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21.
A one-step pathway has been adopted to fabricate biodegradable polylactide (PLA) hollow spheres by interfacial polymerization
in an oil-in-water emulsion system. The mechanism of sphere formation is suggested with respect to interfacial cross-linking
polymerization and subsequent precipitation of the unreacted PLA macromonomers onto the preformed shells. Their hollow nature
and morphology were verified by transmission electron microscopy and scanning electron microscope characterizations. 相似文献
22.
23.
聚碳酸酯合成工艺开发的新进展 总被引:6,自引:0,他引:6
本文从工艺开发的角度,简要评介了目前聚碳酸酯两大工业生产工艺,即光气化界面缩聚工艺和熔融酯交换缩聚工艺的研究开发新动向。 相似文献
24.
In the system of SDS/n-C5H11OH/n-C7H16/H2O with the weight ratio of SDS/n-C5H11OH/H2O system at5.0/47.5/47.5, the upper phase of the system was W/O microemulsion, and the lower phase was the bicontinuous microemulsion. When the n-heptane content was less than 1%, with the increase of the n-heptane content, the capacitance (Co, Cod) in the upper phase (W/O) dropped, the capacitance (CB1, CBld) in the lower phase (BI) raised. At the same time, the W/O-BI inteffacial potential (ΔE), capacitance (Ci), and charge-transfer current (ict) decreased.After the n-heptane content reached 1%, with the increase of the n-heptane content, ΔE, Ci and ict demonstrated no significant change. 相似文献
25.
26.
3-Mercaptopropionic acid monolayer protected gold nanoclusters (MPA-MPCs) were synthesized and characterized by transmission electorn microscopy,UV-Vis spectroscopy,X-ray photoelectron spectroscopy and Fourler transform infrared spectroscopy.The exact value of quantized double-layer capacitance of MPCs in aqueous media was obtained by differential pulse voltammograms. 相似文献
27.
?ystein?BrandalEmail author Ann-Mari?Dahl?Hanneseth Johan?Sj?blom 《Colloid and polymer science》2005,284(2):124-133
Interactions between naphthenic acids and divalent metal cations across model oil–alkaline water interfaces were investigated by correlating changes in dynamic interfacial tension (IFT), to plausible reaction mechanisms. The measurements were carried out by using a CAM 200 optical instrument, which is based on the pendant drop technique. The naphthenic acids used were synthesised model compounds as well as commercial acid mixtures from crude distillation and extracted acid fractions from a North Sea crude oil. The divalent cations involved Ca2+, Mg2+, Sr2+, and Ba2+, which are all common in co-produced formation water and naphthenate deposits. The results show that the dynamic IFT strongly depends on naphthenic acid structure, type of divalent cation, and the concentration of the compounds as well as the pH of the aqueous phase. Introducing divalent cations to systems involving saturated naphthenic acids caused mostly a permanent lowering of the IFT. The decline in IFT is due to electrostatic attraction forces across the interface between the cations in the aqueous phase and the carboxylic-groups at the o/w interface, which cause a higher interfacial density of naphthenic acid monomers. The permanent lowering in IFT is likely due to formation of positively charged monoacid complexes, which possess high interfacial activity. On the other hand, in the case of the aromatic model compounds, the cations affected the IFT differently. This is mainly discussed in light of degree of cation hydration and steric conditions. Various oil-soluble non-ionic surfactant mixtures were also introduced to systems involving a model naphthenic acid and Ca2+ in order to investigate how the interfacial competition affected the local interactions. Based on the behaviour of dynamic IFT, probable inhibition mechanisms are discussed.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
28.
Double-layer parameters of a liquid Sn–Ga electrode in aqueous electrolyte solutions are studied. It is shown that Sn in the alloy with Ga is a surface-active component and is forced out onto a surface layer of the electrode. The double-layer parameters of an Sn–Ga electrode (8 at. % Sn), which are measured in the experimentally accessible range of charges, differ radically from the parameters of Ga electrodes and are close to those of Sn electrode. Hence, an Sn–Ga electrode containing 8 at. % Sn simulates electrochemical properties of a liquid Sn electrode. The difference between reciprocal electronic capacitances of Hg and Sn and a corrected electrochemical work function of Sn are determined. It is shown that the chemisorption interaction of an Sn–Ga electrode with water molecules is virtually absent at charges more negative than –7 C/cm2. A potential drop on uncharged Sn, which is associated with water chemisorption, is –20 mV. Thus, the hydrophilicity of Sn is slightly higher than that of Hg, Bi–Ga, Pb–Ga, and Tl–Ga and significantly lower than that of In–Ga, Cd–Ga, and Ga. 相似文献
29.
Xiao Lian Zhang Joseph T. Hupp Gerald D. Danzer 《Journal of Electroanalytical Chemistry》1995,380(1-2)
The comparative interfacial oxidation kinetics of the approximate structural isomers trans-(O)2ReV(py)+4 and cis-(O)2ReV(bpy)(py)+2 (py, pyridine; bpy, 2,2′-bipyridine) have been assessed in aqueous solution via conventional cyclic voltammetry at a highly ordered pyrolytic graphite (HOPG) electrode. HOPG was employed because of its known propensity to diminish interfacial electron transfer (ET) rates (by ca. three to four orders of magnitude) and because of a probable lack of importance of kinetic work terms (diffuse double-layer corrections). Measured rates for the trans complex exceed those for the cis by about a factor of 3. Expressed as an effective activation Gibbs energy difference ΔG*, this corresponds to a cis-trans difference of ca. 3 kJ mol−1. The actual vibrational barriers to ET have determined from a combination of published X-ray structural results (trans complex) and new resonance Raman results (cis complex). The values are 0.6 kJ mol −1 for the trans oxidation and 4.4 kJ mol−1 for the cis oxidation (i.e. close to the barrier difference inferred from rate measurements). Further analysis shows that most of the barrier difference is associated with displacement of a (predominantly) Re-N(bpy) stretching mode found only in the cis system. Differences in metal-oxo displacements (cis > trans) are also implicated. 相似文献
30.
Allison A. Calhoun Patrick D. Nicholson Alexander B. Barnes 《Polymer Degradation and Stability》2006,91(9):1964-1971
Thermo-oxidative effects on the surface energy of polypropylene were measured by inverse gas chromatography as a function of exposure time and temperature. Unaltered polypropylene had a surface energy of 33 mJ/m2. Oxidized polypropylene, after exposure to air at temperatures of 100 °C and 110 °C, had a range of maximum surface energies from 38 to 41 mJ/m2. Comparisons between FTIR carbonyl peak growth and the surface energy showed that both methods detect oxidation, though the increase in surface energy is detected before the carbonyl peak growth is noticeable. The work of adhesion predicted by the surface free energies obtained in this work between a coated calcium carbonate and polypropylene changes by 10% due to the oxidation of the polymer at 110 °C. 相似文献