posted on 2024-03-13, 22:20authored byBenjamin
R. Magruder, David C. Morse, Christopher J. Ellison, Kevin D. Dorfman
Self-consistent
field theory for thin films of AB diblock polymers
in the double-gyroid phase reveals that in the absence of preferential
wetting of monomer species at the film boundaries, films with the
(211) plane oriented parallel to the boundaries are more stable than
other orientations, consistent with experimental results. This preferred
orientation is explained in the context of boundary frustration. Specifically,
the angle of intersection between the A/B interface and the film boundary,
the wetting angle, is thermodynamically restricted to a narrow range
of values. Most termination planes in the double gyroid cannot accommodate
this narrow range of wetting angles without significant local distortion
relative to the bulk morphology; the (211)-oriented termination plane
with the “double-wave” pattern produces relatively minimal
distortion, making it the least frustrated boundary. The principle
of boundary frustration provides a framework to understand the relative
stability of termination planes for complex ordered block polymer
phases confined between flat, nonpreferential boundaries.