2 research outputs found
Atom Transfer Radical Addition/Polymerization of Perfluorosulfonic Acid Polymer with the C–F Bonds as Reactive Sites
This
work reports the first demonstration of the chemical reactions
on the C–F groups of perfluorosulfonic acid polymers. The Nafion
chains show chemical reactivity for atom transfer radical addition
onto multiwalled carbon nanotubes and ability to serve as a macroinitiator
for atom transfer radical polymerization. The C–F groups and
mainchain −CF<sub>2</sub> groups have been demonstrated, under
a study with <sup>19</sup>F NMR, as the active sites responsible for
the reactions. The results could certainly extend both the scopes
of chemistry and application of perfluorosulfonic acid polymers as
well as the windows of atom transfer radical addition/polymerization
to fluorinated compounds
Versatile Synthesis of Thiol- and Amine-Bifunctionalized Silica Nanoparticles Based on the Ouzo Effect
In this article, we report a novel,
nanoprecipitation-based method
for preparing silica nanoparticles with thiol and amine cofunctionalization.
(3-Mercaptopropyl)Âtrimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane
(APTMS) were used as the organosilane precursors, which were subjected
to acid-catalyzed polycondensation in an organic phase containing
a water-miscible solvent (e.g., dimethyl sulfoxide). A pale colloidal
solution could be immediately formed when the preincubated organic
phase was directly injected into water. The initial composition ratio
between MPTMS and APTMS is an important factor governing the formation
of nanoparticles. Specifically, large, unstable micrometer-sized particles
were formed for preparation using MPTMS as the sole silane source.
In contrast, when APTMS was used alone, no particles could be formed.
By reducing the fraction of APTMS (or increasing that of MPTMS) in
the initial mixture of organosilanes, the formation of nanometer-sized
particles occurred at a critical fraction of APTMS (i.e., 25%). Remarkably,
a tiny fraction (e.g., 1%) of APTMS was sufficient to produce stable
nanoparticles with a hydrodynamic diameter of about 200 nm. Other
factors that would also affect particle formation were determined.
Moreover, an interesting temperature effect on particle formation
was observed. The TEM micrographs show spherical nanospheres with
mean sizes of 130–150 nm in diameter. The solid-state <sup>29</sup>Si NMR spectra demonstrate that the hybrid silica materials
contain fully and partially condensed silicon structures. The bifunctionalized
silica nanoparticles have positive zeta potentials whose magnitudes
are positively correlated with the amount of APTMS. The total thiol
content, however, is negatively correlated with the amount of APTMS.
The cationic nanoparticles can bind an antisense oligonucleotide in
a composition-dependent manner