47 research outputs found
Interfacial chemical oxidative synthesis of multifunctional polyfluoranthene.
A novel polyfluoranthene (PFA) exhibiting strong visual fluorescence emission, a highly amplified quenching effect, and widely controllable electrical conductivity is synthesized by the direct cationic oxidative polymerization of fluoranthene in a dynamic interface between n-hexane and nitromethane containing fluoranthene and FeCl3, respectively. A full characterization of the molecular structure signifies that the PFAs have a degree of polymerization from 22-50 depending on the polymerization conditions. A polymerization mechanism at the interface of the hexane/nitromethane biphasic system is proposed. The conductivity of the PFA is tunable from 6.4 × 10-6 to 0.074 S cm-1 by doping with HCl or iodine. The conductivity can be significantly enhanced to 150 S cm-1 by heat treatment at 1100 °C in argon. A PFA-based chemosensor shows a highly selective sensitivity for Fe3+ detection which is unaffected by other common metal ions. The detection of Fe3+ likely involves the synergistic effect of well-distributed π-conjugated electrons throughout the PFA helical chains that function as both the fluorophore and the receptor units
Highly Efficient and Reversible Iodine Capture in Hexaphenylbenzene-Based Conjugated Microporous Polymers
The effective and safe capture and
storage of radioactive iodine (<sup>129</sup>I or <sup>131</sup>I)
is of significant importance during nuclear waste storage and nuclear
energy generation. Here we present detailed evidence of highly efficient
and reversible iodine capture in hexaphenylÂbenzene-based conjugated
microporous polymers (HCMPs), synthesized via Buchwald–Hartwig
(BH) cross-coupling of a hexakisÂ(4-bromoÂphenyl)Âbenzene (HBB)
core and aryl diamine linkers. The HCMPs present moderate surface
areas up to 430 m<sup>2</sup> g<sup>–1</sup>, with narrow pore
size distribution and uniform ultramicropore sizes of less than 1
nm. Porous properties are controlled by the strut lengths and rigidities
of linkers, while porosity and uptake properties can be tuned by changing
the oxidation state of the HCMPs. The presence of a high number of
amine functional groups combined with microporosity provides the HCMPs
with extremely high iodine affinity with uptake capacities up to 336
wt %, which is to the best of our knowledge the highest reported to
date. Two ways to release the adsorbed iodine were explored: either
slow release into ethanol or quick release upon heating (with a high
degree of control). Spectral studies indicate that the combination
of microporosity, amine functionality, and abundant π-electrons
ensured well-defined host–guest interactions and controlled
uptake of iodine. In addition, the HCMPs could be recycled while maintaining
90% iodine uptake capacity (up to 295%). We envisage wider application
of these materials in the facile uptake and removal of unwanted oxidants
from the environment
Fluorescent Microporous Polyimides based on Perylene and Triazine for Highly CO<sub>2</sub>-Selective Carbon Materials
Carbon dioxide (CO<sub>2</sub>) capture
from point sources like
coal-fired power plants is a potential solution for stabilizing atmospheric
CO<sub>2</sub> content to avoid global warming. Sorbents with high
and reversible CO<sub>2</sub> uptake, high CO<sub>2</sub> selectivity,
good chemical and thermal stability, and low cost are desired for
the separation of CO<sub>2</sub> from N<sub>2</sub> in flue or natural
gas. We report here, for the first time, on the synthesis of new microporous
polyimide (PI) networks from the condensation of perylene-3,4,9,10-tetracarboxylic
dianhydride (PTCDA) and 1,3,5-triazine-2,4,6-triamine (melamine) using
a Lewis acid catalyst zinc acetate/imidazole complex. These PI network
materials, prepared in the absence and presence of dimethyl sulfoxide
(DMSO) as weak solvent template, exhibit strong fluorescence. Nitrogen-containing
carbons can be accessed from our PI networks via a simple thermal
pyrolysis route. The successful construction of new microporous PI
networks and derived N-containing carbons is shown here to provide
promising CO<sub>2</sub> sorbents with high uptake capacities (15
wt %) combined with exceptional selectivities over N<sub>2</sub> (240),
while their fluorescent properties can be exploited for simple sensing
Removal of Mercury(II) from Aqueous Solutions by Adsorption on Poly(1-amino-5-chloroanthraquinone) Nanofibrils: Equilibrium, Kinetics, and Mechanism Studies
Poly(1-amino-5-chloroanthraquinone) (PACA) nanofibrils were applied as novel nanoadsorbents for highly toxic mercury removal from aqueous solutions. A series of batch adsorption experiments were conducted to study the effect of adsorbent dose, pH, contact time, and metal concentration on Hg(II) uptake by PACA nanofibrils. Kinetic data indicated that the adsorption process of PACA nanofibrils for Hg(II) achieved equilibrium within 2 h following a pseudo-second-order rate equation. The adsorption mechanism of PACA nanofibrils for Hg(II) was investigated by Fourier transform-infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm of Hg(II) fitted well the Langmuir model, exhibiting superb adsorption capacity of 3.846 mmol of metal per gram of adsorbent. Lastly, we found out that the as-synthesized PACA nanofibrils are efficient in Hg(II) removal from real wastewater. Furthermore, five consecutive adsorption-desorption cycles demonstrated that the PACA nanofibrils were suitable for repeated use without considerable changes in the adsorption capacity
Removal of Mercury(II) from Aqueous Solutions by Adsorption on Poly(1-amino-5-chloroanthraquinone) Nanofibrils: Equilibrium, Kinetics, and Mechanism Studies
Poly(1-amino-5-chloroanthraquinone) (PACA) nanofibrils were applied as novel nanoadsorbents for highly toxic mercury removal from aqueous solutions. A series of batch adsorption experiments were conducted to study the effect of adsorbent dose, pH, contact time, and metal concentration on Hg(II) uptake by PACA nanofibrils. Kinetic data indicated that the adsorption process of PACA nanofibrils for Hg(II) achieved equilibrium within 2 h following a pseudo-second-order rate equation. The adsorption mechanism of PACA nanofibrils for Hg(II) was investigated by Fourier transform-infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm of Hg(II) fitted well the Langmuir model, exhibiting superb adsorption capacity of 3.846 mmol of metal per gram of adsorbent. Lastly, we found out that the as-synthesized PACA nanofibrils are efficient in Hg(II) removal from real wastewater. Furthermore, five consecutive adsorption-desorption cycles demonstrated that the PACA nanofibrils were suitable for repeated use without considerable changes in the adsorption capacity
Multiscale Understanding of Electric Polarization in Poly(vinylidene fluoride)-Based Ferroelectric Polymers
Poly(vinylidene fluoride) (PVDF) and PVDF-based copolymers with trifluoroethylene (PVDF-TrFE) have attracted considerable academic and industrial interest due to their ferroelectric properties, which are only presented in very few polymers. However, the underlying fundamentals of molecular ordering and induced polarizations are complex and not fully understood. Herein, PVDF, PVDF-TrFE and their blends, prepared using melt extrusion and hot pressing, have been selected to obtain controlled case studies with well-defined chain ordering and microstructures. Impedance analysis and terahertz time-domain spectroscopy are exploited to investigate electric polarization in PVDF-based polymers at different length scales. The extruded ferroelectric films show in-plane chain orientation and higher domain wall density compared to hot pressed films with randomly-distributed polymer chains, which favors the polarization at low frequencies (Hz to MHz), as concluded from the higher dielectric constants and more prominent high electric field polarization switching features. However, the domain walls cannot respond at high frequencies, which leads to lower dielectric constants in the extruded films at THz frequencies