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91.
92.
聚苯胺尿酸酶电极性能的研究 总被引:4,自引:1,他引:4
依据pH对聚苯胺尿酸酶电极最大响应电流的影响, logim~pH图表明尿酸酶电极的催化活性只与其电离基团的碱性形式有关. 扫描电镜的结果表明, 聚苯胺尿酸酶电极的稳定性与其制备方法有关. 电化学法固定的尿酸酶电极具有高的稳定性. 相似文献
93.
The membrane formation of crystalline poly(ethylene-co-vinyl alcohol) (EVAL), poly(vinylidene fluoride) (PVDF), and polyamide (Nylon-66) membranes prepared by dry-cast process was studied. Membrane morphologies from crystalline polymers were found to be strongly dependent on the evaporation temperature. At low temperatures, all the casting solution evaporated into a particulate morphology that was governed by the polymer crystallization mechanism. The rise in the evaporation temperature changed EVAL membrane structure from a particulate to a dense morphology. However, as the temperature increased PVDF and Nylon-66 membranes still exhibited particulate morphologies. The membrane structures obtained were discussed in terms of the characteristics of polymer crystallization in the casting solution theoretically. At elevated temperatures the crystallization was restricted for the EVAL membrane because the increase rate in the polymer concentration was fast relative to the time necessary for growth of nuclei. Nonetheless, the time available for PVDF and Nylon-66 with stronger crystalline properties was large enough to form the crystallization-controlled particulate structure that differed in particle size only. In addition, particles in the PVDF membrane were driven together to disappear the boundary, but those in the Nylon-66 membrane exhibited features of linear grain boundary. The difference in particle morphology was attributed to the Nylon-66 with the most strongly crystalline property. Therefore, the kinetic difference in the crystallization rate of the polymer solution play an important role in dominating the membrane structure by dry-cast process. 相似文献
94.
XRD,DTA,比表面测定等结果表明,制备方法对MoO3/ZrO2结构有决定性影响.仲钼酸铵浸渍仅经干燥的Zr(OH)4再经高温焙烧所得团体超强酸MoO3/ZrO2(Ⅰ)与浸渍晶态ZrO2所得部分氧化催化剂MoO3/ZrO2(Ⅱ)的载体形态有明显不同.(1)MoO3/ZrO2(Ⅰ)的比表面数倍于MoO3/ZrO2(Ⅱ);(2)MoO3含量增加时,MoO3/ZrO2(Ⅰ)的比表面逐步增大至一极大值再缓缓下降,而MoO3/ZrO2(Ⅱ)的比表面随MoO3含量增加而单调下降;(3)在MoO3/ZrO2(Ⅰ)中,ZrO2以介稳四方相存在,而在MoO3/ZrO2(Ⅱ)中则是稳定的单斜相.在此基础上研究了事先引入的活性组分在载体织构形成过程中的作用,包括延迟ZrO2晶化,阻碍晶粒长大及与之相关的相变等,并讨论了MoO3/ZrO2(Ⅰ)中MoO3最佳含量的科学含义. 相似文献
95.
An efficient solution-processable route employing Pb(Ac)2 as lead source and anti-solvent treatment to achieve fully covered and homogenous perovskite films is reported. 相似文献
96.
Production of submicron-sized multihollow polymer particles by alkali/cooling method 总被引:5,自引:0,他引:5
Submicron-sized styrene-methacrylic acid copolymer particles, which were produced by emulsion copolymerization, were changed to those having multihollow structure by treating stepwise the emulsion as follows. First alkali treatment was carried out at higher temperature than the glass transition temperature and subsequently the emulsion was cooled by keeping it at room temperature. This was named alkali/cooling method. The effects of methacrylic acid content, pH, time and temperature in the alkali treatment on the formation of multihollow structure were clarified.Part CLV of the series Studies on suspension and emulsion 相似文献
97.
Reactive compatibilization of immiscible polymers is becoming increasingly important and hence a representative study of a polycarbonate/high density polyethylene (PC/HDPE) system is the focus of this paper. A grafted copolymer PC‐graft‐ethylene‐co‐acrylic acid (PC‐graft‐EAA) was generated as a compatibilizer in situ during processing operation by ester and acid reaction between PC and ethylene‐acrylic acid (EAA) in the presence of the catalyst dibutyl tin oxide (DBTO). As the polyethylene (PE) matrix does not play any part during the synthesis of the copolymer and since PC and EAA are also immiscible, to simplify the system, the influence of this copolymer formation at the interface between PC and EAA on rheological properties, phase morphology, and crystallization behavior for EAA/PC binary blends was first studied. The equilibrium torque increased with the DBTO content increasing in EAA/PC blends on Haake torque rheometer, indicating the in situ formation of the graft copolymer. Scanning electron microscopy (SEM) studies of cryogenically fractured surfaces showed a significant change at the distribution and dispersion of the dispersed phase in the presence of DBTO, compared with the EAA/PC blend without the catalyst. Differential scanning calorimetry (DSC) studies suggested that the heat of fusion of the EAA phase in PC/EAA blends with or without DBTO reduced with the formation of the copolymer compared with pure EAA. Then morphological studies and crystallization behavior of the uncompatibilized and compatibilized blends of PC/PE were studied as functions of EAA phase concentration and DBTO content. Morphological observations in PC/PE blends also revealed that on increasing the EAA content or adding the catalyst DBTO, the number of microvoids was reduced and the interface was intensive as compared to the uncompatibilized PC/PE blends. Crystallization studies indicated that PE crystallized at its bulk crystallization temperature. The degree of crystallinity of PE phase in PC/PE/EAA blends was also reduced with the addition of EAA and DBTO compared to the uncompatibilized blends of PC/PE, indicating the decrease in the degree of crystallinity was more in the presence of PC‐graft‐EAA. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
98.
Summary A polystyrene sample obtained by free radical polymerization has been fractionated by preparative scale GPC and the structure and morphology of the fractions have been studied by13C-NMR spectroscopy, DSC and X-ray measurements. No changes in morphology in the course of fractionation have been obeyed. A distribution of syndiotacticity within the molecular weight distribution does not exist.
List of abbrevations and symbols AIBN a, a-Azo-bis-(iso-butyronitrile) - D Dispersity, M w /M n - DSC Differential scanning calorimetry - EF Efficiency of fractionation - GPC Gel permeation chromatography - m mass of the fraction - M mass of the fractionated polymer sample - MWD Molecular weight distribution - P r content of racemic dyads - PS Polystyrene - THF Tetrahydrofuran - U D-1 - U ss U of the starting sample - U f U of the fraction Auszug aus der Dissertation von U.-D. Standt: Zur Morphologie von Polystyrol, TU Braunschweig 1981. 相似文献
Zusammenfassung Eine Polystyrolprobe, die durch radikalische Polymerisation hergestellt wurde, wurde mit Hilfe der präparativen Gelpermeationschromatographie fraktioniert; die Struktur und Morphologie der Fraktionen wurde mit13C-NMR-Spektroskopie, DSC und Röntgenbeugung untersucht. Im Verlauf der Fraktionierung traten keine Änderungen der Morphologie der Fraktionen auf. Innerhalb der Molekulargewichtsverteilung existiert keine Verteilung der Syndiotaktizität.
List of abbrevations and symbols AIBN a, a-Azo-bis-(iso-butyronitrile) - D Dispersity, M w /M n - DSC Differential scanning calorimetry - EF Efficiency of fractionation - GPC Gel permeation chromatography - m mass of the fraction - M mass of the fractionated polymer sample - MWD Molecular weight distribution - P r content of racemic dyads - PS Polystyrene - THF Tetrahydrofuran - U D-1 - U ss U of the starting sample - U f U of the fraction Auszug aus der Dissertation von U.-D. Standt: Zur Morphologie von Polystyrol, TU Braunschweig 1981. 相似文献
99.
René Androsch 《European Polymer Journal》2007,43(1):93-108
The melt-crystallization of an oligo[(R)-3-hydroxybutyrate] with five repeating units has been analyzed using standard and temperature-modulated calorimetry, optical microscopy, and atomic force microscopy. Specimens of different crystallinity and supermolecular structure were generated by variation of the rate of cooling of a quiescent melt, or by variation of the temperature of isothermal crystallization. Completely amorphous samples can be obtained by cooling of the melt at a rate of 40 K min−1, or faster, to a temperature lower than the glass transition. The crystallinity depends on the crystallization temperature. The maximum enthalpy-based crystallinity of about 40-45% is obtained by crystallization at temperatures lower than the temperature of the maximum crystallization rate, which is between 310 and 320 K. Analysis of the apparent heat capacity in metastable structural equilibrium reveals reversible melting at temperatures between 320 and 370 K by observation of an excess heat capacity above the level of the vibrational heat capacity, i.e., in the temperature range of irreversible reorganization and melting. The reversible melting is discussed in the context of coupling of the crystalline and amorphous phases, and compared to earlier studies on oligoethylene and oligo(oxyethylene). The presence of crystals causes formation of a rigid amorphous fraction of about 30% at a crystallinity of 40%. Optical and atomic force microscopy reveal spherulitic crystallization. At relatively high crystallization temperature, and in the early stage of the crystallization process, dendrites are observed which finally yield spherulites of decreased perfection. Larger spherulites of higher perfection grow at relatively low crystallization temperature, as deduced from the appearance of the Maltese cross, and the regularity of banding. The band spacing is less than 5 μm, as is accurately determined by atomic force microscopy. The temperature dependence of the spherulitic growth rate is in accord with the calorimetric analysis of the crystallization rate. 相似文献
100.
Feng Zhao Yu-Kou Du Ping Yang Ji’an Tang Xing-Chang Li 《Colloid and polymer science》2005,283(12):1361-1365
In the present study, the structure and morphology of single sodium poly(styrenesulfonate) (PSS) molecules adsorbed to mica
surface from the natural aqueous solution is investigated using atomic force microscopy technique. Results show that single
PSS molecules are observed which show a morphology of wormlike coils. Meanwhile, single sodium poly(styrenesulfonate) (PSS)/Hexadecyltrimethylammonium
bromide (CTAB) complexes deposited on mica from the air–water interface are also observed. However, the PSS/CTA+ complexes show different conformations by appearing in the morphology of circular patches. Experimental data are in fair
agreement with the theoretical analysis. 相似文献