Theoretical study of miscibility and glass-forming trends in mixtures of polystyrene spheres
1984; American Institute of Physics; Volume: 80; Issue: 9 Linguagem: Inglês
10.1063/1.447222
ISSN1520-9032
Autores Tópico(s)Adsorption, diffusion, and thermodynamic properties of materials
ResumoWe present a theoretical study of glass-forming trends and miscibility in mixtures of polystyrene spheres (‘‘polyballs’’) of different diameters, suspended in an aqueous solution. The polyballs are assumed to be charged and to interact via a Debye–Hückel screened Coulomb potential. The Helmholtz free energy is calculated from a variational principle based on the Gibbs–Bogolyubov inequality, in which a mixture of hard spheres of different diameters is chosen as the reference system. It is found that when the charges of the two types of polyballs are sufficiently different, the variationally determined ratio of hard-sphere diameters differs substantially, leading to packing difficulties characteristic of glass formation. The experimentally observed range of glass formation corresponds to a ratio of hard-sphere diameters of 0.8 or less. Calculations of the free energy as a function of concentration indicate that the liquid polyball mixture is stable against the phase separation, even for widely different polyball charges.
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