Intramolecular and intermolecular structure functions

A pair of monomers may belong either to the same chain or to two different chains. Thus, two types of correlations correspond to these two kinds of pairs. 

let us write the structure function as the sum of two contributions. In particular, we shall consider here the case of homogeneous but different molecules We can write (7.2.17) in the form 

It is convenient to express H (q) and // (q) in terms of correlation functions in ordinary space. First, let us introduce the following function related to the form of a molecule of species a, in ordinary space 

Its Fourier transform is called the form function of the molecule 

Let us now introduce the pair correlation function of monomers belonging to two different chains 

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The structure function H(q) of a solute can be determined by measuring the intensity I (q) scattered by the solution. However, certain techniques enable the experimentalist to make separate measurements of the intramolecular and intermolecular structure functions, namely H (q) and Ha(q). These functions have different behaviours which are schematically represented in Fig. 7.3. It is from the intramolecular structure function Hl(q) that the scattered intensity gets its characteristic appearance (see Fig. 7.4). 

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