Kinetics of thermally induced phase separation in ternary polymer solutions. I. Modeling of phase separation dynamics

Simulations based on Cahn–Hilliard spinodal decomposition theory for phase separation in thermally quenched polymer/solvent/nonsolvent systems are presented. Two common membrane‐forming systems are studied, cellulose acetate [CA]/acetone/water, and poly(ethersulfone) [PES]/dimethylsulfoxide [DMSO]/water. The effects of initial polymer and nonsolvent composition on the structure‐formation dynamics are elucidated, and growth rates at specific points within the ternary phase diagram are quantified. Predicted pore growth rate curves exhibit a relative maximum with nonsolvent composition. For shallow quenches (lower nonsolvent content) near a phase boundary, the pore growth rate increases with increasing quench depth, whereas for deep quenches, where the composition of the polymer‐rich phase approaches that of a glass, the pore growth rate decreases with increasing quench depth. With increasing initial polymer concentration, the overall rate of structure growth is lowered and the growth rate maximum shifts to higher nonsolvent compositions. This behavior appears to be a universal phenomenon in quenched polymer solutions which can undergo a glass transition, and is a result of an interplay between thermodynamic and kinetic driving forces. These results suggest a mechanism for the locking‐in of the two‐phase structure that occurs during nonsolvent‐induced phase inversion. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1449–1460, 1999     

Synthesis and characterization of side-chain liquid crystal polyurethanes

A series of liquid crystal α-[bis(2-hydroxyethyl)amino]-ω-(4-nitroazobenzene-4′-oxy)alkanes (Cn-diol) with different alkyl chain length has been synthesized. All Cn-diols exhibit a smectic phase that has been identified by means of polarizing microscopy and differential scanning calorimetry. These compounds are suitable monomers for the synthesis of side-chain liquid crystalline polyurethanes and polyesters. They were polymerized with hexamethylene diisocyanate to corresponding SCLC polyurethanes in which the spacer length was varied from 2 to 12 methylene units. Polyurethanes (CnP) with spacer lengths n ≥ 4 exhibited liquid crystalline behavior. Fourier transform infrared temperature studies of the CnP were done focusing on H-bonds between the N H and CO groups of the urethane backbone. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2871–2888, 1997     

Gas transport properties of soluble poly(phenylene sulfone imide)s

Gas transport of helium, hydrogen, carbon dioxide, oxygen, argon, nitrogen, and methane in three soluble poly(phenylene sulfone imide)s based on 2,2-bis(3,4-decarboxyphenyl) hexafluoropropane dianhydride (6FDA) has been investigated. The effects of increasing length of well-defined oligo(phenylene sulfone) units on the gas permeabilities and diffusivities were determined and correlated with chain packing of the polymers. Activation energies of diffusion and permeation were calculated from temperature-dependent time-lag measurements. The influences of the central group in the diamine moiety of 6FDA-based polyimides on physical and gas transport properties are discussed. The incorporation of a long oligo(phenylene sulfone) segment in the polymer backbone decreases gas permeability and permselectivity simultaneously. The decreases in permeability coefficients can be mainly related to decreases in diffusion coefficients. Changing the central group of diamine moiety from  S to  SO₂ leads to a 45–50% decrease in CO₂ and O₂ permeabilities without appreciable increase in the selectivities. This is considered to be due to the formation of charge transfer complexes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1855–1868, 1997     

Effect of chain stiffness on the morphology of diblock copolymer melts

The authors have studied the microphase separation of symmetric diblock copolymers with variable block stiffness and different block chain lengths using coarse-grained molecular dynamics simulations. The simulation results show that for symmetric diblock copolymers, a combination of chain length and relative stiffness between the blocks may play the major role in determining the equilibrium morphology of the system. When the variation in stiffness between blocks is small, the equilibrium morphology of the diblock system is found to be lamellar; this is also the case for systems with small chain lengths, regardless of the difference in block stiffness. However, in systems with longer chains with modest variation in stiffness between the blocks, an ordered cylindrical phase is formed in which the stiffer blocks form cylinders completely surrounded by the flexible components. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2556–2565, 2009     

Improved binary parameters using GA for multi-component aromatic extraction: NRTL model without and with closure equations

Application of genetic algorithm (GA), which leads to globally optimal binary interaction parameters from multi-component liquid–liquid equilibrium data, has been recently demonstrated for some ternary, quaternary and quinary systems. The binary interaction parameters are related to each other through the closure equations. In this work, the binary interaction parameters based on non-random two liquid (NRTL) activity coefficient model have been estimated using GA, without and with closure equations for 65 multi-component aromatic extraction systems: 53 ternary, 9 quaternary and 3 quinary systems. Parameters that satisfy the closure equations exhibit better root mean square deviations than those that do not satisfy the closure equations. Root mean square deviation value without implementation of closure equations is 0–80% better than literature as compared to 0–90% better with implementation of closure equations.     

Coil-to-globule transition by dissipative particle dynamics simulation

The dynamics of a collapsing polymer under a temperature quench in dilute solution is investigated by dissipative particles dynamics. Hydrodynamic interactions and many-body interaction are preserved naturally by incorporating explicit solvent particles in this approach. Our simulation suggests a four-stage collapse pathway: localized clusters formation, cluster coarsening in situ, coarsening involving global backbone conformation change into a crumpled globule, and compaction of the globule. For all the quench depths and chain lengths used in our study, collapse proceeds without the chain getting trapped in a metastable "sausage" configuration, as reported in some earlier studies. We obtain the time scales for each of the first three stages, as well as its scaling with the quench depths ξ and chain lengths N. The total collapse time scales as τ(c) ～ ξ(-0.46 ± 0.04)N(0.98 ± 0.09), with the quench depth and degree of polymerization.     

Phase behavior of ABC-triblock copolymers with two inherently miscible blocks

 The phase behavior of ternary poly-1,4-isoprene-block-poly-1,2-butadiene-block-polystyrene (ABC) triblock copolymers based on a compatible diblock copolymer attached to an incompatible C-block of different lengths is investigated by differential scanning calorimetry, transmission electron microscopy and dynamic mechanical analysis. It is shown that the system behaves like a binary diblock copolymer of a mixed AB-block and a microphase separated C-block. Received: 10 June 1997 Accepted: 19 August 1997     

Scaling analysis of the temperature dependence of intrinsic viscosity

The scaling predictions for the temperature dependence of the intrinsic viscosity of flexible polymers are briefly reviewed. When the predictions are fit to a power law over a fixed range of chain length, a relation between the exponent and prefactor of the Mark–Houwink–Sakurada equation emerges. In comparing with the experimental data compilation of Rai and Rosen, we conclude that real polymer systems are nowhere near the true good solvent limit, even when the exponent matches the good solvent prediction. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1989–1991, 1997     

Morphology and properties of cyanate ester/liquid polyurethane/silica nanocomposites

The high‐speed homogeneous shearing method was applied to prepare nanocomposites of cyanate ester (CE) with liquid polyurethane elastomer (PUR) and silica. To investigate the influence of various components on the morphology and properties of the ternary composites, the binary composites of CE/PUR and CE/silica were also involved in this article. The morphology of the cured materials of binary and ternary systems was investigated by transmission electron microscopy (TEM), and the results show that silica nanoparticles were uniformly distributed in the ternary and binary matrix. Phase separation of elastomer in composites was not observed by TEM. FTIR test and dynamic mechanical analysis (DMA) proved that chemical linking was existent between PUR and CE. Scanning electron microscopy examinations and mechanical properties tests were carried out. The results show that ternary composites displayed higher fracture toughness and impact strength compared with most of the binary systems. This suggests that the addition of PUR and nanosilica can synergistically improve the toughness of CE. DMA studies confirmed that the incorporation of silica can increase the storage modulus and T_g for CE and CE/PUR system, since there are a good adhesion and a strong hydrogen bonding between silica and polymers. The thermal property of ternary composites increases with the increase of silica nanoparticle loading. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1243–1251, 2008     

Molecular weight distribution in nonlinear emulsion polymerization

A modelistic study of the molecular weight distribution (MWD) formed in emulsion polymerization that involves chain transfer to polymer is conducted, by focusing our attention to the effect of very small reaction volume on the formed MWD. In emulsion polymerization, a polymer radical that causes polymer transfer reaction must choose the partner only within the same particle, which makes the expected size of the polymer molecule to be chosen smaller compared with the corresponding polymerization system that involves an infinitely large number of polymeric species. The usual assumption for homogeneous polymerization that the rate of chain transfer to a particular polymer molecule is proportional to its chain length cannot be used, except when branching frequency is low and particle size is large enough. This fact invalidates the direct use of models developed for homogeneous nonlinear polymerizations to emulsion polymerizations. Model equations that could be used to assess the significance of the limited space effects on the MWD under a given polymerization condition are also proposed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1515–1532, 1997     

Dynamic scattering properties of mixtures of cyclic and linear homopolymers and copolymers

The dynamic scattering properties of mixtures of cyclic copolymers and homopolymers are discussed. These properties are compared with those characterizing linear chain mixtures in similar conditions. The differences between cyclic and linear chains are introduced through the form factors only. The interaction parameter between different monomer species are assumed to be the same whether they belong to cyclic or linear chains. The dynamical model is based upon a generalization of the random phase approximation neglecting hydrodynamic interaction and mode coupling effects. Despite these simplifications, substantial differences are found in the dynamics of mixtures containing cyclic copolymers and homopolymers when compared to those of linear chain systems in similar conditions of temperature, concentration, and molecular weight. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1191–1200, 1997     

Polymers of carbonic acid. XXIV. Photoreactive,nematic or cholesteric polycarbonates derived from hydroquinone-4-hydroxybenzoate 4,4′-dihydroxychalcone and isosorbide

Numerous polycarbonates were prepared by means of “diphosgene” in pyridine using hydroquinone 4-hydroxybenzoate (HQHB) as mesogenic diphenol. In addition to the homopolycarbonate, binary copolycarbonates of HQHB and 4,4′-dihydroxychalcone (DHC) with varying molar composition were prepared. A series of ternary copolycarbonates were obtained by incorporation of isosorbide. Furthermore, an alternating copolycarbonate of HQHB and isosorbide was synthesized. All polycarbonates were characterized by inherent viscosities, elemental analyses, IR-, ¹H-NMR, and ¹³C NMR spectroscopy, by WAXS powder patterns DSC measurements, and optical microscopy with crossed polarizers. The homopolycarbonate of HQHB and most binary copolycarbonates were semicrystalline materials forming an enantiotropic nematic melt. Particularly noteworthy is the finding that the alternating copolycarbonate of HQHB and isosorbide forms a broad cholesteric phase despite the unfavorable stereochemistry of isosorbide. The ternary copolycarbonates containing isosorbide formed a cholesteric melt and a Grandjean texture upon shearing. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1611–1619, 1997     

Dissipative particle dynamics study on the interfaces in incompatible A/B homopolymer blends and with their block copolymers

Dissipative particle dynamics, a simulation technique appropriate at mesoscopic scales, has been applied to investigate the interfaces in immiscible binary A/B homopolymer blends and in the ternary systems with their block copolymers. For the binary blends, the interfacial tension increases and the interface thickness decreases with increasing Flory-Huggins interaction parameter chi while the homopolymer chain length is fixed. However, when the chi parameter and one of the homopolymer chain length is fixed, increasing another homopolymer chain length will induce only a small increase on interfacial tension and slight decrease on interface thickness. For the ternary blends, adding the A-b-B block copolymer will reduce the interfacial tension. When the mole number of the block copolymer is fixed, longer block chains have higher efficiency on reducing the interfacial tension than the shorter ones. But for the block copolymers with fixed volume fraction, shorter chains will be more efficient than the longer ones on reducing the interfacial tension. Increasing the block copolymer concentration reduces interfacial tension. This effect is more prominent for shorter block copolymer chains.     

Bulk heterojunction polymer solar cells based on binary and ternary blend systems

Polymer solar cells (PSCs) were fabricated using a ternary blend film consisting two conjugated polymers and a soluble fullerene derivative as the donor and acceptor materials, respectively. And, to compare ternary blend system, the single‐component copolymers consisting of the repeating units of each of the copolymers, used in ternary blend solar cells, were designed and synthesized for use as the electron donor materials in binary blend solar cells. We systematically investigated the field‐effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers. Under optimized conditions, the binary blend polymer systems showed power conversion efficiencies (PCEs) for the PSCs in the range 3.87–4.16% under AM 1.5 illumination (100 mW cm^?2). All polymers exhibited similar PCEs that did not depend on the ratio of repeating units. The binary blend solar cell containing a single‐component copolymer as the electron donor material performed better than the ternary blend solar cell in this work. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Voltammetric stripping analysis of metal concentrates with polymers soluble in aqueous solutions

The conditions were worked out for the simultaneous stripping voltammetric determination of components of the ternary Pb(II)-Cu(II)-Cd(II) and binary Ag(I)-Cu(II) systems at a carbon-paste electrode in 2% aqueous solutions of the water soluble polymer polyethyleneimine (PEI) and its thiourea-containing derivative (TU-PEI). Water-soluble polymers are shown to reduce the mutual effects of the components of the binary and ternary system at the electrode surface. The different complex stability of Ag(I), Pb(II) or Cd(II) and Cu(II) with PEI and TU-PEI allows Ag(I), Pb(II) and Cd(II) to be determined in the presence of a large excess of Cu(II). Received: 17 July 1997 / Revised: 1 December 1997 / Accepted: 3 December 1997     

Thermal and spectroscopy studies on ternary miscibility and phase behavior in blends comprising poly(4‐vinyl phenol) and two aryl polyesters

Thermal analysis and Fourier transform infrared spectroscopy characterizations were performed on three ternary blend systems that comprise poly(4‐vinyl phenol) (PVPh) and any two of the three homologous aryl polyesters [poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT)]. Although PVPh is miscible with any one of the polyesters in forming a binary blend system, miscibility in ternary systems by introducing one more polymer of different structures to the blend system is not always expected. However, this study concludes that miscibility does exist in all these three ternary blends of all compositions investigated. Reasons and factors for such behavior were probed. Quantitative interactions in the ternary blend system were also estimated. The overall interaction energy density (B) by analysis of melting point depression for the PBT/PVPh/PET ternary blend system led to a negative value (B = −5.74 cal/cm³). Similarly, T_g‐composition analyses were performed on two other ternary blend systems, PET/PVPh/PTT and PTT/PVPh/PBT. Comparison of the qualitative results showed that the interaction energy densities in the other two ternary blend systems are similarly negative and comparable to the PBT/PVPh/PET ternary blend system. The Fourier transform infrared spectroscopy results also support the qualitative findings among these three ternary blend systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1339–1350, 2006     

Vapor-liquid and vapor-liquid-liquid equilibria of carbon dioxide/n-perfluoroalkane/n-alkane ternary mixtures

Perfluoroalkanes have numerous applications (e.g., in the medical field and the chemical industry), and their high affinity for carbon dioxide makes them attractive as surfactants and cosolvents. Although research in this area has grown in the past few years, very little phase-equilibrium data is available in the open literature for these systems. In this work, we present, for the first time, predictions of vapor-liquid and vapor-liquid-liquid equilibria of binary and ternary systems of carbon dioxide/n-perfluoroalkane/n-alkane. Our results are based on the SAFT-VR EOS (statistical associating fluid theory of variable range, equation of state), and we study the influence of temperature, pressure, composition, and chain length on the phase diagram. The predicted phase diagrams are based on temperature-independent binary interaction parameters, and no ternary parameters are introduced. Comparisons to the available experimental and molecular simulation data show that the predicted diagrams should provide a good representation of the phase equilibria.     

A thermodynamic analysis on the coincidence of extrema conditions in the sorption equilibrium for ternary polymer systems

Flory-Huggins theory of polymer solutions has been used to express the condition of extrema values in the total sorption, as well as the inversion point in the preferential adsorption parameters for termary polymer systems. Two approaches have been followed, the first considers the binary and ternary interaction parameters independent of polymer concentration and solvent composition. In the second one, this dependence has been introduced. Our attention is focused on the volume fraction of solvent mixture dependence of the above parameters, in order to confirm or not the coincidence between the extrema values and the inversion point. Several cosolvent and cononsolvent ternary polymer systems, have been used to test the validity of the equations obtained. Also, it has been verified, from an experimental point of view, that in cosolvent ternary polymer systems there is coincidence in both compositions while in cononsolvent ternary polymer systems, such coincidence does not appear.     

Deformation,scattering, and birefringence of flexible polymer chains under external forces or electric fields

The effect of a tensile stress or an electric field on the conformation of a flexible polymer chain has been studied by combining theory with numerical simulation. In the presence of such external agents, the macromolecule experiences the action of two opposite forces at the chain ends. Two models are considered: the Gaussian bead-and-spring chain, and the freely jointed chain with segments of fixed length. From simulated Brownian trajectories we calculate steady-state properties of the polymer under the continuing action of the external forces. Thus, we compute the chain deformation and expansion, measured by the square radius of gyration, and analyze the influence of the external force on low-angle scattering of radiation. The effect of the link orientation in the optical anisotropy or birefringence is also analyzed. From existing theories, we predict very simple relationships between expansion, low-angle scattering, and birefringence, valid for Gaussian chains of any length, and for long freely jointed chains. The simulation results confirm those relationships. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 689–697, 1997