A friction factor analysis of the coupling between polymer/solvent self- and mutual-diffusion: Polystyrene/toluene
✍ Scribed by John M. Zielinski
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 671 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0887-6266
No coin nor oath required. For personal study only.
✦ Synopsis
The Bearman statistical mechanical theory, which couples the mutual-diffusion and selfdiffusion coefficients via friction factors, has been applied to polystyrene/toluene solutions with polystyrene molecular weights of 18 kDa and 900 kDa. Toluene and polystyrene selfdiffusion coefficients, obtained from the literature and measured here, along with polystyrene/toluene binary mutual-diffusion coefficients and thermodynamic data, were employed to independently calculate the three friction coefficients fl1, and (zz) required to describe transport within binary solutions. Results reveal that the frequently used geometric mean approximation (GMA) for relating the friction coefficients consistently underestimates (2:22 and worsens with increasing polymer molecular weight. The GMA is found to be appreciably more accurate than the arithmetic mean approximation. A formalism recently proposed by Vrentas et al. has also been evaluated for this system and is found to describe the concentration dependence of Cll very well. The Vrentas model, therefore, can accurately predict mutual-diffusion coefficients from solvent self-diffusion coefficients for polystyrene/ toluene solutions.