Molecular weight distribution methods sedimentation velocity

In the sedimentation equilibrium method, a lower centrifugal field is maintained for a period of time in such a way that sedimentation is balanced by diffusion and M equilibrium distribution of polymer is established in the cell. Although M and Mz are easily determined, the length of time of the experiment is a disadvantage. In contrast to light scattering, this method is not affected by dust particles, and no calibration is needed. The molecular weight distribution may be obtained from the sedimentation velocity data, but not without mathematical difficulties... 

Mimk (144) has recently reviewed the use of sedimentation velocity and sedimentation equilibriiun to characterize molecular weight. A new absolute method for the determination of molecular weight distribution based on band sedimentation and LALLS has been apphed to water-soluble polymers (145). 

Research in this area shows great potential. Over the past 30 years, dual systems have been applied mainly in the paper industry. The applicatimi of PECs, described as particle-forming flocculants, provides new possibilities in solid-liquid separation processes. For an effective system, the application parameters have to be optimized (e.g. polymer type, cmicentratiOTi, charge, molecular weight). Therefore, direct and efficient methods for the characterization of the flocculation behavior (sedimentation velocity, packing density of the sludge, particle size distribution) are necessary and will be described. 

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