Dynamics of a triblock copolymer in a selective solvent for the middle block investigated using pulsed field gradient NMR

The concentration dependence of the self-diffusivity of a hydrogenated polystyrene-block-polybutadiene-block-polystyrene triblock copolymer in an n-heptane solution (c = 0.58-6.9 g/100 mt) was investigated using the pulsed field gradient NMR at 20-35 degrees C. The solvent is a preferential solvent for the middle block. At low concentrations, micelle-like aggregates (flowers) are observed, With increasing concentration larger aggregates (animals) are formed. These aggregates show a tendency to anomalous diffusion: exchange of micelles between the aggregated and the nonaggregated state as well as restricted diffusion. At the highest concentrations, individual diffusion of insoluble domains (nodes) is observed, but no transient network behavior. The width of the distribution of self-diffusivities corroborates the findings. Our results are in agreement with light scattering results published previously.