Interactions between inorganic salts and polyacrylamide in aqueous solutions and gels

The swelling of poly(acrylamide) (PAAm) gels and the osmotic pressure of linear PAAm in aqueous solutions were predominantly affected by anion type and increased according to the lyotropic series ranking of sodium halide anions: F^? < (H₂O) < Cl^? < Br^? < I^?. The osmotic pressure of PAAm in all examined salt solutions followed the scaling theory, with an exponent of 2.3 ± 0.1. In solutions of a sodium halide series, the value of the pre‐exponential factor seemed to depend on salt concentration, anion radius, and the apparent “anionic‐portion radius” of the water molecule. This radius, extracted from the literature data, marks a transition point of the anion radius effect. Larger anions increase the osmotic pressure of PAAm more significantly as their concentration increases and vice versa. The effects of the anions on the osmotic pressure of PAAm are related to their preferential interactions with the polymer. Iodide, which increased the osmotic pressure of PAAm with respect to its value in pure water, seemed to preferentially adsorb onto the polymer with a binding constant of K_b = 9.7 ± 2.0 M^?1 determined by isothermal titration microcalorimetry. However, fluoride, which decreased the osmotic pressure, was preferentially repulsed. The mechanisms of attraction and repulsion were attributed to ion‐water‐polymer interactions and the solvent quality of the hydrated ions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 508–519, 2003     

Water transport properties of thermoplastic polyurethane films

Two linear segmented polyurethanes, based on poly(oxyethylene) (POE) as a soft segment and 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol as hard segments and differing in their soft segment length, have been studied from a water vapor transport point of view. For both polyurethanes, the water sorption is governed by a Fickian process, and the thermoplastic polyurethane with the longer POE segments displays the higher water diffusion rate. The water sorption isotherms are Brunauer Emmet Teller (BET) type III for both thermoplastic polyurethanes, and the water uptakes are directly related to the polymer POE content. The Flory–Huggins theory cannot correctly describe the sorption isotherms. More sophisticated approaches (Koningsveld–Kleinjtens or Guggenheim‐Anderson‐de Boer (GAB) models) are needed to fit the experimental water uptakes. The positive deviation from Henry's law and the decrease in the apparent diffusion coefficient observed at a high activity have been particularly studied. In this activity range, an isotherm analysis based on the cluster integral of Zimm and Lundberg suggests some clustering phenomenon, which seems consistent with the diffusion coefficient variation. In agreement with the sorption results, the water permeability coefficients are small at low activities, and they increase greatly with the relative pressure of water. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 473–492, 2004     

Sorption and partial molar volumes of C2 and C3 hydrocarbons in polypropylene copolymers

The sorption of C₂ and C₃ hydrocarbons in two ethylene–propylene copolymers and a propylene homopolymer and the simultaneous dilation of the polymers were measured at temperatures of 287–363 K and pressures up to 4 MPa. The sorption isotherms were well described by the Flory–Huggins theory of dissolution. Dilation isotherms in the form of elongation versus pressure were similar in shape to the corresponding sorption isotherms. Solubility coefficients, partial molar volumes, and Flory–Huggins interaction parameters were determined from these isotherms. The thermal expansivities of the hydrocarbons dissolved in the polymers were 0.002–0.005 K^?1, and the Flory–Huggins interaction parameters depended not only on temperature but also on concentration. At 323 K, the calculated solubilities of propylene in the ethylene–propylene‐rubber regions of the copolymers were 1.8 times higher than in the amorphous regions of the propylene homopolymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1255–1262, 2001     

A continuous polydisperse thermodynamic algorithm for a modified flory–Huggins model: The (polystyrene + nitroethane) example

A modified Flory–Huggins model is presented, considering a concentration‐ and temperature‐dependent interaction parameter, and using the methodology of Continuous Thermodynamics to take into account both polydispersity and its effect on phase equilibrium of polymeric systems. This model describes all commonly found, as well as other unusual polymer + solvent and polymer + polymer, liquid–liquid phase diagrams and is easily extended to take all possible pressure effects into consideration. Modeling and least‐squares fit of polystyrene + nitroethane liquid–liquid cloud‐point data have produced results in good accord with the experimental ones by using meaningfully physical parameters. These results have been used to discuss polystyrene molecular weight, pressure, and isotopic substitution effects on polystyrene + nitroethane systems. A first‐order interpretation of phase equilibrium isotopic substitution effect has also been applied. It combines the simplest form of the Flory–Huggins model with the statistical theory of condensed phase isotope effects. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 632–651, 2000     

Solvent quality as reflected in concentration‐ and temperature‐dependent Flory–Huggins interaction parameters

Flory–Huggins interaction parameters (χ) between poly(dimethylsiloxane) (weight‐average molecular weight = 152 kg/mol) and various solvents (methyl ethyl ketone, toluene and n‐octane) were determined as a function of composition and temperature with vapor‐pressure measurements. These data, complemented by independent information for dilute and very concentrated solutions, serve as the basis for a discussion of solvent quality via different theoretical relations. Regardless of polymer concentration, the χ values fall from methyl ethyl ketone via toluene to n‐octane, the ketone being the worst solvent and the hydrocarbon being the best solvent. The variation of χ with composition and temperature is complex. Within the range of moderate polymer concentrations, the influences of composition decrease with increasing solvent quality. Additional effects become noticeable at the ends of the composition scale. The enthalpy parts (χ_H) and entropy parts (χ_S) of the Flory–Huggins interaction parameter, obtained from χ(T), vary considerably with composition and change their sign in some cases; these constituents of the Flory–Huggins interaction parameter do not permit a direct assessment of solvent quality. A clear‐cut picture is, however, regained with a comparison of the interdependence of χ_S and χ_H. The elimination of explicit concentration influences re‐establishes the order in the solvent quality setup via χ. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 651–662, 2001     

Swelling of polyacrylamide gels in polyacrylamide solutions

Swelling behavior of polyacrylamide (PAAm) and polyacrylamide-co-polyacrylic acid (PAAm-co-PAAc) gels was investigated in aqueous solutions of monodisperse PAAms with molecular weights (M_w) ranging from 1.5 × 10³ to 5 × 10⁶ g/mol. The volume of the gels decreases as the PAAm concentration in the external solution increases. This decrease becomes more pronounced as the molecular weight of PAAm increases. The classical Flory–Huggins (FH) theory correctly predicts the swelling behavior of nonionic PAAm gels in PAAm solutions. The polymer–polymer interaction parameter χ₂₃ was found to decrease as the molecular weight of PAAm increases. The swelling behavior of PAAm-co-PAAc gels in PAAm solutions deviates from the predictions of the FH theory. This is probably due to the change of the ionization degree of AAc units depending on the polymer concentration in the external solution. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1313–1320, 1998     

Liquid–liquid equilibria of polymer solutions: Flory‐huggins with specific interaction

We have developed a new Flory‐Huggins model by adding a specific interaction parameter derived from a modified double‐lattice model for the Helmholtz energy of mixing for binary liquid mixtures. This model is very simple and could be easily integrated into engineering applications. Using this revised model, we can successfully describe the phase behavior of polymer solutions with an upper critical solution temperature (UCST), a lower critical solution temperature (LCST), both UCST and LCST, and a closed miscibility loop. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 162–167, 2010     

Intramolecular screening effects in nondilute polymer solutions: An equation‐of‐state approach

In a previous article, we presented a simple modification of the traditional Flory–Huggins theory that took intramolecular screening effects (or same chain contacts) into account. In this article, we present a natural extension of that work, in which free‐volume effects are also explained with an equation‐of‐state model. The predictions of the interaction parameter, χ, for several polymer–solvent systems are presented, over the entire concentration range, in θ solvents and good solvents. A geometric mean assumption is applied to the calculation of an exchange energy interaction term. The predictions of χ are successful to various degrees when internal pressures are used, whereas the use of solubility parameters in most cases produces fairly good agreement with experimental results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2911–2922, 2003     

Investigation of polymer–solvent interactions in poly(styrene sulfonate) thin films

The swelling behavior of acid form poly(styrene sulfonate) (PSS‐H) thin films were investigated using in situ spectroscopic ellipsometry (SE) to probe the polymer–solvent interactions of ion‐containing polymers under interfacial confinement. The interaction parameter (χ), related to the polymer and solvent solubility parameters in the Flory–Huggins theory, describes the polymer‐solvent compatibility. In situ SE was used to measure the degree of polymer swelling in various solvent vapor environments, to determine χ for the solvent‐PSS‐H system. The calculated solubility parameter of 40–44 MPa^1/2 for PSS‐H was determined through measured χ values in water, methanol, and formamide environments at a solvent vapor activity of 0.95. Flory–Huggins theory was applied to describe the thickness‐dependent swelling of PSS‐H and to quantify the water‐PSS‐H interactions. Confinement had a significant influence on polymer swelling at low water vapor activities expressed as an increased χ between the water and polymer with decreasing film thickness. As the volume fraction of water approached ～0.3, the measured χ value was ～0.65, indicating the water interacted with the polymer in a similar manner, regardless of thicknesses. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1365–1372     

Basic studies on gas solubility in natural rubber–cellulose composites

This work reports sorption processes of oxygen, carbon dioxide, methane, ethylene, and propylene in films of both vulcanized natural rubber and vulcanized rubber–regenerated cellulose composites. The curves representing the pressure dependence of the concentration of carbon dioxide in the composites clearly exhibit a slight concavity with respect to the abscissa axis as a result of adsorption processes taking place in Langmuir sites located in the glassy cellulose component. Adsorption processes are also detected in the sorption curves of ethylene at low pressures. The concavity with respect to the ordinate axis of the curve concentration of propylene versus pressure at high pressure is pretty well described by the Flory‐Huggins formalism. The solubilities of the other gases mainly obey Henry's behavior, adsorption processes in the glassy component being in most cases negligible. Values of the interaction χ parameter for gas–natural rubber and gas–natural rubber composites are obtained from the comparison of the experimental solubility coefficients with those predicted by the Flory‐Huggins theory. The theory suggests that Henry's constant is a linear function of the boiling temperature of the gases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2131–2140, 2005     

Separation studies of hydrazine from aqueous solutions by pervaporation

Separation of hydrazine from aqueous solutions with ethylcellulose membranes has been investigated by using the pervaporation technique. The effect of membrane thickness, concentration polarization, and feed concentration on flux and selectivity were evaluated. A separation mechanism is proposed based on the measurements of sorption, and diffusion coefficients, and estimations of Flory–Huggins interaction parameters and Hansen's solubility parameter. States of water, hydrazine, and hydrazine hydrate are explained with DSC spectra. The specific interaction sites in ethylcellulose matrix where the solvent interacts extensively with the polymer have been identified by FTIR analysis. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1969–1980, 1999     

Phase behavior of a water/2‐propanol/poly(methyl methacrylate) cosolvent system

A phase diagram of poly(methyl methacrylate) in mixtures of water and 2‐propanol, individually nonsolvents for the polymer, was studied at 25 °C. For this system, there were two liquid–liquid demixing regions separated by a miscible region. This cosolvent phenomenon was thought to be a joint effect of the nonsolvents. The phase behavior was modeled according to modified Flory–Huggins chemical‐potential equations, which accounted for the possible contribution from a ternary interaction in terms of a lumped parameter, χ₁₂₃. The calculated phase‐equilibrium curves (binodals) agreed well with the measured results. By contrast, if only binary interaction parameters were considered, computations yielded binodals whose compositions departed significantly from the measured data. Using the wet phase inversion method with casting dopes selected on the basis of the phase diagram, we prepared membranes with microporous structures in various coagulation baths. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 747–754, 2000     

Binary versus ternary interactions in a completely miscible three‐polymer blend system: Poly(ϵ‐caprolactone) with two different methacrylic polymers

A truly miscible ternary miscible blend consisting of poly(?‐caprolactone) (PCL), poly(phenyl methacrylate), and poly(benzyl methacrylate) (PBzMA) was discovered. The three‐polymer blend system was completely miscible within the entire composition range at ambient temperature up to about 150 °C, and ternary phase diagrams at increasing temperatures were characterized and interpreted. A ternary‐interaction model based on the modified Flory–Huggins expression was used to describe the phase diagrams with the individual binary interaction strengths. The model fitted well with the experimental‐phase diagram for the ternary blend system at T = 250 °C, where the binary PCL‐PBzMA blend system is on the critical points of phase separation. Interpretation of discrepancy between the model and experimental at other temperatures was handled with an empirical approach. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 747–754, 2002     

The link between nanoscale feature development in a negative resist and the Hansen solubility sphere

By systematically studying development of a high resolution, negative electron beam resist, hexa‐methyl acetoxy calix(6)arene, we have elicited a more general understanding of the underlying development mechanisms for negative resists. Using the three dimensional Hansen solubility parameters for more than 40 solvents, we have constructed a Hansen solubility sphere (HSS). From this sphere, we have estimated the Flory Huggins interaction parameter for solvents with hexa‐methyl acetoxy calix(6)arene and found a correlation between resist development contrast, nanoscale patterned feature quality, and the polymer‐solvent solubility. Conducting Atomic Force Microscopy (AFM) in a liquid cell, we have measured swelling for hexa‐methyl acetoxy calix(6)arene in four solvents. The swelling measurements indicate that the HSS gives an indication of the Flory‐Huggins interaction parameter. These measurements provide new insights into the development behavior of nanoscale features – necessary for obtaining the ultimate lithographic resolution. In addition, it demonstrates a methodology for choosing appropriate polymer‐solvent combinations for nanoscience applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2091–2105, 2009     

Kinetics of the volume phase transition in poly(n‐isopropylacrylamide) gels prepared under high pressure

New poly(N‐isopropylacrylamide) gels were prepared under high pressure (ca. 200 MPa) during gelation. The preparation‐pressure dependence of the deswelling speed of the gels was measured with a conventional T‐jump method. The deswelling time of a gel rod 2.2 mm in diameter prepared at 193 MPa was about 200 s, 1000 times faster than that of a homogeneous poly(N‐isopropylacrylamide) gel. Moreover, the collective diffusion coefficient, the thermal fluctuation, and the ensemble‐average intensity of the swollen gel networks were obtained with dynamic light scattering measurements. Both the enthalpy and entropy of the gels were estimated from equilibrium swelling curves with the Flory–Huggins interaction parameter evaluated with mean field theory based on the Flory‐type of the Gibbs free‐energy formula. It was found that the networks of the gels had an inhomogeneous structure newly introduced by the preparation pressure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2315–2325, 2001     

Solubility and partial molar volume of carbon dioxide and ethane in crosslinked poly(ethylene oxide) copolymer

Experimental solubility and sorptive dilation data are reported for carbon dioxide and ethane in a crosslinked poly(ethylene oxide) (XLPEO) rubbery copolymer. Five different temperatures (253 ≤ T(K) ≤ 308) were considered, with a maximum gas pressure of 2.09 MPa (20.6 atm). The polymer was prepared by photopolymerization of a solution containing 70 wt % poly(ethylene glycol) methyl ether acrylate (PEGMEA) and 30 wt % poly(ethylene glycol) diacrylate (PEGDA). Sorption isotherms were described by the Flory‐Huggins model. For each gas, the Flory‐Huggins interaction parameter was a decreasing function of temperature and did not show a composition dependence. Dilation and sorption data were combined to calculate the partial molar volume (PMV) of the gases in the polymer, which was an increasing function of temperature. Based on a comparison with literature data for a XLPEO homopolymer prepared from pure PEGDA over the same range of operating conditions, an effect of the network composition on both gas solubility and PMV was found. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 456–468, 2010     

Evaluation of solubility parameters during polymerisation of amine‐cured epoxy resins

A new procedure for the calculation of solubility parameter evolution during polymerisation has been developed for amine‐cured epoxy systems, which allows quantitative thermodynamic modelling of chemically induced phase separation (CIPS). Solubility parameters calculation, chemical analysis based on near infrared spectroscopy and curing kinetics results obtained by differential scanning calorimetry will allow to model the evolution of the Flory–Huggins interaction parameter in amine‐cured epoxy blends. The resin system investigated was based on a diglycidyl ether bisphenol A (DGEBA) epoxy resin cured with isophorone diamine (IPD) blended with various reactive epoxydised dendritic hyperbranched polymer modifiers (HBP), yielding a CIPS‐controlled morphology. The analysis showed the evolution of the different contributions to the solubility parameters to follow the polymerisation kinetics. The dispersive contribution had the highest value at all stages of polymerisation, but the hydrogen and polar contributions showed the largest variation. By evaluating the dynamic evolution of the solubility parameter components, the Flory–Huggins interaction parameter in the epoxy resin‐hyperbranched polymer blends has been modelled as a function of time. This procedure, combined with thermodynamic modelling, will enable to predict phase diagrams in CIPS thermosetting blends quantitatively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1883–1892, 2000     

Thermodynamics of solutions of cyclic polymethylene ester oligomers in p‐dioxane and chloroform

Differential vapor pressures were measured for mixtures of two cyclic polymethylene ester oligomers in p‐dioxane and chloroform at 25, 30, 35, and 40 °C at five different concentrations ranging from 1 to 20 wt %. The Flory–Huggins interaction parameter (χ) as well as Leonard's interaction parameter (χ′) for flexible and semiflexible rings were calculated and compared to one another. A new method for the estimation of the number of segments of a cyclic polymer is proposed that allows Leonard's equations to be applied correctly to a particular cyclic compound. Consistent differences between χ and χ′ were observed for all studied mixtures, and the differences became smaller if the cyclic oligomers were considered semiflexible. Interestingly, the enthalpic parameter (κ) deduced from values of χ and χ′ did not differ within their uncertainties. This supports the prediction that mixing cyclic polymer compared to its linear counterpart is mainly due to a molecular configurational entropy difference and that this difference should become less pronounced as the cyclic compound becomes larger. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 443–455, 2000     

Theoretical simulation of thermally induced phase separation in a main‐chain liquid‐crystalline polymer solution

Phase diagrams of main‐chain liquid‐crystalline polymer (MCLCP) solutions have been calculated self‐consistently on the basis of a simple addition of the Flory–Huggins free energy for isotropic mixing, the Maier–Saupe free energy for nematic ordering, and the Flory free energy for chain rigidity of the MCLCP backbone. The calculated phase diagram is an upper critical solution type overlapping with the nematic–isotropic transition. The phase diagram consists of liquid–liquid, liquid–nematic, and pure nematic regions. Subsequently, the dynamics of thermally induced phase separation and morphology development have been investigated by the incorporation of the combined free energy density into the coupled time‐dependent Ginzburg–Landau (model C) equations, which involve conserved compositional and nonconserved orientational order parameters. The numerical calculations reveal a variety of the morphological patterns arising from the competition between liquid–liquid phase separation and nematic ordering of the liquid‐crystalline polymer. Of particular interest is the observation of an inflection in the growth dynamic curve, which may be attributed to the nematic ordering of the MCLCP component, which leads to the breakdown of the interconnected domains. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 913–926, 2003