Polyelectrolytes, average molar mass

Alginates behave as polyelectrolytes in the presence of monovalent counterions, and in 0.1 M NaCl, the intrinsic viscosity allows determination of the average molar mass (172). 

By calibrating the column or column set with a set of standards, a calibration curve of retention versus the logarithm of molar mass is constructed so that molar mass averages may be calculated for unknown polymers. Figure 6.10 is an example chromatogram of a separation of a polyDADMAC coagulant polyelectrolyte. The molar mass distribution, see Figure 6.11, is relative to the calibration standards used, polyethylene oxide in this example. 

The determination of single molar mass averages from simple solution properties, such as colligative and viscosity methods, has not been a popular held of research in the past few years. The state of the art has been reviewed by Slade and by Billingham. Since the publication of ref. 2, two major manufacturers (Perkin-Elmer and Hewlett-Packard) have withdrawn from the market so that there is now a much reduced choice in equipment for membrane osmometry and for vapour pressure osmometry. Membrane osmometry as a technique has received virtually no attention during the review period, although its use has been reported in a number of papers. Oman has described studies of the osmotic coefficients of aqueous polyelectrolytes, and Oman and Batho describe theoretical models for... 

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