3 research outputs found
High-Performance Adhesives Resulting from Spontaneous Formation of Nanogels within Miniemulsion Particles
Molecular structure plays a crucial
role in determining the final properties of pressure-sensitive adhesives.
Here, we demonstrate that the molecular structure of polyurethane/(meth)acrylic
hybrids synthesized by miniemulsion photopolymerization changes during
storage of the dispersion at room temperature because of the spontaneous
formation of nanogels by the assembly of polymer chains within the
polymer particles. Analysis of the nanogel structure by asymmetric-flow
field-flow fractionation allows identification of the molecular structure
that provides the unusual combination of high tack adhesion and excellent
shear resistance at high temperature [maximum value of the shear-adhesion
failure temperature (SAFT) test, >210 °C]
Encapsulation of Clay within Polymer Particles in a High-Solids Content Aqueous Dispersion
By using a two-step polymerization
process, it was possible to
encapsulate clay platelets within polymer particles dispersed in water.
First, seed polymer particles with chemically bonded clay were obtained
by batch miniemulsion polymerization. Then, the clay was buried within
the particles by the addition of neat monomer in a second step. The
final stable dispersions can have a solids content of up to 50 wt
%. Transmission electron microscopy images clearly show the presence
of clay platelets inside the polymer colloids, although they are not
totally exfoliated. The obtained nanocomposites showed an increase
in both the storage modulus in the rubbery state and the water resistance
as the clay content increases. The approach presented here might be
useful for encapsulating other high-aspect ratio nanofillers
From Polymer Latexes to Multifunctional Liquid Marbles
A simple method to prepare multifunctional
liquid marbles and dry
water with magnetic, color, and fluorescent properties is presented.
Multifunctional liquid marbles were prepared by encapsulation of water
droplets using flocculated polymer latexes. First, the emulsion polymerization
reaction of polystyrene and poly(benzyl methacrylate) was carried
out using cheap and commercially available cationic surfactants. Subsequently,
flocculation of the latex was provoked by an anion-exchange reaction
of the cationic surfactant by the addition of lithium bis(trifluoromethanesulfonyl)imide
salt. The flocculated polymer latex was filtered and dried, leading
to very hydrophobic micronanoparticulated powders. These powders showed
a great ability to stabilize the air/water interface. Stable liquid
marbles were obtained by rolling water droplets onto the hydrophobic
powders previously prepared. The use of very small polystyrene nanoparticles
led us to the preparation of very stable and the biggest known liquid
marbles up to 2.5 mL of water. Furthermore, the introduction of fluorescent
comonomer dyes into the polymer powders allowed us to obtain new morphological
images and new knowledge about the structure of liquid marbles by
confocal microscopy. Furthermore, the introduction of magnetic nanoparticles
into the polymer latex led to magnetic responsive liquid marbles,
where the iron oxide nanoparticles are protected within a polymer.
Altogether this method represents an accessible and general platform
for the preparation of multifunctional liquid marbles and dry water,
which may contribute to extending of their actual range of applications