Diffusion in microstructured block copolymers: Chain localization and entanglements

The diffusion (${\mathit{D}}_{\mathit{s}}$) of entangled and unentangled symmetric block copolymers is compared, above and below the ordering transition. The lamellar samples were not macroscopically oriented, and thus ${\mathit{D}}_{\mathit{s}}$ reflects a combination of mobilities parallel and perpendicular to the lamellar planes. For unentangled (Rouse) chains, ${\mathit{D}}_{\mathit{s}}$ is unaffected by the microstructure, whereas entangled (reptating) chains are retarded significantly; this difference reflects an interesting combination of thermodynamic and entanglement constraints. Furthermore, this retardation persists into the nominally disordered state.