Chain Diffusion in Lamellar Block Copolymers

Diffusion of symmetric diblock copolymer chains in macroscopically oriented lamellar block copolymers are studied in a molecular dynamics simulation. Results for diffusion constant both parallel D‖ and perpendicular D⊥ to the lamellar planes are compared to results in the disordered one phase region. For diblocks of length N = 40 (1.1Ne) and 100 (3Ne), where Ne is the entanglement length of a homopolymer melt at the same density, D‖ is nearly independent of χ, while D⊥ is strongly suppressed as χ is increased. These results are in agreement with theoretical predictions based on the Rouse model. The isotropic diffusion constant of quenched disordered systems is approximated fairly well by (2D‖ +D⊥)/3 of the corresponding lamellar system. Typeset using REVTEX