Phase Diagram Of Poly Research Articles

Comparison of skyrmion phases between poly- and single-crystal MnSi by composite magnetoelectric method

We have explored the skyrmion phases and phase diagram of poly- and single-crystal MnSi by the measurements of the magnetoelectric coefficient αE and ac magnetic susceptibility of the MnSi/0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 composite. We found that the regular skyrmion lattice phase in the single-crystal sample has been averaged in the MnSi polycrystal due to random grain orientations, which results in an extended skyrmion lattice-conical mixture phase down to 25 K. The magnitude of the out-of-phase component in αE of the polycrystal, not single crystal, decreases gradually with decreasing frequency. With the changing of the driven ac field, we reveal a depinning threshold behavior in both samples. The depinning field is stronger in the polycrystal than that in the single crystal and may be responsible for the diminishing of the dissipative behavior at lower frequency due to grain boundaries and defects. The composite magnetoelectric method provides a unique approach to probe topological phase dynamics.

Phase transitions of poly(oligo(ethylene glycol) methyl ether methacrylate)-water systems

The phase diagrams for poly (oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) hydrogels with varying side chain lengths over broad temperature and composition ranges are shown for the first time. It is also shown that the ability of water to crystallize is strictly correlated with the occurrence of a volume phase transition in hydrogels, as both phenomena require the continuous water pathways in the system. A discontinuity in the water phase appears above wp = 0.83 for PMEO2MA and wp = 0.56 for other POEGMAs. In contrast to PMEO2MA, POEGMA hydrogels with longer oligoether chains are characterized by two distinct regimes for the glass transition as a function of polymer content. It was also confirmed that crystallization of the polymer network can be observed for POEGMA networks with suitably long oligoether chain lengths, namely, n ≥ 7. Moreover, the range of the polymer crystalline phase occurrence was found to increase with the length of the oligoether chain.

Phase diagram of poly(VDF-ter-TrFE-ter-CTFE) copolymers: Relationship between crystalline structure and material properties

Depending on their CTFE content (from 0 to 10 mol %), poly(VDF-ter-TrFE-ter-CTFE), poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene) copolymers, exhibit ferroelectric (FE) or relaxor ferroelectric (RFE) properties at room temperature. Solvent cast films of these terpolymers can crystallize in three orthorhombic phases: FE, DFE (Defective Ferroelectric) or RFE according to their amount of CTFE. The relative amount of each crystalline phase depends on the amount of CTFE and evolves after annealing. We study the dependence of the electric displacement−electric field (D−E) loop with the amount of CTFE and with annealing step. We observed a closely link between the remnant polarization, PR, and the fraction of (FE + DFE) crystalline phase. Macroscopic properties, studied using thermo-mechanical experiments (DSC and DMA) and dielectric spectroscopy, evolve continuously with the CTFE amount and are well correlated with the structural properties. Finally, a temperature versus mol% CTFE phase diagram is established and discussed in relation-ship with material properties.

Phase Behavior and Phase Diagram of Polystyrene-b-Poly(Perfluorooctylethyl Acrylates).

Fluorocontaining polymers bearing special properties are unique and important materials in modern society. In this work, we focused on the phase behavior and phase diagram of poly(styrene-block-perfluorooctylethyl acrylate) with a volume fraction varying from 0.2 to 0.8. Small-angle X-ray scattering and transmission electron microscopy showed the phase formation in the sequence of hexagonally packed cylinders (HEX) to lamellar layers (LAM) to inverse hexagonally packed cylinders (iHEX) in this series of block polymers. Wide-angle X-ray diffraction experiments proved that the fluorodomains of the LAM phases and the matrix of iHEX phases contained layered structures formed by the crystallization of fluorosegments. During heating, the self-assembled lattice remained intact even after the melting of fluorodomain, with barely changed lattice parameters. Such hierarchical structural formation was understood by chain conformation and domain interaction, which may provide new insight into the molecular design of advanced materials.

Spherical nanoparticle effects on the lower critical solution temperature phase behavior of poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends: Separation of thermodynamic aspects from kinetics

ABSTRACTThe effects of spherical nanosilica particles on the lower critical solution temperature (LCST) phase diagram of poly(ε‐caprolactone) (PCL)/poly(styrene‐co‐acrylonitrile) (SAN) blends are investigated by using isochronal dynamic temperature sweep tests at different cooling rates. A stronger dependency of the rheologically determined phase‐transition points on the cooling rate is observed in the presence of nanoparticles, which results from the large contribution of entropic surface tension of chains in the Gibbs free energy of mixing and much slower rate of PCL/SAN phase dissolution. By alleviating the effects of kinetic factors, it is found that the drop in the LCST‐type phase boundary of PCL/SAN blends by adding nanofiller is more apparent than real. However, the closest LCST phase diagram to the real steady‐state thermodynamic diagram shows an unexpected shift to lower temperatures by adding nanosilica. The migration of nanosilica particles to the SAN domains especially at lower cooling rates in the dynamic measurements is the most likely explanation of these observations. The findings that prove the profound impact of kinetic factors in dynamic temperature measurements are reached in a hybrid system, wherein the SAN chains are preferentially absorbed on the surface of a nanofiller having very small primary particle size. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48679.

Effects of molecular complexation on phase equilibria in mixtures of urea/polyethylene glycol derivatives and electrochemical performance of urethane based polymer electrolyte membranes for solid-state lithium ion battery

Phase diagram approach has been extended to the determination of phase diagram of a binary pair of urea with polyethylene glycol (PEG) in order to providence guidance to the formulation window of isotropic polymer electrolyte membranes (PEMs) with emphasis on the electrochemical performance. Effect of molecular weight of PEG on solid-liquid phase diagrams of its mixtures with urea has been demonstrated experimentally and theoretically. The observed change of eutectic, immiscibility loop, azeotrope type phase diagrams with increasing PEG molecular weight (or decreasing chain-ends) has been analyzed in the context of the combined Flory-Huggins (FH) theory of liquid-liquid demixing and phase field (PF) theory of crystal solidification. This rich phase behavior has been captured via the variation of crystalline-crystalline interaction strength of the combined FH-PF free energies. Subsequently, the phase diagram of poly (ethylene glycol) diacrylate (PEGDA)/urea was constructed in the framework of the aforementioned FH-PF theory. The incorporation of urea not only dissociates lithium cation from its salt, but also enhances the ionic conductivity of urea-modified polymer electrolytes dramatically. However, small molecule hydrophilic urea was found to be electrochemically unstable in the charge/discharge cycling test. To alleviate such shortcoming, urea (or urethane) linkage was imparted into the network chains by synthesizing PEG-bis(carbamate dimethacrylate) (PEGBCDMA) and subsequently photopolymerizing in the presence of SCN plasticizer and LiTFSI salt to afford the ion conductive PEM network. The as-synthesized PEGBCDMA based PEM consisting of PEGBCDMA/SCN/LiTFSI (20/40/40 ratio by weight) turned out to be completely amorphous and transparent before and after photo-crosslinking. The incorporation of urethane linkages in the PEM network exhibited enhanced ionic conductivity, improved thermal stability, and superior tensile properties with improved capacity retention during charge/discharge cycling, suggesting potentials for application in solid-state lithium ion battery.

Influence of the molecular weight of polymer, temperature and pH on phase diagrams of poly (ethylene glycol) + di-potassium tartrate aqueous two-phase systems

Phase diagrams and liquid – liquid equilibrium (LLE) data for aqueous two-phase systems (ATPSs) containing di-potassium tartrate (DPT) and poly (ethylene glycols) (PEG) (1500 and 6000) have been determined experimentally at different pH values (6.41, 7.74 and 9.05) and temperatures (298.15 and 308.15 K). The effect of molecular weights of the PEG, temperatures, and pH on the binodal curve, tie-line length (TLL) and slope of tie line (STL) was studied. It was found that an increasing in PEG molecular weight, temperature and pH led to the binodal curve displacement towards the origin and increasing two-phase region. Accordingly, the various empirical equations were used to correlate the binodal curves of these systems such as Merchuk equation and Pirdashti equation and the tie-line compositions were correlated using Guan equation. Also, the refractive index and density of ternary (PEG 1500/6000 + di-potassium tartrate (DPT) + water) system have been measured. The density and refractive index were employed as the physical properties to obtain the phase composition and the tie-lines ends and show a linear variation with mass fraction of the polymers and the salt. Also, it was found that TLL affects the density of ATPS. The density difference between the phases (Δρ) increased with an increment in the TLL and pH values and PEG molecular weights and temperatures. Finally, the salting-out ability of the systems were explained by using “Effective Excluded Volume (EEV) model”.

Alkyl side chain length dependent compatibility of poly(4‐n‐alkylstyrene)s and 1,4‐rich polyisoprene blends

ABSTRACTWe investigated the compatibility of blends of 1,4‐rich polyisoprene (1,4‐PI) and poly(4‐n‐alkylstyrene)s with six kinds of n‐alkyl side groups, that is, methyl, ethyl, propyl, butyl, hexyl, and octyl focusing on carbon number of alkyl groups. Poly(4‐methylstyrene)/1,4‐PI blend was turned out to be immiscible at all temperature range adopted in this work and poly(4‐ethylstyrene)/1,4‐PI blend revealed UCST type phase behavior, while the others were found to be compatible. The phase diagrams of poly(4‐ethylstyrene)/1,4‐PI blends were obtained by optical microscopy, and the temperature dependence of the Flory‐Huggins interaction parameter χ has been estimated to be χ = −0.036 + 24/T by applying lattice theory, where T is the absolute temperature. From this relationship χ value at room temperature (298 K) was calculated to be 0.045, the value is reasonably low for miscible polymers system. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1791–1797

Nonlinear depression of the lower critical solution temperatures in aqueous solutions of thermo‐sensitive random copolymers

ABSTRACTWe develop a theoretical model of cooperative hydration to clarify the molecular origin of the observed nonlinear depression of the lower critical solution temperature (LCST) in the aqueous solutions of thermosensitive random copolymers and find the monomer composition at which LCST shows a minimum. Phase diagrams of poly(N‐isopropylacrylamide‐co‐N,N‐diethylacrylamide) copolymer solutions are theoretically derived on the basis of the theory of cooperative hydration by introducing the microscopic structure parameter η which characterizes the distribution of the monomer sequences along the chains. We compared them with the experimental data of LCST of random copolymers with various monomer compositions and also of the diblock copolymers with equimolar monomer composition. The transition temperature shifts to lower than those of homopolymer counterparts when the monomer sequence of the chains has an alternative tendency. On the contrary, for the blocky polymers such as diblock copolymers, the transition temperature remains almost the same as those of the homopolymers. Thus, the nonlinear effect in phase separation appears when the average block length of the copolymers is shorter than the average sequence length of the cooperative hydration. The degree of hydration is calculated as a function of the temperature and polymer concentration for varied distribution of the copolymer compositions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1112–1123

Poly(vinylidene fluoride)–acrylic rubber partially miscible blends: Phase behavior and its effects on the mechanical properties

A phase diagram of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) was plotted, and the effects of the extent of miscibility on the mechanical properties of the polymer blends were examined. A compressible, regular solution model was used to forecast the phase diagram of this blend. The model prediction, the lower critical solution temperature (LCST) over the upper critical solution temperature (UCST), was done qualitatively according to the experimentally determined phase diagram by differential scanning calorimetry (DSC), optical microscopy, and rheological analysis. These experimental methods showed that this system was miscible in ACM‐rich blends (>50% ACM) and partially miscible in PVDF‐rich blends. A wide‐angle X‐ray diffraction study revealed that PVDF/ACM blends such as neat PVDF had a characteristic α‐crystalline peak. The partially miscible blends displayed up to 350% elongation at break; this was a significant increment of this parameter compared to that of neat PVDF(20%). However, the miscible blends showed elongation of up to 1000% [again, a remarkable increase compared to chemically crosslinked ACM (220%)] and displayed excellent mechanical properties and tensile strength and a large elongation at break. For the miscible and partially miscible blends, two different mechanisms were responsible for this improvement in the mechanical properties. It was suggested that in the partially miscible blends, the rubbery depletion layer between the spherulite and the conventional rubber cavitations mechanism were responsible for the increase in the elongation at break, whereas for the miscible blends, the PVDF spherulite acted as a crosslinking junction. The stretched part of the tensile samples in the partially miscible blends showed characteristic β‐crystalline peaks in the Fourier transform infrared spectra, whereas that in the miscible blends showed α‐crystalline peaks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1247‐1258, 2013

Plasmid DNA partitioning and separation using poly(ethylene glycol)/poly(acrylate)/salt aqueous two-phase systems

Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coli can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coli homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60–70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH.

Extractive bioconversion of xylan for production of xylobiose and xylotriose using a PEG6000/sodium citrate aqueous two-phase system

Aqueous two-phase system (ATPS) was applied for extraction bioconversion of xylan by xylanase from Trichoderma viride. Phase diagrams for poly (ethylene glycol) (PEG) and sodium citrate were determined at room temperature. The ATPS composed of 12.99% (w/w) PEG6000 and 12.09% (w/w) sodium citrate was favorable for partition of xylanase and used for extraction bioconversion of xylan. Batch hydrolysis demonstrated that higher concentrations of xylobiose and xylotriose were obtained in the PEG6000/sodium citrate ATPS compared to those in the aqueous system. These results present the potential feasibility of production of xylo-oligosaccharides by extraction bioconversion in ATPS.

Phase diagrams of poly(ethylene‐co‐vinyl alcohol) and dimethylformamide solutions exhibiting both liquid–liquid and solid–liquid phase separation

AbstractThe binary solutions of poly(ethylene‐co‐vinyl alcohol) (EVOH), with 38 and 32 wt % ethylene content, and N,N‐dimethylformamide were submitted to experiments to determine the cloud temperature by optical microscopy and the dynamic crystallization temperature by differential scanning calorimetry (DSC). The thermally induced phase separation (TIPS) process was used with the EVOH/DMF solutions that showed liquid–liquid phase separation at temperatures higher than EVOH crystallization and with a decrease of the temperature‐UCST behavior. The binary interaction model was applied to estimate the interaction energy densities (B) considering both intermolecular (ethylene‐Et/DMF and vinyl alcohol‐VA/DMF) and intramolecular (Et/VA) interactions. According to this model the liquid–liquid line for the EVOH‐38/DMF solutions should be situated at higher temperatures in comparison with EVOH‐32/DMF solutions. Moreover, the phase separation results from low affinity between the hydrophobic segments of EVOH and the segments of the copolymer containing hydroxyl or the solvent. The equilibrium melting temperature of EVOH increases with the increase of EVOH volume fraction in the solution. This effect is more pronounced for EVOH‐32/DMF solutions, which means that there is an influence of the VA content in EVOH during the melting. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Selective solubility of E7 components in poly (n-butylacrylate)

Recently, the phase diagram of poly (n-butyl acrylate) and the nematic liquid crystal (LC) mixture E7 has revealed an anomalous behaviour that was attributed to the multicomponent nature of the LC which is made of four cyanoparaphenylenes. The anomalous emergence of a nematic phase at relatively low LC concentration above 60∘C cannot be rationalized in terms of standard meanfield models commonly used to calculate phase diagrams of analogous systems. It was then suspected that the only possibility to explain this observation is to invoke the hypothesis of a selective solubility of the LC components with respect to the polymer. A detailed analysis of the composition of the LC within droplets as a function of the E7 concentration in the samples was made by HPLC. The corresponding measurements indicate unambiguously that E7 undergoes a phase separation in the presence of poly (n-butylacrylate) and exhibits a selective miscibility that is reminiscent of the preferential solvation phenomenon. HPLC chromatograms exhibit peaks that correspond to the four single compounds included in the E7 mixture and can precisely identify those present in the sample droplets. We find that both nature of components and composition depend upon samples under consideration. The overall analysis of data enables us to understand the anomalies revealed by the complete phase diagram obtained by polarized optical microscopy (POM).

Phase Diagram of P3HT/PCBM Blends and Its Implication for the Stability of Morphology

In this work, the phase diagram of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends is measured by means of standard and modulated temperature differential scanning calorimetry. Blends were made by solvent-casting from chlorobenzene, as blends cast from toluene or 1,2-dichlorobenzene prove to retain effects of phase segregation during casting, hindering the determination of the phase diagram. The film morphology of P3HT/PCBM blends cast from chlorobenzene results from a dual crystallization behavior, in which the crystallization of each component is hindered by the other component. A single glass transition is observed for all compositions. The glass transition temperature (Tg) increases with increasing concentration of PCBM: from 12.1 degrees C for pure P3HT to 131.2 degrees C for pure PCBM. The observed Tg defines the operating window for the thermal annealing and explains the long-term instability of both the morphology and the photovoltaic performance of the P3HT/PCBM solar cells.

A new polymerization method and kinetics for acrylamide: Aqueous two‐phase polymerization

AbstractThe concept of aqueous two‐phase polymerization and a new polymerization method for the preparation of water‐soluble polymers are presented. The phase diagram of poly(acrylamide) (PAAm)‐poly (ethylene glycol) (PEG)‐water two‐phase system was measured by the gel permeation chromatography (GPC). The aqueous two‐phase of PAAm‐PEG‐water system can be easily formed. The critical concentration of phase separation was affected by the molecular weight of PEG. The aqueous two‐phase polymerization of acrylamide (AAm) has been successfully carried out in the presence of PEG by using ammonium persulfate (APS) as the initiator. The polymerization behaviors with varying concentration of AAm, initiator and PEG, the polymerization temperature, the molecular weight of PEG, and emulsifier types were investigated. The activation energy of aqueous two‐phase polymerization of AAm was 132.3 kJ/mol. The relationship of initial polymerization rate (Rp0) with APS and AAm concentrations was Rp0 ∝ [APS]0.72 [AAm]1.28. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Phase Diagram of Poly(ethylene oxide) and Poly(propylene oxide) Triblock Copolymers in Aqueous Solutions

The phase behavior of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers in aqueous solutions is studied by using a self-consistent-field theory. The spectral method is extended to polymer models with internal degrees of freedom. Phase diagrams of PEO−PPO−PEO and PPO−PEO−PPO triblock copolymers in water are constructed in the concentration−temperature space. A variety of lyotropic liquid crystalline phases is found. The effects of temperature, copolymer concentration, the block (EO/PO) ratio and the chain architecture are investigated. Good agreements were found between experimental results and theory.

Polyphosphazene microspheres: Preparation by ionic complexation of phosphazene polyacids with spermine

AbstractPolyphosphazene polyacids are potent immunostimulating compounds. Formulation of these water‐soluble macromolecules into a microparticulate form can extend their utility in vaccine delivery applications. A simple method for the preparation of microspheres and nanospheres using polyphosphazene polyacids is reported. The key element of the process is ionic complexation of polyphosphazenes in aqueous solutions with physiologically occurring amines, such as spermine. A phase diagram of poly[di(carboxylatophenoxy)phosphazene] (PCPP)–spermine–water system is established, which shows an extensive area of microsphere formation. Microsphere size distribution is studied as a function of reaction conditions and concentrations of reactants. This method can be applied to polyphosphazene polyacids containing carboxylic acid and sulfonic acid functionalities and can be used for protein encapsulation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 414–419, 2006

The phase diagram of poly(4-hydroxybenzoic acid) and poly(2,6-hydroxynaphthoic acid) and their copolymers from X-ray diffraction and thermal analysis

Homopolymers and copolymers of 4-hydroxybenzoic acid (HBA) and 2,6-hydroxynaphthoic acid (HNA) have been studied with differential scanning calorimetry and temperature-resolved wide angle X-ray diffraction. All polymers have more than one disordering transition between the glass transition (between 400 and 430K) and decomposition (between 710 and 750K). The first transition in PHBA at 616–633K is from orthorhombic rigid crystals to a conformationally disordered pseudo-hexagonal phase (condis phase). The two higher transitions are first, a further disordering process to a hexagonal condis crystal, and then a change to an anisotropic melt (liquid crystal) at about 800K, with increasing decomposition above 750K. In PHNA, orthorhombic crystals change above 600K to an orthorhombic condis crystal structure, which go to an anisotropic melt at 750K, and subsequent decomposition. In addition, using empirical entropy rules that account for the changes during the transitions from the crystal to the disordered mobile phases, an effort is made to understand the disorder and mobility, and to arrive at a non-equilibrium phase diagram of the copolymer system. The existence of a single, but up to 200K wide, glass transition and remaining high crystallinity of the copolyesters, indicate partial solubility of the repeating units in all phases. The new data are compared to and brought into agreement with the large number of prior measurements and often unclear interpretations.

Conformational phase diagram of poly(l-lysine) in sodium alkanesulfonate aqueous solutions at various temperatures

The conformation of poly(l-lysine) (PLL) was investigated in sodium alkanesulfonate CnSO3Na (n=8, 7) at various temperatures by circular dichroism spectrum measurements. C8SO3Na induced a double-step conformational change from a coil, to a β-sheet, and then to an α-helix, in which C7SO3Na induced a single-step coil-to-helix conformational change. Binding isotherms of C8SO3Na by PLL were constructed from the potentiometry of equilibrium concentration of the surfactant using a surfactant ion-selective electrode. The curves indicated the cooperative binding characteristic and were analyzed by a linear lattice model using the Bethe approximation. The thermodynamic parameters obtained from the model revealed that the binding of C8SO3Na by PLL was an entropy-driven process. The conformational change was observed at nearly full binding, presumably due to the surfactant clustering of the ordered conformation.