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Download fileControlling the Morphology of Model Conjugated Thiophene Oligomers through Alkyl Side Chain Length, Placement, and Interactions
journal contribution
posted on 2014-04-22, 00:00 authored by Hilary
S. Marsh, Eric Jankowski, Arthi JayaramanWe have performed coarse-grained
molecular dynamics simulations
of thiophene-based conjugated oligomers to elucidate how the oligomer
architecture, specifically the orientation and density of alkyl side
chains extending from the thiophene backbones, impacts the order–disorder
temperatures and the various ordered morphologies that the oligomers
form. We find that the orientation of side chains along the oligomer
backbone plays a more significant role than side chain density, side
chain–side chain interactions, or side chain length in determining
the thermodynamically stable morphologies and the phase transition
temperatures. Oligomers with side chains oriented on both sides of
the backbone (“anti”) form lamellae,
while oligomers with side chains oriented on one side of the backbone
(“syn”) assemble into hexagonally packed
cylinders that can undergo a second, lower temperature transition
to lamellae or ribbons depending on side chain–side chain interaction
strength. The strength of side chain–side chain interactions
affects the order–disorder temperature, with oligomers having
moderately attractive side chains exhibiting higher transition temperatures
than those with weakly attractive side chains. Side chain length modulates
the spacing between morphological features, such as cylinders and
lamellae, and affects the order–disorder temperature differently
depending on oligomer architecture.