28 research outputs found
Fabrication of Polymer Ellipsoids by the Electrospinning of Swollen Nanoparticles
Electrospinning is used to deform originally spherical
polymer
nanoparticles into ellipsoidal nanoparticles. The polymer nanoparticles
are swollen and the dispersion is then electrospun. Under certain
conditions, the stretching generated in the electrospinning jet is
enough to generate elongated nanoparticles embedded in fibers. The
formation of the anisotropic particles is observed by stimulated emission
depletion (STED) microscopy performed on fluorescent nanoparticles
and by electron microscopy measurements on the nanoparticles recovered
after removal of the fiber matrix
pH-Sensitive Polymer Conjugates for Anticorrosion and Corrosion Sensing
In
2015, the global cost of corrosion in the world was estimated to be
around 2.5 trillion dollars and has been continuously increasing.
The active protection by corrosion inhibitors is a well-known technique
for protecting metals against corrosion. However, one major disadvantage
is that corrosion inhibitors can be leached in the environment, even
when corrosion does not occur. We design and synthesize smart polymer/corrosion
inhibitor conjugates as a new generation of materials for corrosion
protection. These materials release inhibitors upon acidification,
which may occur either by acidic rain or as a consequence of the metal
corrosion process itself. A polymerizable derivative of 8-hydroxyquinoline
(8HQ), an effective corrosion inhibitor, is prepared so that it contains
acid-labile β-thiopropionate linkages. The monomer is copolymerized
with ethyl acrylate, and the obtained functional polymer is processed
to form nanoparticles. Under acidic conditions, >95% 8HQ is released
from the nanoparticles of the polymer conjugates after 14 days. However,
the release was significantly slower under neutral conditions, reaching
only 15% during the same period. Additionally, nonconjugated 8HQ can
be physically entrapped in the nanoparticles of the polymer conjugates
by encapsulation. The nonconjugated 8HQ is then released in less than
30 min so that the coexistence of both conjugated and nonconjugated
8HQ in the nanoparticles allows a release profile, which is a hybrid
of sustained and burst releases. Furthermore, the nanoparticles are
advantageously used as nanosensors. The 8HQ released from the nanoparticles
displays enhanced fluorescence upon chelation with aluminum ions.
Therefore, the nanoparticles can be used simultaneously for corrosion
sensing and protection
Stimuli-Selective Delivery of two Payloads from Dual Responsive Nanocontainers
Stimuli-Selective Delivery of two Payloads from Dual
Responsive Nanocontainer
Nanocontainers in and onto Nanofibers
ConspectusHierarchical structure is a key feature explaining the superior
properties of many materials in nature. Fibers usually serve in textiles,
for structural reinforcement, or as support for other materials, whereas
spherical micro- and nanoobjects can be either highly functional or
also used as fillers to reinforce structure materials. Combining nanocontainers
with fibers in one single object has been used to increase the functionality
of fibers, for example, antibacterial and thermoregulation, when the
advantageous properties given by the encapsulated materials inside
the containers are transferred to the fibers. Herein we focus our
discussion on how the hierarchical structure composed of nanocontainers
in nanofibers yields materials displaying advantages of both types
of materials and sometimes synergetical effects. Such materials can
be produced by first carefully designing nanocontainers with defined
morphology and chemistry and subsequently electrospinning them to
fabricate nanofibers. This method, called colloid-electrospinning,
allows for marrying the properties of nanocontainers and nanofibers.
The obtained fibers could be successfully applied in different fields
such as catalysis, optics, energy conversion and production, and biomedicine.The miniemulsion process is a convenient approach for the encapsulation
of hydrophobic or hydrophilic payloads in nanocontainers. These nanocontainers
can be embedded in fibers by the colloid-electrospinning technique.
The combination of nanocontainers with nanofibers by colloid-electrospinning
has several advantages. (1) The fiber matrix serves as support for
the embedded nanocontainers. For example, through combining catalysts
nanoparticles with fiber networks, the catalysts can be easily separated
from the reaction media and handled visually. This combination is
beneficial for the reuse of the catalyst and the purification of products.
(2) Electrospun nanofibers containing nanocontainers offer the active
agents inside the nanocontainers a double protection by both the fiber
matrix and the nanocontainers. Since the polymer of the fibers and
the polymer of the nanocontainers have usually opposite polarities,
the encapsulated substance, for example, catalysts, dyes, or drugs,
can be protected against a large variety of environmental influences.
(3) Electrospun nanofibers exhibit unique advantages for tissue engineering
and drug delivery that are a structural similarity to the extracellular
matrix of biological tissues, large specific surface area, high and
interconnected porosity which enhances cell adhesion, proliferation,
drug loading, and mass transfer properties, as well as the flexibility
in selecting the raw materials. Moreover, the nanocontainer-in-nanofiber
structure allows multidrug loading and programmable release of each
drug, which are very important to achieve synergistic effects in tissue
engineering and disease therapy.The advantages offered by these materials encourage us to further
understand the relationship between colloidal properties and fibers,
to predict the morphology and properties of the fibers obtained by
colloid-electrospinning, and to explore new possible combination of
properties offered by nanoparticles and nanofibers
Responsive Polymer-Layered Silicate Hybrids for Anticorrosion
Two-dimensional
materials have been introduced in polymer coatings
to increase the lifetime of metallic materials by providing barrier
properties against corrosive species. Corrosion inhibitors can be
inserted into a 2D filler to mitigate the corrosion of metallic materials
caused by corrosive species. Current drawbacks of this approach include
a poorly controlled release of the inhibitor and the incompatibility
of the filler and polymer. To achieve long-term anticorrosion performance,
a layered silicate (octosilicate) is modified by surface-graft polymerization
with a monomer functionalized with a corrosion inhibitor, 8-hydroxyquinoline.
A pH-responsive polymer-inhibitor conjugate, poly(methyl methacrylate-co-8-quinolinyl acrylate), is covalently attached to the
silicate and then provides a sustainable release of the corrosion
inhibitor upon acidification. The corrosion current density of aluminum
alloy substrates (AA2024) coated with poly(methyl methacrylate-co-butyl acrylate) embedding the octosilicate containers
is decreased due to a synergistic effect of barrier properties provided
by the 2D filler and the pH-responsive release of corrosion inhibitor.
This conceptual design can be potentially applied to release molecules
such as drugs, fertilizers, or pesticides
Hydrophobic Nanocontainers for Stimulus-Selective Release in Aqueous Environments
The preparation of nanocontainers
with a hydrophilic core from
water-in-oil emulsions and their subsequent transfer to aqueous medium
is crucial because it enables the efficient encapsulation of hydrophilic
payloads in large quantities. However, major challenges are associated
with their synthesis including low colloidal stability, leakage of
encapsulated payloads due to osmotic pressure, and a demanding transfer
of the nanocontainers from apolar to aqueous media. We present here
a general approach for the synthesis of polymer nanocontainers that
are colloidally stable, not sensitive to osmotic pressure, and responsive
to environmental stimuli that trigger release of the nanocontainer
contents. Additionally, the nanocontainers can selectively deliver
one or two different payloads upon oxidation and changes of pH or
temperature. Our approach uniquely enables the synthesis of nanocontainers
for applications in which aqueous environments are desired or inevitable
Osmotic Pressure as Driving Force for Reducing the Size of Nanoparticles in Emulsions
We
describe here a method to decrease particle size of nanoparticles
synthesized by miniemulsion polymerization. Small nanoparticles or
nanocapsules were obtained by generating an osmotic pressure to induce
the diffusion of monomer molecules from the dispersed phase of a miniemulsion
before polymerization to an upper oil layer. The size reduction is
dependent on the difference in concentration of monomer in the dispersed
phase and in the upper oil layer and on the solubility of the monomer
in water. By labeling the emulsion droplets with a copolymer of stearyl
methacrylate and a polymerizable dye, we demonstrated that the migration
of the monomer to the upper hexadecane layer relied on molecular diffusion
rather than diffusion of monomer droplets to the oil layer. Moreover,
surface tension measurements confirmed that the emulsions were still
in the miniemulsion regime and not in the microemulsion regime. The
particle size can be tuned by controlling the duration during which
the miniemulsion stayed in contact with the hexadecane layer, the
interfacial area between the miniemulsion and the hexadecane layer
and by the concentration of surfactant. Our method was applied to
reduce the size of polystyrene and poly(methyl methacrylate) nanoparticles,
nanocapsules of a copolymer of styrene and methyl methacrylic acid,
and silica nanocapsules. This work demonstrated that a successful
reduction of nanoparticle size in the miniemulsion process can be
achieved without using excess amounts of surfactant. The method relies
on building osmotic pressure in oil droplets dispersed in water which
acts as semipermeable membrane
Osmotic Pressure as Driving Force for Reducing the Size of Nanoparticles in Emulsions
We
describe here a method to decrease particle size of nanoparticles
synthesized by miniemulsion polymerization. Small nanoparticles or
nanocapsules were obtained by generating an osmotic pressure to induce
the diffusion of monomer molecules from the dispersed phase of a miniemulsion
before polymerization to an upper oil layer. The size reduction is
dependent on the difference in concentration of monomer in the dispersed
phase and in the upper oil layer and on the solubility of the monomer
in water. By labeling the emulsion droplets with a copolymer of stearyl
methacrylate and a polymerizable dye, we demonstrated that the migration
of the monomer to the upper hexadecane layer relied on molecular diffusion
rather than diffusion of monomer droplets to the oil layer. Moreover,
surface tension measurements confirmed that the emulsions were still
in the miniemulsion regime and not in the microemulsion regime. The
particle size can be tuned by controlling the duration during which
the miniemulsion stayed in contact with the hexadecane layer, the
interfacial area between the miniemulsion and the hexadecane layer
and by the concentration of surfactant. Our method was applied to
reduce the size of polystyrene and poly(methyl methacrylate) nanoparticles,
nanocapsules of a copolymer of styrene and methyl methacrylic acid,
and silica nanocapsules. This work demonstrated that a successful
reduction of nanoparticle size in the miniemulsion process can be
achieved without using excess amounts of surfactant. The method relies
on building osmotic pressure in oil droplets dispersed in water which
acts as semipermeable membrane
Osmotic Pressure as Driving Force for Reducing the Size of Nanoparticles in Emulsions
We
describe here a method to decrease particle size of nanoparticles
synthesized by miniemulsion polymerization. Small nanoparticles or
nanocapsules were obtained by generating an osmotic pressure to induce
the diffusion of monomer molecules from the dispersed phase of a miniemulsion
before polymerization to an upper oil layer. The size reduction is
dependent on the difference in concentration of monomer in the dispersed
phase and in the upper oil layer and on the solubility of the monomer
in water. By labeling the emulsion droplets with a copolymer of stearyl
methacrylate and a polymerizable dye, we demonstrated that the migration
of the monomer to the upper hexadecane layer relied on molecular diffusion
rather than diffusion of monomer droplets to the oil layer. Moreover,
surface tension measurements confirmed that the emulsions were still
in the miniemulsion regime and not in the microemulsion regime. The
particle size can be tuned by controlling the duration during which
the miniemulsion stayed in contact with the hexadecane layer, the
interfacial area between the miniemulsion and the hexadecane layer
and by the concentration of surfactant. Our method was applied to
reduce the size of polystyrene and poly(methyl methacrylate) nanoparticles,
nanocapsules of a copolymer of styrene and methyl methacrylic acid,
and silica nanocapsules. This work demonstrated that a successful
reduction of nanoparticle size in the miniemulsion process can be
achieved without using excess amounts of surfactant. The method relies
on building osmotic pressure in oil droplets dispersed in water which
acts as semipermeable membrane
Osmotic Pressure as Driving Force for Reducing the Size of Nanoparticles in Emulsions
We
describe here a method to decrease particle size of nanoparticles
synthesized by miniemulsion polymerization. Small nanoparticles or
nanocapsules were obtained by generating an osmotic pressure to induce
the diffusion of monomer molecules from the dispersed phase of a miniemulsion
before polymerization to an upper oil layer. The size reduction is
dependent on the difference in concentration of monomer in the dispersed
phase and in the upper oil layer and on the solubility of the monomer
in water. By labeling the emulsion droplets with a copolymer of stearyl
methacrylate and a polymerizable dye, we demonstrated that the migration
of the monomer to the upper hexadecane layer relied on molecular diffusion
rather than diffusion of monomer droplets to the oil layer. Moreover,
surface tension measurements confirmed that the emulsions were still
in the miniemulsion regime and not in the microemulsion regime. The
particle size can be tuned by controlling the duration during which
the miniemulsion stayed in contact with the hexadecane layer, the
interfacial area between the miniemulsion and the hexadecane layer
and by the concentration of surfactant. Our method was applied to
reduce the size of polystyrene and poly(methyl methacrylate) nanoparticles,
nanocapsules of a copolymer of styrene and methyl methacrylic acid,
and silica nanocapsules. This work demonstrated that a successful
reduction of nanoparticle size in the miniemulsion process can be
achieved without using excess amounts of surfactant. The method relies
on building osmotic pressure in oil droplets dispersed in water which
acts as semipermeable membrane