Determination of thermodynamic parameters of polymer-solvent systems by light scattering
DSM1
TL;DR: In this article, the chemical potential of a given polymer and the solvent was determined from the intensities of light scattered from dilute and concentrated solutions of polystyrenes in a poor solvent (cyclohexane) and a good solvent (toluene) at different temperatures and at concentrations up to 30 per cent by weight.
About: This article is published in European Polymer Journal.The article was published on 1970-08-01. It has received 80 citations till now. The article focuses on the topics: Flory–Huggins solution theory & Dispersity.
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DSM1
TL;DR: In this paper, a lattice-based free enthalpy expression is used to describe actual phase relations; however, it cannot quantitatively predict their temperature, chain length, and concentration dependence.
Abstract: Polymer compatibility, to be understood here in the sense of thermodynamic stability, depends in a subtle way on molecular parameters. Some of these are traceable with the aid of model calculations based upon Flory and Huggins' expression for the free enthalpy of mixing. It appears that, in oligomeric mixtures in particular, the average chain lengths and the distributions of chain lengths in the two constituents markedly affect the location and shape of the miscibility gap. The entropy of mixing tends to shift the gap towards the composition region in which the constituent with the smaller average chain length dominates. The interaction parameter, if depending on concentration, can outweigh this effect. Examples, taken from literature and our own data, indicate that this situation does occur in practice. Hence, the lattice-based free enthalpy expression is an accurate tool for describing actual phase relations; however, it cannot quantitatively predict their temperature, chain length, and concentration dependence. In the last respect Flory's equation of state theory appears to be very superior. This was recently shown by McMaster, who analysed Flory's new free enthalpy function and found that small differences inter al. in the thermal expansion coefficients of two compatible polymers will cause the system to become incompatible upon a rise in temperature. The latter phenomenon is known to occur; examples are given. Compatibility being a subtle phenomenon, the question seems to be justified whether two samples of the same polymer of widely differing chain length might be immiscible. For linear polyethylene and anionic polystyrene the available data point to chain length compatibility. Two methods for the determination of compatibility are discussed, viz. the mutual solvent method and a light-scattering technique.
111 citations
TL;DR: In this article, solvent vapor swelling of ultrathin polymer films was used to determine Flory-Huggins solventpolymer and polymerpolymer interaction parameters (χi-j) for poly(3-hexylthiophene) (P3HT) and polystyrene (PS) over a wide solvent composition range.
Abstract: We report the use of solvent vapor swelling of ultrathin polymer films to determine Flory–Huggins solvent–polymer and polymer–polymer interaction parameters (χi–j) for poly(3-hexylthiophene) (P3HT) and polystyrene (PS) over a wide solvent composition range. From the calculated interaction parameters, we constructed a polymer/polymer/solvent phase diagram that was validated experimentally. χtetrahydrofuran–P3HT (1.04 ± 0.04) and χCHCl3–P3HT (0.99 ± 0.01) were determined through swelling of ultrathin P3HT films. Similar experiments using PS films gave χtetrahydrofuran–PS = 0.41 ± 0.02 and χCHCl3–PS = 0.39 ± 0.01, consistent with literature values. As expected, these χi–j parameters indicated that P3HT is less compatible than PS with either solvent. From δPS (17.9 ± 0.2 MPa1/2) and δP3HT (14.8 ± 0.2 MPa1/2), determined through regular solution theory, we calculated χPS–P3HT = 0.48 ± 0.06 at 23 °C. The resulting phase diagram was validated by solution-based transmission measurements of PS/P3HT blends in o-xyl...
107 citations
TL;DR: In this paper, a linear correlation function is found for cloudpoint composition curves of ternary systems consisting of one polymer, one solvent and one non-solvent, and the conditions for validity of this correlation function appear to be that the polymer is strongly incompatible with the nonsolvent and that only liquid-liquid demixing occurs.
93 citations
TL;DR: In this paper, spectroscopic ellipsometry was used to determine the Flory-Huggins parameters in thin films of polystyrene, poly(2vinyl pyridine), and poly(tert butyl methacrylate) swollen in controlled atmosphere of various common solvents.
81 citations
TL;DR: In this paper, the authors present zero shear viscosity and longest relaxation time measurements on semi-dilute solutions in the θ region, as a function of concentration and temperature.
Abstract: We present zero shear viscosity and longest relaxation time measurements on semi-dilute solutions in the θ region, as a function of concentration and temperature. Our results cannot be described using scaling laws. We show that viscoelastic properties are governed by two differents lengths.
77 citations
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TL;DR: In this paper, a statistical treatment of high polymer solutions has been carried out on the basis of an idealized model, originally proposed by Meyer, which is analogous to the one ordinarily assumed in the derivation of the ''ideal'' solution laws for molecules of equal size.
Abstract: A statistical mechanical treatment of high polymer solutions has been carried out on the basis of an idealized model, originally proposed by Meyer, which is analogous to the one ordinarily assumed in the derivation of the ``ideal'' solution laws for molecules of equal size. There is obtained for the entropy of mixing of n solvent and N linear polymer molecules (originally disoriented), ΔS=−k[(n/β) ln v1+N ln v2] where v1 and v2 are volume fractions and β is the number of solvent molecules replaceable by a freely orienting segment of the polymer chain. This expression is similar in form to the classical expression for equal‐sized molecules, mole fractions having been replaced by volume fractions. When the disparity between the sizes of the two components is great, this expression gives entropies differing widely from the classical values, which accounts for the large deviations of high polymer solutions from ``ideal'' behavior. The entropy of disorientation of a perfectly arranged linear polymer is found t...
3,513 citations
718 citations
TL;DR: In this article, a general equation for the fluctuation of refractive index in multi-component systems was developed, thus permitting the interpretation of turbidities for such systems in the absence of angular dissymmetry.
Abstract: A general equation is developed for the fluctuation of refractive index in multi‐component systems, thus permitting the interpretation of turbidities for such systems in the absence of angular dissymmetry. Applications to several special cases of interest are presented.
334 citations
314 citations