Ruke Bai

Flavone-Based ESIPT Ratiometric Chemodosimeter for Detection of Cysteine in Living Cells

We have designed and synthesized a novel ratiometric fluorescent chemodosimeter MHF-based ESIPT process for specific detection of cysteine among the biological thiols. The probe MHF shows very weak blue fluorescence under UV excitation. Upon addition of cysteine (Cys), the reaction of Cys with MHF induces acrylate hydrolysis, thereby enabling the ESIPT process to shift the weak blue emission to a strong green emission with about 20-fold enhancement. We utilized 1H NMR spectra to elucidate the fluorescence sensing mechanism. Moreover, the cellular imaging experiment indicated the MHF possessed excellent selectivity, low cytotoxicity, and desirable cell permeability for biological applications.

Photo‐Initiated Living Free Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate

The polymerizations of styrene (St), methyl acrylate (MA), and butyl acrylate (BuA), carried out under UV irradiation at room temperature in the presence of dibenzyl trithiocarbonate (DBTTC) were found to display living free-radical polymerization characteristics as evidenced by: narrow molecular weight distribution, linear increase of molecular weight with increasing conversion, well-controlled molecular weight, and first-order polymerization kinetics. The triblock copolymer, PMA-PSt-PMA, with narrow polydispersity and well-defined structure was successfully prepared using PMA-S-C(=S)-S-PMA as macro-photoinitiator under UV irradiation at room temperature. Based on GPC, NMR and FT-IR analyses, the structures of the polymers were obtained and the mechanism of the polymerization was proposed.

A novel poly(2,6-dimethyl-1,4-phenylene oxide) with trifunctional ammonium moieties for alkaline anion exchange membranes

2,4,6-Tri(dimethylaminomethyl)-phenol was synthesized as a trifunctional moiety and incorporated onto poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to obtain a novel quaternary ammonium functionalized PPO (PPO-TQA). Membranes of the polymer were fabricated and exhibited high conductivity, a low swelling ratio and water uptake.

60Co γ-Irradiation-Initiated “Living” Free-Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate

The free-radical polymerization of vinyl monomers in the presence of dibenzyl trithiocarbonate (DBTTC) and under 60 Co γ-irradiation is of living character. Under 60 Co irradiation, the bonds between benzyl group and sulfur were cleaved, benzyl radicals initiate the polymerization. The propagating radical together with trithiocarbonate radicals form a dormant polymer chain. The fast equilibrium between propagation radical and dormant polymer chain controls the polymerization.

A Facile Approach for the Fabrication of Highly Stable Superhydrophobic Cotton Fabric with Multi-Walled Carbon Nanotubes−Azide Polymer Composites

Homogeneous dispersion and functionalization of pristine multiwalled carbon nanotubes (MWNTs) in various organic solvents was achieved by a simple ultrasonic process in the presence of an azide copolymer, poly(4-azidophenyl methacrylate-co-methyl acrylate)(P(APM-co-MA)). The copolymes were noncovalently attached to the surface of the MWNTs via pi-pi interactions to form MWNT-P(APM-co-MA) composites. The composites were characterized by transmission electron microscopy, thermogravimetric analysis, Raman spectra and UV-vis spectra. The solution dispersion of the MWNT-P(APM-co-MA) composites were used to prepare superhydrophobic cotton fabric by a facile dip-coating approach. MWNTs were covalently attached to the surface of the cotton fabric through the chemical reactions between the azide groups of P(APM-co-MA) with both MWNTs and cotton fibers. The reactions are based on UV-activated nitrene chemistry. Owing to the nanoscale roughness introduced by the attachment of MWNTs, the cotton fabric surface was transformed from hydrophilic to superhydrophobic with an apparent water contact angle of 154 degrees . Since MWNTs were covalently attached on the surface of the cotton fabric, the superhydrophobicity possesses high stability and chemical durability.

An efficient conjugated polymer sensor based on the aggregation-induced fluorescence quenching mechanism for the specific detection of palladium and platinum ions

Based on the aggregation-induced fluorescence quenching mechanism, a 2,6-dithienyl-4-phenylpyridine-containing conjugated polymer (P-A) has been designed and synthesized via a Sonogashira coupling reaction as an efficient fluorescent sensor for palladium and platinum ions. The metal ion-sensitivity of P-A was evaluated using a series of transition metal ions in aqueous solution. On binding to Pd2+ or Pt4+, fluorescence quenching of P-A was demonstrated by an approximately 80% reduction in the fluorescence intensity, while no obvious fluorescence change could be observed in the presence of other metal ions. Compared with its small molecular counterpart, P-A exhibits higher sensitivity and selectivity. The fluorescence intensity of P-A has shown a linear response to both Pd2+ and Pt4+ in the concentration range of 1–10 μM with a detection limit of 1 × 10−6 M in aqueous solution. It has been demonstrated that the sensitive property of the polymer sensors for the palladium and platinum ions is highly dependent on the fine structure of the conjugated polymers. The fluorescence quenching can be attributed to the Pd/Pt-induced aggregation of the polymer chains, which has been proved by fluorescence anisotropy methods. These results indicate that the fluorescence-amplifying method based on the aggregation-induced fluorescence quenching mechanism has enormous potential for the development of highly efficient fluorescence sensors towards the detection of palladium and platinum ions.

Hydroxide-conducting polymer electrolyte membranes from aromatic ABA triblock copolymers

A new ABA triblock copolymer (QPPO-PAES-QPPO) was successfully synthesized by combining one block of poly(arylene ether sulfone)s (B, PAES) and two blocks of quaternary ammonium functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (A, QPPO). Membranes of the triblock copolymer with distinct nanophase separation showed high performance.

Controlled Polymerization Under 60Co γ-Irradiation in the Presence of Dithiobenzoic Acid

The polymerization of methyl acrylate and styrene was carried out under 60 Co γ-irradiation in the presence of dithiobenzoic acid (DTBA) and the kinetics of the polymerization of methyl acrylate was studied. The polymerizations are of a controlled free radical character. The molecular weight of the polymers increases with increasing monomer conversion, and the polydispersities of polystyrene and poly(methyl acrylate) are less than 1,4

A Novel Approach to Triblock Copolymers: 60Co γ-Irradiation-Induced Copolymerization in the Presence of a Trithiocarbonate Macroinitiator

Triblock copolymers were prepared under 60 Co γ-irradiation in the presence of a trithiocarbonate macroinitiator. The triblock copolymers, PSt-PMA-PSt and PMA-PSt-PMA have well-defined structures, controlled molecular weight and narrow molecular weight distribution. The reaction mechanisme is discussed

Preparation and characterization of composite membranes with ionic liquid polymer-functionalized multiwalled carbon nanotubes for alkaline fuel cells

Multiwalled carbon nanotubes functionalized with an imidazolium-type ionic liquid polymer, PIL(BF4)–MWCNTs, have been successfully prepared via in situ free radical polymerization of 1-vinyl-3-methylimidazolium iodide ([VMIm][I]) and then blended with poly(2,6-dimethyl-1,4-phenylene oxide) containing imidazolium groups (PPO–MIm) in solution to fabricate composite membranes. The composite membranes were characterized by scanning electron microscopy (SEM) and the SEM images of the membranes show that the PIL(BF4)–MWCNTs can be homogeneously dispersed in the PPO–MIm matrix. The conductivity and mechanical properties of the composite membranes were examined. It was demonstrated that the incorporation of the PIL(BF4)–MWCNTs into the membranes of PPO–MIm can increase both conductivity and mechanical properties. The composite membrane containing 0.3 wt% of PIL(BF4)–MWCNTs (P(0.3)) exhibits a dramatic enhancement in ionic conductivity (95.3%) and tensile strength (82.9%) in comparison with the membrane without PIL(BF4)–MWCNTs. Therefore, this research demonstrates that the incorporation of functionalized carbon nanotubes is a facile and useful strategy for improving both ionic conductivity and mechanical properties of alkaline polymer electrolyte membranes.