Static Light Scattering by Dilute Polymer Solutions

3 STATIC LIGHT SCATTERING BY DILUTE POLYMER SOLUTIONS 

The theory of thermodynamic fluctuations in the context of light scattering was introduced first by Smoluchowski and Einstein [12, 13]. Einstein considered that the scattering of light in a solution arises from local density and concentration fluctuations. However, it was only till the late 40s and early 50s that Brinkman and Hermans [14], Stockmayer [15], and Kirkwood and Goldberg [16] adopted this approach in the context of light scattering by poiymer solutions. Here, we summarize only the basic results for a binary mixture. 

In a binary mixture, there are 3 degrees of freedom and it can be proved that the fluctuations in the dielectric constant can be reduced to the sum of the fluctuation in the density of the pure solvent plus the fluctuations in the molar concentration of macromolecules. 

Using the virial expansion for the osmotic pressure, we can write tt as 

Since V depends of the solvent used, the molecular weight determined in this way is necessarily apparent. 

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STATIC LIGHT SCATTERING BY DILUTE POLYMER SOLUTIONS 375 TABLE 18.1 Form Factors for Different Geometries in the RDGA... 

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