Flory theory of light scattering in dilute solution

8 Flory theory of light scattering in dilute solution 

The excess Rayleigh ratio can also be calculated for the general case of a dilute solution at all scattering angles. The scattering function at finite scattering vector is defined as  

To evaluate this expression, it is convenient to express the location of each subchain in terms of fhe location of the center of mass of each macromolecule, R, and the location of the subchain relative to the center of mass, % 4 =. The scattering function can then be expressed in terms 

The difference in fhe moment of inertia vectors is equal to the difference in the absolute location vectors of the subchains 4 - Sy = 4. The second average is then equal to the scattering fxmction for a single molecule, S i(ij) (Equation 3.7). The total scattering fxmction is then expressed as the product of the center-of-mass structure factor and the intramolecular structure factor  

The center-of-mass structure factor can be expressed in terms of the pair correlation fxmction, g[Ru), for the centers of mass of different molecxiles. Within the limit of infinite dilution, the pair correlation is defined exactly in terms of the pair potential of mean force  

---