Synthesis and characterization of a novel waterborne stilbene-based polyurethane fluorescent brightener

A novel waterborne stilbene-based polyurethane fluorescent brightener dispersion WPU-VBL was synthesized by incorporating chemically disodium 4,4’-bis[(4-anilino-6-hydroxyethylamino-1,3,5-triazin-2-yl)amino]stilbene-2,2’-disulphonate(VBL) into the polyurethane chain using isophorone diisocyanate,poly(propylene glycol) and 2,2-dimethylol propionic acid.The structure of WPU-VBL was confirmed by means of Fourier transform infrared spectroscopy.The UV-vis absorption analysis showed a hypsochromic shift of 16 nm when VBL was blocked into polyurethane chain.Number average molecular weight of 2.1×10~4, molecular weight distribution of 2.1 and average latex particle size of about 70 nm for WPU-VBL were determined based on the analysis of gel permeation chromatography and laser particle size analyzer.It was found that the fluorescence intensity of WPU-VBL was prominently enhanced because of the micro-circumstance of VBL and the fluorescence of WPU-VBL was very stable.     

Synthesis of nanocrystal-polymer transparent hybrids via polyurethane matrix grafted onto functionalized CdS nanocrystals

We reported the first synthesis of CdS nanocrystal-polymer transparent hybrids by using polyurethane (PU) grafted onto quantum dots (QDs) CdS nanocrystals. In a typical run, the appropriate amounts of cadmium chloride (CdCl2) and sodium sulfide (Na2S) in the presence of 2-mercaptoethanol (ME) as the organic ligand are well dispersed in H2O/DMF solution without any aggregation. From a combination of transmission electron microscopy (TEM) and a computing method of Brus's model according to UV-vis absorption spectra, the particle size of as-prepared hydroxyl-coated CdS nanocrystals is about 5 nm. Then, PU-CdS transparent nanocomposites hybrids were synthesized by a two-step reaction. The effect of the different ratios of ME/Cd2+ and H2O/DMF on the resulting particle size of CdS nanocrystals was investigated by UV-vis absorption measurements. FT-IR and TGA characterizations indicate the formation of robust bonding between CdS nanocrystals and the organic ligand. The fluorescence measurement shows that CdS-PU hybrids exhibit good optical properties.     

Fluorescent and thermal properties of siloxane-polyurethanes based on 1,8-naphthalimide

A series of fluorescent siloxane-polyurethanes(HPMS-PUs) containing an amino-functionalized,1 8-naphthalimide,fluorescent monomer(AABD) as a chain extender were synthesized.The properties of the HPMS-PUs were investigated by UV–vis and fluorescence spectroscopies,thermogravimetric analysis and thermal migration behavior.The maximum absorption and emission wavelengths of HPMS-PUs showed a red shift of about 4 nm and a blue shift of about 9 nm,respectively,compared to those of AABD.The Stokes shifts of AABD and HPMS-PU2 were 3514 and 2931 cm 1,respectively.The quantum yield of HPMS-PU2 was 0.79,which was six times higher than that of AABD.Concentration self-quenching was observed in both AABD and HPMS-PUs.The fluorescence of HPMS-PUs was quite stable with respect to both temperature and fluorescence quencher effects.The thermal stability of HPMS-PUs increased with AABD content.The fluorophore units in the HPMS-PUs did not readily migrate.     

Copolymer nanosphere encapsulated CdS quantum dots prepared by RAFT copolymerization: synthesis,characterization and mechanism of formation

Cadmium sulfide (CdS) quantum dots (QDs) encapsulated in block copolymer spheres were synthesized by an aqueous emulsion polymerization process. First, stable dispersions of CdS QDs in water were prepared using a polymer dispersant, either poly(acrylic acid) or a random copolymer having an average of ten acrylic acid and five butyl acrylate units. These polymer dispersants were prepared by reversible addition-fragmentation chain transfer polymerization. Then, the CdS QDs dispersed in water were encapsulated in a polystyrene shell using an emulsion polymerization process. Spectroscopic and microscopic techniques were used to characterize the resulting nanocomposites. Optical properties of QDs in polymer microspheres were investigated by UV-vis and fluorescence spectroscopic studies. Particle sizes of all CdS QD samples were calculated from absorption edges using Henglein's empirical curve. Transmission electron microscopy was used to determine the size and morphology of CdS QD samples. These observations were used to elucidate the mechanism of formation of the resulting well-defined polymer-encapsulated CdS nanoparticles.     

Reversible modulation in luminescence intensity of a single vesicle composed of diblock azo-copolymer and tris(dibenzoylmethanate)(phenanthroline)europium(III)

Tris(dibenzoylmethanate)(phenanthroline)europium(III)[Eu(DBM)(3)Phen]-doped amphiphilic vesicles were obtained by self-assembling of poly(N-isopropylacrylamide)-b-poly[6-[4-(4-methylphenyl-azo) phenoxy] hexylacrylate] (PNIPAM(83)-b-PAzoM(20)) in presence of Eu(DBM)(3)Phen in the mixed solvent of THF/H(2)O (50/50 vol.%). Their optical properties were studied by UV-vis and fluorescence spectroscopies. The UV-vis spectrum showed that the electronic transition bands of azobenzene and Eu(DBM)(3)Phen were overlapped at about 365 nm and the main peak of fluorescence emission band appeared at 612 nm. So the vesicles showed obvious red luminescence. It was found that the fluorescence intensity of a single Eu(DBM)(3)Phen-doped vesicle could be modulated by irradiation with UV and visible light due to the reversible trans-cis-trans photoisomerization reaction of azobenzene moiety. Possible energy allocation process for this property was discussed in details.     

Synthesis and Fluorescent Performance of Fluorescein-functionalized Waterborne Polyurethane

A novel yellow fluorescent diisocyanate 3,6-di(hexamethylene urethano)spiro[xanthene-9,3′-phthalide] diisocyanate (DIX) was synthesized by the reaction of fluorescein with hexamethylene diisocyanate first. Using DIX to substitute partially isophorone diisocyanate (IPDI), a kind of yellow fluorescent waterborne polyurethane DIX-WPU was prepared by blocking the fluorophore of DIX into the polyurethane chain using IPDI, polytetramethylene ether glycol and 2,2-dimethylol propionic acid. The molecular structure of DIX and DIX-WPU was confirmed by means of Fourier transform infrared spectroscopy. The fluorophore is fixed permanently in the polyurethane chain and is difficult to migrate due to the covalent bonding with other component during the synthesis. The fluorescence intensity of DIX-WPU fluorescent dispersion was enhanced greatly comparing with that of fluorescein in a wide range of fluorophore content between 1 × 10^–7 and 1 × 10^–3 mol/L. The fluorescence of DIX-WPU dispersion is very stable not only for the long term storage but also for the fluorescence quencher. It was found that the fluorescence intensity of DIX-WPU increased with the increase of temperature.     

硅氧烷改性水性聚氨酯的制备及性能

A series of novel aqueous emulsion of siloxane modified polyurethane (PU(PE-PSI)) were synthesized based on poly(propylene glycol) (PPG), polyether-grafted polysiloxane (PE PSI), 2,4-tolylene diisocyanate (TDI), dimethylol propionic acid (DMPA) and 1,4 butanediol (BDO) through a direct water emulsification of triethylamine (TEA). The aqueous emulsion was transparent and had a good stability. Fourier transform infrared spectroscopy (FTIR) was used to identify the structure of PU (PE PSI), indicating that the polysiloxane segment had been incorporated with polyurethane chain. Investigation of Electron Spectroscopy for Chemical Analysis (ESCA) and the water contact angle demonstrated that the siloxane migrated to the surface of film. The results also showed that PU(PE-PSI) was still a very good elastomer. With increasing the content of PE PSI, the resistance to water improved and tensile strength increased, while the ultimate elongation decreased slightly for the PU(PE-PSI) film.     

阳离子聚氨酯/CeO2纳米复合材料的制备

二氧化铈;阳离子聚氨酯/CeO2纳米复合材料的制备     

Synthesis of a Novel Core-shell Type Acrylic-polyurethane Hybrid Emulsion Containing Siloxane and Fluorine as well as Water and the Oil Resistances of Cured Film

Aqueous acrylic-polyurethane dispersions have become one of the major types of materials used in coating, paint and adhesive industries, because of excellent properties and environmental advantages1-5. However, some properties for cured film such as water…     

Preparation of high molecular weight polyurethane particles by nonaqueous emulsion polyaddition

A versatile nonaqueous emulsion polyaddition process for the one-step fabrication of spherical polyurethane nanoparticles is presented. Three different emulsion systems were used consisting of N,N′-dimethylformamide (DMF) dispersed in n-hexane, acetonitrile dispersed in cyclohexane, and acetonitrile dispersed in tetradecane. After successful stabilization of the emulsion systems by using a poly(isoprene)-poly(methylmethacrylate) block copolymer, the fabrication of the polyurethanes was carried out within the dispersed polar phase. The polyurethane particles showed average diameters as small as 35 nm. Additionally, infrared (IR) characterization revealed that the formation of any urea, which decreases the mechanical properties of the polyurethanes, was prevented during the polyaddition. This was attributed to the anhydrous reaction conditions. Gel permeation chromatography (GPC) analysis demonstrated the average molecular weights (M _n) of the polyurethanes to be as high as 16,500 g/mol, corresponding to conversions of 0.98. Comparable molecular weights and conversions have not previously been achieved without the formation of urea.     

Absorption and fluorescence spectroscopy of growing ZnO quantum dots: size and band gap correlation and evidence of mobile trap states

ZnO nanoparticles constitute a convenient model system for fundamental studies with many possible technical applications in, for example, sensors and the field of catalysis and optoelectronics. A large set of ZnO quantum dots in the size range 2.5-7 nm have been synthesized and analyzed in detail. Time resolved in situ UV-vis absorption measurements were used to monitor the growth of these particles in solution by correlating the optical band gap to particle size given from X-ray diffraction (XRD) measurements. The particles formed were isotropic in shape, but small initial deviations gave indications of a transition from thermodynamic to kinetically controlled growth for particles around 4 nm in diameter. On the basis of this, the behavior and mechanisms for the particle growth are discussed. The fluorescence dependence on particle size was investigated by combining fluorescence and UV-vis measurements on growing particles. This revealed that the positions of the fluorescence trap states are mobile toward the conduction- and valence band. A broadening of the trap states was also found, and a surface dependent mechanism of the trap state shift and broadening is proposed.     

Phase inversion of UV-curable anionic polyurethane in the presence of acetone solvent

UV-curable self-emulsified polyurethane acrylates were synthesized in acetone and then dispersed in water. The effect of acetone’s ratio on the emulsification of the polyurethane acrylate was investigated. With a proper amount of acetone as a solvent, stable emulsion with small particle size and narrow particle size distribution was successfully produced and the viscosity during the process of emulsification was greatly reduced. However, stable emulsion could not be obtained when the acetone level was larger than a critical value. A ternary phase diagram was mapped. It was found that only those systems experiencing a phase inversion process lead to a stable emulsion. The carboxylic content is another important factor influencing the properties of emulsion and the process of emulsification. The effect of the carboxylic content on the emulsification was also studied in the experiment. There was another critical carboxylic content for stability. Stable emulsions with small drop sizes less than 50 nm were produced.     

Comparative study between core-shell and interpenetrating network structure polyurethane/polyacrylate composite emulsions

Anionic aqueous polyurethane dispersion was prepared by using carboxyl acid group to make the polyurethane dispersible, and then nanograde core-shell and crosslinked IPN structure polyurethane/polyacrylate composite latex (PUA) were synthesized by soap-free emulsion polymerization method with polyurethane dispersion as seed. FTIR, DSC, dynamic light scattering, TEM, ESCA, TGA, electronic tensile machine were employed to investigate the structures and properties of the composite latex and their polymers. Meanwhile the core-shell composite PUA emulsion and the crosslinked IPN composite PUA emulsion were compared. The results showed that the particle morphology of PUA composite emulsion is inverted core-shell structure with polyacrylate as the core and with polyurethane as the shell. The morphology of the crosslinked PUA emulsion was multi-core structure. The surface in core-shell PUA contains rich PU phase. The phase structure of the crosslinked PUA is more uniform. Three transition temperatures are observed for the core-shell composite PUA, two transitions are observed for the film from the crosslinked PUA. The TGA curves of core-shell PUA and crosslinked PUA exhibit two stages, the first stage corresponds to the thermal decomposition of hard segments in seed polyurethane; the second stage corresponds to the decomposition of soft segments in PUA and decomposition of polyacrylate. With the increase of glycidyl methacrylate (GMA) amounts in PUA composite emulsions, the tensile strength of the PUA films as well as the average diameter of the PUA composite emulsion particles increase, the elongation at break of the PUA films decreases.     

Spectral assignments to the light emissions of fluorescent organic small molecules in aqueous medium

Spectrofluorometric identifications of artificial organic dyes have important environmental significance, but both scattered light signals and the fluorescence signals were twins in fluorospectroscopy, and the light scattering signals are always the interference sources of spectrofluorometry. In order to investigate the relationship between the light scattering and fluorescence in the spectrofluorometric measurements, herein we discuss the scattered light and fluorescence emission properties of organic small molecules (OSMs) using Lignin Pink (LP) in neutral medium as an example. With the help of UV-vis measurements, and starting from three-dimensional light emission measurements, scattered light and fluorescence emissions could be assigned. Investigations by increasing LP concentration showed that the light emission at 282.0 and 344.0 nm could be attributed to the resonance light scattering (RLS) signals and that at 420.0 and 570.0 nm are composed of both RLS and fluorescence emissions, respectively. UV-vis measurements showed that LP does not have the tendency of aggregation, and the strong RLS signals should be ascribed to the large hydrodynamic diameter of LP itself in aqueous medium, supported by dynamic light scattering (DLS) measurements.     

Synthesis and Characterization of New Self-Colored Blue Waterborne Polyurethane Based on a Colorant Diol as Chain Extender

A series of novel self-colored blue waterborne polyurethanes (BPUs) were successfully synthesized by incorporating a self-made colored diol 1,4-bis(2-hydroethylamino)anthrancene-9,10-dione (BHAD) into the polyurethane backbone via step growth polymerization. FTIR, ¹H NMR, ultraviolet-visible (UV-vis) spectroscopy were used to characterize BHAD and BPUs. Compared with BHAD, BPUs showed hypochromic change in UV-visible spectroscopy. The obtained BPUs have good thermal dye migration. The effect of BHAD content on BPUs’ emulsion stability, water resistance, mechanical properties, and thermal performance were investigated systematically by particle size analysis, water absorption ratio, tensile strength test, and thermogravimetric analysis.     

Heteroaromatic alanine derivatives bearing (oligo)thiophene units: synthesis and photophysical properties

A series of new benzoxazolylalanine derivatives bearing (oligo)thiophene units at the side chain were synthesized in good yields. The photophysical characterization of these amino acids was performed by UV-vis absorption and fluorescence emission studies and revealed that some of the compounds display high fluorescent quantum yields, making them good candidates for application as fluorescent probes.     

Fabrication of symmetric hierarchical hollow PbS microcrystals via a facile solvothermal process

Symmetric hierarchical hollow PbS structures consisting of nanowalls were successfully fabricated by a facile solvothermal process in ethylenediamine at 120 degrees C for 12 h, employing lead acetate trihydrate and dithizone as precursors; the thickness of the nanowalls is about 80 nm. No surfactants or other templates were used in the process. The synthesized product was characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), ultraviolet-visible spectrometer (UV-vis), near-infrared absorption spectroscopy (near-IR), and fluorescence spectrophotometer. The effect of the reaction conditions on the size and morphologies of PbS structures was investigated. The results show that the temperatures, solvent, and sulfur sources are crucial factors on the morphologies and sizes of the symmetric hierarchical hollow PbS microcrystals. A possible growth mechanism of hierarchical hollow PbS structures is presented. UV-vis absorption spectrum holds a weak peak at 253 nm; the near-infrared absorption spectrum of PbS microcrystals has the two absorption peaks centered at 9613 cm(-1) (1040 nm) and 6771 cm(-1) (1477 nm), showing a blue shift compared with the bulk PbS (approximately 3020 nm). And the fluorescence spectrum of PbS microcrystals consists of an emission peak with a maximum at 305 nm. These PbS microcrystals may have potential applications in the fundamental study of nanostructures as well as fabricating nanodevices.     

Determination of vitamin E and carotenoid pigments by high performance liquid chromatography in shell of Chionoecetes opilio

This study reports the optimization of a method for the determination of vitamin E and carotenoids in shells of Chionoecetes opilio samples by online HPLC coupled with UV-vis and fluorescence detectors. The carotenoids were determined with diode-array detector (lambda 450 nm) and vitamin E with fluorescence detection (lambda(ex) 288, lambda(em) 331 nm). Two extractions methods were compared, saponification followed by an extraction step and a simple extraction with acetone. The last one was selected because allows to determine all compounds. Linearity, precisions and recoveries achieved for all compounds were satisfactory. Mean concentrations (mg per 100 g dry weight) were; 23.3 for vitamin E, 9.49 for astaxanthin and 0.2 mg for beta-carotene.     

端羟基聚丙烯酸酯改性水性聚氨酯

将丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)通过溶液自由基聚合,用巯基乙醇作为链转移剂调控合成了一定分子量的端羟基聚丙烯酸酯(PA),再与聚氨酯(PU)预聚体反应,在水中分散得到PA-PU-PA三嵌段共聚复合乳液。 采用FTIR和¹HNMR测试技术对共聚物结构进行了表征。 结果表明,随着PU与PA质量比的降低,共聚物中丙烯酸酯含量随之增加;PU软硬链段之间的氢键化作用减弱。 TEM显示,复合乳胶粒子形态均匀规整,并呈现明显的核壳结构。改性后的乳胶膜耐水、耐热性能均随着PU/PA质量比的减小而提高,吸水率由25%降低至5%,最大热失重温度由369 ℃提高至432 ℃。     

CdS量子点的制备及细胞膜初步荧光标记

以巯基乙酸为稳定剂,通过控制反应温度、反应时间及pH值,在水相中合成了稳定的受激发出紫光、蓝光、绿光、黄光和红光的CdS量子点;通过紫外可见吸收光谱、荧光光谱和X射线衍射谱(XRD)对产物的光学性能和晶体结构进行了表征,结果表明所合成的CdS量子点分散性较好,量子产率为8%,为立方晶型,粒径约1 nm;利用荧光倒置显微镜观察了量子点在洋葱内表皮细胞膜上聚集及受激发射荧光行为,实现细胞膜初步标记.