Dynamical relaxations in mixtures of different polymers and nonsymmetrical copolymers in solution

Dynamical relaxation properties of nonsymmetrical mixtures of homopolymers and of copolymers in solution are examined. In particular, examples of bimodal mixtures in solution, ternary mixtures of two different homopolymers and a solvent, and nonsymmetrical diblock copolymers in solution are examined. The frequencies of the eigenmodes Γ and Γ′, those of the cooperative mode Γ_T and the interdiffuse mode Γ_I are calculated for these systems. It is found that the variations of T_T and T_I, with the scattering wave number q are practically identical to those of Γ_T and Γ_I, respectively. This identity is rigorous only for mixtures or copolymers where the two polymer components are identical except for their contrast factors (i.e., indices of refraction or scattering lengths). Here, it is argued that the identification of the eigenmodes with the cooperative and interdiffuse modes can be extended qualitatively to mixtures of different polymers and to nonsymmetrical copolymers in solution.