Thermal Diffusion in Polymer Solutions

Abstract

Thermal diffusion measurements have been made on a series of solutions of polystyrene as follows: (1) Five molecular weights (10 000 to 336 000) in toluene; (2) 136 000 molecular weight in o-xylene, styrene, ethyl benzene, dioxane, and pyridine; (3) Styrene dimer in toluene and styrene; measurements were also made on some binary monomeric mixtures. The thermodynamic property X∂μ/∂X describes adequately the concentration dependence of the thermal diffusion ratio α. It appears that that portion of the motion of the polystyrene molecule in dilute and somewhat concentrated solutions which is segmental involves 10—13 chain atoms in the moving segment. The results seem consistent with Kauzmann and Eyring's picture for motion of long chain molecules.

Advances in Thermodiffusion and Thermophoresis (Soret Effect) in Liquid Mixtures

“…This may give a reasonable estimate of the polymer activation energy of viscous flow and the net heat of transport; however, viscosity data are required for various polymer-solvent combinations at various polymer molecular weights. Emery and Drickamer (1955), therefore, proposed a universal number for the activation energy, which is not accurate enough bearing in mind that different combinations of polymer-solvent may have very different activation energies. Eslamian and Saghir assumed that the activation energy of viscous flow of a long-chain polymer molecule is proportional to the activation energy of viscous flow of the monomers (that represent the moving segments) of that polymer, usually in the liquid phase.…”

“…Thermodiffusion experimental data in polymer solutions have been available since 1950s, e.g., (Emery and Drickamer, 1955;Whitmore, 1960;Schimpf and Giddings, 1989). Schimpf and Giddings (1989) also provide a good review of previous experimental and theoretical works.…”

“…Therefore, it is not possible to estimate the activation energy of viscous flow of a polymer at a mixture temperature, which is usually the room temperature. Emery and Drickamer (1955) argued that the viscosity data of a given polymer solution at low concentrations may be used to calculate the activation energies of viscous flow of the solution at various concentrations. Then the activation energy of viscous flow of the polymer (at the limit where no solvent is present in the solution) may be estimated by linear extrapolation of the solution activation energies with respect to the polymer concentration.…”

Study of the thermal diffusion behavior of simple binary mixtures

“…48) where r is the distance between two atoms , ϕ is a bond angle, δ is a harmonic dihedral angle, τ is a torsional angle (p is the periodicity of the potential) and k is the force constant. The subscript "0" identifies the equilibrium value.…”

“…A thermal diffusion cell is a traditional experimental method for measuring the Soret coefficient [48,178,95,102,60]. …”