A modulated dsc study on the in situ polymerization of cyclic butylene terephthalate oligomers

The polymerization of a cyclic butylene terephthalate (CBT) oligomer was studied as a function of temperature (T=200 and 260°C, respectively) by modulated DSC (MDSC). The first heating was followed by cooling after various holding times (5, 15 and 30 min) prior to the second heating which ended always at T=260°C. This allowed us to study the crystallization and melting behavior of the resulting polybutylene terephthalate (PBT), as well. In contrary to the usual belief, the CBT polymerization is exothermic and the related process is superimposed to that of the CBT melting. The melting behavior of the PBT was affected by the polymerization mode (performed below or above the melting temperature of the PBT product) of the CBT. Annealing above the melting temperature of PBT yielded a product featuring double melting. This was attributed to the presence of crystallites with different degrees of perfection. The crystals perfection which occurred via recrystallization/remelting was manifested by a pronounced exothermic peak in the non-reversing trace.     

基于三维静电势参数研究C60溶解性的构效关系

在量子化学从头算基础上,对一系列溶剂化合物分子进行了结构优化和三维静电势参数计算,运用多元线性回归分析和神经网络方法对C60在121种不同溶剂的溶解性与计算的结构参数进行了构效关系研究.用建立起来的QSPR 关系式对15种不同结构类型溶剂进行了预测,并阐述了C60溶质与不同溶剂之间的相互作用,获得了满意的结果.     

Effect of the sixth axial ligand in CS-ligated iron(II)octaethylporphyrinates: structural and Mössbauer studies

The effect of a sixth ligand in a series of low-spin thiocarbonyl-ligated iron(II)octaethylporphyrinates has been investigated. Six-coordinate complexes have been synthesized and characterized by M?ssbauer and infrared spectroscopy and single-crystal X-ray structure determinations. The results are compared with the five-coordinate parent complex. The crystal structures of [Fe(OEP)(CS)(1-MeIm)] and [Fe(OEP)(CS)(Py)] are reported and discussed. The 1-methylimidazole and pyridine derivatives exhibit Fe-C(CS) bond distances of 1.703(4) and 1.706(2) A that are significantly longer than the 1.662(3) A reported for five-coordinate [Fe(OEP)(CS)] (Scheidt, W. R.; Geiger, D. K. Inorg. Chem. 1982, 21, 1208). The trans Fe-N(ligand) distances of 2.112(3) and 2.1550(15) A observed for the 1-methylimidazole and pyridine complex are approximately 0.13 A longer than those observed for analogous bis-ligated complexes and are consistent with a significant structural trans effect for the CS ligand. M?ssbauer investigations carried out for five- and six-coordinate thiocarbonyl derivatives with several different sixth axial ligands reveal interesting features. All derivatives exhibit very small isomer shift values, consistent with a very strong interaction between iron and CS. The five-coordinate derivative has delta(Fe) = 0.08 mm/s, and the six-coordinate complexes exhibit delta(Fe) = 0.14 to 0.19 mm/s at 4.2 K. The five-coordinate complex shows a large quadrupole splitting (DeltaE(q) = 1.93 mm/s at 4.2 K) which is reduced on coordination of the sixth ligand (DeltaE(q) = 0.42-0.80 mm/s at 4.2 K). Addition of a sixth ligand also leads to a small decrease in the value of nu(CS). Correlations in structural, IR, and M?ssbauer results suggest that the sixth ligand effect is primarily induced by changes in sigma-bonding. The structure of [Fe(OEP)(CS)(CH(3)OH)] is briefly reported. Crystal data: [Fe(OEP)(CS)(1-MeIm)] crystallizes in the monoclinic system, space group P2(1)/n, Z = 4, a = 9.5906(5) A, b = 16.704(4) A, c = 23.1417(6) A, beta = 100.453(7) degrees. [Fe(OEP)(CS)(Py)] crystallizes in the triclinic system, space group P1, Z = 5, a = 13.9073(6) A, b = 16.2624(7) A, c = 22.0709(9) A, alpha = 70.586(1) degrees, beta = 77.242(1) degrees, gamma = 77.959(1) degrees. [Fe(OEP)(CS)(CH(3)OH)] crystallizes in the triclinic system, space group P1, Z = 1, a = 9.0599(5) A, b = 9.4389(5) A, c = 11.0676(6) A, alpha = 90.261(1) degrees, beta = 100.362(1) degrees, gamma = 114.664(1) degrees.     

A novel neutral receptor for selective recognition of H2PO 4 −

A new urea-based receptor was designed to selectively recognize H₂PO₄⁻ among other anions (such as F^-, Cl^-, Br^-, I^-, OH^-, AcO^-) in organic solvent (DMSO) through intermolecular hydrogen bonding. Addition of anions to the receptor caused changes in UV–vis spectrum which provided the first indication of its anion binding ability. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

荧光光度法测定水体中痕量邻苯二酚

在pH 3.2的酸性介质中,邻苯二酚与染料天青Ⅰ相互作用导致荧光强度明显增强,以发射波长343.0nm测定时,邻苯二酚的浓度在0.075～30μmol.L-1范围内与其荧光的增强程度呈线性关系,方法的检出限(3s/k)为7.51nmol.L-1。方法用于实际水样分析,加标回收率在97.0%～104%之间,测定值的相对标准偏差(n=5)在2.8%～3.9%之间。     

Analysis of financial stock markets through multidimensional scaling based on information measures

In this paper, a novel multidimensional scaling (MDS) based on information measures method is proposed to analyze financial stock markets. In order to examine the effectiveness of this method, we applied it to the classification of two types of artificial series, the logistic map model and the cubic map model, as well as stock time series. Moreover, the traditional MDS using Euclidean dissimilarity is also provided as a reference for comparisons. The results show that the MDS based on information measures can give us more detailed, exact and clearer information on the classification of simulation series and stock time series than the MDS using Euclidean dissimilarity. In addition, the proposed graphical method may also assist in the construction of multivariate econometric models.     

The influences of amplified spontaneous emission,crystal temperature and round-trip loss on scaling of CW thin-disk laser

In this paper, a model is built to explore how the parameters (amplified spontaneous emission (ASE), temperature and round-trip loss) influence the output power in a thin-disk laser. It is found that optical efficiency of the disk laser is reduced with the increase of ASE, temperature or round-trip loss. The parameters are optimized to maximize the output power based on our model. We find that it is necessary to balance the need to lower the temperature with the need to control ASE during the optimization process. But the balance becomes more difficult to achieve with the increase of round-trip loss. We conclude that output power of more than 2.6 MW with a single disk can be achieved, but the necessary disk size (more than 0.5 m) is far beyond the actual technical limits. But it is possible to achieve output power of over a hundred kilowatts using a 10 cm disk in the near future.     

Facile Synthesis of Alkylidene Phthalides by Rhodium-Catalyzed Domino C−H Acylation/Annulation of Benzamides with Aliphatic Carboxylic Acids

The Rh-catalyzed ortho-C(sp²)−H functionalization of 8-aminoquinoline-derived benzamides with aliphatic acyl fluorides generated in situ from the corresponding acids has been developed. This reaction initiated with 8-aminoquinoline-directed ortho-C(sp²)−H acylation, which was accompanied by subsequent intramolecular nucleophilic acyl substitution of amide group to produce alkylidene phthalides This approach exhibits high stereo-selectivity for Z-isomer products, and tolerates a variety of functional groups as well as aliphatic carboxylic acids with diverse structural scaffolds.     

Rack-mounted chemistry IV: the thermal rearrangement of 7-oxabenzonorbornadienes into benzo[b]oxepines on and off the polycyclic rack

The thermal rearrangement of [3]polynorbornane bis-imide rack-mounted 7-oxabenzonorbornadienes has been conducted using flash vacuum pyrolysis (FVP) at 520 °C and is compared with the FVP of similar 7-oxabenzonorbornadienes off the rack. The isomerisation is considered to involve (a) C–O bond cleavage to a vinylogous 1,5-dipole, (b) formation of a benzene epoxide by nucleophilic ring-closure and (c) valence-isomerisation of the benzene epoxide to the oxepine. Competing fragmentation to the isobenzofuran by ejection of acetylene and other rearrangements become prominent pathways off the rack, whereas isomerisation to the oxepine is highly favored on the rack.