Overlap factor and relative concentration

For the experimentalist, the quantity of monomers expresses itself naturally in terms of the mass-concentration p of solute. However, the important parameter is the rate of chain overlap, which can be defined as the ratio p/p where p represents the overlap concentration. More precisely, theory shows that overlap 

The quantity CXd is therefore a basic quantity, and it is important to determine it with great accuracy. However, it is not possible to propose a method which would be valid in all cases for example, it is perfectly possible to use osmotic pressure to study solutions with overlap without being able to determine in this way the mean square distance R2 — X2d. 

There are, in fact, three methods of determining CXd experimentally. 

In this case, it is necessary to know the basic quantities S, b, and p, whose values are determined mainly by light scattering (Section 1). From the area S and the interaction b, we get the parameter 

In this case, the radius of gyration flg is measured in the limit of zero concentration. We set 

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