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311.
V. Nelliappan M. S. El-Aasser A. Klein E. S. Daniels J. E. Roberts 《Journal of polymer science. Part A, Polymer chemistry》1996,34(15):3173-3181
In this work poly(methyl methacrylate) (PMMA) macromonomer is used as a compatibilizing agent in a poly(butyl acrylate) (PBA)/PMMA core/shell latex system. The incorporation of the PMMA macromonomer was achieved by copolymerizing it with BA monomer using miniemulsion polymerization. PBA seed latex was also synthesized without the macromonomer present to compare the compatibilizing effects with the PMMA macromonomer. The second stage methyl methacrylate monomer was added semi-continuously to the PBA seed latexes under monomer-starved conditions. Solid-state 13C-NMR [H]T1ρ relaxation studies were used to determine the effect of PMMA compatibilizer on these PBA/PMMA core/shell latex interphase regions. The thickness of the interphase of the core/shell particles prepared with and without the PMMA macromonomer compatibilizing agent are calculated to be in the range of 15–16 nm and 10–12 nm, respectively. Electron microscopy revealed that the seed latex prepared with the PMMA macromonomer achieved a more uniform coverage with the second stage PMMA polymer as compared to the latex synthesized without the compatibilizing agent present. It is concluded that the PMMA macromonomer is effective in increasing the thickness of the interphase region and also the amount of interfacial PMMA. © 1996 John Wiley & Sons, Inc. 相似文献
312.
A Balland J A Mahan-Boyce D A Krasts M Daniels W Wang W R Gombotz 《Journal of chromatography. A》1999,846(1-2):143-156
We present here the purification and the characterization of the isoforms of PIXY321, a genetically engineered fusion of granulocyte-macrophage-colony stimulating factor and interleukin-3 expressed in yeast. The isoforms of PIXY321 were isolated using preparative isoelectric focusing (IEF) on immobilized pH gradients. Analysis of the collected fractions on analytical IEF gels showed that PIXY321 was resolved into four discrete isoforms of isoelectric point (pI) 5.0, 5.1, 5.2 and 5.3 with excellent yields. Subsequent analysis of purified isoforms of PIXY321 by peptide mapping and mass spectrometry linked the microheterogeneity of the original molecule to three parameters, the presence of deamidated residues, charged glycans and the pattern of O-linked glycosylation along the peptide sequence. This last parameter emphasizes the role of conformational aspects as key factors influencing the apparent isoelectric point of protein isoforms. 相似文献
313.
Laszlo Szarvas Zoltan Bajko Stefan Fusz Sebastian Burck Jrg Daniels Martin Nieger Dietrich Gudat 《无机化学与普通化学杂志》2002,628(11):2303-2310
The bis‐phosphonio‐1, 2, 4‐diazaphospholide salt ( 1 [Cl]) reacts with complex boron hydrides under selective extrusion of one PPh3 moiety to give borane adducts of a novel zwitterionic phosphonio‐1, 2, 4‐diazaphospholide. Both the Et3B adduct 2b and the free zwitterionic heterocycle 3 , which was liberated by further reaction of 2b with NEt3, were characterized by spectroscopic data and 2b , as well, by a single crystal X‐ray diffraction study. The comparison of the structural data with those of a neutral 1, 2, 4‐diazaphosphole and a lithium‐1, 2, 4‐diazaphospholide which was formed by deprotonation of the parent 1, 2, 4‐diazaphosphole 4a discloses trends in endocyclic bonding distances which can be rationalized in terms of a charge dependent shift in the π‐electron distribution. First studies of the co‐ordination properties reveal for both 2b and 4a a marked preference to bind two M(CO)5‐fragments (M = Cr, W) via the lone‐pairs of the phosphorus and one nitrogen atom; mononuclear complexes with P‐co‐ordinated heterocycles are formed as intermediates. A single crystal X‐ray diffraction study of the dinuclear complex [Cr2(CO)10(μ2‐C2H3N2P‐κP, κN)] ( 10a ) together with spectroscopic studies (including 183W NMR studies of tungsten complexes) suggests that M→L back donation is more efficient for P‐ than for N‐bound metal fragments. No evidence for π‐co‐ordination of the 1, 2, 4‐diazaphosphole ring to a Cr(CO)3 fragment was obtained. 相似文献
314.
Manfredo Hrner Ivan Carlos Casagrande Herton Fenner Jrg Daniels Johannes Beck 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(10):m424-m426
In the title complex, [Au(C12H8N5O4)(C18H15P)], the coordination geometry about the AuI ion is linear, with one deprotonated 1,3‐bis(4‐nitrophenyl)triazenide ion, [O2NC6H4N=N–NC6H4NO2]−, acting as a monodentate ligand (two‐electron donor), and one neutral triphenylphosphine molecule completing the metal coordination. The triazenide ligand is almost planar (r.m.s. deviation = 0.0767 Å), with the largest interplanar angle being 11.6 (7)° between the phenyl ring of one of the terminal 4‐nitrophenyl substituents and the plane defined by the N=N—N triad. The Au—N and Au—P distances are 2.108 (5) and 2.2524 (13) Å, respectively. Pairs of molecules generated by centrosymmetry are associated into a supramolecular array via intermolecular C—H⋯O interactions, and N⋯C and N⋯O π–π interactions. 相似文献
315.
Jiansheng Tang Victoria L. Dimonie Eric S. Daniels Andrew Klein Mohamed S. El‐Aasser 《Macromolecular Symposia》2000,155(1):139-162
Latex blending is a strategy used to eliminate volatile organic compounds from latex coatings formulations. This paper focuses on the study of the drying kinetics of model hard/soft latex blends and the influence of the presence of carboxyl groups on these particles as well as the extent of neutralization of the carboxyl groups with different bases. The model latex blend was comprised of clean, well‐defined polystyrene hard and poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) soft latex particles with monodisperse particle sizes, homogeneous copolymer composition, and independent control of particle size and carboxyl group content. Drying models are discussed. It was found that the presence of carboxyl groups in the latex particles retarded the drying rate of the model latex blends. When the carboxyl groups present in the latex blends with low carboxyl group coverage on polystyrene particles were neutralized by using ammonium hydroxide or sodium hydroxide, the drying rate increased. When the carboxyl groups present in the latex blends with a high carboxyl group coverage on polystyrene particles were neutralized by sodium hydroxide, potassium hydroxide, or cesium hydroxide, the drying rate first decreased and then increased as the extent of the neutralization increased. However, the neutralization of these carboxyl groups with ammonium hydroxide increased the drying rate of the latex blends within a broad range of neutralization conditions (from 0 to 100%). A cluster model was proposed to explain these phenomena. 相似文献
316.
Formation and Crystal Structure of Tribarium Tetradecaphosphide‐Ammonia(1/18) Ba3P14_.18NH3 Tribarium tetradecaphosphide‐ammonia(1/18) Ba3P14_.18NH3 was prepared by the reduction of red phosphorus with a solution of Ba in liquid NH3. It contains heptaphosphanortricyclane anions P73–, which are joined via P–Ba contacts resulting in <$>^1_\infty<$>[Ba2(P7)2]2–‐chains separated by barium octaammine complexes Ba(NH3)82+. 相似文献