Preferential adsorption in polymer/solvent-1 /solvent-2 solutions by infrared spectroscopy (original) (raw)
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Preferential Adsorption onto Polystyrene in Mixed Solvent Systems
Macromolecules, 1979
A previously developed technique using the ultracentrifuge as a differential refractometer has been modified and applied for the evaluation of preferential adsorption onto polymers. Three polystyrene samples in two combinations of solvent mixtures, benzene (l)-cyclohexane (2) and ethyl acetate (l)-cyclohexane (2), were measured over the entire range of composition of the solvent mixture. Semiempirical relations were developed for the binary solvent interaction parameter, g,,, as a function of temperature and solvent composition. The experimental results are discussed in relation to preferential adsorption, thermodynamical interaction parameters, and excess free energy of mixing of the two liquid components. The results confirmed and refined the conclusions drawn from sedimentation equilibrium experiments for the same experimental system.
Interfacial Properties and Adsorption of Polymer-Solvent Binary Mixtures
Journal of Physical Chemistry C, 2007
The phase behavior and interfacial properties of mixtures of chain molecules built of 2, 4, and 10 segments with monomeric species are studied using density functional theory. The chain molecules are modeled as fully flexible chains of tangentially bonded spherical segments. The chain segments and the solvent molecules interact via the truncated Lennard-Jones potential. Within density functional theory, we investigate the structure of the fluid-fluid interface and interfacial tension. In general we find an accumulation of the solvent particles at the interface. For mixtures with longer chains, we find the complete wetting transition at the gas-liquid interface upon approaching the triple point. We also report mean field density functional theory results for adsorption of tetramer-monomer mixtures in slit-like pores. We present density profiles, adsorption isotherms, and phase diagrams and discuss the effects of the model parameters on the capillary condensation. The main effect is that confinement gives rise to a substantial enrichment of tetramers, relative to bulk phases. However, the global phase diagrams for confined mixtures belong to the same class of phase behavior as those for bulk phases.
European Polymer Journal, 1981
The cosolvent system poly(p-tert butylphenyl methacrylatei (3)/acetone(l)/cyclohexane (2~ has been studied at 298 K by light scattering, refractive index increment of dialysis equilibrium and viscomerry. The preferential adsorption coefficient, 2", for the whole composition range of the binary mixture acetone (1 i/cyclohexane(2) has been determined. The values have been compared with the theoretically calculated values. The results indicate that in this system it is necessary to take into account the tertiary interaction parameters Z a 23, Z ~ 2: and Z-, 33.
Colloid and Polymer Science, 1993
Sorption equilibrium of polystyrene and poly (dimethyl siloxane) in mixed solvents has been monitored by means of the preferential adsorption coefficient experimentally determined from intensity light scattering measurements. The pairs of solvents used to dissolve each polymer sample have been selected for the purpose to perform cosolvent and cononsolvent ternary polymer systems. Flory-Huggins formalism including ternary interactions has been used to predict the sorption equilibrium for the cosolvent system and, for the first time, for cononsolvent ones. Moreover, the proportionality between binary and ternary interactions, recognized by Pouchly, is also corroborated for both ternary polymer systems. From a thermodynamic standpoint, the sorption equilibrium has been described by approaching the behavior of the "bulk solvent" to the binary liquid mixture through the excess Gibbs free energy.
Sorption phenomena of organic solvents in polymers: Part I
European Polymer Journal, 2005
In this work we use the vapor-sorption equilibrium data to show the degree of solvent upturn in each solvent-polymer system. For this purpose, sixty-one isothermal data sets for forty copolymer + solvent binaries and for fourteen of their parent homopolymer + solvent binaries have been used in the temperature range of 23.5-80°C. Solvents studied are acetone, acetonitrile, 1-butanol, 1,2-dichloroethane, chloroform, cyclohexane, hexane, methanol, octane, pentane, and toluene. Copolymers studied are poly(acrylonitrile-co-butadiene), poly(styrene-co-acrylonitrile), poly(styreneco-butadiene), poly(vinyl acetate-co-ethylene), and poly(vinyl acetate-co-vinyl chloride). All copolymers are random copolymers. Some homopolymers are also studied: polyacrylonitrile, poly(cis-1,4-butadiene), poly(ethylene oxide), polystyrene and poly(vinyl acetate). According to these data sets, solvent weight fraction in the polymer is plotted against solvent vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory-Huggins theory to obtain dimensionless interaction parameter, v. Also the Zimm-Lundberg clustering theory and non-ideality thermodynamic factor, C are used to interpret the equilibrium data.
The effect of polymer polydispersity on the adsorption isotherm
Journal of Colloid and Interface Science, 1981
Adsorption isotherms of polyvinyl alcohol (PVA) from water onto silver iodide and oxidized carbon black are analyzed in terms of the model of Cohen Stuart et al. [J. Polym. Sci. Polym. Phys. Ed. 18, 559 (1980)] in which the polydispersity of the polymer is taken into account. It is shown that the shape of the isotherms is affected by the time of adsorption and the adsorbent content. This behavior is explained on the basis of preferential adsorption of larger PVA molecules over smaller ones. The effect of the surface area to solution volume ratio is eliminated when the adsorption is plotted as a function of the polymer concentration times the ratio solution volume/adsorbent area. Hence, for the adsorption of polydisperse polymers the relevant variable is not the solution concentration but the dissolved amount of polymer expressed per unit area. The fractionation due to adsorption and the molecular weight dependence of the adsorption are studied on the basis of the known polymer molecular weight distribution and the isotherm. The experimentally observed molecular weight dependence of the adsorption is compared with results obtained from the adsorption model of Hoeve. Reasonable agreement can be attained.
Adsorption of water-soluble polymers with surfactant character
Journal of Colloid and Interface Science, 2007
A comparative study between Langmuir and Gibbs monolayers of a hyperbranched polyol, poly(propylene glycol) homopolymers, and poly(propylene glycol)-poly(ethylene glycol) copolymers with different structure and molecular weight, is reported. Dynamic surface tension (DST) and surface pressure measurements have been carried out to characterize these amphiphilic water-soluble polymers. The adsorption kinetics results are consistent with a rapid diffusion stage followed by a slow reorganization at the air-water interface. The characteristic times of these steps, calculated by the Joos model, point out differences among the polymers in the diffusion rate and rearrangement mechanisms for diluted solutions. Short time analysis of DST data leads to diffusion coefficients in qualitative agreement with the diffusion times calculated with Joos' model. Spread monolayers remain stable for long periods of time. The desorption process seems quite inoperative. As a consequence, the surface pressure of the spread monolayers can be studied over a broad surface concentration range. 2D first-order phase transitions have been evidenced from plateaux observed in Langmuir and Gibbs isotherms. It has been found that Gibbs monolayers lead to lower surface tension states than the Langmuir ones.
European Polymer Journal, 1990
The behaviour of poly(ethyl methacrylate) in the system ethyl acetate (l)/iso-propanol (2) is studied; liquid 1 is a solvent for the polymer and liquid 2 is a precipitant. The techniques laser light scattering, differential refractometry and viscometry are used. Preferential adsorption of 2 over the whole composition range is observed as well as a remarkable influence of temperature on the inter-and intra-molecular interactions of the system. Various theoretical expressions for the preferential and total adsorption coefficients are used; their agreement or disagreement with the experimental results is explained on the basis of polymer-solvent interactions.
ACS Omega, 2018
Molecular selective adsorption processes at the solid surface of biopolymers in mixed solvent systems are poorly understood due to manifold interactions. However, the ability to achieve adsorptive fractionation of liquid mixtures is posited to relate to the role of specific solid−liquid interactions at the adsorbent interface. The hydration of solid biopolymers (amylose, amylopectin, cellulose) in binary aqueous systems is partly governed by the relative solvent binding affinities with the biopolymer surface sites, in accordance with the role of textural and surface chemical properties. While molecular models that account for the surface area and solvent effects provide reliable estimates of hydration energy and binding affinity parameters, spectroscopic and thermal methods offer a facile alternative experimental approach to account for detailed aspects of solvation phenomena at biopolymer interfaces that involve solid−liquid adsorption. In this report, thermal and spectroscopic methods were used to understand the interaction of starch-and cellulose-based materials in water−ethanol (W−E) binary mixtures. Batch adsorption studies in binary W−E mixtures reveal the selective solvent uptake properties by the biomaterials, in agreement with their solvent swelling in pure water or ethanol. The nature, stability of the bound water, and the thermodynamic properties of the biopolymers in variable hydration states were probed via differential scanning calorimetry and Raman spectroscopy. The trends in biopolymer− solvent interactions are corroborated by dye adsorption and scanning electron microscopy, indicating that biopolymer adsorption properties in W−E mixtures strongly depend on the surface area, pore structure, and accessibility of the polar surface groups of the biopolymer systems, in agreement with the solvent-selective uptake results reported herein.
Experimental aspects of polymer adsorption at solid/solution interfaces
Advances in Colloid and Interface Science, 1985
Several recent review articles have been concerned with the topic of polymers at interfaces from the theoretical standpoint. This reflects the extensive effort made in this area over the last 10 – 15 years. However, new experimental techniques for studying polymers at interfaces have also begun to appear in recent years; so have better defined model systems. This article is therefore directed more to a survey of these experimental aspects of the subject. However, a short review of the current state of the theory is given first as background and to define concepts. In the following chapter, details of the modern experimental methods are given. The last chapter comprises an extensive comparative review of results obtained using these techniques with model systems, covering homopolymers, copolymers and polyelectrolytes.