11 research outputs found
Coassembly of Nanorods and Photosensitive Binary Blends: “Combing” with Light To Create Periodically Ordered Nanocomposites
Using computational modeling, we establish a means of
controlling
structure formation in nanocomposites that encompass nanorods and
a photosensitive binary blend. The complex cooperative interactions
in the system include a preferential wetting interaction between the
rods and one of the phases in the blend, steric repulsion between
the coated rods, and the response of the binary blend to light. Under
uniform illumination, the binary mixture undergoes both phase separation
and a reversible chemical reaction, leading to a morphology resembling
that of a microphase-separated diblock copolymer. When a second, higher
intensity light source is rastered over the sample, the binary blend
and the nanorods coassemble into regular, periodically ordered structures.
In particular, the system displays an essentially defect-free lamellar
morphology, with the nanorods localized in the energetically favorable
domains. By varying the speed at which the secondary light is rastered
over the sample, we can control the directional alignment of the rods
within the blend. Our approach yields an effective route for achieving
morphological control of both the polymeric components and nanoparticles,
providing a means of tailoring the properties and ultimate performance
of the composites
Coassembly of Nanorods and Photosensitive Binary Blends: “Combing” with Light To Create Periodically Ordered Nanocomposites
Using computational modeling, we establish a means of
controlling
structure formation in nanocomposites that encompass nanorods and
a photosensitive binary blend. The complex cooperative interactions
in the system include a preferential wetting interaction between the
rods and one of the phases in the blend, steric repulsion between
the coated rods, and the response of the binary blend to light. Under
uniform illumination, the binary mixture undergoes both phase separation
and a reversible chemical reaction, leading to a morphology resembling
that of a microphase-separated diblock copolymer. When a second, higher
intensity light source is rastered over the sample, the binary blend
and the nanorods coassemble into regular, periodically ordered structures.
In particular, the system displays an essentially defect-free lamellar
morphology, with the nanorods localized in the energetically favorable
domains. By varying the speed at which the secondary light is rastered
over the sample, we can control the directional alignment of the rods
within the blend. Our approach yields an effective route for achieving
morphological control of both the polymeric components and nanoparticles,
providing a means of tailoring the properties and ultimate performance
of the composites
Harnessing Interfacially-Active Nanorods to Regenerate Severed Polymer Gels
With newly developed computational
approaches, we design a nanocomposite
that enables self-regeneration of the gel matrix when a significant
portion of the material is severed. The cut instigates the dynamic
cascade of cooperative events leading to the regrowth. Specifically,
functionalized nanorods localize at the new interface and initiate
atom transfer radical polymerization with monomers and cross-linkers
in the outer solution. The reaction propagates to form a new cross-linked
gel, which can be tuned to resemble the uncut material
Harnessing Interfacially-Active Nanorods to Regenerate Severed Polymer Gels
With newly developed computational
approaches, we design a nanocomposite
that enables self-regeneration of the gel matrix when a significant
portion of the material is severed. The cut instigates the dynamic
cascade of cooperative events leading to the regrowth. Specifically,
functionalized nanorods localize at the new interface and initiate
atom transfer radical polymerization with monomers and cross-linkers
in the outer solution. The reaction propagates to form a new cross-linked
gel, which can be tuned to resemble the uncut material
Harnessing Interfacially-Active Nanorods to Regenerate Severed Polymer Gels
With newly developed computational
approaches, we design a nanocomposite
that enables self-regeneration of the gel matrix when a significant
portion of the material is severed. The cut instigates the dynamic
cascade of cooperative events leading to the regrowth. Specifically,
functionalized nanorods localize at the new interface and initiate
atom transfer radical polymerization with monomers and cross-linkers
in the outer solution. The reaction propagates to form a new cross-linked
gel, which can be tuned to resemble the uncut material
Effect of Fluorophobic Character upon Switching Nanoparticles in Polymer Films from Aggregated to Dispersed States Using Immersion Annealing
For
nanoparticle (NP) polymer composites, the state of dispersion
vs aggregation significantly affects optical, electronic, thermal,
and mechanical properties. The switching of NP distribution states
thus far was limited to polymer solutions or bulky polymer-grafted
NPs. Herein, for the first time, NP distribution states within polymer
films are switched by adjusting fluorophobic interactions and the
enthalpy of mixing with immersion annealing. The fluorophobic effect
is the tendency of fluorinated molecules to strongly phase-separate
from non/less fluorinated molecules. A highly fluorophobic homopolymer,
poly(perfluorooctyl acrylate) (PFOA), was combined with gold NPs of
variable fluorophobic character, prepared using mixtures of small-molecule
ligands (xF-NP, where x is the mol
% fluorinated ligands). Low-to-moderately fluorophobic F-NPs with
PFOA were aggregated after spin coating where film swelling via immersion
annealing with moderately fluorophobic trifluoro toluene (TFT) generally
led to a dispersed state. In contrast, the highly fluorophobic 100F-NPs
were dispersed regardless of immersion annealing. This behavior was
attributed to the PFOA acting like a surfactant to enable dispersion
of highly fluorophobic NPs in TFT. Since these two distinct behaviors
favor nonoverlapping ranges of xF-NP compositions,
the NPs with intermediate compositions exhibited limited dispersibility.
This fluorophobic switchability could enable time- and chemical-selective
sensing of fluorinated compounds in the future
Modeling the Transport of Nanoparticle-Filled Binary Fluids through Micropores
Understanding the transport of multicomponent fluids
through porous
medium is of great importance for a number of technological applications,
ranging from ink jet printing and the production of textiles to enhanced
oil recovery. The process of capillary filling is relatively well
understood for a single-component fluid; much less attention, however,
has been devoted to investigating capillary filling processes that
involve multiphase fluids, and especially nanoparticle-filled fluids.
Here, we examine the behavior of binary fluids containing nanoparticles
that are driven by capillary forces to fill well-defined pores or
microchannels. To carry out these studies, we use a hybrid computational
approach that combines the lattice Boltzmann model for binary fluids
with a Brownian dynamics model for the nanoparticles. This hybrid
approach allows us to capture the interactions among the fluids, nanoparticles,
and pore walls. We show that the nanoparticles can dynamically alter
the interfacial tension between the two fluids and the contact angle
at the pore walls; this, in turn, strongly affects the dynamics of
the capillary filling. We demonstrate that by tailoring the wetting
properties of the nanoparticles, one can effectively control the filling
velocities. Our findings provide fundamental insights into the dynamics
of this complex multicomponent system, as well as potential guidelines
for a number of technological processes that involve capillary filling
with nanoparticles in porous media
Designing Highly Thermostable Lysozyme–Copolymer Conjugates: Focus on Effect of Polymer Concentration
Designing
biomaterials capable of functioning in harsh environments
is vital for a range of applications. Using molecular dynamics simulations,
we show that conjugating lysozymes with a copolymer [polyÂ(GMA-<i>stat</i>-OEGMA)] comprising glycidyl methacrylate (GMA) and
oligoÂ(ethylene glycol) methyl ether methacrylate (OEGMA) results in
a dramatic increase of stability of these enzymes at high temperatures
provided that the concentration of the copolymer in the close vicinity
of the enzyme exceeds a critical value. In our simulations, we use
triads containing the same ratio of GMA to OEGMA units as in our recent
experiments (N. S. Yadavalli et al., <i>ACS Catalysis</i>, <b>2017</b>, <i>7</i>, 8675). We focus on the dynamics
of the conjugate at high temperatures and on its structural stability
as a function of the copolymer/water content in the vicinity of the
enzyme. We show that the dynamics of phase separation in the water–copolymer
mixture surrounding the enzyme is critical for the structural stability
of the enzyme. Specifically, restricting water access promotes the
structural stability of the lysozyme at high temperatures. We identified
critical water concentration below which we observe a robust stabilization;
the phase separation is no longer observed at this low fraction of
water so that the water domains promoting unfolding are no longer
formed in the vicinity of the enzyme. This understanding provides
a basis for future studies on designing a range of enzyme–copolymer
conjugates with improved stability
Harnessing Fluid-Driven Vesicles To Pick Up and Drop Off Janus Particles
Using dissipative particle dynamics (DPD) simulations, we model the interaction between nanoscopic lipid vesicles and Janus nanoparticles in the presence of an imposed flow. Both the vesicle and Janus nanoparticles are localized on a hydrophilic substrate and immersed in a hydrophilic solution. The fluid-driven vesicle successfully picks up Janus particles on the substrate and transports these particles as cargo along the surface. The vesicle can carry up to four particles as its payload. Hence, the vesicles can act as nanoscopic “vacuum cleaners”, collecting nanoscopic debris localized on the floors of the fluidic devices. Importantly, these studies reveal how an imposed flow can facilitate the incorporation of nanoparticles into nanoscale vesicles. With the introduction of a “sticky” domain on the substrate, the vesicles can also robustly drop off and deposit the particles on the surface. The controlled pickup and delivery of nanoparticles <i>via</i> lipid vesicles can play an important step in the bottom-up assembly of these nanoparticles within small-scale fluidic devices
Stackable, Covalently Fused Gels: Repair and Composite Formation
Combining
modeling and experiment, we created multilayered gels
where each layer was “stacked” on top of the other and
covalently interconnected to form mechanically robust materials, which
could integrate the properties of the individual layers. In this process,
a solution of new initiator, monomer, and cross-linkers was introduced
on top of the first gel, and these new components then underwent living
(co)Âpolymerization to form the subsequent layer. We simulated this
process using dissipative particle dynamics (DPD) to isolate factors
that affect the formation and binding of chemically identical gel
as well as incompatible layers. Analysis indicates that the covalent
bond formation between the different layers is primarily due to reactive
chain-ends, rather than residual cross-linkers. In the complementary
experiments, we synthesized multilayered gels using either free radical
(FRP) or atom transfer radical polymerizations (ATRP) methods. Polymerization
results demonstrated that chemically identical materials preserved
their structural integrity independent of the polymerization method.
For gels encompassing incompatible layers, the contribution of reactive
chain-ends plays a particularly important role in the integrity of
the material, as indicated by the more mechanically robust systems
prepared by ATRP. These studies point to a new approach for combining
chemically distinct components into one coherent, multifunctional
material as well as an effective method for repairing severed gels