3 research outputs found
Orientation-Dependent Order–Disorder Transition of Block Copolymer Lamellae in Electric Fields
Electric fields have been shown to
stabilize the disordered phase
of near-critical block copolymer solutions. Here, we use in situ synchrotron
small-angle X-ray scattering to examine how the initial orientation
of lamellar domains with respect to the external field (φ) affects
the shift in the order–disorder transition temperature (<i>T</i><sub>ODT</sub>) of lyotropic solutions of polyÂ(styrene-<i>b</i>-isoprene) in toluene. We find a downward shift of the
transition temperature, which scales with lamellar orientation as
Δ<i>T</i><sub>ODT</sub> ∼ cos<sup>2</sup> φ,
in accordance with theory
Block Copolymer Nanocomposites in Electric Fields: Kinetics of Alignment
We investigate the kinetics of block copolymer/nanoparticle
composite
alignment in an electric field using in situ transmission small-angle
X-ray scattering. As a model system, we employ a lamellae forming
polystyrene-<i>block</i>-polyÂ(2-vinyl pyridine) block copolymer
with different contents of gold nanoparticles in thick films under
solvent vapor annealing. While the alignment improves with increasing
nanoparticle fraction, the kinetics slows down. This is explained
by changes in the degree of phase separation and viscosity. Our findings
provide extended insights into the basics of nanocomposite alignment
Electric Field Induced Selective Disordering in Lamellar Block Copolymers
External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the order–disorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the order–disorder transition and well below it