the total energies of 40-50 configurations for each system (obtained using density functional theory) with the cluster expansion and Monte Carlo techniques.
Abstract: In this paper, we report the calculated phase diagrams of V-Nb, V-Ta, and Nb-Ta alloys computed by combining the total energies of 40–50 configurations for each system (obtained using density functional theory) with the cluster expansion and Monte Carlo techniques. For V-Nb alloys, the phase diagram computed with conventional cluster expansion shows a miscibility gap with consolute temperature T_c=1250 K. Including the constituent strain to the cluster expansion Hamiltonian does not alter the consolute temperature significantly, although it appears to influence the solubility of V- and Nb-rich alloys. The phonon contribution to the free energy lowers T_c to 950 K (about 25%). Our calculations thus predicts an appreciable miscibility gap for V-Nb alloys. For bcc V-Ta alloy, this calculation predicts a miscibility gap with T_c=1100 K. For this alloy, both the constituent strain and phonon contributions are found to be significant. The constituent strain increases the miscibility gap while the phonon entropy counteracts the effect of the constituent strain. In V-Ta alloys, an ordering transition occurs at 1583 K from bcc solid solution phase to the V_(2)Ta Laves phase due to the dominant chemical interaction associated with the relatively large electronegativity difference. Since the current cluster expansion ignores the V_(2)Ta phase, the associated chemical interaction appears to manifest in making the solid solution phase remain stable down to 1100 K. For the size-matched Nb-Ta alloys, our calculation predicts complete miscibility in agreement with experiment.
TL;DR: In this article, a simple lattice-based equation of state was applied to search for patterns in a large sample of experimental blend, which revealed new correlations revealed by their study of polymer mixture miscibility.
Abstract: We present new correlations revealed by our study of polymer mixture miscibility. Applying our simple lattice-based equation of state, we search for patterns in a large sample of experimental blend...
TL;DR: The aerogel formation occurs only in the presence of semicrystalline nanofibrils of syndiotactic polystyrene, a polymer presenting molecular miscibility with polyphenyleneoxide in the amorphous phase as discussed by the authors.
Abstract: Monolithic and robust aerogels exhibiting nanoporous–crystalline modifications of an industrially relevant polymer (poly(2,6-dimethyl-1,4-phenylene)oxide, generally known as polyphenyleneoxide, PPO), have been obtained from thermoreversible gels, by sudden solvent extraction with supercritical carbon dioxide. The aerogel formation occurs only in the presence of semicrystalline nanofibrils of syndiotactic polystyrene, a polymer presenting molecular miscibility with PPO in the amorphous phase. These mixed monolithic aerogels can present nanoporous–crystalline phases of both polymers and hence are very promising for water and air purification. For instance, the carbon tetrachloride uptake from 10 ppm aqueous solutions can be as high as 19 wt%.
TL;DR: Analysis and spectral deconvolution revealed composition and miscibility dependent variations in the strength of drug-polymer intermolecular H-bonding and solution state interactions data such as PVP globular size distribution and solution infrared spectral profiles showed substantial processing method dependence.
Abstract: In this work, we investigated the relationship between various intermolecular hydrogen-bonding (H-bonding) interactions and the miscibility of the model hydrophobic drug naproxen with the hydrophilic polymer polyvinylpyrrolidone (PVP) across an entire composition range of solid dispersions prepared by quasi-equilibrium film casting and nonequilibrium melt quench cooling. The binary phase behavior in solid dispersions exhibited substantial processing method dependence. The solid state solubility of crystalline naproxen in PVP to form amorphous solid dispersions was 35% and 70% w/w naproxen in solution-cast films and quench-cooled films, respectively. However, the presence of a single mixed phase glass transition indicated the amorphous miscibility to be 20% w/w naproxen for the films, beyond which amorphous–amorphous and/or crystalline phase separations were apparent. This was further supported by the solution state interactions data such as PVP globular size distribution and solution infrared spectral pro...
TL;DR: There seems to be a dynamic factor to separate drug phase from the excipient phase, depending on their molecular weight and miscibility during the electrospray deposition process, with emphasis on the miscibility between drug and excipient.
TL;DR: In this article, X-ray diffraction (XRD), infrared spectroscopy (FT-IR) and viscometry measurements showed that the two polymers can form miscible blends.
TL;DR: In this article, a new kind of homogeneous cation exchange membrane was prepared for new applications by blending polyvinylidene fluoride (PVDF) and sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO).
TL;DR: In this paper, the ability of water miscible ionic liquids to build aqueous two-phase systems for the separation of 1,3-propanediol from water is investigated.
TL;DR: In this article, the miscibility and mechanical properties of isotactic polypropylene (iPP) and olefin block copolymer (OBC) blends were examined.
Abstract: This study examines the miscibility and mechanical properties of isotactic polypropylene (iPP) and olefin block copolymer (OBC) blends (70/30 wt %). The blends exhibit phase-separated morphology. The OBC do- main size decreases with increasing the 1-octene content in the soft segment. The crystallization, melting behavior, and the long spacing of the iPP component in the blends are nearly the same as those of neat iPP, while the Tg of the iPP component shifts slightly to lower temperature. ''Blocky'' OBC is immiscible with iPP, while the soft seg- ment rich polymers in OBC could be partially miscible with iPP. The impact strength of the blends is greatly increased with increasing the 1-octene content in the OBC soft segment. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 125: 666-675, 2012
TL;DR: The phase separation and the intermolecular interactions of a series of extruded plasticised starch (PlS)/polyvinyl alcohol (PVOH) blends with various starch to PVOH ratios has been studied in this article.
TL;DR: In this article, an extraction method was used to optimize the miscibility of supercritical water (SCW) with asphaltene (AS) at 400-450°C and 20-35 MPa.
Abstract: An extraction method was used to optimize the miscibility of supercritical water (SCW) with asphaltene (AS) at 400–450 °C and 20–35 MPa. The optimal temperature for the determination was 440 °C due to the improved balance between solubility and the coking rate. With increasing the pressure at 440 °C, the degradative extraction yield of AS using SCW reached a maximum at around 30 MPa. The extraction behavior was thought to be controlled mainly by the water properties represented by the dielectric constant (DC) and Hansen solubility parameter (HSP). These properties affected the miscibility with AS and consequently the extraction yield. As a result, the optimal water properties to achieve the highest miscibility with AS were DC = 2.2, δp = 6.4, and δh = 9.7.