Modelling the Influence of Nanoparticles in the Phase Behaviour of an Epoxy/Polystyrene Mixture, 2

The influences of nanoparticle size and concentration on the thermodynamic behaviour of epoxy/polystyrene blends are evaluated in the framework of Ginzburg's simple analytical theory. Two approaches have been employed: NPEPO (for particles coated with epoxy groups) and NPFEN (for particles coated with phenyl groups). Using NPEPO, the particles are found to prefer the phase richer in epoxy, whereas the opposite occurs for NPFEN. The particles size significantly influences blend compatibility. When the particle radius Rp is about the same size as the radius of gyration R g of PS, the compatibility of blends increases with particle concentration, whereas for R p > R g , higher particle concent…

Solution properties of polyelectrolytes XII. Semi-quantitative approach to mixed electrostatic and hydrophobic polymer-gel interactions

Abstract Aqueous size-exclusion chromatography of polyanions, where secondary effects affect the total separation mechanism, was investigated. For elution of polyelectrolytes on inorganic silica-based supports, the electrostatic polymer-gel repulsive interactions were evaluated through the values for a hypothetical repulsion layer, X e , according to the model developed by other workers. Using a similar procedure, the existence of an effective barrier defined as X e − X h is proposed for those systems in which electrostatic repulsion and hydrophobic interactions take place simultaneously as secondary mechanisms. X h can be viewed as a measure of the “enlargement” of the geometrical pore rad…

Miscibility of a DGEBA Based Epoxy Resin Blended with Thermoplastic Mixtures of Poly(styrene) and Block Copolymers: Influence of the Copolymer Content and Chemical Nature

The miscibility and phase behavior of ternary systems formed by a DGEBA based epoxy resin, polystyrene (PS), and diblock copolymers has been investigated through phase diagrams experimentally obtai...

Size‐Exclusion Chromatography in Single and Mixed Eluents: Effects of Sorption of Solvent and Polymer Solutes on Novel TSK‐Gel Super AW Columns

Abstract The novel TSK Gel Super AW column packing is based on a polymeric gel with residual hydrophobic and hydrophilic groups on the gel surface. These groups can act as active sites making the chromatographic support compatible both with polar and apolar eluents. This interesting property allows the elution of systems of very different polarities but also induces binary polymer–gel, polymer–solvent, and solvent–gel enthalpic interactions that lead to a mixture of separation mechanisms: repulsion, partition, or adsorption besides the main size‐exclusion chromatography (SEC) mechanism. For this reason, the elution behaviour of many and diverse polymer/solvent systems has been studied in th…

Thermodynamics of a polymer blend solution system studied by gel permeation chromatography and viscosity

Binary and ternary interaction parameters and their derivatives have been calculated with the Flory-Huggins formalism developed for a ternary polymer system. The equilibrium compositions of the ternary system tetrahydrofuran/polybutadiene/polystyrene that forms two phases in equilibrium at 25°C have been used to solve the binodal equations. With this set of parameters, the viscosimetric interaction parameters have been computed. For the sake of comparison, the experimental viscosimetric parameter has been determined from intrinsic viscosity data of a polymer (3) in a "binary solvent" (solvent + polymer (2)). It has been clearly shown that composition-dependent parameters are necessary to re…

Porous fractal gels: secondary effects in SEC

Abstract The fractal nature of porous silica gels, Spherosil XOA 200 and of a Lichrospher mixture, has been tested through size exclusion chromatography of polystyrene in pure and mixed eluents. Fractal parameters, D f and L , depend on eluent with D f values close to 2.0 for Spherosil and higher than 2.0 for Lichrospher. D f and L changes with eluent have been related to secondary separation effects and partition and adsorption contributions have been evaluated.

Ionomers in solution: 1. Viscometric and chromatographic studies in cononsolvent and cosolvent mixtures

Abstract The viscosity and elution behaviour of polystyrene sulfonate ionomers with varying ionic content has been studied in the pure solvents chloroform (CHL), tetrahydrofuran (THF), dioxan (DIO), ethyl acetate (EA) and dimethylformamide (DMF) as well as in their cononsolvent mixtures CHL/THF (50:50), DIO/CHL (75:25) and in the cosolvent mixture EA/DMF (50:50). In the pure solvents with low dielectric constant the reduced viscosities of ionomers are lower at low concentrations and higher at moderate ones than the respective viscosities of the polystyrene precursor. These results can be explained by formation of intramolecular and intermolecular associations. Moreover, differences in visco…

On the thermodynamic treatment of poly(vinylidene fluoride)/polystyrene blend under liquid—liquid phase separation conditions

Abstract This paper deals with experimental and theoretical investigations on the compatibility of binary of polymer blends in solution. The experimental phase boundary of a crystalline polymer such as poly(vinylidene fluoride) with polystyrene (an amorphous polymer) in dimethylformamide as solvent has been determined by size-exclusion chromatography at 25°C. The composition of the coexisting phases has been used to calculate interaction parameters by means of the Flory—Huggins-type function for the free energy of mixing, including composition dependence of the polymer-polymer interaction parameter and a first correction term denoted as ternary interaction parameter. The calculation of thes…

Ternary Polymer Solutions with Hydrogen Bonds, 1

The Flory Huggins methodology coupled to AET has been extended to ternary polymer systems, in particular to solvent (A)/polymer 1 (B)/polymer 2 (C) systems, with the two polymers displaying H-bonding interactions. Because the H-bonding can perturb the randomness of polymeric conformations, the change in Gibbs free energy of mixing, AG, should arise from changes in combinatorial entropy as well as in interaction energy. The combinatorial part of AG is evaluated through AET as a function of the association constant η between B and C components, the autoassociation constant a between B components, and the independent number m of interaction sites of acceptor C. The enthalpic contribution is ev…

The Fractal Approach to Secondary Mechanisms in SEC

Abstract Size‐exclusion chromatography (SEC) is one of the most used experimental techniques to characterize polymers in solution; it has been applied to interpret the elution behaviour of many polymer‐solvent systems in five types of column packings. The experimental data have revealed that the classical universal calibration is not accomplished. Deviations from a unique curve are a consequence of two effects: entropic (exclusion by size) and enthalpic (binary and ternary interactions between solvent, polymer, and gel), which results in secondary mechanisms accompanying the main “ideal” SEC separation mechanism. Therefore, three approaches of building a calibration curve have been compared…

Time-dependent monomerization of gramicidin A, enhanced by phosphatidylcholine in non-polar solvents

Abstract The usefulness of size-exclusion high-performance liquid chromatography for the study of gramicidin A dimer—monomer conformational equilibrium in non

Viscometric study of mixtures of neutral and charged polymers in aqueous solution

The viscosity behaviour of aqueous mixtures formed by a polyelectrolyte (A) and a neutral polymer (B) such as polystyrene sulfonate (PSS)-polyvinylpyrrolidone (PVP) and polylysine (PLL)-PVP has been studied at 25°C. The intrinsic viscosity and viscosity interaction parameter of each polymer in water have been determined and have served us to estimate the compatibility of the different mixtures according to two different methodologies: (i) mixtures of two polymers in water as solvent and (ii) mixtures of either polymer A OFB in a solvent formed by either polymer B or A in water ("polymer solvent method"). By comparing the experimental and theoretical viscosity data it is clearly seen that: m…

Thermodynamic study on phase equilibrium of epoxy resin/thermoplastic blends

Abstract The experimental phase diagrams (cloud point curves) of three series of epoxy/thermoplastic blends, namely, epoxy/polystyrene (PS), epoxy/poly(ether sulfone) (PES), and epoxy/poly(ether imide) (PEI) as a function of molar mass and composition have been analysed from a thermodynamic point of view. A model based on the Flory–Huggins lattice theory considering the concentration dependence of the interaction parameter as predicted by Koningsveld was employed to determine the equilibrium compositions, and concentration and temperature dependent interaction parameters. Binodal, spinodal, and critical point data have been computed and show good agreement with experimental data.

A comparative study on Kθ evaluation from [η]-M data in single and mixed solvents through various excluded volume theories

Abstract By allowing for the dependence of B on molecular weight, through its relationship with A2, modified Flory-Fox-Schaefgen, Kurata-Stockmayer-Roig, Berry and Inagaki-Suzuki-Kurata equations are obtained, relating [η] to A2 and to Kθ. Through these equations, Kθ can be determined from data sets for [η]-A2. Because of the scarcity of these data sets, A2 values have been calculated from experimental data for [η] and trial Kθ values through two parameter theories, namely, through the Flory-Krigbaum-Orofino theory for Ψ. Iterative processes were followed until coincidence was obtained between trial Kθ values and those evaluated from the modified excluded volume equations. The method has be…

Cover Picture: Macromol. Theory Simul. 1/2007

Polymer Retention Mechanism in GPC on Active Gels

Abstract The elution behaviour of low molecular weight polystyrene (PS) down to the monomer on spherosil gel in several eluents has been studied. In the medium range of molecular weights the elution behaviour is similar to that followed by high molecular weight PS, the differences in elution volumes among different eluents increasing monotonically with decreasing molecular weight and partition rather than adsorption probably being responsible for the shifts in retention volumes. However, at the total permeation limit, the situation is alike to that found in liquid-solid chromatography, the elution volumes of solutes with molecular sizes very close to that of styrene being determined by solv…

Influence of the Copolymer Content on the Miscibility, Phase Behaviour and Morphology of a DGEBA/Polystyrene/Styrene-co-Maleic Anhydride Ternary Blend

The miscibility, phase behaviour and morphology of ternary systems, formed by a DGEBA-based epoxy resin, polystyrene (PS) and styrene-co-maleic anhydride (SMA) copolymers have been investigated through phase diagrams. The analysis has been done in the absence and in the presence of 4,4'-methylene bis(2,6-diethyl aniline) (MDEA) as curing agent. In both cases, the influence of the copolymer content on blend compatibility, has been discussed. The results show that miscibility is enhanced by the presence of SMA copolymer in the blend and as the MA content in the copolymer is increased (from 7 to 14wt.-%), due to specific H-bonding interactions between the H-donor hydroxyl groups on the epoxy r…

Polymer-polymer interaction parameters in solvent/polymer/polymer ternary systems

Abstract Empirical equations defining the relationships between b23 and χ23 interaction parameters for the ternary systems toluene (1)/poly(dimethylsiloxane), PDMS, (2)/polystyrene, PS, (3) and benzene (1)/PDMS(2)/PS(3) have been determined. The dependences of both interaction parameters on the mean molecular weights of the macromolecular components have also been studied. A single dependence of b23 (or χ23) upon the mean molecular weight is found when both polymeric components have intermediate to high molecular weights. However, that single dependence is not found when the molecular size of polymer (2) is low.

Static measurements of refractive index increments at 633 nm with a modified refractive index detector

A R 401 Waters Assoc. differential refractometer has been modified to obtain the variation of refractive index increments, dn/dc, of polymer solutions at 633 nm. The introduced modifications were in the sample injection system and in the light source. The performance of the modified refractometer both with aqueous and organic solutions is analyzed. In order to localize a conformational transition in lysozyme, the dependence of dn/dc on temperature for lysozyme solutions in phosphate buffer is studied. Similarly, (dn/dc)k values for the ternary n-alkane/butanone/poly(dimethyl siloxane) systems over the whole composition range of the binary solvent mixtures are evaluated.

Taking into account the dependency on molar mass of the viscometric interaction parameter B, the modified Stockmayer-Fixman-Burchard equation ([η]/M1/2) = KΘ + C″ · A2 · M1/2 is obtained. It relates the intrinsic viscosity, [η], to the second virial coefficient, A2, and to the unperturbed dimensions parameter, KΘ, with C″ being a constant. Hereupon, KΘ can be determined from [η] and A2 data of any binary (solvent/polymer) and/or ternary (solvent 1/solvent 2/polymer) system, BPS and/or TPS. Because of the scarcity of reliable sets of [η] and A2 values mostly for TPS, the application of the above equation to obtain KΘ coefficients rests limited. This limitation can be surmounted by an A2 eval…

Association Equilibria Theory for Polymers in Mixed Solvents with Specific Interactions

Hydrogen bonding plays an important role in determining the physical and thermodynamic properties of polar fluids. Theoretical and experimental aspects of polymers, in mixed solvents with hydrogen-bonding-specific interactions, are investigated using a simple association model based on the theory of association equilibria developed by Pouchly et al. The thermodynamic non-idealities are accounted for using a modified Flory-Huggins theory with effective g ij parameters. The entropic term of the above formalism has been formulated taking into account the pplymer segment-solvent as well as the solvent-solvent hydrogen-bond formation. Four equilibrium constants are introduced to make a realistic…

Intrinsic viscosities, [η], second virial coefficients, A2, and interaction potentials, g12, for the ternary systems alcohol (1)/3-heptanone (2)/poly(1-vinyl-2-pyrrolidone) (3), with the unbranched alcohols methanol, ethanol and 1-propanol, were determined at 25°C. Taking into account the dependence of the viscometric interaction parameter, B, with the molecular weight of the polymer, the unperturbed dimensions parameter, KΘ, of the polymer was unambiguously obtained. Relationships between ΔKΘ (defined as ΔKΘ = ΔK − KΘ) and excess Gibbs energies, GE, and between excess viscosity, Δ[η], and GE allow to obtain equations relating A2 to ΔKΘ or to Δ[η]. Therefore, A2 can be evaluated from experi…

Elution curves on spherosil gels in pure and mixed eluents of poly(dimethylsiloxane), PDMS, and poly(methyl methacrylate), PMMA, as well as those of polystyrene, PS, just for comparison, have been determined. In a general way, PDMS elution volumers fit to those of PS, whereas PMMA elution curves shift to higher retention volumes. The differences in retention volumes between the different polymeric solutes have been interpreted in terms of differences in polymer-gel and polymer-solvent interactions. Hydrogen-bonding seems to be the main contribution to solute-substrate interactions.

Ternary Polymer Solutions with Hydrogen Bonds, 2

Experimental ternary phase diagrams for ternary systems CHL/PS-MAA/PVPy with diverse MAA contents have been determined by GPC. The presence of MAA in the copolymers gives rise to specific interactions, by hydrogen bond formation between both polymeric components, so strong that the isotherm for the system with the highest MAA content so far studied, CHL/PS-MAA(8%)/PVPy, is representative of a complex coacervation situation. By applying the theoretical background deduced by coupling the Flory-Huggins lattice model to the AET developed for ternary polymeric systems SPP with specific intermolecular interactions (via hydrogen bonds), free energy surfaces for the CHL/PS-MAA/PVPy systems are cons…

Estimation of the Compatibility Between Poly(Methylmethacrylate) and Poly(Styrene Co Vinyl Phenol) Blends from Dilute Solution Measurements

Abstract The compatibility of poly(methyl methacrylate) (PMMA) with poly(styrene‐co‐vinyl phenol) (PS‐VPh) with two different contents of vinyl phenol, 5.8 and 7.2%, in dilute tetrahydrofuran solutions has been investigated by size exclusion chromatography and fluorescence spectroscopy at 25°C. The chromatographic technique permits the evaluation of the preferential solvation at different PMMA/PS‐VPh ratios. Changes in the fluorescence properties of PS‐VPh, caused by its association with PMMA, were used to obtain the fraction of copolymer bound to PMMA at diverse PMMA compositions. Both techniques agree quantitatively in every system, indicating that the association increases when the PMMA …

Viscometric study on the compatibility of polymer–polymer mixtures in solution

Abstract The viscosity behaviour of mixtures formed by two uncharged polymers in dilute solution has been studied at 25°C. The ternary systems assayed, and denoted solvent (1)/ polymer (2)/ polymer (3), have in common the poly(ether sulphone) (PES) as polymer 2, and poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA) or poly(styrene) (PS) as polymer 3. The intrinsic viscosity and the viscometric interaction parameters have been experimentally measured for the binary (solvent/polymer) as well as for the ternary systems, and also theoretically evaluated for the latter. The estimation of the compatibility degree of the above polymer pairs have been done by means of three criteri…

Solution properties of polyelectrolytes

Abstract Aqueous size-exclusion chromatography was used to analyse the elution behaviour of several standard ionic polymers, including poly( l -glutamic acid), sodium poly(styrene sulphonate) and poly(acrylic acid), different in nature and chain flexibility, as a function of the pH and ionic strength of the eluent. Two organic-based hydrophilic packings, Spherogel TSK PW4000 and Ultrahydrogel 250, were tested in order to select the optimal conditions of macromolecular separation, and the results obtained for each column were compared. A set of calibration graphs for the above polyions as a function of eluent pH and ionic strength were obtained and compared with those obtained for uncharged …

A Study of Lipid-Lipid and Lipid-Polypeptide Interactions by High Performance Liquid Chromatography

Abstract Ternary systems containing phosphatidylcholine-cholesterol, phosphatidylcholine-gramicidin A or cholesterol-gramicidin A in tetrahydrofuran have been examined by high performance liquid chromatography. Preferential solvation of cholesterol and especially gramicidin A by phosphatidylcholine is observed. These results are interpreted in terms of hydrophobic interactions between membrane components.

Determination of χ from liquid-liquid phase data in ternary polymer systems (solvent/polymer/polymer) with hydrogen bonding

Two different models accounting for the dependences of χ and g interaction parameters on both temperature and composition have been applied to different ternary polymer systems (TPS) solvent(1)/polymer(2)/polymer(3). The ana- lyzed TPS have consisted on ten different polymer mixtures in chloroform as common solvent that can specifically interact via hydrogen bond. Experimental ternary phase diagrams determined by liquid chromatography were taken from literature. The application of the two models to the experimental data have served to obtain χij and gij interaction parameters for all the binary ij (ij = 12, 13, 23) interactions established between the three components of the system, with si…

Quantitative Prediction of Concentration Effects in Steric Exclusion Chromatography

Abstract A semiempirical model, based on a previous one quantitatively describing the dependence of the elution volume, V(cA), on the concentration of injected polymer, cA, in exclusion chromatography (SEC) at dilute solutions, has been developed. In the derived equation, concentration effects are mainly governed by the Huggins' coefficient, kA, and by the quadratic coefficient in the polynomial expansion of the reduced specific viscosity, kA. Because of the incertitudes on reliable kA and kA' values, these are respectively removed from the model through she Imai's equation and the empirical correlation kA' + 0.122=kA, here obtained. Thus, A predicted elution volumes besides polymer concent…

Evaluation of thermodynamic parameters for blends of polyethersulfone and poly(methyl methacrylate) or polystyrene in dimethylformamide

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…

Study on resolution capacity and secondary mechanisms of three different TSK gels for organic SEC.

A comparative study on the elution behavior in size-exclusion chromatography (SEC) of three polymeric TSK gel packings, named H, H H R , and H X L types, is performed. The deviations of the universal calibration (u.c.) curves of seven solvent-polymer systems show evidence that the existence of secondary effects accompanying the main SEC mechanism. These secondary mechanisms are a consequence of the binary enthalpic interactions between the different components of the chromatographic system, such as polymer-solvent, polymer-gel and solvent-gel. However, in the present case, the observed deviations from a unique u.c. curve can mainly be attributed to adsorption of polymeric solutes (analytes)…