| 1. |
- Liu, X. H., et al.
(författare)
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High-temperature X-ray diffraction studies on polyamide6/clay nanocomposites upon annealing
- 2002
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Ingår i: Polymer Bulletin. - : Springer Science and Business Media LLC. - 0170-0839 .- 1436-2449. ; 48:05-apr, s. 381-387
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Tidskriftsartikel (refereegranskat)abstract
- The influence of nanodispersed clay on the alpha crystalline structure of polyamide 6 (PA6) was examined in-situ with X-ray diffraction (XRD) between room temperature and melting. In pure PA6 upon annealing the alpha crystalline phase was substituted by an unstable pseudohexagonal phase at 150degreesC, then it transformed into a new stable crystalline structure - high temperature alpha' phase above the transition temperature. However, in PA6/clay nanocomposite (PA6CN), the alpha phase did not present crystalline phase transition on heating. The increase in the annealing temperature only led to continuous intensity variation. The different behaviors were caused by the confined spaces formed by silicate layers, which constrained the mobility of the polymer chains in-between.
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| 2. |
- Liu, X. H., et al.
(författare)
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Polyamide 6/clay nanocomposites using a cointercalation organophilic clay via melt compounding
- 2003
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 88:4, s. 953-958
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Tidskriftsartikel (refereegranskat)abstract
- Polyamide 6/clay nanocomposites (PA6CN) were prepared via the melt compounding method by using a new kind of organophilic clay, which was obtained through cointercalation of epoxy resin and quaternary ammonium into Na-montmorillonite. The dispersion effect of this kind of organophilic clay in the matrix was studied by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM); the silicate layers were dispersed homogeneously and nearly exfoliated in the matrix. This was probably the result of the strong interaction between epoxy groups and amide end groups of PA6. The mechanical properties and heat distortion temperature (HDT) of PA6CN increased dramatically. The notched Izod impact strength of PA6CN was 80% higher than that of PA6 when the clay loading was 5 wt%. Even at 10 wt% clay content, the impact strength was still higher than that of PA6. The finely dispersed silicate layers and the strong interaction between silicate layers and matrix decreased the water absorption. At 10 wt% clay content, PA6CN only absorbs half the amount of water compared with PA6. The dynamic mechanical properties of PA6CN were also studied.
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| 3. |
- Liu, X. H., et al.
(författare)
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Polyamide 6-clay nanocompositles/polypropylene-grafted-maleic anhydride alloys
- 2001
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 42:19, s. 8235-8239
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Tidskriftsartikel (refereegranskat)abstract
- Polyamide 6-clay nanocomposites (PA6CN) based on montmorillonite typically show some brittleness with clay addition. In order to address this problem, PA6CN/PP-g-MAH alloys were prepared through blending PA6CN with polypropylene-grafted-maleic anhydride (PP-g-MAH). The mechanical properties, dynamic mechanical temperature spectra, morphology and water absorption of the alloys were studied. Compared with PA6CN, the notched impact strength of the alloys increased greatly while the alloys still maintained higher stiffness and strength than that of PA 6. The morphological studies via scanning electron microscopy (SEM) showed a PP-g-MAH toughen phase dispersed in PA6CN matrix. As the PP-g-MAH content was increased, reduced water absorption was observed.
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| 4. |
- Chen, C. N., et al.
(författare)
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Aggregate manganese Schiff base moieties by terephthalate or acetate : Dinuclear manganese and trinuclear mixed metal Mn-2/Na complexes
- 2003
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42:11, s. 3540-3548
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Tidskriftsartikel (refereegranskat)abstract
- A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn-2(mu-phth)(CH3OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn-2(mu-phth)(CH3OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn-2(mu-phth)(CH3OH)(H2O) (3), and (salen)(2)Mn-2(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH3OH)(NO3) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H{Mn2Na(salpn)(2)(mu-OAc)(2)(H2O)(2)}(OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. H-1 NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/0.12V has been assigned to the redox of Mn-2(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.
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| 5. |
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| 6. |
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| 7. |
- Gao, Y. L., et al.
(författare)
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Crystal structure and electrochemical behavior of copper complex with 6-hydroxymethyl-substituted tris(2-pyridylmethyl) amine, CuCl(C19H20N4O) ClO4
- 2004
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Ingår i: Chinese journal of structural chemistry. - 0254-5861. ; 23:11, s. 1262-1265
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Tidskriftsartikel (refereegranskat)abstract
- A Cu(II) complex [CuCl(C19H20N40)]ClO4 1 containing hydroxymethyl substituted TPA (TPA = tris(2-pyridylmethyl)amine) was prepared. It crystallizes in monoclinic, space group P2(1)/c with a = 11.7628(2), b = 13.0083(3), c = 15.11280(10) Angstrom, beta = 108.724(2)degrees, V = 2190.09(7) Angstrom(3), M-r = 518.83, Z = 4, T = 293 (2) K, D-c = 1.574 g/cm(3), mu = 1.280 mm(-1), F(000) = 1060 and S = 1.085. The final R = 0.0543 and wR = 0.1433 for 2693 observed reflections with I >2sigma(I). The penta-coordinated copper (H) complex. assumes an approximate square pyramidal geometry. Cyclic voltammetry measurement of the complex showed a quasi-reversible Cu-II/Cu-I redox couple with E-1/2 -0.467 v and DeltaE = 68 mv.
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| 8. |
- Han, W. G., et al.
(författare)
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A theoretical study of the UV/visible absorption and emission solvatochromic properties of solvent-sensitive dyes
- 2003
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 4:10, s. 1084-1094
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Tidskriftsartikel (refereegranskat)abstract
- Using the density-functional vertical self-consistent reaction field (VSCRF) solvation model, incorporated with the conductor-like screening model (COSMO) and the self-consistent reaction field (SCRF) methods, we have studied the solvatochromic shifts of both the absorption and emission bands of four solvent sensitive dyes in different solutions. The dye molecules studies here are: S-TBA merocyanine, Abdel-Halim's merocyanine, the rigidified amino-coumarin C153, and Nile red. These dyes were selected because they exemplify different structural features likely to impact the solvent-sensitive fluorescence of push-pull, or merocyanine, fluorophores. All trends of the blue or red shifts were correctly predicted, comparing with the experimental observations. Explicit h-bonding interactions were also considered in several protic solutions like H2O, methanol and ethanol, showing that including explicit H-bonding solvent molecule(s) in the calculations is important to obtain the correct order of the excitation and emission energies. The geometries, electronic structures, dipole moments, and intra- and intermolecular charge transfers of the dyes in different solvents are also discussed.
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| 9. |
- He, Q, et al.
(författare)
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The clinical significance of thymidine kinase 1 measurement in serum of breast cancer patients using anti-TK1 antibody
- 2000
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Ingår i: The International journal of biological markers. - : SAGE Publications. - 0393-6155 .- 1724-6008. ; 15:2, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- The activity of total thymidine kinase in serum (S-TK) has been used as a tumor maker for decades. To date such activity has been determined using[125]I-iodo-deoxyuridine as a substrate. The aim of this study was to develop a new, antibody-based technique for the measurement of cytoplasmic thymidine kinase (TK1) in serum. Both mono- and polyclonal antibodies against S-TK1 were used in dot blot assay. S-TK1 was characterized by SDS and IEF techniques. Sixty-five breast cancer patients were studied, including 17 preoperative and 38 postoperative tumor-free patients and 10 patients with metastases to the lymph nodes (N1–2). They were compared to patients with benign tumors (n=21) and healthy volunteers (n=11). S-TK1 was low (0–1.0 pM) in healthy volunteers, while in preoperative patients the level was increased 6–110-fold. Significant differences were observed between preoperative patients and healthy volunteers (p=0.005), preoperative patients and patients with benign tumors (p<0.001), and preoperative patients and postoperative patients without metastases (p<0.001). No significant difference was observed between preoperative patients and postoperative patients with metastases (p=0.191). The S-TK activity in preoperative patients was also high in serum, but no decrease was observed following surgery. In conclusion, the anti-TK1 antibody could be a good marker for monitoring the response of breast cancer patients to therapy.
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| 10. |
- Huang, D. G., et al.
(författare)
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Synthesis, structural characterizations and magnetic properties of a series of mono-, di- and polynuclear manganese pyridinecarboxylate compounds
- 2004
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :7, s. 1454-1464
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Tidskriftsartikel (refereegranskat)abstract
- Seven new manganese(II, III, IV) pyridinecarboxylate compounds (Et4N)[MnCl2(pic)(2)] (1, Hpic = picolinic acid) [MnCl(Pic)(2)(H2O)].H2O (2), [MnCl(pic)(H2O)2](n) (3), [Mn(Pic)(2)](n) (4), [MnCl(pic)](n) (5), [MnCl2(4-C5H4NHCOO)](n) (6) and [Mn2O2(pic)(4)] (7) were synthesized and structurally characterized. The picolinate ligand coordinates to the Mn ion forming a chelating five-membered ring which constructs diverse architectures by various bridging modes, such as mu-Cl, mu(1,1)(-) and mu(1,3)-carboxylate bridges (syn-syn and syn-anti modes). The interaction between the pyridyl rings is discussed, displaying a face-to-face pi-pi stacking for complex 6 and a T-shaped C-H...pi attraction for complex 4. Complex 3 has an infinite zigzag chain structure in which two neighboring Mn ions are linked by a carboxylate bridge in a syn-anti mode. In complex 4, the Mn(pic)(2) fragments are joined to each other by double mu(1,1)-carboxylate bridges, forming a 2D layer structure. Complex 5 contains Mn4O4 square subunits which are connected by double mu-Cl bridges to form a grid-like 2D structure. The isonicotinate complex 6 has a zigzag chain structure containing mixed double mu-Cl and mu(1,3)-carboxylate bridges in a syn-syn mode. Protonation at the pyridyl-N position was found and identified by the IR and magnetic properties of 6. The participation of an oxidizing agent like MnO4- leads to complexes containing higher valent manganese (1, 2 and 7). The IR spectra of these complexes are discussed and found to be consistent with the structural features. The magnetic properties of complexes 4, 5 and 6 have been investigated. Antiferromagnetic coupling interactions were observed and satisfactory fitting results were obtained with J values ranging from -0.63 cm(-1) to -2.35 cm(-1). The magnetic parameters of these complexes, together with the parameters of other Mn complexes with comparable structures, are compared and discussed based on the bridging modes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).
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