Solution Characterization of Monodisperse Atactic Polystyrenes by Static and Dynamic Light Scattering
Abstract:Anionically polymerized polystyrene standards have been characterized by static and dynamic light scattering in toluene at 25°C. The molecular weights ranged from 3000 to two million g/mol. An appropriate standard for light scattering intensity was developed and the absolute Rayleigh ratio for toluene was determined for the experimental conditions. The molecular weight dependence of the second virial coefficient A2 could be represented as a power law. The present results are in good agreement with previous measurements of A2. For the higher molecular weight polymers, the mean-square radius of gyration was determined. The present results could also be represented as a power law, which was in good agreement with previous results. Dynamic light scattering was analyzed to obtain the mutual-diffusion coefficient as a function of concentration and molecular weight. These results were then used to obtain the self-diffusion coefficient, hydrodynamic radius, and virial coefficient for the mutual-diffusion coefficient. Hydrodynamic radii could be represented as a power law, which was also in good agreement with previous reports. The virial coefficient for the mutual friction was calculated as well. The relationship between molecular weight distribution and the polydispersity index determined from dynamic light scattering was calculated and compared to actual data. The samples used here conformed to the manufacturers' reported weight to number-average molecular weight ratios.
Keywords: Hydrodynamic radius; Light scattering; Molecular weight distributions; Molecular weight scaling laws; Osmotic second virial coefficient; Polystyrene characterization; Radius of gyration; Self-diffusion coefficient
Document Type: Research Article
Affiliations: Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
Publication date: 2003-05-01