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1.
Heterometal alkoxide clusters of lanthanide and sodium, LnNa8[OC(CH3)3]10(OH) [where Ln = Nd ( 1 ) or Yb ( 2 )], which were synthesized by the metathesis reaction of LnCl3 with NaOC(CH3)3 and NaOH in a 1 : 10 : 1 molar ratio in high yields and fully characterized including X‐ray analysis for 2 , were found to be highly active catalysts in the ring‐opening polymerization of ε‐caprolactone and trimethylene carbonate and their copolymerization. All of the polymers obtained showed a unimodal molecular weight distribution, indicating that 1 and 2 could really be used as single‐component catalysts. The dependence of catalytic activity on the lanthanide metals was observed: Yb < Nd. A coordination–insertion mechanism for the ring‐opening polymerization is proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
2.
Polymerization of glycidyl methacrylate (GMA), methacrylic acid (MAA), acrylamide (Aam) and their binary mixtures with cotton cellulose fabrics using Fe2+-thioureadioxide-H2O2 redox system was investigated under a variety of conditions. While temperatures of 50, 80, 65, and 95°C constituted the optimal polymerization temperature for GMA, MAA, Aam and GMA/MAA (8:2), respectively, maximum polymerization of GMA/MAA (2:8), Aam/MAA (8:2) and Aam/MAA (2:8) occurred at 75°C. The polymerization reaction proceeded initially very fast then levelled off irrespective of the monomer or monomer mixtures used. However, the magnitude of the polymer add-on at levelling off of polymerization followed the order GMA > GMA/MAA (2:8) ≥ GMA/MAA (8:2) > Aam/MAA (2:8) ≥ MAA ≥ Aam/MAA (8:2) > Aam. The polymer add-on enhanced by increasing the H2O2 concentration up to a certain limit and then decreased. The same situation was encountered with respect to thioureadioxide concentration. The involvement of the epoxy ring of GMA with MAA during polymerization of their mixture with cellulose occurred only at a higher ratio of GMA in the mixture. Also a significant contribution of Aam in the polymer add-on obtained with a Aam/MAA mixture could only be achieved at a higher ratio of Aam in this mixture. 相似文献
3.
Self-associating copolymers of methacrylic acid (MAA) with poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by free radical copolymerization of MAA with PEGMA using dispersion polymerization in D2O, or solution polymerization in a 50/50 ethanol–D2O mixture. These copolymers have been studied as components of reversible hydrogels1 and in medical applications.2 In order to understand the relationship between the copolymer structure and its performance, it is important to determine the sequence distribution of the copolymer. The copolymer architecture is determined by the reactivity ratios and integrated instantaneous feed compositions. The reactivity ratios were determined using the first-order Markov method3 by running a series of reactions at various initial monomer ratios and determining the monomer incorporation into the copolymer as a function of time, via 1H nuclear magnetic resonance. The reactivity ratios for dispersion copolymerizations of MAA with PEGMA in water were determined to be r1 = 1.03 and r2 = 1.02, whereas solution copolymerization in 50/50 EtOH–H2O gave reactivity ratios of r1 = 2.0 and r2 = 3.6. These results show that the reactivity ratios and copolymer architecture are influenced by the solvent system. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1019–1025, 1998 相似文献
4.
Monika Zab?ocka-Malicka Bart?omiej Ciechanowski Wies?aw Gawe? 《Electrochimica acta》2010,55(9):3409-3413
CsCl-NdCl3 is the next of binary MCl-NdCl3 systems (M: alkali metal) investigated for determination of relative internal mobilities of cations (bCs, bNd) by countercurrent electromigration method (Klemm's method). The results have been presented as isotherms of internal mobilities of Cs+ and Nd3+ ions on NdCl3 equivalent fraction (yNd). It has been found that internal mobility of cesium cations is higher than neodymium ones in the entire composition range (what is typical for nonsymmetrical MCl-LnCl3 systems (M: Li, Na, K; Ln: La, Nd, Dy)) and decreases with increase of NdCl3 concentration in the melt. Generally, dependence of internal mobility of lanthanide cations in melts with alkali metal chlorides on lanthanide (i.e. its atomic number and concentration) seems strongly related to stability of chloride complex anions of lanthanides in the melt. Investigated systems may be divided into two classes. The first class includes MCl-NdCl3 systems (M: Li, Na) characterized by decrease of bNd with increase of NdCl3 concentration. The second includes KCl-LnCl3 systems (Ln: La, Nd, Dy) and presented here CsCl-NdCl3 system, and is characterized by increase of bLn with concentration of Ln3+ cation. The dependence of bNd on NdCl3 concentration at 1073 K was fitted (as for other systems) by a simple equation of the form: , where is the internal mobility of Ln3+ cations in pure molten LnCl3, a the difference between internal mobility of Ln3+ cations in pure molten LnCl3 and infinitely diluted LnCl3 in molten alkali metal chloride (extrapolated), and yLnCl3 is the equivalent fraction of LnCl3. 相似文献
5.
Thomas Chenal 《Polymer》2007,48(7):1844-1856
The rare-earth metallocene chloride complexes (C5Me5)2LnCl2Li(OEt2)2 (Ln = Nd, Sm or Y) combined with an excess of dialkyl-magnesium compounds (butyl-ethyl-magnesium) afford active species for the polymerization of ethylene in alkanes or aromatic solvents at atmospheric pressure. A dynamic equilibrium between dormant species and a low concentration of catalytically active species is suggested to explain the living character of the polymerization process observed at temperatures up to 80 °C. A fluxional behavior of the polynuclear structure of the dormant species accounts for the fast and reversible exchange/transfer reaction of alkyl chains between lanthanide and magnesium metallic centers. The resulting mixture contains mainly di(polyethylenyl)magnesium compounds and can be directly used either for block copolymerisation with polar monomers or for any classical Grignard-like reaction for the synthesis of functionalized polyethylenes. 相似文献
6.
Maria Atanassova 《溶剂提取与离子交换》2013,31(2):159-171
The solvent extraction of the lanthanide(III) ions (without Pm) with a 4‐benzoyl‐3‐phenyl‐5‐isoxazolone(HPBI) alone and in the presence of the quaternary ammonium salt Aliquat 336 in perchlorate form (QClO4) in C6H6 was investigated by the slope analysis method. The composition of the extracted species was determined as Ln(PBI)3 and Q[Ln(PBI)4] (Q+ is the quaternary ammonium salt cation). The values of the equilibrium constant were calculated. Synergistic effects were found for all lanthanide metals when they were extracted with a binary mixture of HPBI and QClO4. The influence of the synergistic agent on the extraction process has been discussed. The parameters of the extraction process were determined. The separation factors between adjacent metals were evaluated. 相似文献
7.
Uniform polystyrene (PSt) particles with the size of 1.9 μm were first prepared via dispersion polymerization, and then used as the seeds in a second‐stage dispersion copolymerization of styrene (St) and methacrylic acid (MAA) to produce carboxyl‐carrying microspheres. The PSt seed particles were swollen by monomer mixture of St and MAA, including an oil‐soluble initiator 2,2′‐azobisiso‐butyronitrile (AIBN), before polymerization. Finally, uniform PS/P(St/MAA) (polydispersity index, PDI = 1.02) microspheres with the size of 2.2 μm were obtained. The average particle size and size distribution of the final microspheres were investigated. MAA contents between 54 and 97 mg/g were detected from the PS/P(St/MAA) particles produced under different conditions. Dispersion medium has great influence on the kinetics of polymerization, due to its effect on the partitioning of monomers, solvents, and initiator in the particle phase, probably as well as on the conformation of the dispersion agent on the surface of the particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3586–3591, 2006 相似文献
8.
Ok Hyung Kim 《Polymer》2006,47(6):1953-1959
Monodisperse poly(methylmethacrylate) microspheres having a diameter of 2.6 μm and a molecular weight of 102,277 g/mol with 5.3% of the Cv (the coefficient of variation) were synthesized by the dispersion polymerization using hydrophilic polyvinylalcohol (PVA) in methanol/water mixture media. Then, the structural verification of the synthesized materials is confirmed by using 1H NMR and FT-IR spectroscopy. The effects of PVA and the polymerization parameters such as the initiator, monomer and stabilizer concentrations, and the reaction time on the characteristics of the final particles were studied. Thus, the role of PVA in the dispersion polymerization of MMA is not only a steric stabilizer by physically adsorbed in methanol phase, but also a colloid protective to give relatively monodisperse polymer particles in water phase, simultaneously. 相似文献
9.
The effects of the various salts onto the emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) were investigated. It was found that the kind and amount of the salts were very effective on the polymerization even onto the polymeric products. It is known that the ionic strength of the electrolyte is effective for the polymerization. However, our investigation with the same ionic strength of different electrolyte produced the different effect on the polymerization. It was found that the Stokes radiuses of ions are very important for the reaction kinetics and type of the product. At the same electrolyte concentration, as increased Stokes radii of cation of salts that not react (the fragments of initiator, ions, etc.) in polymerization, polymerization rate and average molecular weight of polymer decreased, polymer particle diameter increased. In the case of Br? and SO4= the anions of the salt are also demonstrated some unexpected reactions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2494–2500, 2007 相似文献
10.
Molecular imprinted polymer microspheres (MIPs) were prepared by precipitation polymerization using melamine as template molecule, methacrylic acid (MAA) as functional monomer, trimethylol‐propane trimethacrylate (TRIM) as crosslinking agent, acetonitrile as solvent and dispersion medium. Release of the template was performed by continuous extraction with methanol containing 10% acetic acid. The microspheres were observed by scanning electron microscopy (SEM). The perfect microspheres were produced when the addition of crosslinker was 7.48 mmol. The binding capacity of MIPs was examined, Qmax = 68.36 μmol g?1, and the dissociation constant at binding site of MIPs, Kd = 0.761, was estimated. Compared with the performance of conventional imprinted polymer, the imprinted microspheres showed high selectivity in special binding to template molecule. The imprinted microspheres could be used as the stationary phase in HPLC or SPE for selective extraction of melamine in daily products. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
11.
Egle Grazenaite Vitalija Jasulaitiene Rimantas Ramanauskas Aivaras Kareiva 《Journal of the European Ceramic Society》2018,38(9):3361-3368
Cobalt chromite based pigments CoCr2–xLnxO4 (Ln?=?Tm3+ and Yb3+) with different substitutional level of lanthanide (x?=?0–0.5) have been synthesized using aqueous sol–gel synthetic approach. The XRD analysis revealed that single phase spinel was obtained only with low content of lanthanide ions (x?=?0.01–0.04). The sol–gel derived powders with higher concentration of lanthanide (x?=?0.05–0.2) contained minor amount of orthochromite phase. At the highest substitutional level (x?≥?0.2) the perovskite phase became the main crystalline phase. The colour of obtained pigments and corresponding ceramic glazes were analogous. Depending on the dominant phase, the colour varied from bluish-green (prevailing spinel phase) to dark brownish green (the main perovskite phase). This study proved that the replacement of chromium ions by thulium and ytterbium was successful at low content of lanthanides influencing the shade of pigment and corresponding glazes. 相似文献
12.
The equilibrium.extraction behavior for a series of tervalent lanthanide ions (Ln3+) using a chloroform solution containing di(2-ethyl-hexyl) phosphoric acid (HDEHP), diphenylphosphinic acid (HDPP), dibutylphosphorothioic acid (HDBPT), di-n-octylphosphorodithoic acid (HDOPDT), or di(2-ethylhexyl)phosphorodithioic acid (HDEHPDT), either alone or combined with adduct forming agents is studied. The extracted species are Ln(DEHP) 3(HDEHP) 3, Ln(DPP)3 (HDPP)3, Ln(DBPT)3, and are Ln(DBPT)3(HDERP)3 in the presence of o-phen and its analogs (B). Extraction constants for the lanthanides follow the order HDPP > HDEHP > HDBPT » HDOPDT. HDPP was the most selective of all the extractants examined. HDOPDT and HDEHPDT were found to be ineffective lanthanide extractants. 相似文献
13.
《分离科学与技术》2012,47(5):821-832
Abstract The elemental composition, molecule, and crystal structure of precipitates obtained from an acetone solution of Ln(NO3)3 (Ln = Pr + Er or La + Nd) with a mixture of bis- and mono-(2-ethylhexyl) phosphoric acids and their sodium salts were studied. In this study we found enrichment of the precipitate with the heavier lanthanide. The separation factor for the La-Nd couple is much greater than for the Er-Pr couple, and decreases with increasing rare-earth yield in the precipitate. We discuss the significant role of the stability of LnA3 against HNO3, especially the formation of La complexes with mono-(2-ethylhexyl) phosphoric acid during enrichment. 相似文献
14.
Marco Sangermano Ignazio Roppolo Guobin Shan Mark P. Andrews 《Progress in Organic Coatings》2009,65(4):431-434
New epoxy-based nanostructured materials containing lanthanide ions doped LaF3 nanoparticles were obtained by cationic UV-induced ring-opening polymerization.The lanthanide Er3+ and Yb3+ ions were added as dopant to LaF3 nanoparticles. The synthesized NPs were solubilized into cyclohexene oxide and afterwards dispersed, in the range between 3 and 20 wt.%, into CE as dicycloaliphatic epoxy resin. The cured films were completely transparent and TEM analysis showed the absence of macroscopic agglomeration. The fast UV curing process was shown to be efficient on “freezing” the good nanometric dispersion achieved in the liquid formulations. These new materials could find suitable applications in optical communication and in LASER waveguide direct writing. 相似文献
15.
Radical polymerization of acrylonitrile (AN) with methacrylic acid (MAA) and itaconic acid (IA) was carried out in a mixture of dimethylformamide (DMF) and water at 70°C using α, α′‐azobisisobutyronitrile (AIBN) as an initiator. Monomer feed in the polymerization vessel was 98:2 (AN:MAA/IA) in the molar ratio, and the DMF:H2O ratio was varied between 20:80 and 80:20 (w/w). Copolymers were characterized by FTIR, carbon, hydrogen, nitrogen elemental CHN analysis, 1H‐ and 13C‐NMR, and viscometry. The rate of polymerization (Rp) was found to decrease with an increase in DMF concentration in the reaction medium, that is, in 20% DMF for AN–MAA system, the Rp is 1.23% min−1 in 1 h of polymerization, while in 80% DMF, Rp is reduced to 0.37% min−1. The nature of the vinyl acid also affects the Rp. It has been shown that the rate of polymerization is higher for an AN–MAA system as compared to an AN–IA system (Rp = 1.0% min−1) and the methacrylic or itaconic acid content in the copolymer increases with an increase in the DMF concentration. The MAA content in the poly(AN–MAA) polymer produced in 20% DMF is 3.2 mol %, which increases to 6.1 mol % (calculated through FTIR spectra) when DMF is increased to 80% in the reaction medium. The intrinsic viscosity [η] of the poly(AN–IA) and poly(AN–MAA) copolymers in DMF was found to be in the range of 0.67–2.90 dLg−1 depending on the reaction medium. In determining the intrinsic viscosity, a definite deviation from rectilinearity of the concentration dependence in the high‐dilution region is observed, thereby demonstrating the polyelectrolyte behavior of these polymers. Through FTIR and NMR spectral studies, PAN homopolymer and other copolymers have shown the formation of a small quantity of acrylamide units. In addition copolymer P10, which contains 10.1 mol % IA, has shown anhydride formation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1640–1652, 2001 相似文献
16.
Reaction of LnCl3 first with three equivalent of C5H5Na in THF, then with one equivalent of benzyl mercaptan, led to complexes of [(C5H5)2Ln(SCH2Ph)]2 (Ln?=?Sm(1), Yb(2)), being characterized by infrared spectra, elemental analyses and X-ray crystallography for 2. Complex 2 is a dimer with two thiolate ligands as bridging groups in eight coordinate. The Yb-S(benzyl) bonds in 2 (2.703(19) and 2.719(2) Å, respectively) were longer than the Yb-S(aryl) bonds (about 2.640 Å) in analogous complexes. The catalytic property for the polymerization of ε-caprolactone by 1 and 2 was studied. Similar experiment was also made with [(C5H5)2Ln(SPh-p-CH3)(THF)]2 (Ln?=?Sm(3), Yb(4)) for comparison. It was found that complex 2 showed the activity best, and the activity decreased in the order of 2?>?3?>?1?>?4. When [ε-CL]0/[Ln] was 500 and the polymerization temperature was 35°C, complex 2 catalyzed the polymerization in living character, which could not be achieved by lanthanide arylthiolates such as 3 and 4. 相似文献
17.
Methyl methacrylate–methacrylic acid (MMA–MAA) copolymers were prepared from the polymerization reaction of the methyl methacrylate (MMA) monomer with concentrated nitric acid (65% HNO3) at different reaction times in the absence of other reagents in the reaction mixture. The hydrolysis degrees of the MMA–MAA (sodium salts) copolymers estimated by thermogravimetry (TG) corroborated the data obtained by chemical titration. By calorimetry (DSC), a relationship between the glass transition temperature (Tg) and the hydrolysis degree was obtained. The results presented a deviation from linear behavior and it was related to the strength of the interactions involved in the copolymer chains. The equation that relates the glass transition temperature to the interaction parameter, χ, for miscible binary polymer blends was applied for the MMA–MAA copolymers and demonstrated the composition dependence of χ. The molecular mobility was determined by nuclear magnetic resonance (NMR) in the solid state and through the proton spin‐lattice relaxation time in the rotating frame. The NMR data were in a good agreement with the results obtained by calorimetry. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 495–507, 2000 相似文献
18.
In this study, the luminescent macromolecular lanthanide complexes Ln‐PSt/AA (Ln = Eu and Tb; St = styrene; AA = acrylic acid) have been synthesized, and an extensive characterization has been carried out by means of elemental analysis, FTIR, thermal analysis, and fluorescence determination. The results showed that the carboxylic groups on the chain of the polymers acted as bidentate ligands coordinated to lanthanide ions; and the coordination degree of ? COO?/Ln3+ in the macromolecular complexes was closely dependent on both the pH value of the solution and the molar ratio of St to AA in the polymeric ligands. Thermal analysis manifested that these Ln‐PSt/AA (Ln = Eu and Tb) complexes had high thermal stability and solvent resistance, and these macromolecular complexes were highly crosslinked. The fluorescence determination indicated that Ln‐PSt/AA complexes could emit characteristic fluorescence with comparatively high brightness and good monochromaticity, and the fluorescence intensity changed with increasing lanthanide ions content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
19.
The effect of the incorporation of several lithium salts on the electrical and mechanical properties of polyurethane rigid (PUR) foams was investigated. Different amounts of lithium chloride (LiCl), lithium perchlorate (LiClO4), and lithium trifluoromethanesulfonate (LiCF3SO3) were added to the polyuretanic precursor. The salts affected the cellular microstructures and consequently the mechanical properties of the composite. Composite foams containing an amount of LiCl greater than 2 wt% showed low‐surface resistivity (~106 Ω), whereas the LiClO4 and LiCF3SO3 composites showed, in all range of filler percentage analyzed, high‐surface resistivity values (~1011 Ω). This behavior was related to the different interactions between PUR and lithium salts, as confirmed by FTIR/Attenuated Total Reflectance analysis. Only the LiCl was able to create a motion of the ions Li+ and Cl? along the polyurethanic chains, because LiCl was completely dissociated. On the contrary, LiClO4 and LiCF3SO3 that affected the macromolecular structure of the polymeric network did not permit the formation of polyurethanic channels, where the ions could move, thus creating a charge motion. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers 相似文献
20.
For the safe and trouble‐free operation of a manufacturing plant and the safe storage of acrylic, as well as methacrylic monomers, it is important to know the polymerization stability as a function of the process parameters (temperature, oxygen concentration, and impurities, e.g., metal ions). Contamination with metal ions can be caused by the corrosion of steel units. Therefore, the influence of the metal ions Cr3+, Fe3+, Ni2+ and Cu2+ in the concentration range of 0–10 ppm (g g–1) on the polymerization behavior and the oxygen consumption of acrylic and methacrylic acid were examined in this work. It was shown that Cr3+, Ni2+, and Cu2+ ions extend the inhibition period of acrylic acid (AA) and methacrylic acid (MAA) and reduce the O2 consumption. Fe3+ ions, however, cause a decrease of the inhibition period and in the case of AA an increase of the O2 consumption, which leads, in the end, to a faster unintentional polymerization. Therefore, alloys which contain iron should be avoided as far as possible in the construction of AA plants. Fe3+‐ions show the opposite influence towards MAA, here the presence of Fe3+ shows a stabilizing effect. 相似文献