Some General Relationships and Assumptions

1 Some General Relationships and Assumptions Before proceeding further, it is useful at this point to introduce some general relationships, notations, and assumptions to be used in the rest of the chapter. 

Segment. As discussed in Chapter 1, the intensity of scattering depends on the positions of all the atoms or atomic nuclei in the system. The amplitude A(q) of scattering is specified completely by 

Such an approximation is allowed as long as the intensity data of interest is confined to regions of small q. To see this in more detail we rewrite (6.25) as follows  

Partial Structure Factor. We consider a binary mixture containing Na molecules of polymer a (a = 1 or 2), each of molecular volume va so that there are Za va/v ua 

The partial structure factor defined by (6.29) can be written in an alternative way. In terms of the local number density na (r) of type a segments at position r, it becomes 

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