Chaolong Yang

An efficient long fluorescence lifetime polymer-based sensor based on europium complex as chromophore for the specific detection of F−, CH3COO−, and H2PO4−

A novel long fluorescence lifetime europium-complexed copolymer (Eu-polymer) has been designed and synthesized via the classic free radical copolymerization reaction as an efficient fluorescent sensor for F−, CH3COO−, and H2PO4−. The anions-sensitivity of Eu-polymer was evaluated using a series of anions in DMSO solution. On binding to F−, CH3COO−, or H2PO4−, fluorescence quenching of Eu-polymer was demonstrated by an approximately 95% reduction in the fluorescence intensity, while no obvious fluorescence change could be observed in the presence of other anions. Compared with its small molecular counterpart, Eu-polymer exhibits higher sensitivity and selectivity. Most importantly, the Eu-polymer sensor can efficiently recognize and sense F− even in the presence of competitive anions, such as CH3COO− and H2PO4−, which demonstrates the ability of Eu-polymer to function as a selective fluorescence sensor for F−. The fluorescence quenching can be attributed to the strong hydrogen bonding interaction (and deprotonation interaction at high concentration for F−) between anions and the imidazole group of Eu-polymer. Due to the long fluorescence lifetime of this Eu-polymer, it can efficiently eliminate the effects of auto-fluorescence and light scattering from surrounding biological environments, so this sensor will be very significant for application in biological and environmental fields.

Efficient monochromatic red-light-emitting PLEDs based on a series of nonconjugated Eu-polymers containing a neutral terpyridyl ligand

Three novel Eu-polymers containing hole transporting units and light-emitting units in the main chain have been designed and synthesized via radical copolymerization of N-vinylcarbazole and polymerizable Eu(TTA)3vinyl-tpy, where TTA is 2-thenoyltrifluoroacetonate. The chemical structure and composition of the Eu-polymers were characterized by FTIR, UV-vis, 1H NMR, 13C NMR spectroscopy, GPC, ESI-MS, and elemental analysis. The geometry of the polymerizable monomer Eu(TTA)3vinyl-tpy was predicted using the Sparkle/PM6 model and suggested to be in a chemical environment with very low symmetry around the Eu3+ ions (C1), in agreement with the fluorescence spectrum. All Eu-polymers exhibited good solubility, as well as good thermal stability and high glass transition temperatures. The photoluminescence (PL) properties of the copolymers in solution and in the solid state were investigated in detail. Intramolecular energy transfer from the carbazole groups to the europium complexes occurred even in diluted solutions. The efficiency of this process also depended on the composition of the Eu-polymers. In the solid state, emission from the carbazole groups was suppressed and the absorbed excitation energy was transferred effectively to the europium complexes in the Eu-polymers. Most importantly, the EL performances of eight pure red-emission PLEDs based on P1, P2, and P3 as the emitting layer have been studied in detail. Bright electroluminescence with a maximum luminance of 68.2 cd m−2 from the double-layer devices of P1 was demonstrated. Although the EL performance was only the third-best among those of the Eu-chelated polymers reported so far, to the best of our knowledge, this is the first example of electroluminescent devices of Eu-polymers based on tpy as a neutral ligand. These results illustrate the potential application of polymerizable tpy ligands in high performance EL Eu-chelated polymers.

Efficient red emission from poly(vinyl butyral) films doped with a novel europium complex based on a terpyridyl ancillary ligand: synthesis, structural elucidation by Sparkle/RM1 calculation, and photophysical properties

A novel efficient antenna Eu-complex Eu(TTA)2Tpy-OCH3·2H2O, based on the terpyridyl derivative 4′-(4-methoxyphenyl)-2,2′:6′,2′′-terpyridine(Tpy-OCH3) as the ancillary ligand, has been synthesized, structurally characterized, and its photophysical properties have been examined. Upon irradiation at the ligand-centered band in the range of 200–450 nm, the new Eu-complex displays bright red luminescence, irrespective of the medium. A Sparkle/RM1 calculation was utilized for predicting the ground-state geometries of this complex. Theoretical Judd–Ofelt and photoluminescence parameters, including quantum efficiency, as predicted from this model are in good agreement with the experimental values, proving the efficiency of this theoretical approach as implemented in the LUMPAC software (http://lumpac.pro.br). The kinetic scheme for modelling energy transfer processes shows that the main donor state is the ligand triplet state and that energy transfer occurs on both the 5D1 (20.7%) and 5D0 (79.3%) levels. As an integral part of this work, the synthesis, characterization, and luminescence properties of poly(vinyl butyral) (PVB) polymer films doped with the Eu-complex are also reported. After the Eu-complex Eu(TTA)2Tpy-OCH3·2H2O was doped into the PVB matrix to form the films, the PVB polymer matrix, acting as a co-sensitizer for Eu3+ ions, enhances the luminescence lifetimes and quantum efficiencies of the complex in comparison with its precursor complex. The new luminescent Eu/PVB films therefore show considerable promise for polymer light-emitting diode and active polymer optical fiber applications. To the best of our knowledge, this is the first report which studies in detail the photophysical properties of doped europium fluorescent films based on PVB as the polymer matrix.

Reversible Addition-Fragmentation Chain Transfer Polymerization of Methyl Methacrylate in Microemulsion: The Influence of Reaction Conditions on Polymerization

The reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) using cetyltrimethylammonium bromide (CTAB) as surfactant and a difunctional RAFT agent S,S′-bis (α, α′-dimethylacetic acid) trithiocarbonate (BDAT) as chain transfer were conducted in microemulsion. The influence of polymerization temperature and concentration of RAFT agent on the polymerization were investigated, respectively. The results showed that the molecular weight of products increased linearly with conversion, the polydispersity indexes remained low value, and the polymerization processes were totally under control with increasing concentration of RAFT agent, the polymerization behavior exhibited living polymerization characters. In addition, the influence of RAFT concentration on the particle size was investigated by TEM. The results indicated that the particles were highly monodispersed and the particle size increased with increasing concentration of RAFT agent.

Structure and Properties of Glass Fiber Reinforced Polypropylene/Liquid Crystal Polymer Blends

A liquid crystal polymer (LCP) was used to improve the physical properties of glass fiber reinforced polypropylene (GFRPP). The LCP was beneficial to improve the mechanical and heat resistant properties of the GFRPP/LCP composite. Compared with the GFRPP with 30% (w%) glass fiber (GF), the yield strength and the impact strength for the GFRPP/LCP composites increased by 62.7% and 18.1%, respectively, with a 6.8°C increase in the Vicat softening temperature for a 5% LCP addition to the GFRPP composites. The crystallinity of the polypropylene (PP) matrix for the GFRPP/LCP composites increased for 5% LCP and then decreased with increasing the LCP content. The γ-phase crystals for the PP matrix occurred in the shear layer of the injection molded GFRPP/LCP samples. The improved adhesion interface between the GF and the PP matrix was beneficial to reinforce and toughen the GFRPP/LCP composites with a small addition of the LCP.