聚硅氧烷/甲基丙烯酸甲酯核壳结构复合粒子的制备

聚硅氧烷/甲基丙烯酸甲酯核壳结构复合粒子的制备;种子乳液聚合;核壳结构     

Synthesis of core-shell latexes by redox initiation at ambient temperatures

Core-shell polymer composites made by two-stage emulsion polymerizations are useful in many applications. In systems involving a hydrophilic/hydrophobic polymer pair, a core-shell arrangement is thermodynamically unfavorable and may be difficult to achieve. To counteract the thermodynamic forces in such a system, the mobility of the phases can be reduced to such an extent that a core-shell morphology is achieved. This was accomplished in a PMMA/PS two-stage system by lowering the second-stage polymerization temperature to room temperature using a redox initiator. At this relatively low temperature, a core-shell morphology was obtained even when the second-stage was carried out as a batch polymerization. © 1992 John Wiley & Sons, Inc.     

The effect of first-stage polymer Tg on the morphology and thermomechanical properties of structured polymer latex particles

A series of heterogeneous latexes having stage ratios of 40:60 between the first and second stage polymers were prepared by emulsion polymerization. The first-stage polymers were non-polar S-BuA with T_gs ranging from + 100 °C to + 20 °C and the second stage polymer was polar MMA–BuA–MAA having a T_g of 20 °C. The latex particle morphologies were studied using TEM and the thermomechanical properties of the resulting latex films were studied with DSC and DMA. Calculated diffusion rates for propagating species during the reactions were correlated to the observed morphologies and to the amount of interphase in the latex particles. To cite this article: O.J. Karlsson et al., C. R. Chimie 6 (2003).     

Surface morphology of polypyrrole core/polyacrolein shell latex by atomic force microscopy (AFM)

 Polypyrrole latex (P(P)), synthesized in Redox polymerization of pyrrole, was used as seed for radical polymerization of acrolein initiated with K₂S₂O₈. In this process the polypyrrole core/polyacrolein shell latex (P(P–A)) was obtained. Morphology of the surface of P(P–A) particles was investigated by atomic force microscopy (AFM). It was found that macromolecules of polyacrolein are not randomly distributed on the surface of polypyrrole but form patches. Apparently, attraction between macromolecules of poly-acrolein in the surface layer is high and the enthalpy of formation of polyacrolein macromolecule clusters is sufficient to compensate, at least, the negative entropy change due to ordering of these macromolecules. Thickness of the polyacrolein layer on the surface of polypyrrole particles, which were covered only partially with polyacrolein, was equal to only 1.6 nm (standard deviation σ= 0.2 nm) and thus, it was reasonable to assume that it corresponded to the monolayer coverage. Received: 30 April 1997 Accepted: 25 August 1997     

Synthesis and Characterization of Surfactant-encapsulated Polyoxoanions: [(C_nH_(2n+1))_2N(CH_3)_2]_(12)[Mo_(36)(NO)_4O_(108)(H)2O)_(16)] (n=12, 18)

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钯铜纳米电催化剂的制备方法及应用

贵金属钯(Pd)基纳米材料是一类具有优异催化活性的电催化材料,其中钯-铜(Pd-Cu)二元材料由于具有低成本和高活性的优点,近年来备受瞩目。铜(Cu)的引入不但降低了Pd的用量,还带来了诸如配体效应、应力效应、聚集体效应等协同作用,这为优化材料的电催化性能带来了多种切入角度。特殊形貌及结构的构建可以使催化剂暴露更多的活性位点,增大电化学活性表面积,提高电催化性能。此外,对Pd-Cu组分的调整或构建复合结构可以实现对d带中心的调控,从而优化电极界面吸附能,最终实现增强活性和改善稳定性的目的。本文总结了具有球形、多面体、核壳、多孔、枝晶状以及单原子等结构的Pd-Cu二元材料的制备方法,并概述了它们在有机小分子(甲醇、乙醇、甲酸等)电氧化、无机小分子(氧、二氧化碳、氮、水等)电还原以及化学镀铜上的应用。最后展望了Pd-Cu电催化剂的发展前景。     

核壳复合材料NH2-MIL-125@TPA-COF用于高效液相色谱分离位置异构体

该文通过在金属－有机骨架材料（MOF）NH2－MIL－125表面原位生长共价有机骨架材料（COF）TPA－COF,制备了核壳复合材料（MOF@COF）NH2－MIL－125@TPA－COF,采用X-射线粉末衍射（PXRD）、红外光谱（FTIR）和扫描电镜（SEM）等手段对该复合材料进行表征,并将其作为固定相成功制备了NH2－MIL－125@TPA－COF色谱填充柱（25 cm long × 2.1 mm i.d.）。在正相（正己烷－异丙醇（9∶1））、反相（甲醇－水（9∶1））高效液相色谱（HPLC）条件下,考察了该柱对一系列位置异构体的分离性能。结果表明,该柱在较低的背景压力（60～100 kPa）下对9种位置异构体（溴硝基苯、硝基苯胺、氯苯酚、二硝基苯、碘苯胺、溴苯胺、苯二胺、甲苯胺和氯苯胺）表现出较好的分离能力,其中溴硝基苯、硝基苯胺和二硝基苯能达到基线分离,且最大分离度（Rs）为9.71。在反相HPLC条件下,邻-溴硝基苯、间-硝基苯胺和邻-氯苯酚的柱效分别为18 424、19 053、12 954 plates·m－1。以溴硝基苯为分析物,在正相HPLC条件下,考察了该柱的重现性和稳定性。该柱通过5次重复进样（第50次、第100次、第150次、第200次、第250次）,溴硝基苯保留时间和峰面积的相对标准偏差（RSD）分别为0.29%和0.89%,表明所制备的色谱柱具有较好的重现性和稳定性。核壳复合材料NH2－MIL－125@TPA－COF作为一种新型的HPLC固定相用于位置异构体分离具有良好的应用前景。     

Development of a Core–Shell Heterojunction TiO2/SrTiO3 Electrolyte with Improved Ionic Conductivity

Lately, semiconductor-membrane fuel cells (SMFCs) have attained significant interest and great attention due to the deliverance of high performance at low operational temperatures, <550 °C. This work has synthesized the nanocomposite core-shell heterostructure (TiO₂−SrTiO₃) electrolyte powder by employing the simple hydrothermal method for the SMFC. The SrTiO₃ was grown in situ on the surface of TiO₂ to form a core-shell structure. A heterojunction mechanism based on the energy band structure is proposed to explain the ion transport pathway and promoted protonic conductivity. The core-shell heterostructure (TiO₂−SrTiO₃) was utilized as an electrolyte to reach the peak power density of 951 mW cm⁻² with an open-circuit voltage of 1.075 V at 550 °C. The formation of core-shell heterostructure among TiO₂ and SrTiO₃ causes redistribution of charges and establishes a depletion region at the interface, which confined the protons′ transport on the surface layer with accelerated ion transport and lower activation energy. The current work reveals novel insights to understand enhanced proton transport and unique methodology to develop low-temperature ceramic fuel cells with high performance.     

基于量子点-CBP混合层的量子点LED的制备

采用一锅法制备出高质量的具有核壳结构的Cd Se@Zn S、Cd Zn S/Zn S量子点。将量子点混入空穴传输材料CBP中形成复合的有源材料,经过几步简单的旋涂操作,制备出相应的绿光、蓝光量子点LED器件。这种方法利用了油溶性量子点和CBP材料的相容性,减少了旋涂操作的步骤,有利于快速制备基于量子点的电致发光器件。基于两步旋涂操作制备的量子点LED,由于阴极与复合有源层之间的能级差较大,导致需要较高的开启电压。在CBP材料中,注入的载流子有可能会被量子点表面缺陷捕获,形成表面态的发光。表面态发光的相对强度依赖于载流子浓度。     

核-壳结构CdSe/ZnS量子点的制备、硫醇修饰及其光学性能

采用高温有机相包覆技术制备了CdSe/ZnS核壳结构量子点材料,考察了包覆量对量子点材料的光学性能的影响,研究了含脂肪链和芳香基的双硫醇分子1,4-苯二甲硫醇和1,8-辛二硫醇对于具有核-壳结构的CdSe/ZnS量子点材料的修饰作用,考察了修饰作用对于量子点的量子效率和荧光强度等光学性能的影响.实验结果表明:随着硫化锌包覆量的增加,量子点的量子效率及其荧光发射强度明显提高;硫醇的修饰能显著增强量子点的发光强度,随着硫醇浓度的增加,其发光性能增强,但是达到一定程度后,光学性能基本不随硫醇浓度的变化而变化.根据固体核磁共振等实验结果推测:硫醇分子可能部分替代了量子点体系中的正三辛基氧膦配体,稳定了量子点体系,对量子点起修饰保护作用,从而提高了量子点的光学性能.