Determination of absolute polydispersity and molecular weight distribution of high molecular weight polymers from dynamic light scattering

Jena, Sidhartha S.; Bohidar, Himadri B.
July 1993
Journal of Chemical Physics;7/1/1993, Vol. 99 Issue 1, p673
Academic Journal
Intensity correlation function obtained from dynamic light scattering (DLS) experiments has been theoretically analyzed within the framework of the Schulz molecular weight distribution. The correlation function has been expanded about the mean molecular weight instead of the average linewidth as is normally done in cumulant analysis. This allows the explicit determination of polydispersity (Z). In addition to this, it has been shown that the molecular weight exponent of diffusion coefficient ν, occurring in the Mark–Houwink equation DM-ν and the average molecular weight M, can in principle be determined from DLS data. Finally, from the knowledge of Z and M it is possible to construct the Schulz molecular weight distribution function. Experiments performed on three model systems, polystyrene in cyclohexane at 35 °C (θ system), polystyrene in toluene at 20 °C (good system), and latex beads in a deionized aqueous medium (hard spheres system), provide excellent matching between the experimental data and results obtained using our proposed method of analysis of DLS studies.


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