Qianbiao Li

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.

POSS-containing red fluorescent nanoparticles for rapid detection of aqueous fluoride ions

Polyhedral oligomeric silsesquioxane (POSS)-containing red fluorescent nanoparticles were designed and prepared for rapid detection of aqueous fluoride ions by virtue of the fluoride-triggered self-quenching of perylene bisimide dyes in nanoparticle cores.

A facile and highly efficient strategy for esterification of poly(meth)acrylic acid with halogenated compounds at room temperature promoted by 1,1,3,3-tetramethylguanidine

Esterifications of poly(methacrylic acid) (PMAA) and poly(acrylic acid) (PAA) have been investigated with a wide variety of halogenated compounds such as iodide, bromide, and chloride using 1,1,3,3-tetramethylguanidine as a promoter. The results demonstrate that the poly(meth)acrylates can be obtained with an excellent degree of esterification at room temperature. The influence of solvent, reaction conditions, and halogenated compounds on the esterification reaction was examined. It was found that polar solvents, such as dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), are favorable for the esterification and high degree of esterification can be achieved in a short time. Moreover, the esterification reaction of PMAA has been successfully performed in an aqueous solution of DMSO, which indicates that the solvent does not necessarily have to be dried for this reaction. Primary and secondary halogenated compounds can successfully react with PMAA or PAA, while tertiary halogenated compounds fail to react. In addition, combining this esterification reaction with atom transfer radical polymerization (ATRP), macromonomers were conveniently prepared by the reaction of halogen-capped polymers with methacrylic acid under mild conditions.

An amphiphilic conjugated polymer as an aggregation-based multifunctional sensing platform with multicolor fluorescence response

We designed and synthesized an amphiphilic conjugated polymer P1 based on the 2,2′-biimidazole unit, and then investigated its sensing properties as an aggregation-based platform. P1 shows multicolor emission in organic solvents at different water contents, and is demonstrated to be the first multicolor fluorescent sensor for water. And it exhibits visually noticeable multicolor fluorescence response to Ag+ in aqueous dioxane and to Hg2+ ions in aqueous ethanol. In addition, the polymer–Hg2+ complex system can be used as an efficient cysteine fluorescent sensor based on the aggregation–disaggregation strategy. These results validate P1 as an efficient multifunctional platform with multicolor fluorescence response.

A novel poly(2,6-dimethyl-1,4-phenylene oxide) with pendant imidazolium groups for high-temperature proton exchange membrane

We designed and synthesized a novel poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with imidazolium-functionalized aromatic side chains by the reaction of imidazole-functionalized PPO and methyl iodide, and then prepared the acid doped PPO membrane by immersing the polymer membrane in phosphoric acid (PA). To achieve a high acid doping level and a high dimensional stability, the cross-linked membranes were prepared by the reaction of the imidazole groups of the polymer and 1,4-bis(bromomethyl) benzene. The PA content, area swelling, and tensile strength of the non-crosslinked and the crosslinked membranes doped with a H3PO4 solution were measured. The results showed that the crosslinked membrane with a PA content of 438% possessed the highest conductivity of 54 mS cm−1 at 140 °C with high dimensional stability and high tensile strength. Moreover, no shape change of the membranes was observed in 15 days in a Fenton solution containing 3% H2O2 and 4 ppm Fe2+ at 80 °C, indicating a high oxidative stability. Therefore, this new polymer can be considered as a promising candidate for preparing a high temperature proton exchange membrane for use in fuel cells.

Synthesis of Photodegradable Polystyrene with Trithiocarbonate as Linkages

Multiblock polystyrenes (PS) with trithiocarbonate groups as linkages are prepared via reversible addition-fragmentation chain-transfer polymerization using polytrithiocarbonate as a chain transfer agent. The photodegradability of the multiblock PS in the solid state is investigated under UV irradiation at room temperature in an air atmosphere. The experimental results demonstrate that the trithiocarbonate linkages in the multiblock PS can be broken under UV light irradiation at room temperature and the multiblock PS is degraded into separate PS blocks. Gel permeation chromatography measurement reveals that the molecular weight of multiblock PS is reduced from 27 900 to 7900 g mol(-1) after UV light irradiation for 745 h. Moreover, the thermal stability of the multiblock PS is examined and the results indicate that the incorporation of trithiocarbonate shows little influence on the thermal stability of multiblock PS.