Slow mode solvent quality

The kinetics of phase separation between polymers of widely differing mobilities generated a long debate over fast-mode and slow-mode views. It is now recognised that, depending on degree of overlap and solvent quality. 

Systematic studies refute suggestions that the slow mode is simply correlated to solvent quality. As discussed below, slow modes are obtained in some but not all good. Theta, and marginal solvents. Sun and Wang demonstrate the presence of slow modes in many polymer good solvent combinations(36). Brown and collaborators, among others, find slow modes for polymers in Theta and marginal solvents. 

The dynamics of concentration fluctuations expressed by eqn [161] (or eqn [34]) of the Omstdn-Zemike type exhibits the diflrrsion coeflrdent D =feT/(6nj 0), eqn [72], which can also be derived from fluctuations of gel-like networks with screening of hydrodynamic interactions. Thus, it is often rderred to as the gd mode. A decrease in mesh size increases the rdaxation rate of the gel mode. Experimentally, DLS for semidilute solutions rrsually exhibits another mode of motions with a very slow decay rate. This slow mode may be assodated with some inhomogeneity depending on solvent quality and sample preparation, or may be rdated to the translational... 

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