Simulations on a swollen gyroid nanostructure in thin films relevant to systems of ionic block copolymers
Knychała P.1,2, Banaszak M.1
- 1Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614, Poznan, Poland
- 2The President Stanislaw Wojciechowski Higher Vocational State School in Kalisz, ul. Nowy Swiat 4, Kalisz, Poland
European Physical Journal E (37: 67), 2014
DOI:: 10.1140/epje/i2014-14067-4
Abstract: Self-assembly of symmetric A/S-B copolymer melt to gyroid nanostructure, partitioning space
into interpenetrating nano-labyrinths (channels), in thin films, is investigated using a minimal lattice
model with short-range interactions. This model is relevant to poly(styrenesulfonate)-b-polymethylbutylene
melt consisting of three types of segments, A, B and S, corresponding to styrene, methylbutylene and
styrenesulfonate, respectively. A single sequence of A, B, and S is used in simulations and the fraction of S
segments is fixed at p = 0.647 which corresponds to experimental data. The film thickness, Lz , is restricted
to nine values (Lz = 17, 22, 26, 30, 34, 42, 51, 60, and 68 in units of the underlying lattice constant). The
gyroid nanostructure is found to be stable if the film thickness is equal to or greater than the bulk period
of the nanophase. The observed gyroid is referred to as swollen since the volume fraction of two continuous
networks made of the B segments is anomalous with respect to that of conventional diblock copolymers.
In contrast to bulk state, we do not directly observe the order-disorder transition to the gyroid nanophase
for thin films. In this case, however, simulations indicate a direct order-disorder transition to a lamellar
phase and the order-disorder transition temperature is higher than that in the bulk state, varying strongly
with the film thickness.
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