Structure Factor - Polymers

Polymers

In polymer systems, the general definition (4) holds; the elementary constituents are now the monomers making up the chains. However, the structure factor being a measure of the correlation between particle positions, one can reasonably expect that this correlation will be different for monomers belonging to the same chain or to different chains.

Let us assume that the volume contains identical molecules, each composed of monomers, such that ( is also known as the degree of polymerization). We can rewrite (4) as:

,

(7)

where indices label the different molecules and the different monomers along each molecule. On the right-hand side we separated intramolecular and intermolecular terms. Using the equivalence of the chains, (7) can be simplified:

,

(8)

where is the single-chain structure factor.