橡胶粒子和刚性纳米粒子对注塑级硬质聚氯乙烯复合材料断裂行为的影响

采用核壳型丙烯腈-苯乙烯-丁二烯共聚物(ABS)和纳米碳酸钙(CaCO3)协同改性聚氯乙烯(PVC),制备了注塑级硬质PVC纳米复合材料.通过透射电镜(TEM)、扫描电镜(SEM)、力学性能测试研究了其结构与性能,并采用有限元模拟方法研究了ABS与纳米CaCO3粒子对复合材料断裂行为的影响.当CaCO3含量低于12 p...     

Synthesis of polyacrylate core-shell structure latex by radiation techniques

A series of poly(butyl acrylate-co-methyl methacrylate)/poly (ethyl acrylate-co-acrylic acid) interpenetrating polymer network (IPN) was synthesized in latex form by emulsion polymerization. The multiphase morphology of the latex particles was studied after two-stage polymerization by using transimission electron microscope (TEM), the result indicated that the morphology of the particles comprises gradient shell structure, cellular structure and core-shell structure. The change of morphology might stem from emulsion polymerization by radiation initiation or chemical initiation and the weight composition of poly(EA-co-MMA) seed latex which formed the core. By radiation techniques, we successfully synthesized poly( BA-co-MMA)/poly(EA-co-AA) latex of core-shell structure having (42-8)/(46-4) weight compositions. The PA core-shell structure latex applied to textile as a water proofing coating showed higher water-pressure and easier handling than that with PA homogeneous phase structure latex.     

Dielectric behavior of double emulsions with "core-shell droplet" morphology

The dielectric behavior of double emulsions with "core-shell droplet" morphology is investigated over a broad range of frequency. A new modified Pauly-Schwan model is proposed for the complex permittivity of double emulsions. The proposed model takes into consideration the morphology and packing limit of droplets. The dielectric behaviors of oil-in-water-in-oil (O/W/O) and water-in-oil-in-water (W/O/W) types of double emulsions, as predicted by the proposed model, are discussed.     

Synthesis of SiCN@TiO2 core-shell ceramic microspheres via PDCs method

A facile and effective polymer-derived ceramics (PDCs) emulsification-crosslinking-pyrolysis method was developed to fabricate SiCN@TiO₂ core-shell ceramic microspheres with polyvinylsilazane (PVSZ) and tetrabutyl titanate (TBT) as precursors. The TBT: PVSZ mass ratios, emulsifier concentrations and the pyrolysis temperature were examined as control parameters to tune the size and morphology of microspheres. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the synthesized SiCN@TiO₂ microspheres to be comprised of SiCN core coated with TiO₂ crystals, with an average size of 0.88 μm when pyrolyzed at 1400 °C. The analysis of Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) ensured that SiCN@TiO₂ core-shell ceramic microspheres composed of rutile TiO₂, β-SiC and Si₃N₄ crystalline phases, The thermal properties were characterized by thermogravimetric analysis (TGA). The obtained SiCN@TiO₂ core-shell ceramic microspheres were the promising candidate of the infrared opacifier in silica aerogels and this technique can be extended to other preceramic polymers.     

核-壳结构氧还原反应电催化剂

The high cost of platinum in catalyst layers hinders the commercialization of proton exchange membrane fuel cells. This Account reviews recent progress on core-shell nanostructures for oxygen reduction reaction (ORR) in acidic media, which is the cathodic reaction in fuel cells. The synthesis, characterization and evaluation of different types of core-shell electrocatalysts are summarized. Various strategies to improve the performance of core-shell electrocatalysts, including dealloying, morphology control, and surface modification are presented. The issues of mass production and fuel cell performance of core-shell electrocatalysts are also discussed.     

碳纤维表面羰基铁的原位生长及吸波性能

以Fe(CO)5为前驱体,通过金属有机化学气相沉积(MOCVD),在碳纤维(CF)表面构筑厚度为纳米级的羰基铁(CI)壳层,通过改变沉积温度,调控核壳粉体的形貌结构和吸波性能。用X射线衍射仪、扫描电子显微镜和矢量网络分析仪对粉末的结构及电磁性能进行表征并对其吸波性能进行研究。结果表明:随着沉积温度升高(210~240℃),沉积到CF表面的羰基铁颗粒互相“吞并-融合”,此时CF-CI形成了完整的薄膜包覆型核壳结构;沉积温度太高时(270℃)会造成CF表面羰基铁壳层形貌的恶化。通过调节沉积温度,在纳米尺度上可以有效调控CI壳层的形貌,从而调节CF-CI核壳粒子的电磁性能。以核壳形貌及吸波性能为考察指标,最终确定最佳的沉积温度为240℃。以沉积温度为240℃时所获样品的电磁参数,模拟计算出涂层厚度为0.9 mm时,小于-10 dB的吸波带宽最大为4.6 GHz(13.4~18 GHz);涂层厚度为2.0 mm时,反射率达到最小值为-21.5 dB;厚度为0.9~3.9 mm时,在2~18 GHz均能实现吸波强度低于-10 dB。     

Design of Blends with an Extremely Low Viscosity Ratio between the Dispersed and Continuous Phases. Dependence of the Dispersed Phase Size on the Processing Parameters

Summary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components.     

Characterization of polymer-silica nanocomposite particles with core-shell morphologies using Monte Carlo simulations and small angle X-ray scattering

A two-population model based on standard small-angle X-ray scattering (SAXS) equations is verified for the analysis of core-shell structures comprising spherical colloidal particles with particulate shells. First, Monte Carlo simulations of core-shell structures are performed to demonstrate the applicability of the model. Three possible shell packings are considered: ordered silica shells due to either charge-dependent repulsive or size-dependent Lennard-Jones interactions or randomly arranged silica particles. In most cases, the two-population model produces an excellent fit to calculated SAXS patterns for the simulated core-shell structures, together with a good correlation between the fitting parameters and structural parameters used for the simulation. The limits of application are discussed, and then, this two-population model is applied to the analysis of well-defined core-shell vinyl polymer/silica nanocomposite particles, where the shell comprises a monolayer of spherical silica nanoparticles. Comprehensive SAXS analysis of a series of poly(styrene-co-n-butyl acrylate)/silica colloidal nanocomposite particles (prepared by the in situ emulsion copolymerization of styrene and n-butyl acrylate in the presence of a glycerol-functionalized silica sol) allows the overall core-shell particle diameter, the copolymer latex core diameter and polydispersity, the mean silica shell thickness, the mean silica diameter and polydispersity, the volume fractions of the two components, the silica packing density, and the silica shell structure to be obtained. These experimental SAXS results are consistent with electron microscopy, dynamic light scattering, thermogravimetry, helium pycnometry, and BET surface area studies. The high electron density contrast between the (co)polymer and the silica components, together with the relatively low polydispersity of these core-shell nanocomposite particles, makes SAXS ideally suited for the characterization of this system. Moreover, these results can be generalized for other types of core-shell colloidal particles.     

Synthesis and Structure Control of A New Kind of Inelastomer Impact Modifier with Core-shell Structure and Impact Modification to PVC/CPE

Introduction　　 As a structure material,a polymer has two important mechanical properties,i.e.,strength and toughing.Therefore,plastic toughening isalwaysa fundamental study on poly-mer materials.Traditionally,toughnessmodification isto make rubberasan elastomerimpactmodifier dispersed to plastic matrix which is hence toughened[1 ,2 ] .But as the toughness ofplastic is improved,the elastomerimpactmodifieralso reducesthe othermechanical propertiesof the material.Consequently,whether rigid par…     

Particle morphology of self-hydrolyzed acrylate polymer colloids: A 13C NMR and DSC study

Methyl acrylate polymer colloids can be hydrolyzed self-catalytically by bound strong acid surface groups derived from the polymerization initiator. The kinetics of hydrolysis were earlier shown to be apparently pseudo-zeroth-order for any given latex, and first order with respect to surface strong acid concentration. A surface reaction zone model was proposed to explain the kinetics. This model leads to the prediction that the polymer particles will possess a core-shell morphology after some hydrolysis has occurred. This study employs ¹³C NMR spectroscopy to investigate the particle morphology in the wet latex, a new application for this method. The temperature dependence of the ¹³C NMR integrated intensities at various levels of hydrolysis provides strong evidence that the particles do possess core-shell morphology, and that the shell is composed of PAA/PMA copolymer. This shell is swollen and plasticized by water, resulting in greatly enhanced segmental mobility of the polymer chains as evidenced by marked narrowing of the NMR lines. Thermal measurements alone cannot distinguish particle morphology because PMA appears to be somewhat compatible with its partially hydrolyzed analog at the temperatures of measurement.     

Synthesis and characterization of a novel silane-based vinylic monomer and its application in the multilayer core-shell latex

A novel monomer methacrylamidophenoxy dimethylsiloxy phenylphthalimide was obtained by a reaction of 4,4′-bis-aminophenoxy dimethylsilane, phthalic anhydride and methacryloyl chloride. Then it has been used in the synthesis of phase-separated polymer latex with a multilayer core-shell morphology by surface cross-linking emulsion polymerization. Poly(butyl acrylate) was used for the seed and the core of the latex, the inner shell was poly(butyl acrylate/styrene) cross-linked with divinylbenzene to avoid phase inversion, and the poly(methyl methacrylate/butyl acrylate/methacrylamidophenoxy dimethylsiloxy phenylphthalimide) was the outer shell. The structural elucidation of monomer was carried out by elemental analysis, FTIR, ¹H NMR, and ¹³C NMR spectroscopic techniques. The morphology and glass transition temperatures of the synthesized product were investigated by transmission electron microscopy and differential scanning calorimetry, respectively. The multilayer core-shell structure was clearly shown in TEM micrographs, and the three-phase separation was confirmed by DSC analysis. The obtained results demonstrated that the average particle size is 81.8, 108 and 132 nm for the core, core-shell and multilayer core-shell particles, which agrees with the TEM micrograph measurement of 75, 103, and 131 nm, respectively.     

核-壳结构壳聚糖/聚乙烯醇-聚碳酸亚丙酯超细纤维的制备

利用同轴电纺丝技术制备出具有核-壳结构的壳聚糖/聚乙烯醇-聚碳酸亚丙酯电纺丝纤维,考察了溶剂复配对成纤的影响,采用扫描电镜和透射电镜对纤维的形貌、结构、直径分布等进行了探索,并在优化的工艺条件下,将羟基磷灰石负载在内层结构中.研究表明,采用氯仿/N,N-二甲基甲酰胺(1/1)复配溶剂可有效避免聚合物溶液在喷丝口处的凝结现象.同单纺纤维相比,核壳结构的纤维直径分布较宽,纤维壳层和核层界限清晰;红外谱图分析证明羟基磷灰石可负载在纤维的核结构中.     

Preparation of Hybrid Nanocapsules

Hybrid nanoparticles with a polystyrene core and a hybrid copolymer shell were used to produce hybrid nanocapsules by dissolving the polystyrene core from the previously elaborated core-shell particles. Following previous works, the core-shell particles were prepared by emulsion polymerization of styrene and subsequent addition of γ-methacryloxy propyl trimethoxy silane (MPS) to produce the shell by copolymerization reaction of MPS with the residual styrene. Core extraction was performed by diluting the core-shell particles in an excess of tetrahydrofuran (THF). Two procedures were investigated to separate the dissolved polymer chains from the nanocapsules. In the first procedure, the polymer was isolated by successive centrifugation and redispersion in THF, whereas in the second procedure, the free polymer chains were removed by dialysis. The polymer molecular weight was optimized in order to promote dissolution of the polymer chains and allow them to diffuse through the shell.     

一维铜(核)-镍(壳)纳米结构的制备及其表面增强拉曼光谱

采用多孔阳极氧化铝模板(AAO)结合直流电化学沉积法, 通过一种新的两步法合成一维铜(核)-镍(壳)纳米结构. 首先制备铜纳米线, 然后对AAO进行扩孔, 利用铜纳米线和AAO孔壁之间的间隙,沉积镍纳米线/纳米管. 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对其结构和形貌进行表征分析, 所得结果验证了这种方法的可行性. 以腺嘌呤为探针分子研究此种纳米结构的表面增强拉曼散射(SERS)效应, 结果表明, 这种一维纳米材料是一种潜在的SERS活性基底, 拓宽了过渡金属在SERS中的应用.     

Designing Organic/Inorganic Colloids by Heterophase Polymerization

Polymer/silica and polymer/Laponite nanocomposite colloids with various morphologies have been elaborated through emulsion polymerization using a polymerizable organosilane (route I) and a methyl methacrylate-terminated macromonomer (route II) as coupling agents. Depending on the synthetic strategy and on the nature of the mineral particles, either core-shell, raspberry-like, multipod-like, currant bun or inverted core-shell morphologies (the mineral forming the shell) were achieved. Beyond the control of particle shape, we have demonstrated that some of the polymerizations exhibited particular kinetics behaviors which could be correlated to the mechanism of formation of the composite particles. Interestingly, conversion versus time curves of a series of soap free polymerizations performed in the presence of the macromonomer showed a significant increase in the polymerization rate with increasing the inorganic particles concentration. Characterization of the composite latexes by transmission electron microscopy showed that the mineral was located at the surface of the latex spheres and participated therefore to their stabilization. The higher the amount of inorganic particles, the lower the particles size and the higher the polymerization rate.     

荧光探针法研究核壳结构有机硅-丙烯酸酯乳液的聚合行为

以芘为荧光探针,探讨了有机硅-丙烯酸酯核壳乳液聚合过程中,芘的第一振动峰(373 nm处)与第三振动峰(384 nm处)荧光强度的比值I1/I3与乳化剂、有机硅单体(D4)和引发剂(KPS)用量之间的关系,并结合聚合过程中探针芘的I1/I3峰值与单体转化率及乳胶粒形态演变之间的关系,研究了核壳结构有机硅-丙烯酸酯乳液的聚合行为.研究结果表明,探针芘的I1/I3峰值随乳化剂用量,D4用量,KPS用量不同发生相应的变化,随单体转化率的增加而增大.当乳化剂用量、D4用量、KPS与总单体的质量比依次为2 g、8 g、0.7%时,得到的乳液具有优良的综合性能.聚合反应过程中,当种子乳胶粒转变为核壳乳胶粒时,芘的I1/I3峰值仍呈现出明显的转变,说明有机硅-丙烯酸酯核壳乳液具有互穿聚合物网络结构.因此,荧光探针可用于研究有机硅-丙烯酸酯核壳乳液聚合反应进程.     

Morphology and grafting in polybutylacrylate-polystyrene core-shell emulsion polymerization

The morphology of polybutylacrylate–polystyrene (PBA–PS) core-shell latex particles prepared by seeded emulsion polymerization was investigated as a function of the addition method of styrene (St). The thin layer chromatography/flame ionization detector (TLC–FID) technique was used to characterize the morphology of the core-shell latexes. It was found that grafting PS to the PBA core occurs during seeded emulsion polymerization. The percentage of grafting depended on the method of addition of St, being greatest for the batch reaction, less for the preswollen batch reaction, and least for the semibatch reaction. Upon aging the PBA core-polymer migrated out of the latex particles with a low degree of grafting to form dumbellshaped particles, whereas the PBA–PS core-shell particles with a high degree of grafting remained spherical because of the emulsifying ability of graft copolymer.     

单个Fe2O3@Au粒子的偏振表面增强拉曼光谱

本文首次报道了单个纺锤形Fe2O3@Au颗粒的偏振相关的SERS光谱, 为研究SERS机理提供了实验依据.     

溶剂热法合成In2S3/CuSe核壳结构粉体

本文以氯化铜、氯化铟、硫脲、亚硒酸以及硒粉为原料,乙二醇及乙二胺为溶剂,采用常压溶剂热法制备了硫化铟为核硒化铜为壳(In2S3/CuSe)的核壳结构复合粉体。主要探讨了反应温度、不同反应原料以及不同表面活性剂对产物物相以及形貌的影响。通过采用X射线衍射(XRD)、扫描电镜(SEM)对产物的物相、形貌以及组成进行了表征。实验结果表明:常压溶剂热条件下可以制备得In2S3/CuSe复合粉体,其最佳反应工艺参数是:于160℃下合成In2S3粉体为核,于100℃下合成包裹在In2S3表面的CuSe粉体从而获得In2S3/CuSe核壳结构复合粉。在该工艺参数下合成产物的形貌主要由圆球状颗粒组成,粉体的粒径分布在1~2μm。此外,本文也通过添加不同种类表面活性剂对产物的形貌进行了控制。     

Synthesis of a hierarchical three-component nanocomposite structure system with enhanced electrocatalytic and photoelectrical properties

Effective control over the morphology and size of Pd/Pt nanoparticles is currently of immense interest because their electronic, optical, and catalytic properties are superior to pure platinum nanoparticles. However, control over the nanoparticle shape is still challenging. Therefore, a novel design and synthetic route needs to be developed to obtain a high-performance catalyst. Herein, a hierarchical three-component nanocomposite structure system (HTNSS) composed of graphene, TiO(2), and Pd@Pt core-shell nanoparticles was designed and synthesized by a sequential strategy that focuses on constructing the monolithic structure rather than limited single-component counterparts. The resulting composites were characterized by various techniques, which showed that the Pd@Pt core-shell nanoparticles were preferentially deposited on the peripheral interface of the graphene and TiO(2) nanoparticles. The photoelectrical and catalytic performances were obviously improved relative to the commercially available E-TEK Pt/C owing to their synergistic effect.