Sensitivity of ternary phase diagrams of miscible polymer pairs in common solvents on traces of water: solvent-poly(ethyl acrylate)-poly(vinyl propionate) and solvent-poly(methyl acrylate)-poly(vinyl acetate) systems (original) (raw)
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Macromolecules, 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 miscibility of all three components. In this case, one ternary interaction parameter must be treated as a function of composition in order to match experiment and theory. On the basis of the present results, it can be concluded that the preparation of homogeneous mixtures with arbitrary composition from a pair of compatible polymers and a common solvent is only possible on rare occasions.
Dilational rheology of monolayers of a miscible polymer blend: From good- to poor-solvent conditions
European Physical Journal E, 2002
The viscoelastic moduli (elasticity and dilational viscosity) of monolayers of PVAc + P4HS has been studied over a broad frequency range (0.1 mHz-200 kHz) using a combination of relaxation and capillary-waves techniques. The analysis of the surface pressure, the elasticity and the viscosity on the semidilute regime show that the air-water interface is a good solvent for the monolayers of PVAc-rich blends, and a poor (near-Θ) solvent for the monolayers of P4HS-rich blends. The solvent quality changes continuously over a broad concentration range. The results of viscoelastic moduli show that there is a broad relaxation process in the low-frequency range ( ω
Salt effects on solvent features of coexisting phases in aqueous polymer/polymer two-phase systems
Journal of Chromatography A, 2012
The solvatochromic parameters characterizing the solvent dipolarity/polarizability (*), solvent hydrogen-bond donor acidity (˛), and solvent hydrogen-bond acceptor basicity (ˇ) of aqueous media were measured in the coexisting phases of aqueous Dextran-Ficoll, Dextran-Ucon, Dextran-PEG, PEG-Ucon, Ficoll-Ucon, and Ficoll-PEG two-phase systems (ATPS). Ionic composition of each ATPS included 0.15 M KCl, 0.15 M KBr, 0.15 M NaBr, 0.1 M Na 2 SO 4 , and 0.1 M Li 2 SO 4 in 0.01 M sodium phosphate buffer (NaPB), pH 7.4; and 0.01 M and 0.11 M sodium phosphate buffer, pH 7.4. Partition ratios of sodium salts of dinitrophenylated (DNP) amino acids with aliphatic side-chains (glycine, alanine, norvaline, norleucine, and ˛-amino-n-caprylic acid) were measured in all ATPSs, and the results were evaluated in terms of the differences between the relative hydrophobicity (parameter E) and the electrostatic properties (parameter C) of the aqueous media of the coexisting phases. It was established that parameter E is described by a linear combination of the differences between the solvent dipolarity/polarizability (*) and between the solvent hydrogen-bond acidity (˛) of the media in the coexisting phases. Parameter C depends on the phase forming polymer pair and is shown to be described by a linear combination of three parameters: the differences between the solvent hydrogen-bond acidity (˛) and between the solvent hydrogen-bond basicity (ˇ) of the media in the coexisting phases, and a measure of the effect of a given salt additive on the hydrogen bonds in water. This effect was represented by a parameter (K b−l), characterizing the equilibrium between populations of hydrogen bonds with a bent hydrogen bond conformation and with linear hydrogen bond conformation affected by a given salt additive.
Polymer, 1960
An experimental study is reported of phase equilibria in ternary systems comprising two polymers and one liquid. The measured distribution of the two polymers between two coexisting phases is used, in conjunction with the Flory-Huggins theory, to derive polymer-polymer interaction 'constants'. These can be used to predict the miscibility and heat of mixing of the same polymers in binary mixtures. Experimental studies on fluid polymers show that miscibility is less and heat of mixing larger than predicted. It is concluded that these studies on ternary systems do not afford a reliable guide to the behaviour of binary polymers mixtures. Possible reasons ]or the discrepancy are discussed.
Evolution and disappearance of solvent drops on miscible polymer subphases
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018
† Equal contribution their drop shapes obey the Augmented Young-Laplace Equation. Over time, the miscible interface diffuses and the shape of the drop evolves. We place 2-microliter drops of water atop miscible poly(acrylamide) solutions. The drop is completely wetted by the subphase, and then remains detectable beneath the surface for many minutes. An initial effective interfacial tension can be approximated to be on the order of 0.5 mN/m using the capillary number. Water and poly(acrylamide) are completely miscible in all concentrations, and yet, when viewed from the side, the drop maintains a capillary shape. Study of this behavior is important to the understanding of effective interfaces between miscible polymer phases, which are pervasive in nature.
Solvent effects on polymer surface structure
Surface and Interface Analysis, 2001
The surface modification of polymeric materials has been of great research interest in the last few years because of its importance in applications such as biomaterials and coatings. The bulk composition of polymeric materials often cannot provide the desired surface properties in these applications. For example, low-surface-energy materials can be obtained via the process of surface segregation. The properties of the solvents used in these processes are critical for surface formation in these polymers. Solvent properties such as polarity, volatility and specific interaction properties with the polymer material are important factors in the process of surface formation. The present paper reviews recent studies of solvent effects no surface segregation in multicomponent polymer systems. Copolymers, polymer blend and multicomponent polymer solution systems are discussed.
Colloid and Polymer Science, 1998
The surface pressure (Π) vs surface concentration (Γs) curves of the hydrogen-bonded polymer blend poly(vinylacetate)+ poly(4-hydro-xystyrene) (PVAc+P4HS) have been measured at 25 °C onto a water subphase at pH=2.0. While PVAc forms extended monolayers, and the free surface of water is found to be a good solvent for it, P4HS forms compressed monolayers, and the surface is a near Θ-type solvent for it. PVAc and P4HS form miscible non-ideal monolayers until near the collapse pressure through the whole concentration range. The composition dependence of the Π–Γs curves is rather complex. Contrary to what might be expected, the addition of PVAc to the blend does not reduce the rigidity of the monolayer until its weight fraction is larger than 0.5. The compressibility data of the P4HS-rich monolayers suggest the existence of a second maximum at high surface coverages, a result already observed in some polysiloxanes.
Phase separation in polystyrene/poly(vinyl methyl ether) blends as studied by excimer fluorescence
Macromolecules, 1982
Excimer fluorescence has been used to study spinodal decomposition in a polystyrene (PS)/poly(vinyl methyl ether) (PVME) blend phase separated by thermal means. From the measurement of the ratio of excimer-to-monomer fluorescence emission intensities, the time dependence of the rich-and lean-phase compositions during phase separation has been determined. Cahn's theory of spinodal decomposition appears to describe adequately the early stages of phase separation. Fluorescence results indicate, however, that equilibrium is not reached during this time period. From the measured growth rate of decomposition, the macroscopic diffusion coefficient for a 10% PS/PVME blend annealed at 423 K is calculated to be of the order -lo-" cm*/s. ABSTRACT: A numerical method for the calculation of the binodal of liquid-liquid phase separation in a ternary system is described. The Flory-Huggins theory for three-component systems is used. Binodals are calculated for polymer/solvent/nonsolvent systems which are used in the preparation of asymmetric ultrafiltration or reverse osmosis membranes: cellulose acetate/solvent/water and polysulfone/solvent/water. The values for the binary interaction parameters are taken from literature sources. The effect of a concentration-dependent solvent/nonsolvent interaction parameter is discussed. Although knowledge of the interaction parameters for all compositions in the ternary system is rather poor, fairly good agreement has been found between calculated and experimentally found miscibility gaps when the solvent/nonsolvent parameter is taken to be concentration dependent and the other parameters, the polymer/solvent and the polymer/ nonsolvent interaction parameter, are kept constant.
Journal of Applied Polymer Science, 2010
The interaction between poly(acrylamide) (PAM) and poly(ethylene glycol) (PEG) in their solid mixture was studied by Fourier transform infrared spectroscopy (FTIR); and their interaction in aqueous solution was investigated by nuclear magnetic resonance spectroscopy (NMR). For the solid PAM/PEG mixtures, an induced shift of the >C¼ ¼O and >NAH in amide group was found by FTIR. These results could demonstrate the formation of intermolecular hydrogen bonding between the amide group of PAM and the ether group of PEG. In the aqueous PAM/PEG solution system, the PAM and PEG associating with each other in water, i.e., the amide group of PAM interacting with the ether group of PEG through hydrogen bonding was also found by 1 H NMR. Furthermore, the effects of different molecular weight of PAM on the strength of hydrogen bonding between PAM and PEG in water were investigated systemically. It was found that the hydrogen bonding interaction between PAM and PEG in water did not increase with the enlargement of the PAM molecular weight as expected. This finding together with the viscosity reduction of aqueous PAM/PEG solution with the PAM molecular weight increasing strongly indicated that PAM molecular chain, especially having high molecular weights preferred to form spherical clews in aqueous PEG solution. Therefore, fewer amide groups in PAM could interact with the ether groups in PEG. Based on these results, a mechanism sketch of the interaction between PAM and PEG in relatively concentrated aqueous solution was proposed. The fact that the phase separation of aqueous PAM/PEG solution occurs while raising the temperature indicates that this kind of hydrogen bonding between PAM and PEG in water is weak and could be broken by controlling the temperature.