4 research outputs found
Threading Subunits for Polymers to Predict the Equilibrium Ensemble of Solid Polymer Electrolytes
We
present a computational method for polymer growth
called “threading
subunits for polymers (TSP)” that can efficiently sample solid
polymer electrolyte structures with extended conformations. The TSP
method involves equilibrating subunit (e.g., monomer) conformations
that form favorable solvation ion shells, followed by consecutively
connecting the subunits and minimizing the structures. The TSP method
can sample polymers with good solvent-like conformations and from
near-equilibrium structures in which ions are well-dispersed, avoiding
unusual ion clustering under ambient conditions. Using the TSP method,
the equilibration time can be reduced significantly by effectively
sampling the polymer conformations near equilibrium. We anticipate
that the TSP method can be applied to simulate various polymer electrolytes
Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology
Shape
and morphology of polymeric particles are of great importance
in controlling their optical properties or self-assembly into unusual
superstructures. Confinement of block copolymers (BCPs) in evaporative
emulsions affords particles with diverse structures, including prolate
ellipsoids, onion-like spheres, oblate ellipsoids, and others. Herein,
we report that the evaporation rate of solvent from emulsions encapsulating
symmetric polystyrene-<i>b</i>-polybutadiene (PS-<i>b</i>-PB) determines the shape and internal nanostructure of
micron-sized BCP particles. A distinct morphological transition from
the ellipsoids with striped lamellae to the onion-like spheres was
observed with decreasing evaporation rate. Experiments and dissipative
particle dynamics (DPD) simulations showed that the evaporation rate
affected the organization of BCPs at the particle surface, which determined
the final shape and internal nanostructure of the particles. Differences
in the solvent diffusion rates in PS and PB at rapid evaporation rates
induced alignment of both domains perpendicular to the particle surface,
resulting in ellipsoids with axial lamellar stripes. Slower evaporation
rates provided sufficient time for BCP organization into onion-like
structures with PB as the outermost layer, owing to the preferential
interaction of PB with the surroundings. BCP molecular weight was
found to influence the critical evaporation rate corresponding to
the morphological transition from ellipsoid to onion-like particles,
as well as the ellipsoid aspect ratio. DPD simulations produced morphologies
similar to those obtained from experiments and thus elucidated the
mechanism and driving forces responsible for the evaporation-induced
assembly of BCPs into particles with well-defined shapes and morphologies
Block Copolymer with an Extremely High Block-to-Block Interaction for a Significant Reduction of Line-Edge Fluctuations in Self-Assembled Patterns
Directed
self-assembly (DSA) of block copolymers (BCPs) with a
high Flory–Huggins interaction parameter (χ) provides
advantages of pattern size reduction below 10 nm and improved pattern
quality. Despite theoretical predictions, however, the questions of
whether BCPs with a much higher χ than conventional high-χ
BCPs can further improve the line edge roughness (LER) and how to
overcome their extremely slow self-assembly kinetics remain unanswered.
Here, we report the synthesis and assembly of poly(4vinylpyridine-<i>b</i>-dimethylsiloxane) BCP with an extremely high χ-parameter
(estimated to be approximately 7 times higher compared to that of
poly(styrene-<i>b</i>-dimethylsiloxane) – a conventional
high-χ BCP) and achieve a markedly low 3σ line edge roughness
of 0.98 nm, corresponding to 6% of its line width. Moreover, we demonstrate
the successful application of an ethanol-based 60 °C warm solvent
annealing treatment to address the extremely slow assembly kinetics
of the extremely high-χ BCP, considerably reducing the self-assembly
time from several hours to a few minutes. This study suggests that
the use of BCPs with an even larger χ could be beneficial for
further improvement of self-assembled BCP pattern quality
Single Nanoparticle Localization in the Perforated Lamellar Phase of Self-Assembled Block Copolymer Driven by Entropy Minimization
Although
precisely controlled microdomains of block copolymers
(BCP) provide an excellent guiding matrix for multiple nanoparticles
(NPs) to be controllably segregated into a desired polymer block,
localization and positioning of individual NPs have not been demonstrated.
Here, we report a unique one-to-one positioning phenomenon of guest
Au NPs in the host BCP microdomains; each of polystyrene-functionalized
Au NPs is embedded within the perforation domain of hexagonally perforated
lamellar (HPL) morphology of poly(dimethylsiloxane-<i>b</i>-styrene) BCP. The local minimization of free energy achieved by
the placement of Au NPs into the center of the perforation domain
is theoretically supported by the self-consistent field theory (SCFT)
simulation. We propose a novel design principle for more precisely
controllable nanocomposites by developing a new route of NP arrangement
within a polymer matrix