Effect of hydrophilic comonomer and surfactant type on the colloidal stability and size distribution of carboxyl- and amino-functionalized polystyrene particles prepared by miniemulsion polymerization

Carboxyl and amino-functionalized polystyrene latex particles were synthesized by the miniemulsion copolymerization of styrene and acrylic acid or 2-aminoethyl methacrylate hydrochloride (AEMH). The reaction was started by using an oil-soluble initiator, such as 2,2'-azobis(2-methylbutyronitrile) (V-59). The effect of the functional monomer content and type of surfactant (non-ionic versus ionic) on the particle size and particle size distribution was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). A bimodal particle size distribution was observed for functionalized latex particles prepared in the presence of the non-ionic surfactant (i.e., Lutensol AT-50) when 1 wt % of acrylic acid or 3 wt % of AEMH as a comonomer was employed. The copolymer particle nucleation was studied by using a highly hydrophobic fluorescent dye. From the obtained results, the formation of bimodal particle size distribution may be attributed to a budding-like effect, which takes place during the earlier stage of polymerization and is caused by the additional stabilizing energy originated from the ionic groups of a functional polymer. The reaction mechanism of particle formation in the presence of non-ionic and ionic surfactants has been proposed. The amount of the surface functional groups was determined from polyelectrolyte titration data.     

Nonionic latices in aqueous media part 1. Preparation and characterization of polystyrene latices

A series of non-ionic polystyrene latices in aqueous media containing particles with a narrow size distribution have been prepared using a nonyl phenol poly(ehylene glycol) condensate as the surfactant, methoxy poly(ethylene glycol methacrylate) as the comonomer/stabilizer, and ascorbic acid/hydrogen peroxide as the initiator system. As a control synthesis for comparison with the above latex, a charge stabilized polystyrene latex was prepared, using an anionic surfactant and potassium persulphate as the initiator. Latices employing a combination of charge plus steric stabilization mechanisms were also prepared, in order to investigate the effect of the non-ionic surfactant and the comonomer/stabilizer. The particle size of the latices was measured by transmission electron microscopy, the surface charge density by conductimetric titration and the glass transition temperature of the polymer by differential scanning calorimetry. The latex prepared using non-ionic ingredients, showed no titratable charge and exhibited a profound lowering of the glass transition temperature, with respect to the charge stabilized latex. On the basis of these results, schematic models for the polymerization mechanism and the morphology of the latex particles are proposed.     

单分散聚丙烯酸丁酯-二氧化硅核壳粒子的制备

近年来,有机-无机核壳材料因其具有可调的光、电、磁等特性而备受关注．无机物外壳可以增强粒子的热力学稳定性、机械强度和抗拉性能．高分子乳胶粒内核具有弹性,且易成膜,外部包覆无机物的乳胶粒可结合两者特性并产生协同效应．     

MMA-EA-AA无皂乳液聚合中粒径及粒径分布的控制

系统研究了MMA EA AA三元无皂乳液聚合体系中各种因素对乳胶粒大小及分布的影响 ,制得了单分散、粒径在 30 0～ 6 0 0nm可控聚合物乳胶粒 .结果表明 ,在过硫酸铵用量一定的条件下 ,聚合初期加入大量引发剂可同时提高单体转化率和乳胶粒的单分散性 ;随着引发剂和AA用量的增加以及聚合温度的升高 ,胶粒粒径逐渐减小 ,转化率逐渐升高 ;随着NH4 HCO3用量的增加 ,粒径逐渐增大 ,当NH4 HCO3用量达到 0 5g以后 ,转化率逐渐降低 ;搅拌速率为 30 0r min左右时 ,单体转化率最高 ,所得乳胶粒粒径最均一 .     

无乳化剂乳液聚合法合成单分散大粒径高分子微球的研究

无乳化剂乳液聚合法合成单分散大粒径高分子微球的研究朱世雄杜金环金熹高陈柳生（中国科学院化学研究所北京１０００８０）关键词无乳化剂乳液聚合，单分散，均相成核，低聚物胶束微米级大粒径单分散高分子微球在标准计量、情报信息、分析化学等许多领域都有广泛的...     

Preaparation of cationic latexes of poly(styrene-CO-butyl acrylate) and their properties evolution in latex dilution

Cationic latexes were prepared through emulsion copolymerization of styrene(St) and butyl acrylate(BA) with a cationic surfactant,cetyl trimethyl ammonium bromide(CTAB).Latex properties,including particle size,size distribution,ζpotential,surface tension and monomer conversion,were determined for latexes prepared with different CTAB amounts. Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation.Results showed that both particle size andζpotential were function of polymerization time and latex solids.Parallel emulsion polymerizations with cationic,anionic charged initiator and charge-free initiators were also carried out,the latex properties were determined at different polymerization time.All these results were attentively interpreted based on the mechanisms of emulsion polymerization,surfactant adsorption and latex particle stabilization.     

Synthesis of monodisperse anionic submicron polystyrene particles by stabilizer-free dispersion polymerization in alcoholic media

In this work, monodisperse polystyrene (PS) particles were synthesized in ethanol/water medium using sodium salt of styrene sulfonic acid and 2,2′-azobis(isobutyronitrile) as ionic comonomer and nonionic initiator, respectively. The polymerization was carried out at low agitation speed, and no stabilizer (or surfactant) was added to the polymerization medium. This polymerization system (stabilizer-free dispersion polymerization) was initiated as a homogeneous solution of monomer, comonomer, medium, and initiator. With the production of free radicals, polymerization developed into a heterogeneous system. The effect of various polymerization conditions on the size and size distribution of the obtained particles was evaluated. The experimental results showed that with an increase in ethanol content, the size of the particles increased while no significant change was observed in particle size distribution. Furthermore, with increasing ionic comonomer content, the size of the particles decreased and their size distribution became broader. Moreover, it was observed that addition of an electrolyte to the polymerization medium also increased the particles’ size and broadened their size distribution. It is noteworthy to point out that the coagulation occurred in higher amounts of electrolyte. Finally, it is concluded that the polar component of Hansen solubility parameter of the polymerization medium affects the particle size and particle size distribution greatly.     

Synthesis and properties of soap-free poly(methyl methacrylate-ethyl acrylate-methacrylic acid) latex particles prepared by seeded emulsion polymerization

In order to obtain functional polymer latex particles with clean surface and with surface carboxyl groups, P(MMA-EA) seed particles with the diameter of 335 nm were first synthesized via soap-free batch emulsion polymerization of methyl methacrylate (MMA) and ethyl acrylate (EA), and then the seeded emulsion copolymerization of MMA, EA and MAA (methacrylic acid) onto the seed particles were performed in the absence of emulsifier. Influences of ingredients and conditions on polymerization, latex particle size (D_p) and its distribution were investigated. Results showed that most of the monomers polymerized onto the seed latex particles in the second step of polymerization by using drop-wise addition method, and D_p increased from 483 nm to 829 nm with the mass ratio of core/shell monomers [C]/[S] decreased from 1:2 to 1:15. It was found that D_p decreased with the increase of MAA and initiator amounts, and the size of the latex particles became uniform with the decrease of MAA amount and with the increase of [C]/[S] value.     

Synthesis of silanol-functionalized latex nanoparticles through miniemulsion copolymerization of styrene and gamma-methacryloxypropyltrimethoxysilane

The polystyrene latex nanoparticles bearing silanol groups on their surfaces were successfully synthesized via miniemulsion polymerization using gamma-methacryloxypropyltrimethoxysilane (MPS) as the functional comonomer and oil-soluble AIBN as the initiator at neutral conditions. FTIR and 29Si NMR spectra showed that the condensation of silanol groups was suppressed effectively. zeta potential and XPS analyses demonstrated that the silanol groups were enriched at the surfaces of the latex particles and could be tailored by MPS concentration. These silanol-functionalized latex particles could be easily coated with silica or other inorganic or organic compounds to prepare novel hybrid particles and hollow microspheres.     

聚硅氧烷/丙烯酸酯核/壳复合胶乳的粒径分布与成核机理

通过种子乳液法合成出具有高有机硅含量核 壳结构的聚硅氧烷 丙烯酸酯复合粒子 .研究了聚合方法、乳化剂浓度、引发剂浓度、单体滴加速度等工艺条件对复合乳液粒径尺寸、分布与形态的影响 ,并对复合乳液的成核机理进行了探讨 .研究表明 ,乳化剂浓度对乳液粒子的粒径分布和形态、结构有显著影响 ,引发剂浓度增加将使粒子粒径减小 ;相对一次投料法 ,种子乳液法生成的粒子分布窄 ,具有明显核壳结构 ,通过壳层单体滴加速度可以控制粒子的粒径尺寸和分布 ;而壳层丙烯酸酯聚合物主要是在聚硅氧烷种子表面的“过渡层”聚合、富集而成 .     

一种单分散醋-丙乳液的合成与应用研究

以醋酸乙烯酯(VAc)、丙烯酸正丁酯(BA)和甲基丙烯缩水甘油酯(GMA)为共聚单体,采用预乳化-半连续种子乳液聚合的方法,合成了一类改性醋丙乳液.用透射电子显微镜(TEM)、激光光散射(LLS)等测定了乳胶粒的粒径、粒径分布和粒子形态,发现其粒径在120 nm左右,并呈现较好的单分散特性;Zeta电位和流变测定结果显...     

Synthesis and emulsion copolymerization of amphiphilic poly(2-oxazoline) macromonomer possessing a vinyl ester group

The present article describes the synthesis and emulsion copolymerization of a block-type amphiphilic poly(2-oxazoline) macromonomer possessing a polymerizable vinyl ester group. The macromonomer was synthesized by one-pot two-stage block copolymerization of 2-oxazolines using vinyl iodoacetate as initiator. 2-Methyl- and 2-n-butyl-2-oxazolines were employed for the construction of hydrophilic and hydrophobic segments, respectively. The surface activities evaluated by the surface tension of the macromonomer in water were fairly good. Emulsion copolymerization of vinyl acetate with the macromonomer was carried out. The macromonomer acted as a polymeric surfactant, as well as a comonomer. The resulting copolymer latex particles were spherical and their diameter was in the sub-micron range. The effects of the composition of the macromonomer on the emulsion copolymerization and the resulting latex particles were examined. © 1993 John Wiley & Sons, Inc.     

单分散交联聚（4—乙烯吡啶／丙烯酸丁酯）无皂正电性共聚乳胶

以偶氮二异丙基脒盐酸盐（V50)为引发剂,采用4－乙烯吡啶（4－VP）／丙烯酸丁酯（BA）为混合单体,分别以二乙烯苯（DVB）或双甲基丙烯酸乙二醇酯（EGDMA）为交联剂,用无皂乳液聚合的方法合成了一系列正电性共聚乳液,并用扫描电镜（SEM）、Zeta电位测定仪详细研究了单体配比、交联剂种类和交联度对粒径大小及其分布、粒子形态和乳液电性能的影响,并探讨了该三元无皂乳液聚合的成核机理。结果表明：4VP／BA的无皂乳液聚合遵循均相成核机理。当BA含量低或者微球交联度较小时,高分子亲水性强,临界链长度大,生成粒子数目少,所以粒径大;随着BA含量的增加或者交联度的增大,高分子疏水性增强,临界链长度沽小,生成粒子数目增多,粒径变小,当BA／4VP＝1／4（g/g)时,得到单分散共聚乳胶,少量BA与4VP共聚可以明显提高乳液的稳定性。     

Tailoring of carboxyl‐decorated magnetic latex particles using seeded emulsion polymerization

In this research, submicron and carboxyl‐functionalized magnetic latex particles were elaborated by using seeded emulsion polymerization technique in presence of oil‐in‐water (o/w) magnetic emulsion as seed. The polymerization conditions were optimized in order to get well‐defined latex particles with magnetic core and polymer shell bearing carboxylic (–COOH) functionality. Starting from (o/w) magnetic emulsion as seed, synthesis process was performed by copolymerization of styrene (St) monomer with the cross‐linker divinylbenzene (DVB) in presence of 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as a carboxyl‐bearing initiator. The prepared magnetic latex particles were first characterized in terms of particle size, chemical composition, morphology, magnetic properties, magnetic content, and colloidal stability using various techniques, e.g. particle size analyzer using dynamic light scattering (DLS) technique, Fourier transform infrared, transmission electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, and zeta potential measurements as a function of pH of the dispersion media, respectively. The prepared magnetic latex particles were then used as second seed for further functionalization with methacrylic acid (MAA) in order to enhance carboxylic groups on the magnetic particle's surface. The results showed that final magnetic latex particles possessed spherical morphology with core‐shell structure and enriched carboxylic acid functionality. More importantly, they exhibited superparamagnetism with high magnetic content (58.42 wt%) and high colloidal stability, which considered as the main requirements for their application in the biomedical diagnostic domains. Copyright © 2017 John Wiley & Sons, Ltd.     

氧化-还原引发剂引发苯乙烯超浓乳液聚合的研究

以过氧化羟基二异丙苯(CHPO)和四乙烯五胺(TEPA)为氧化-还原引发剂,以十二烷基硫酸钠(SDS)为乳化剂,十六醇(CA)为共乳化剂,通过超浓乳液聚合方法制备了聚苯乙烯乳胶粒子.探讨了乳化剂浓度及配比、分散相体积分数、引发剂种类、引发剂浓度及配比和温度等各因素对乳液稳定性、聚合速率、乳胶粒子大小、形态及分布的影响.用透射电子显微镜(TEM)观察了乳胶粒子的形态,用粘度法测定了聚苯乙烯的粘均分子量.考察了苯乙烯进行超浓乳液聚合的反应动力学,求得在30℃时聚合速率方程为Rp=K[M]^0.36[I]^0.49[E]^0.72,表观活化能为19.72kJ/mol.所得乳胶粒子的直径在0.1～0.3μm之间,粘均分子量在2×10⁶～4×10⁶之间.为低温下实现超浓乳液薄层聚合提供了参考数据.     

Formation of highly monodispersed emulsifier-free cationic poly(methylstyrene) latex particles

Highly monodispersed emulsifier-free poly(methylstyrene) (PMS) latex particles were prepared via an emulsifier-free emulsion polymerization in the presence of 2,2′-azobis-(2-amidineopropane) dihydrochloride (V-50) as an initiator. A combination of kinetics and molecular weight distribution studies revealed that the polymerization followed the micellization nucleation mechanism. Results showed that an appropriate initiator concentration was necessary to obtain monodisperse and stable latex particles. Conversion of methylstyrene was found to increase significantly with increasing initiator concentrations. However, the size of PMS latex particles decreased with both the increase of initiator concentration and the reaction temperature at a constant ionic strength. The particle size was increased as the ionic strength of the aqueous phase increased, yet the variation of ionic strength had little effect on the particle size distribution. SEM micrographs showed that an agitation rate of 350 rpm or higher was required in order to produce highly monodispersed poly(methylstyrene) latex particles. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2069–2074, 1999     

Polymerization of styrene with ionic comonomer,nonionic comonomer,or both

Nanosized polystyrene latexes with high polymer contents were obtained from an emulsifier-free process by the polymerization of styrene with ionic comonomer, nonionic comonomer, or both. After seeding particles were generated in an initial emulsion system consisting of styrene, water, an ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2-hydroxyethyl methacrylate (HEMA)], and potassium persulfate, most of the styrene monomer or a mixture of styrene and HEMA was added dropwise to the polymerizing emulsion over 6 h. Stable latexes with high polystyrene contents (≤25%) were obtained. The latex particle weight-average diameters were largely reduced (41 nm) by the continuous addition of monomer(s) compared with those (117 nm) obtained by the one-pot polymerization method. Latex particles varied from about 30 to 250 nm in diameters, whereas their molar masses were within 10⁴ to 10⁵ g/mol. The effect of the comonomer concentration on the number of polystyrene particles per milliliter of latex and the weight-average molar masses of the copolymers during the polymerization are discussed. The surface compositions of the latex particles were analyzed by X-ray photoelectron spectroscopy, which indicated that the surface of the latex particles was significantly enriched in NaSS, HEMA, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1634–1645, 2001     

Controlled radical emulsion polymerization of polystyrene

In this paper, a new water-soluble initiator system, 2-bromopropane/CuSO₄/sodium ascorbate, was used as the initiator for emulsion polymerization. Radical emulsion polymerization of styrene was successfully carried out at 80 °C by using sodium dodecylbenzenesulfonate as the emulsifier. The 2-bromopropane/CuSO₄/sodium ascorbate-initiated emulsion polymerization shows the controlled free-radical polymerization features with linear growth of molecular weight. Polystyrene with a relatively high molecular weight and a narrow molecular weight distribution can be synthesized by this method. On the other hand, stable polystyrene latex can be obtained, and the size of the polystyrene latex increased with the increase in monomer conversion.     

Chemical properties of water-soluble,nonionic azo compounds as initiators for emulsion polymerization

Four kinds of water-soluble, nonionic azo compounds were studied in terms of their decomposition rate and initiator efficiency in radical polymerization, and then used for emulsion polymerization. They had relatively low initiator efficiency from 0.09 to 0.46. It was attributed to the susceptibility to a cage effect, depending on their molecular size and hydrophobicity. Four azo compounds initiated emulsion polymerization but nonionic latex particles were not obtained unexpectedly. Methanol-containing medium results in the formation of a bimodal particle size distribution as well as a bimodal molecular weight distribution. © 1996 John Wiley & Sons, Inc.     

丙烯酸甲酯与醋酸乙烯酯的种子乳液聚合

以过硫酸铵（ＡＰＳ） 为引发剂,合成了粒径分布较均匀的聚醋酸乙烯酯种子乳液（ＰＶＡｃ） ,然后以丙烯酸甲酯（ ＭＡ） 为第二单体和以油溶性偶氮二异丁腈（ＡＩＢＡ） 为引发剂,分别进行不溶胀与溶胀条件下的无皂种子乳液聚合,并用透射电子显微镜（ＴＥＭ） 表征了胶粒形态．表明在不溶胀条件下,胶粒形态随ＰＶＡｃ／ ＭＡ 重量比的不同而变化,当ＰＶＡｃ／ ＭＡ 为１／２ 时,形成以ＰＭＡ 为核,ＰＶＡｃ 为壳的胶粒．在溶胀条件下则得到类似互穿网络型乳胶粒．