Chain Diffusion in Lamellar Block Copolymers
Abstract
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 (1.1 N_e) and
100(3
N
e
)
, where
N
e
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
(2
D
∥
+
D
⊥
)/3
of the corresponding lamellar system.