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showing 10 items of 121 documents
Phase separation of symmetric polymer mixtures in a common good solvent in the semidilute concentration regime
1994
Monte Carlo simulations of lattice models of binary (AB) symmetric polymer mixtures (chain lengthsN A=N B=N) in a common good solvent are carried out and the phase diagrams and critical properties of the unmixing transitions are estimated and interpreted in terms of recent theories. Polymers are modeled by self-avoiding walks of lengthN=16, 32 and 64 on the simple cubic lattice. Data for vacancy concentrations of φV=0.6, 0.8 and 0.85 are analyzed. It is shown that forN=16, φV=0.85 no phase separation occurs, down to the lowest temperature, while forN=32, φV=0.85 still phase separation occurs but no longer is complete. Our results are compatible with a scaling theory based on a “renormalizat…
A thermodynamic approach to study hydrogen-bonding interactions in solvent/solvent/polymer ternary systems
2007
Abstract A thermodynamic approach based on both the classical Flory–Huggins (FH) formalism and the association equilibria (AE) theory has been developed to study the solubility properties of a system formed by a proton-donor solvent (A), a proton-acceptor solvent (B) and a proton-acceptor polymer (C). The miscibility of this ternary system is attained by competitive specific interactions via hydrogen-bonding established between the hydroxyl and carbonyl interacting groups of either solvent–solvent (AB) or solvent–polymer (AC) system components. The binary AB and AC specific interactions and their dependence with the system composition as well as with the extent of the association equilibriu…
Predictability of properties of ternary systems solvent/solvent/polymer from interaction parameters of the binary systems—III. Analysis of binary pot…
1990
Abstract The assumption that the ternary parameter, g τ , and its derivative with respect to polymer concentration, ( ∂g τ / ∂φ 3 ) μ 1 , φ 3 → 0 , can be described by three binary interaction parameters, g o i 3 ( i = 1, 2) and g 12 , implies that these must be independent functions. This feature has been demonstrated by using g o i 3 values obtained from A/B/polymer(P) and C/D/P ternary polymer systems to predict the ternary properties, namely preferential solvation (λ), second virial coefficient ( A 2 ) and intrinsic viscosity ([η]), of a A/C/P ternary system. Two distinct polymers, polystyrene(PS) and poly(dimethylsiloxane)(PDMS), have been utilized in three solvent mixtures, benzene(BZ…
Islands of Immiscibility for Solutions of Compatible Polymers in a Common Solvent: Experiment and Theory
2009
Experimentally obtained islands of immiscibility are reported for the systems PS/PVME/THF at 20 °C and for PS/PVME/CH at 55 °C (PS: polystyrene, PVME: poly(vinyl methyl ether), THF: tetrahydrofuran, CH: cyclohexane). THF is a good solvent and CH is a marginal solvent for both polymers. In the case of THF, information on the Flory−Huggins interaction parameters of the three binary subsystems suffices for a qualitative prediction of the phase behavior of the ternary system. Quantitative agreement can be achieved by means of composition-independent ternary interaction parameters. For the marginal solvent CH, the exclusive use of binary interaction parameters wrongly predicts complete miscibili…
Evaluation of thermodynamic parameters for blends of polyethersulfone and poly(methyl methacrylate) or polystyrene in dimethylformamide
1998
Liquid-liquid phase separation phenomena have been investigated for a ternary system containing two polymers and a solvent. Namely, dimethylformamide (DMF)/polyethersulfone (PES)/poly(methyl methacrylate) (PMMA) and DMF/PES/Polystyrene (PS). The composition of the three components in the two phases in equilibrium has been determined by size exclusion chromatographic (s.e.c.) analysis. The lattice-based mean-field theory, first developed by Flory and Huggins, has been modified to adequately describe these systems. In this respect, we have assumed that the parameters depend on the polymer concentration, and we have included a ternary parameter. The phase equilibrium compositions have been use…
Thermodynamics of pseudo-ternary systems as a tool to predict the morphologies of cellulose acetate/polystyrene blends cast from tetrahydrofuran solu…
2003
Abstract The demixing behavior of the ternary system THF/CA/PS (tetrahydrofuran/cellulose acetate/polystyrene) was investigated at 25 °C. Cloud point measurements show that the system exhibits a large miscibility gap caused by the incompatibility of CA and PS. Both ends of the experimentally determined tie lines are located inside the two-phase area of the phase diagram. By means of the measured critical composition of the ternary system and the Flory–Huggins interaction parameters published for two of the binary subsystems ( χ CA/THF =0.442 and χ PS/THF =0.475) the polymer/polymer interaction parameter was adjusted (directly minimizing the Gibbs energy) to χ CA/PS =0.057. These thermodynam…
Phase Equilibria in the Systems 2-Methyl-2-propanol + Methyl 1,1-Dimethylpropyl Ether and 2-Methylpentane + 2-Methyl-2-propanol + Methyl 1,1-Dimethyl…
1999
Consistent vapor−liquid equilibrium data for the binary and ternary systems 2-methyl-2-propanol (TBA) + methyl 1,1-dimethylpropyl ether (TAME) at temperatures from 353 to 359 K and 2-methylpentane + 2-methyl-2-propanol (TBA) + methyl 1,1-dimethylpropyl ether (TAME) from 332 to 353 K are reported at 101.3 kPa. The results indicate that the systems deviate positively from ideality and that only the binary system presents an azeotrope. The ternary system is well predicted from binary data. The activity coefficients and boiling points of the solutions were correlated with composition by Wilson, UNIQUAC, NRTL, and Wisniak−Tamir equations.
Isobaric vapor–liquid equilibrium for binary and ternary mixtures of ethanol+2-methyl-2-propanol and 2-methylpentane+ethanol+2-methyl-2-propanol
1999
Abstract Consistent vapor–liquid equilibrium data for the binary and ternary systems ethanol+2-methyl-2-propanol (TBA) and 2-methylpentane+ethanol+TBA are reported at 101.3 kPa. In the binary system, the results indicate a negative deviation from ideality and no azeotrope is present. The ternary system shows negative and positive deviations from ideality, does not present azeotrope, and is well predicted from binary data. The activity coefficients and boiling points of the solutions were correlated with its composition by Wilson, UNIQUAC and NRTL equations.
Densities, refractive indices, and derived excess properties of tert-butyl alcohol, methyl tert-butyl ether and 2-methylpentane binary and ternary sy…
2000
Abstract This paper reports experimental densities and refractive indices of the binary systems tert-butyl alcohol (TBA)+methyl tert-butyl ether (MTBE), TBA+2-methylpentane, and MTBE+2-methylpentane, and the ternary system TBA+MTBE+2-methylpentane, over the entire range of composition at 303.15 K. Excess molar volumes and changes of refractive indices were evaluated from the experimental data obtained. These derived properties were fitted to variable-degree polynomials. The experimental values of physical properties were compared with the values estimated by different methods of prediction.
Densities, refractive indices, and derived excess properties of the binary systems tert-butyl alcohol+toluene, +methylcyclohexane, and +isooctane and…
1999
Abstract This paper reports experimental densities and refractive indices of the binary systems tert -butyl alcohol (TBA)+toluene, +isooctane, and +methylcyclohexane, and toluene+methylcyclohexane, and the ternary system TBA+toluene+methylcyclohexane, over the entire range of composition at 298.15 K. Excess molar volumes and changes of refractive indices were evaluated from the experimental data obtained. These derived properties were fitted to variable-degree polynomials. The experimental values of physical properties were compared with the values estimated by different methods of prediction.