Diffusion of Entangled
Rod–Coil Block Copolymers
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Abstract
The diffusion of entangled rod–coil block copolymers
is
investigated by molecular dynamics (MD) simulations, and theories
are introduced that describe the observed features and underlying
physics. The reptation of rod–coil block copolymers is dominated
by the mismatch between the curvature of the rod and coil entanglement
tubes, which results in dramatically slower diffusion of rod–coils
compared to the rod and coil homopolymers. For small rods, a local
curvature-dependent free energy penalty results in a rough energy
surface inside the entanglement tube, causing diffusivity to decrease
with rod length. For large rods, rotational hindrances on the rod
dominate, causing the coil block to relax by an arm retraction mechanism
and diffusivity to decrease exponentially with coil size