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《Composite Interfaces》2013,20(8-9):787-803
Poly(amide)-6/clay nanocomposites are investigated by means of modulated temperature differential scanning calorimetry. The importance of polymer–filler interaction is explored by comparing nanocomposites based on untreated and organically modified clay. During quasi-isothermal crystallization experiments, an excess contribution is observed in the recorded heat capacity signal due to reversible melting and crystallization. The magnitude of this excess contribution depends on the nanocomposite investigated. We suggest that it is directly related to the segmental mobility of the polymer chains in the interphase region. As such, the magnitude of this excess contribution can be used to quantify the efficiency of the polymer–clay interaction. Depending on the clay type used, differences in interfacial interaction can be achieved, which is of great importance with respect to the improvement of material properties. Based on thermal analysis results, a simple interphase model is proposed that is able to account for both the thermal and mechanical properties of poly(amide)-6/clay nanocomposites. 相似文献
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The effect of sintering dispersed and bulk, low molecular weight (Mn = 50,000 Da), nano-emulsion polytetrafluoroethylene (PTFE) particles near their melting point is described. With the nascent particles consisting of ca.75 nm diameter, hexagonal, single crystals, sintering at, e.g., 350℃, results, initially, in merger of neighboring particles,followed by individual molecular motion on the substrate and the formation of folded chain, lamellar single crystals and spherulites, and on-edge ribbons. It is suggested these structures develop, with time, in the mesomorphic "melt". Sintering of the bulk resin yields extended chain, band structures, as well as folded chain lamellae; end-surface to end-surface merger,possibly by end-to-end polymerization, occurs with increasing time. 相似文献
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应用对称性约化计算方案, 完成了铜原子簇Cu~13(I~h)三种基组下的从头计算, 最大维数390。为了进行比较, 也进行了Cu~2、Cu~4、Cu~6及Cu~8的计算。经过优化, 获得基态及平衡几何、布居、结合能等数据, 表明Cu~13可能稳定存在。Cu~13中以d成分为主的分子轨道均已填满, 对化学键无实际贡献, 成键作用为s, p性质; 再者, d带与s带不相交叠, 无金属Cu能带的特征。无论平衡几何、布居及结合能数值均与采用的其组很有关系, 虽然定性趋势是一致的。 相似文献
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钴(II)与色氨酸极谱催化前波的研究 总被引:2,自引:0,他引:2
对钴(II)离子与色氨酸在H~3BO~3-NaOH(pH=9)缓冲底液中的极谱催化前波进行了形成条件、吸附性能和电极还原过程的研究。 相似文献
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一类新型的双β-氨基醇的合成及催化硼烷对芳酮的不对称还原反应 总被引:7,自引:0,他引:7
以L-半胱氨酸盐酸盐出发,经与二卤代烷偶联,成酯和格氏反应制得三种双手性β-氨基醇,1,2-双[R-2-氨基-3-羟基-3,3-二苯基丙硫基]乙烷(4a),1,3-双[R-2-氨基-3-羟基-3,3-二苯基丙硫基]丙烷(4b),1,4-双[R-2-氨基-3-羟基-3,3-二苯基丙硫基]丁烷(4c)。将此类双手性β-氨基醇与硼烷在THF溶液中反应,in situ制备双手性恶唑硼烷催化硼烷对芳酮的不对称还原,产物苯乙醇的光学收率达72.8%、α-溴代苯乙醇的光学收率达91.4%。 相似文献
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M. Mohammad A. Y. Khan M. S. Subhani N. Bibi Safeer Ahmad Saba Saleemi 《Research on Chemical Intermediates》2001,27(3):259-267
Rate constants for the reaction of superoxide O-
2 with various substrates were obtained through stationary electrode polarography theory and technique. In solvent acetonitrile, the substrate and the rate constants of the reaction O-
2 + AH-
k2Product, are, AH = isopropanol (k2 < 0.01 M-1 s-1); ethanol (k2 = 1.42 × 102 M-1 s-1); methanol (k2 = 1.1 × 107 M-1 s-1), H2O (k2 = 1.0 × 105 M-1 s-1). In MeCN, O-2 was found to be rather unreactive towards glucose and acetone but it reacts with fructose and sucrose catalytically. However, in DMF2, O-
2reacts with glucose and fructose with k2 order of 105 M-1 s-1. The mechanism of the reaction of O-
2 with the substrates (AH) is proposed as O-
3 + AH k2O, AHk2
k-1 k [O2H + AH]-, k-2O2H + A- with k1 = 109 M-1 s-1 and k-1 = 108 -109 s-1. With these values of k-1 and k1, k k2(obs). The reversible E1/2 for O2 + e O-
2 in various solvents: MeCN, acetone, isopropanol, methanol, H2O were obtained either directly from the reversible voltammogram or from experimental voltammograms and the rate constants obtained (as above) using stationary electrode polargraphy theory; E1/2 being -0.82 (MeCN),-0.85 (acetone),-0.72 (isopropanol);-0.66 (MeOH),-0.56 (H2O) vs SCE. 相似文献