Issue |
Europhys. Lett.
Volume 61, Number 3, February 2003
|
|
---|---|---|
Page(s) | 334 - 340 | |
Section | Condensed matter: structure, mechanical and thermal properties | |
DOI | https://doi.org/10.1209/epl/i2003-00179-4 | |
Published online | 01 January 2003 |
Polar order in nanostructured organic materials
1
Department of Materials Science and Engineering,
Northwestern University Evanston, IL 60208, USA
2
Department of Chemistry, and Feinberg School of
Medicine Northwestern University - Evanston, IL 60208, USA
Corresponding authors: m-olvera@northwestern.edu, s-stupp@northwestern.edu
Received:
11
July
2002
Accepted:
12
November
2002
Achiral multi-block liquid crystals are not expected to form
polar domains. Recently, however, films of nanoaggregates formed
by multi-block rodcoil molecules were identified as the first
example of achiral single-component materials with macroscopic
polar properties. By solving an Ising-like model with dipolar and
asymmetric short-range interactions, we show here that polar
domains are stable in films composed of aggregates as opposed to
isolated molecules. Unlike classical molecular systems, these
nanoaggregates have large intralayer spacings (
),
leading to a reduction in the repulsive dipolar interactions
which oppose polar order within layers. In finite-thickness films
of nanostructures, this effect enables the formation of polar
domains. We compute exactly the energies of the possible
structures consistent with the experiments as a function of film
thickness at zero temperature (T). We also provide Monte Carlo
simulations at non-zero T for a disordered hexagonal lattice that
resembles the smectic-like packing in these nanofilms.
PACS: 61.30.Cz – Molecular and microscopic models and theories of liquid crystal structure / 61.46.+w – Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals
© EDP Sciences, 2003
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