粒径单分散高聚物微球制备研究进展

粒径单分散高聚物微球在许多领域里有着广同的应用前景。简要介绍了粒径单分散微米级高聚物微球的制备方法和进展情况。介绍影响分散聚合的单体浓度、介质、稳定剂、交联剂、引发刺等影响因素对分散聚合的影响和种子溶胀法的进展情况。对国内原子转移自由基研究进行简单的介绍。     

单分散球形硫化镉膜的电化学沉积

提出一种在ITO玻璃上电化学沉积制备单分散近球形硫化镉粒子的新方法.在S-CdCl2-DMSO电沉积体系中加入少量的水制备出单分散膜层,调节沉积电流、电沉积时间或Cd2 浓度可以改变膜层的粒子分布密度.结果表明,在电沉积的整个ITO玻璃表面上均分布有硫化镉沉积,且不同厚度膜层上的沉积其S与Cd的原子比不同.在电沉积硫化镉膜层上蒸镀铜酞菁制备出p-n异质结,其Ⅰ-Ⅴ特性表明,单分散近球形硫化镉膜层载流子的传输由带导电控制机制向跳跃导电控制机制转变.     

高分子分散剂对分散聚合制备聚甲基丙烯酸甲酯微球分散效果的影响EI北大核心CSCD

以甲基丙烯酸甲酯为聚合单体、偶氮二异丁腈为引发剂,通过分散聚合方法在甲醇/水介质中制备了1~2μm的聚甲基丙烯酸甲酯(PMMA)微球,研究了4种高分子分散剂对微球粒径和均匀性的影响并探讨了其影响机制。通过傅里叶变换红外光谱仪和扫描电子显微镜对微球的化学组成和形貌进行了表征,结果表明,不同分散剂对微球尺寸及其分布有着显著影响,以聚乙烯醇(PVA)作分散剂时体系容易失稳,产生颗粒沉降,有小颗粒产生,微球平均粒径(Dn)为1.2μm、多分散系数(PDI)为0.045;以聚乙烯吡咯烷酮(PVP)作分散剂微球均一性较差,体系也会产生颗粒聚并沉降,Dn为1.45μm、PDI为0.105;以聚丙烯酸(PAA)作分散剂,得到均一性更差的微球,Dn为1.85μm、PDI为0.3;以聚乙二醇(PEG)为分散剂则能得到均匀的微球,Dn为1.15μm、PDI为0.041,微球粒径和多分散系数随着PEG相对分子质量的增大呈先减小后增大的趋势;粒径随PEG浓度增加呈先增大后减小趋势,在添加量超过20%后,粒径随浓度增加而减小,PDI随PEG浓度的变化趋势与粒径基本一致。     

单分散聚苯乙烯微球的制备

用分散聚合方法制备单分散聚苯乙烯微球，用扫描电镜测定了微球粒径大小和分布，随着介质溶解度的大小，微球的粒径先增大而后减小，引发剂浓度的提高微粒径的增大和粒径分散系数的变大。     

分散聚合法制备二氧化硅/ 聚苯乙烯单分散复合微球

在醇/ 水混合介质中用分散聚合方法制备二氧化硅/ 聚苯乙烯单分散复合微球。探讨了分散聚合法制备无机/ 有机复合微球的过程, 考察了分散聚合反应的动力学过程。SEM 和TEM 观察结果表明: 在醇/ 水混合介质中, 用PVP K-30 作为稳定剂, 用分散聚合法制备了单分散的以二氧化硅为核、聚苯乙烯为壳的复合微球,成功实现了聚苯乙烯对二氧化硅的包覆, 复合微球的平均粒径为1.25μm , 分散系数ε为0.035 , 达到了单分散水平。还考察了稳定剂的浓度对复合微球粒径的影响, 当稳定剂PVP K-30 浓度增加时, 发现微球的粒径有所减小, 而微球的单分散性提高。      

二氧化硅@硫化镉核壳结构粒子的制备及表征

本文利用化学水浴沉积法,在单分散的二氧化硅球表面包覆硫化镉,制备出二氧化硅@硫化镉核壳结构.通过改变反应物质的量以及反应温度等条件,得到了具有不同核壳比的二氧化硅@硫化镉核壳结构.实验发现随着二氧化硅@硫化镉核壳结构中硫化镉晶粒尺寸的减小,其吸收边和光致发光峰都产生了蓝移;这主要是由于随着硫化镉晶粒尺寸的减小,该材料体系的光学特性由体效应向量子尺寸效应的转变造成的.     

单分散聚苯乙烯微球的制备及二维胶体晶体的自组装

以苯乙烯为原料、过硫酸钾为引发剂,采用无皂乳液聚合法成功地制备出具有良好球形度的单分散聚苯乙烯微球.研究了在聚苯乙烯微球合成过程中单体浓度、引发剂浓度、聚合时间对粒径及分布的影响.实验结果表明,适当改变单体浓度、引发剂浓度、聚合时间可以得到不同粒径的聚苯乙烯微球,且微球单分散性良好.采用自组装技术组装单分散聚苯乙烯微球,获得了二维有序聚苯乙烯胶体晶体.     

盐水介质中分散聚合法制备两性聚电解质的研究

利用聚丙烯酰氧乙基三甲基氯化铵(PDAC)作为分散稳定剂,阴离子单体丙烯酸(从)、阳离子单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)和非离子单体丙烯酰胺(AM)在硫酸铵水溶液中通过分散共聚合,制备了稳定分散在盐水中的聚合物微球.考察了无机盐浓度、分散剂用量对分散共聚合的影响.研究结果表明:体系内无机盐浓度的增加导致聚合物分子量降低;而随分散剂浓度的增加,微球粒径先减小后增加.制备的两性聚电解质溶液在等电点附近时,聚合物的特性黏度随盐浓度的增加而增加,显示明显的反聚电解质效应.     

氧化还原引发无皂乳液聚合制备单分散热敏性微球

在可聚合乳化剂甲基丙烯磺酸钠存在下,以过硫酸钾和亚硫酸氢钠为氧化还原引发体系,将苯乙烯和N-异丙基丙烯酰胺进行无皂乳液聚合,制得粒径大小在200 nm~300 nm范围内的单分散热敏性聚(苯乙烯/甲基丙烯磺酸钠/N-异丙基丙烯酰胺)微球。通过透射电镜观察微球形态和大小,并采用激光光散射粒度仪考察微球粒径大小随温度变化情况。探讨了水溶性单体/油溶性单体比、引发剂用量等对微球粒径大小的影响。结果表明,制备的乳胶粒粒径在32℃附近明显减小,呈现出热敏性质;微球粒径随水溶性单体/油溶性单体比的增大而减小,随引发剂用量的增大而增大。     

基于微流控技术合成单分散聚丙烯酰胺微球

采用T型微流控芯片产生单分散液滴技术制备了尺寸均匀的交联聚丙烯酰胺(PAM)水凝胶微球,考察了芯片中分散相和连续相压力与液滴尺寸的关系,以及丙烯酰胺单体、交联剂和引发剂用量对PAM水凝胶溶胀能力的影响。结果表明,通过调节芯片中连续相和分散相的压力可以获得直径为5~25μm的单分散液滴;PAM微球的体积溶胀能力随引发剂量增加而增强,随单体或交联剂量增加而减弱;当交联剂加入量为单体质量的0.06%时,PAM微球在水中溶胀后的体积是干燥状态下的40倍;交联剂可实现大范围调控PAM水凝胶微球的溶胀能力。     

Preparation and characterization of CdS hollow spheres

CdS hollow spherical particles with average diameter of 800 and 850 nm have been prepared using core/shell fabrication method with poly-(styrene-acrylic acid) (PSA) latex particles as template. TEM images show that smoothly coated core/shell composite particles have been fabricated by multicycles of coating in optimum concentration of reactants. CdS hollow spheres were obtained after removing the template by dissolving the polymer in the organic solvent, and the wall thickness is about 40-100 nm.     

Electrospun Proficient Polymer Based Nano Fibers with Ceramic Particles

Cobaltite of magnesium, embedded in polyvinylpyrrolidone (PVP) polymeric fibers forming nanocomposite were synthesized by combining conventional sol-gel method with electrospinning method. Ultrathin diameter polymer fibers containing nanoregime ceramic particles were obtained by varying various process parameters like voltage, concentration, feed rate, distance between nozzle tip and base plate on an indigenously assembled electrospinning unit. Polyvinylpyrrolidone (PVP) and polyvinylalcohol (PVA) polymeric fibers in nanoregime were also synthesized separately and the effect of the process parameters was observed on the fiber thickness and continuity. Characterization was done to verify the synthesis parameter effect on structural morphology of polymer based nanofiber composite. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) were used as tools for study of structural morphology and its correlation with process parameters.     

一种制备单分散超小粒径氧化硅颗粒的新方法

在氨水催化水解正硅酸乙酯(TEOS)过程中,采用一种新方法制备了单分散的超小粒径氧化硅。加入聚乙烯吡咯烷酮(PVP)能够有效的减小氧化硅颗粒的粒径大小,氧化硅粒径随着PVP的增加而减小。通过优化工艺参数,制备得到了单分散的、粒径只有11nm的氧化硅颗粒。而且,在相同的反应体系中,所制备的氧化硅颗粒能够作为晶种再次生长,通过滴加不同浓度的TEOS能够得到粒径大小可控的氧化硅颗粒。     

Photoluminescence study of PVP capped CdS nanoparticles embedded in PVA matrix

Photoluminescence properties of polyvinyl pyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles embedded in polyvinyl alcohol matrix (PVA) are reported. The PVP-CdS nanoparticles are prepared by non-aqueous method wherein cadmium nitrate is used as the cadmium source and hydrogen sulphide as the sulphur source. The synthesized nanoparticles are dispersed in polyvinyl alcohol (PVA) matrix and cast as self-standing flexible (PVP-CdS)-PVA films. The nanocomposites are characterized by optical absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. XRD and TEM studies show the formation of cubic CdS particles with average size ∼3-5 nm. Thermal studies, carried out to observe the changes in PVA matrix due to the incorporation of PVP-CdS nanoparticles show strong interaction between the polymer matrix and nanoparticles. The photoluminescence emission spectra of the nanocomposites show two peaks, at 502 and 636 nm, which are attributed to the band edge and surface defects respectively, of CdS nanoparticles. Effective surface capping with optimum concentration of polyvinyl pyrrolidone leads to the quenching of surface defect-related emission.     

Effects of PVP and KCl concentrations on the synthesis of gold nanoparticles using a solution plasma processing

Application of plasma in an aqueous environment, so called Solution Plasma Processing (SPP) is a recent development. Solution plasma processing for the synthesis of gold nanoparticles by reducing HAuCl₄ in the presence of Polyvinylpyrrolidone (PVP) and potassium chloride (KCl) was investigated in this work. Effects of PVP and KCl concentrations on the size and the shape of the gold nanoparticles in SPP were studied using a UV-vis nir spectrophotometer, and high resolution transmission electron microscopy (HRTEM). The results showed that the shape and size of the nanoparticles were affected by various KCl and PVP concentrations. The average particle size of the gold nanoparticles synthesized by SPP decreased with an increase in PVP concentration and the particle shape became more spherical with the addition of KCl. The HRTEM results indicated that gold nanoparticles with a diameter less than 10 nm were single crystals, while particles with a diameter greater than 15 nm were polycrystalline.     

In situ hydrothermal preparation of CdS/polymer composite particles with cadmium-containing polymer latexes

Employing the hydrothermal technique, CdS/polymer composite particles were prepared with the surfactant-free cadmium-containing polymer latexes synthesized via a surfactant-free emulsion copolymerization. The CdS/polymer composite particles have been characterized by FTIR spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM).     

A novel approach to the synthesis of hollow silica nanoparticles

Hollow silica nanoparticles were synthesized with incorporation of silanol groups (SiOH) onto polymer particles in dispersion polymerization and the polycondensation reaction of tetraethyl orthosilicate (TEOS) exclusively took place at the particles surface in the presence of ammonia following the so-called Stöber process and the silica-coated polymer powers were calcined at 800 °C. The diameters of hollow silica spheres are found to be very close to the original diameter and the average pore diameter is less than 100 nm. Moreover, the hollow silica nanoparticles have uniform aperture, do not agglomerate and collapse.     

Solid-CdS and hollow-ZnS porous submicrospheres: Direct preparation by C-S decomposition of thiol via solvothermal processing

Porous solid-CdS or hollow-ZnS submicrospheres (SMSs) were prepared by reaction of 2-mercaptoethanol as S-source with Cd²⁺ or Zn²⁺ in ethanol using solvothermal route. Without any alkaline, solid-CdS SMSs with an average diameter of 440 nm were obtained and their size distribution in the range of 390-490 nm is above 80%; With the addition of alkaline, single crystal CdS nanorods with high-temperature-stable hexagonal phase were synthesized. With or without poly(N-vinyl-2-pyrrolidone) (PVP), solid-CdS SMSs can be prepared, but the addition of the PVP leads to the preparation of relative uniform CdS-SMSs. Hollow-ZnS SMSs with an average diameter of 340 nm were obtained under the existence of alkaline. The longer reaction time hardly influences on the size of the hollow-ZnS SMSs. More or less amount of alkaline directly influences the morphology of final product. Close-ring-shaped ZnS was prepared under the existence of less alkaline. With or without PVP under preparation reaction, hollow-ZnS SMSs can also be synthesized. Thus, during preparation of either CdS or ZnS, the PVP function is not as template, but as surfactant. The BET measurement results show that the special surface areas of solid-CdS and hollow-ZnS SMSs are 25.56 and 83.55 m²/g, respectively. The adsorption of methylene blue shows that the hollow-ZnS SMSs have very strong adsorption and decomposition ability.     

原位表面修饰纳米CdS粒子的表面结构和光学性能

采用微乳液法合成了纳米尺度硫化镉粒子,并用硫醇和咪唑对粒子进行了原位表面修饰.对纳米硫化镉粒子的形貌与表面结构进行了表征,证实了表面修饰剂与粒子间的键合.电镜观察和紫外-可见吸收光谱的测定发现,表面修饰明显地提高了纳米粒子在溶剂中的分散性,改变了纳米粒子的表面结构,消除了粒子表面导致无辐射弛豫的缺陷,因而提高了纳米粒子分散于溶剂体系的荧光性能.修饰剂与溶剂间的相互作用决定了表面修饰粒子在溶剂中的分散性,对纳米粒子的光学性能也有一定的影响.     

Preparation of submicrometer-sized titania hollow spheres by templating sulfonated polystyrene latex particles

Submicrometer-sized titania hollow spheres with tunable shell thickness and smooth surfaces have been successfully synthesized by employing sulfonated polystyrene (PS) latex particles as a template in sol-gel method. The structure of the particles was characterized by scanning electron microscopy and transmission electron microscopy. The shell thickness was readily tuned by altering the concentration of titanium tetrabutoxide (TBOT) in ethanol solutions. The surface roughness as well as the shell thickness has the tendency to increase with the increase in the concentration of TBOT. The diameter of the hollow spheres was on the average of 20-26% smaller than the diameter of template PS latex particles. Some titania fragments were also observed for the sample with the highest TBOT concentration.