EFFECT OF MOLECULAR WEIGHT OF PDMS ON MORPHOLOGY AND MECHANICAL PROPERTIES OF PP/PDMS BLENDS

 A series of polydimethylsiloxane (PDMS) with varied molecular weights (Mw = 3  106, 1  106 and 0.5  106) were melt blended with PP to investigate the effect of PDMS molecular weight (MW) on the morphology and mechanical properties of PP/PDMS blends. Scanning electron microscopic (SEM) examination showed that the size of PDMS domains was dependent on the MW of PDMS. It was found that the lower the value of PDMS MW, the better dispersion of the PDMS domains in the PP matrix. Tensile and Izod impact tests revealed that the addition of PDMS with lower MW would lead to a more significant increase in impact strength of the blends compared with the blends with higher MW ones, while the influence of the molecular weight on tensile strengths of the blends was relatively small in the MW range studied. Differential scanning calorimetry (DSC) results also showed that the crystallization temperature of PP was increased with decreasing PDMS MW, indicating a better nucleation capability of lower MW of PDMS. Melting flow rate (MFR) measurements indicated that the processibility of PP could be enhanced by adding PDMS, and again the lower MW PDMS resulted in better data. Our work demonstrates that not only the processibility but also the mechanical properties of PP could be enhanced to a more significant degree by using low MW PDMS than the higher ones.     

Sensitive Determination of DNA by Resonance Light Scattering with Pentamethoxyl Red

A novel sensitive method for the determination of nucleic acid (DNA) using the resonance light scattering (RLS) spectra of pentamethoxyl red has been developed. It is based on the effects on the resonance light scattering of Pentamethoxyl Red. The effective factors and the optimum conditions were studied, and the enhanced intensity of RLS is in proportion to the concentration of nucleic acids in the range of 0–2.54 µg mL⁻¹ for ct-DNA, 0–4.54 µg mL⁻¹ for hs-DNA. The limits of detection are 1.1 and 2.1 ng mL⁻¹, respectively. Most foreign substances do not interfere in the determination, and the method has good selectivity and high sensitivity. It has been applied to the determination of DNA in synthetic samples and in real samples with satisfactory results.     

Agonist–PPARγ interactions: Molecular modeling study with docking approach

Docking simulation of 18 agonists with the ligand binding pocket (LBP) of PPARγ has been performed. The binding conformations and binding affinities of these agonists were obtained by use of the flexible docking protocol FlexX. Test compound calculations indicated that FlexX can reproduce the binding conformation of the crystal structure (root mean square deviation = 1.43 Å); moreover, the predicted binding affinities correlate well with the activities of these agonists. The interaction model and pharmacophore of PPARγ agonists were derived and the difference in biologic activities of these agonists can be well explained. The PPARγ agonists must have both polar head and the hydrophobic tail, which form hydrogen bonds and hydrophobic contacts with hydrophilic and hydrophobic regions of the LBP of PPARγ, respectively. In addition, a suitable linker is also necessary. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 405–410, 2003     

The detection of formaldehyde in textiles using interdigitated microelectrode array diffusion layer titration with electrogenerated hypobromite

An interdigitated microelectrode array (IDA) was applied to the determination of formaldehyde released from textiles produced in industry. The proposed method is based on formaldehyde reaction with hypobromite which is formed in weakly basic media by control current electrooxidation of bromide on the generator segment of the IDA array. The unreacted hypobromite diffuses through the gap between individually polarisable IDA segments and it is amperometrically detected on the collector segment of the IDA. The efficiency of this nonconvective transfer process in the absence of formaldehyde was substantially higher (78%) in comparison with that when using the rotating ring disc electrode. The influence of the added formaldehyde on the transfer process can be utilised to develop a simple and sensitive analytical procedure for formaldehyde detection with a detection limit of 4×10⁻⁶ mol dm⁻³.     

4,4′-(多苯基三联苯)双(有机硅烷)的合成

前文曾经报道利用四苯基环戊二烯酮为双烯体,乙烯基或烯丙基三乙氧基硅烷及其硅氧烷为亲双烯体通过Diels-Alder反应合成的多苯基芳基有机硅化合物作为硅橡胶的热     

一个新的铀（Ⅵ）三元协萃体系

研究了由４，４＇－癸二酰－双－（１－苯基－３－甲基－５－吡唑啉酮）（ＤＢＰＭＰ，简作Ｈ２Ａ），氧化三辛基膦（ＴＯＰＯ），吡啶（Ｐｙ）组成的三元体系从硝酸溶液中对铀的协同萃取，斜率法确定萃合物组成为ＵＯ２Ａ．ＴＯＰＯ．Ｐｙ，制取了固体协萃配合物，并用元素分析、ＩＲ及ＨＮＭＲ等进行了表征。     

Micro-sized Sb2O3 octahedra fabricated via a PEG-1000 polymer-assisted hydrothermal route

The micro-sized Sb₂O₃ octahedra can be synthesized on a large scale via a simple PEG-1000 polymer-assisted hydrothermal route (PAHR) in the temperature range of 160-180 °C for 10-14 h. The structures, compositions, and morphologies of the as-synthesized products are derived from X-ray power diffraction pattern, X-ray photoelectron spectra, and field emission scanning electronic microscope. Meanwhile, the optical properties of the micro-sized Sb₂O₃ octahedra are studied by their photoluminescene spectroscopy and Raman spectrum. Furthermore, the possible growth mechanism of the micro-metered Sb₂O₃ octahedra is discussed on the basis of a series of supplementary experiments. And it has been found that PEG-1000, sodium tartrate, the reaction temperature, and the reaction time have considerable effects on the final morphology of Sb₂O₃, while the pH value has an influence on the formation of the Sb₂O₃ crystals.     

Energetic preferences for alpha,beta versus beta,gamma unsaturation

Density functional theory has been applied at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level to examine the energetics of alpha,beta- versus beta,gamma-unsaturation for some common organic functional groups. Specifically, the relative stabilities of allyl-X (H2C=CHCH2X) and 1-propenyl-X (H3CCH=CHX) isomers have been computed for X = methyl, vinyl, phenyl, formyl, acetyl, methoxy, methylthio, methylsulfinyl, methylsulfonyl, sulfamoyl, and methoxysulfonyl, and the results are compared to available experimental data. The intrinsic preference of 3 kcal/mol for the 1-propenyl isomer when X = CH3 is exceeded by 2-4 kcal/mol for first-row conjugating groups, but it is not met for the sulfur-containing groups. In particular, alpha,beta-unsaturation is favored by less than 1 kcal/mol for the sulfone and sulfonamide analogues, while it is preferred by 8 kcal/mol for the vinyl-substituted case. Detailed structural results and torsional energy profiles are also reported.     

Single‐Crystalline and Near‐Monodispersed NaMF3 (M=Mn,Co, Ni,Mg) and LiMAlF6 (M=Ca,Sr) Nanocrystals from Cothermolysis of Multiple Trifluoroacetates in Solution

We report the synthesis of single‐crystalline and near‐monodispersed NaMF₃ (M=Mn, Co, Ni, Mg), LiMAlF₆ (M=Ca, Sr), and NaMgF₃:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1‐octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF₃ (M=Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF₃ nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC–MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF₃ square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF₃:Yb,Er nanorods under 980‐nm near‐IR laser excitation suggests that NaMgF₃ may be a good candidate host material for red upconversion luminescence.     

On the copolymerization of acrylates in the modified microemulsion process

Copolymerization of methyl methacrylate, methyl acrylate, butyl methacrylate, and butyl acrylate in turn was performed in the modified microemulsion polymerization process, i.e., continuous addition of monomer to a preemulsified system. It was found that the particle size of the copolymer microlatex did not change distinctly with the monomer composition. The estimation of emulsifier coverage on the microlatex particles indicated that the process switched from a traditional microemulsion to a normal seeded emulsion polymerization very soon after monomer dropping began. Therefore, a longer dropping time is needed to produce a microlatex with narrow dispersed particle size. Besides, in the modified microemulsion polymerization less emulsifier is needed to produce a stable microlatex. This behavior is related to the mechanism of normal seeded emulsion polymerization during monomer dropping.