Theoretical Outline - The Interdiffusion Mode

Using the random phase approximation (RPA), the coherent scattering intensity Icoh(Q, t) of a polymer blend/solvent or a diblock copolymer/solvent system can 

For both systems Ac becomes zero if the condition of zero average contrast (Pm Ps)x + (Pm Ps)(l -x) = 0 

For the special case of a symmetric (x = 1/2) diblock copolymer, Ay is given by 

In the absence of hydrodynamic, thermodynamic or topological interactions, the corresponding characteristic frequencies Qpp(Q) and 2pp(Q) in the regime Q Rg)1/2 1 are derived from Eq. (94) assuming p(Q) = N/q (Rouse dynamics) 

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