The relationship between rheological behavior and structures of styrene–butadiene (PS–PB) diblock copolymers was examined in a PB‐selective solvent,n‐tetradecane (C14). At low temperatures the behavior of concentrated PS–PB/C14 micellar solutions was dominated by plasticity due to a macrolattice of micelles. Thermodynamic confinement (balance of elastic and osmotic requirements) on corona PB blocks led to macrolattice formation. Differing from the PS–PB/C14 solutions, blends of PS–PB and homo‐PB chains did not suffer from the confinement and exhibited linear viscoelastic relaxation that was retarded by entanglements of PB blocks. In further investigation of entanglement dynamics, constraint release (CR) relaxation in PS/PS binary blends was found to be reasonably but not completely described by a Rouse‐type CR model. This model was further examined for dielectric relaxation of polyisoprene (PI) chains having dipoles parallel to the chain contour. Specifically, eigenfunctions associated with a local correlation function were evaluated from dielectric data of dipole‐inverted PI chains. Those eigenfunctions were nonsinusoidal, most clearly exhibiting non‐Rouse nature of actual CR processes.