Screening in semi-dilute solutions

There is an analogy between eq. (in.42) fw the amelations and the Debye-HQckel law for screened coulomb interactions in an electrolyte. The notion of screening was first introduced by Edwards for polymer solutions. His argument may be presented as follows. We assume that one monomer is fixed at point O in the solution, and we ask for the excess concentration (r) which will result from this condition, at a distance r from O. 

Note that go satisfies the analog of a Laplace equation 

00 in the following discussion, since it is a constant potential, giving no interesting spatial effects.) 

If we know U(r), how do we calculate the resulting concentration profile (r) An approximate answer is written below  

It may be explained as follows locally at point r, the potential l/(r ) shifts the monomer concentration from c to  

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