Preparation of poly(amino‐amide) particles complexed with ZnO particles using silane coupling agents

Poly(amino‐amide) particles were prepared by reacting 4,4′‐diphenyldicarbonyl chloride and 3,3′‐diaminobenzidine using a precipitation polymerization method with ultrasonic irradiation. The resulting particles had a narrow size distribution with an average diameter of 334 nm and showed excellent dispersion stability in water. The particles obtained were then modified with silane coupling agents (GPES) by reacting the amino groups of the poly(amino‐amide) particles with the epoxide rings of the GPES molecules in N,N‐dimethylformamide or N‐methylpyrrolidone using di‐n‐butyltin dilaurate as a catalyst. The amount of GPES covalently bonded to the poly(amino‐amide) particles was found to depend strongly on the reaction solvent and catalyst used. The resulting particles showed a narrow size distribution and the connections among the particles were not observed. On the other hand, the particles before and after modification showed different thermal properties and dispersion stability in water. The GPES‐modified aromatic polyamide particles were then complexed with ZnO particles with an average diameter of about 20 nm in aqueous acetic acid solution. It was found that the surface of the aromatic polyamide particles was covered with ZnO particles via hydrolysis reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4908–4918, 2009     

Stabilizer-free precipitation copolymerization of renewable bio-based α-methylene-γ-butyrolactone and styrene

Stabilizer-free precipitation copolymerization of α-methylene-γ-butyrolactone (MBL) and styrene (St) was carried out in isoamyl acetate with BPO as initiator at 80°C. The influence of monomer feed ratio, initiator concentration and reaction time on the size and morphology of the obtained polymer particle was investigated in details. It was found that the monomer feed ratio play an important role on the particle formation process. When the monomer feed ratio of MBL to St was 1:2, narrow size distributed spherical polymer particles were formed with number average diameters in the range of 785–2620 nm. The formation process of polymer particle was studied to get a deep insight into the polymerization process of this reaction system. It was found that the formation mechanism of the poly(MBL-co-St) particles was similar to that of conventional precipitation polymerization. After a short nucleation stage (10 min), the amount of polymer particles remained constant and the particle growth mainly came from the capturing of newly formed polymer chains. The chemical composition and thermal property of the poly(MBL-co-St) were fully characterized by FTIR, ¹H-NMR spectra, and DSC.     

Synthesis of Sub-100 nm and Narrow Particle Size Distribution Cationic Latex by One-Step Emulsion Polymerization

A novel approach to synthesize narrow particle size distribution cationic latex particles based on styrene and butyl acrylate was proposed. The effect of monomer/water ratios, surfactant (cetyltrimethylammonium chloride) concentrations, and monomer compositions on the evolution of particle size, distribution, number, and morphology as a function of monomer conversion was concerned in order to confirm the optimum polymerization condition. As expected, the particle size of the ultima latex increased with monomer/water ratios and styrene contents decreased with increasing surfactant concentrations. Continuous nucleation phenomena occurred when monomer/water ratio was lesser than 30/70, resulting in a gradual increase in the number of particles in the whole polymerization process. Combined with the previous work (Colloid and Polymer Science, 2014, 292: 519–525), it was concluded that particle coagulation easily took place in cationic emulsion polymerization of styrene. Thus, the narrow particle size distribution cationic latexes with particle scale between 50 nm and 80 nm, 30 wt% solid content could be prepared in a short reaction time.     

Study on soap‐free P(MMA‐EA‐AA or MAA) latex particles with narrow size distribution

Soap‐free poly(methyl methacrylate‐ethyl acrylate‐acrylic acid or methacrylic acid) [P(MMA‐EA‐AA or MAA)] particles with narrow size distribution were synthesized by seeded emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA) and acrylic acid (AA) or methacrylic acid (MAA), and the influences of the mass ratio of core/shell monomers used in the two stages of polymerization ([C/S]_w) and initiator amount on polymerization, particle size and its distribution were investigated by using different monomer addition modes. Results showed that when the batch swelling method was used, the monomer conversion was more than 96.0% and particle size distribution was narrow, and the particle size increased first and then remained almost unchanged at around 600 nm with the [C/S]_w decreased. When the drop‐wise addition method was used, the monomer conversion decreased slightly with [C/S]_w decreased, and large particles more than 750 nm in diameter can be obtained; with the initiator amount increased, the particle size decreased and the monomer conversion had a trend to increase; the particle size distribution was broader and the number of new particles was more in the AA system than in the MAA system; but the AA system was more stable than the MAA system at both low and high initiator amount. Copyright © 2006 John Wiley & Sons, Ltd.     

Nitroxide-mediated photo-controlled/living radical dispersion polymerization of methyl methacrylate

The nitroxide-mediated photo dispersion polymerization of methyl methacrylate (MMA) was performed by irradiation at room temperature using (2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator, (4-tert-butylphenyl)-diphenylsulfonium triflate as the photo-acid generator, and polyvinylpyrrolidone (PVP) as the surfactant in a mixed solvent of methanol/water = 3/1 (v/v). The MTEMPO-mediated photo dispersion polymerization produced spherical particles of PMMA, while the uncontrolled photo dispersion polymerization without MTEMPO provided nonspherical particles. The size distribution of the spherical particles decreased as the PVP concentration increased. The spherical particles showed a comparatively narrow molecular weight distribution of ca. 1.6. The livingness of the polymerization was confirmed on the basis of the linear correlations of the first-order time–conversion plots and conversion–molecular weight plots. The simultaneous control of the size distribution and molecular weight was possible as long as the light penetrates into the particles.     

Crosslinking network structure governing particle shape and size distribution by one-step emulsion polymerization in the presence of particle coagulation

In this study, sub-200?nm, crosslinked latex particles with a narrow particle size distribution were prepared by one-step emulsion polymerization in the presence of particle coagulation. The relationship between the particle shape and particle coagulation was investigated by varying the time of crosslinking network structure formation and particle coagulation. Particles with irregular shapes such as doublet, triplet, and ellipsoid were obtained using divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agents, because the crosslinking network structure of particles was formed before the particle coagulation. In contrast, latex particles with a uniform spherical shape were also prepared using triallyl isocyanurate (TAIC) or dihydrodicyclopentadienyl acrylate (DCPA) as the crosslinking agents by delaying the time of crosslinking network structure formation. Alternatively, uniform spherical latex particles were prepared by bringing forward the particle coagulation time using cationic initiator, 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). This study presents a new idea that would further broaden the application of particle coagulation in emulsion polymerization.     

乳液聚合法制备纳米金/聚苯乙烯复合粒子

以氯金酸为前驱体,十二烷基硫醇和硼氢化钠分别作为稳定剂和还原剂,采用相转移法制备了单分散的金纳米粒子.将金纳米粒子通过乳液聚合的方法制备了纳米金/聚苯乙烯复合粒子.通过紫外-可见吸收光谱(UV-Vis)研究了纳米金和纳米金/聚苯乙烯复合粒子的光吸收特性,使用傅立叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电子显微镜(TEM)和动态光散射(DLS)对产物的组成、晶体结构、形貌、以及粒径进行了表征.结果表明,复合粒子为粒径分布较窄的球形,其中的金纳米粒子为面心立方结构.热失重分析(TGA)说明制备的纳米金/聚苯乙烯复合粒子具有很好的热稳定性.     

Iron oxyhydroxide colloid formation by gamma-radiolysis

Gamma-irradiation of deaerated aqueous solutions containing FeSO(4) leads to the formation of uniform-sized colloidal particles of γ-FeOOH. At short irradiation times, or in solutions with a low initial [Fe(2+)](0), spherical particles with a size less than 10 nm are formed. These primary particles grow to form a dendritic structure upon longer irradiation, and the final size of the large particles is ～60 nm with a very narrow size distribution. Further prolonged irradiation does not change the final particle size. The narrow size distribution is attributed to rapid homogeneous radiolytic oxidation of soluble Fe(2+) to relatively insoluble Fe(3+) hydroxides [Fe(H(2)O)(6-n)(OH)(n)](3-n) leading to particle nucleation by spontaneous condensation. These primary particles then grow into γ-FeOOH particles with a dendritic structure. The final size reached at long times is regulated by the steady-state redox conditions established during long-term irradiation at the aqueous-solid interface.     

The synthesis of polymer suspension with narrow particle size distribution for immunochemical investigations

 Heterophase polymerization of styrene in the presence of di-p-tolyl-o-carbalkoxyphenylcarbinol (DTC) soluble in monomer and insoluble in water, as stabilizer, was investigated. The factors affecting polymer particle diameter, their size distribution and stability were investigated. It was suggested that polymer particles are formed from monomer droplets. The polystyrene suspension with narrow particle size distribution synthesized in the presence of DTC, was used for immunochemical research. Received: 10 March 1998 Accepted: 8 June 1998     

New Method for Fabricating Aromatic Polyamide Particles with a Narrow Particle Size Distribution

Three types of aromatic polyamide particles have been prepared from reacting diamines and diacid chlorides in an acetone or dioxane solution that includes water, using the precipitation polymerization method employing ultrasonic irradiation. The particle diameters were in the range from 300 nm to 1.2 µm with a narrow size distribution. The surface morphology and crystallinity differed greatly among the particles. They began to degrade at temperatures above 400 °C. Also the morphology depended on the ultrasonic frequency. The addition of water was essential to form particles using this polymerization method. Further it was useful to increase the molecular weights of polyamide products.

     

Effect of temperature on styrene emulsion polymerization in the presence of sodium dodecyl sulfate. II

The batch emulsion polymerization kinetics of styrene initiated by a water‐soluble peroxodisulfate at different temperatures in the presence of sodium dodecyl sulfate was investigated. The curves of the polymerization rate versus conversion show two distinct nonstationary‐rate intervals and a shoulder occurring at a high conversion, whereas the stationary‐rate interval is very short. The nonstationary‐state polymerization is discussed in terms of the long‐term particle‐nucleation period, the additional formation of radicals by thermal initiation, the depressed monomer‐droplet degradation, the elimination of charged radicals through aqueous‐phase termination, the relatively narrow particle‐size distribution and constant polydispersity index throughout the reaction, and a mixed mode of continuous particle nucleation. The maximum rate of polymerization (or the number of polymer particles nucleated) is proportional to the rate of initiation to the 0.27 power, which indicates lower nucleation efficiency as compared to classical emulsion polymerization. The low activation energy of polymerization is attributed to the small barrier for the entering radicals. The overall activation energy was controlled by the initiation and propagation steps. The high ratio of the absorption rate of radicals by latex particles to the formation rate of radicals in water can be attributed to the efficient entry of uncharged radicals and the additional formation of radicals by thermally induced initiation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1477–1486, 2000     

Living Ab Initio Emulsion Polymerization of Methyl Methacrylate in Water Using a Water‐Soluble Organotellurium Chain Transfer Agent under Thermal and Photochemical Conditions

Ab initio emulsion polymerization of methyl methacrylate (MMA) using a water‐soluble organotellurium chain transfer agent in the presence of the surfactant Brij 98 in water is reported. Polymerization proceeded under both thermal and visible light‐irradiation conditions, giving poly(methyl methacrylate) (PMMA) with controlled molecular weight and low dispersity (?<1.5). Despite the formation of an opaque latex, the photoactivation of the organotellurium dormant species took place efficiently, as demonstrated by the quantitative monomer conversion and temporal control. Control of polymer particle size (PDI<0.030) was also achieved using a semi‐batch monomer addition process. The PMMA polymer in the particles retained high end‐group fidelity and was successfully used for the synthesis of block copolymers.     

Synthesis of monodisperse submicron spherical poly(methylmethacrylate) particles and the molecular dynamics simulation

The molecular-dynamics method has been used to determine the conformational states of poly(methyl methacrylate) chains in a medium composed of water and a monomer (methyl methacrylate). Experimentally detected spherical particles resulting from polymerization have been found to take the form of droplet-type aggregates containing several chains, with the water and monomer concentrations in the aggregates differing from those in the dispersion medium. It has been shown that the methyl methacrylate concentration in an initial reaction mixture of about 20% is optimal for the formation of spherical droplet-type aggregates. It has been experimentally established that spherical poly(methyl methacrylate) particles with a narrow size distribution are formed at a methyl methacrylate concentration of ≈23%.     

Design of New Reaction Fields for Spherical Polypyrrole Particle Synthesis

Summary: Polypyrrole conducting polymers have been investigated widely for various applications because of their thermal and environmental stability and good electrical conductivity. Using chemical oxidative polymerization for the synthesis of polypyrrole particles, the reaction rate is very fast. In this study, we designed two new reaction fields for the synthesis of spherical polypyrrole nanoparticles. In the first system, oxidative polymerization of monomer droplets infused in a water/oil (W/O) emulsion reaction field was investigated. The second system employed dispersed monomer in an aqueous solution with a low concentration of oxidant in which polymerization was augmented by ultrasonic irradiation. Effective control of the reaction rate was important for enabling the synthesis of fine spherical polypyrrole particles.     

Polymer mediated peptide immobilization onto amino-containing N-isopropylacrylamide-styrene core-shell particles

Monodisperse cationic core-shell latex particles have been prepared using a shot polymerization process, with N-(3-aminopropyl)-methacrylamide-hydrochloride (APMH) as the functional monomer. The final latexes were characterized with respect to final polymerization conversion, water soluble polymer formation, particle size and size distribution, surface charge density and electrokinetic properties. Then the covalent grafting of maleic anhydride-alt-methyl vinyl ether (MAMVE) copolymer onto aminated latex particles was investigated. The most efficient conditions to obtain derivatised particles with no alteration of the colloidal stability were to control both polymer amount/latex particles concentration ratio and the mixing method of the two species. The charge inversion of the hydrolysed MAMVE functionalized particles was demonstrated by measuring the electrophoretic mobility as a function of pH. Finally, the covalent binding approach was implemented with peptide-MAMVE conjugates, confirming the great potential of this promising methodology for the preparation of reactive latex particles bearing peptides.     

Visible-Light Initiated Dispersion Photopolymerization of Styrene

Polystyrene (PS) particles were synthesized in ethanol/water mixture by dispersion polymerization using visible light irradiation, with either a N-heterocyclic carbene borane-based photoinitiating system (PIS) or a disulfide. With the full PIS and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as stabilizer, the size distributions were broad and the amount of PEGMA had a strong impact on the experiment reproducibility. The addition of a base solved the problem, leading to faster polymerizations, narrower size distributions and larger particles. With the disulfide as sole PIS, bigger and narrowly distributed PS particles were again formed. Quantitative conversion was achieved in each system, with particle size ranging between 100 and 350 nm. The use of poly(N-vinylpyrrolidone) as stabilizer led to significantly larger particles, up to 1.2 μm, with narrow size distributions. The production of such large latex particles by photoinitiated polymerizations is unprecedented.     

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 .     

Preparation of Eu-Doped Y(2)O(3) Luminescent Nanoparticles in Nonionic Reverse Microemulsions

In this study, Y(2)O(3):Eu luminescent nanoparticles were prepared by precipitation of aqueous yttrium nitrate/europium nitrate solution using ammonium hydroxide in the reverse microemulsions based on polyoxyethylene (5) nonylphenyl ether/polyoxyethylene (9) nonylphenyl ether, cyclohexane, and water. With Eu-doped Y(2)O(3) nanoparticles obtained, particle size, shape, chemical composition, crystalline formation rate, crystallinity, and photoluminescence were measured and compared with those of particles formed by a bulk precipitation method. The nanoparticles synthesized in microemulsion showed a narrow size distribution, spherical shape, fast crystalline formation rate, high crystallinity, and strong photoluminescence. This stronger photoluminescence of particles formed in a microemulsion might be attributed to more densely packed particles with very few voids and higher crystallinity at a relatively low temperature than those synthesized through a bulk precipitation method. Copyright 2000 Academic Press.     

Cationic amino-containing N-isopropyl- acrylamide–styrene copolymer latex particles: 1-Particle size and morphology vs. polymerization process

 Cationic hydrophilic copolymer latexes were synthesized at 70 °C either by batch or two-step emulsifier-free emulsion poly-merization of styrene (St), N-iso-propylacrylamide (NIPAM), and aminoethylmethacrylate hydro-chloride (AEM) using 2,2′-azobis (2-amidinopropane) dihydrochloride as initiator. At first, batch polymerization kinetics were followed by gas chromatography (GC), revealing that NIPAM rapidly homopolymerized, before the polymerization of styrene had started. Particle size analysis by quasi-elastic light scattering (QELS) and transmission electron microscopy (TEM) showed that monodispersed particles were obtained with the formation of a poly[NIPAM] rich shell. Adding a small amount of the cationic monomer caused a strong decrease of the particle size without affecting the size monodispersity. When a shot process was used, a narrow particle size distribution was maintained, provided that the monomer addition was performed at a relatively high conversion of the first batch step. The poly[NIPAM] rich shell layer was larger with the shot process, but increasing the amino-containing monomer in the recipe resulted in a dramatic decrease of the thickness. Combination of transmission, scanning and atomic force microscopy techniques showed that these hydrophilic particles exhibited odd-shaped structures, the unevenness being dependent upon the performed process. Kinetic data and particle morphology information were inferred for discussion of the polymerization mechanism of this system. Received: 21 August 1997 Accepted: 22 October 1997     

核/壳乳液聚合工艺中乳化剂的定量研究

以十二烷基硫酸钠(SDS)为乳化剂,采用多步种子乳液聚合方法制备了核/壳结构乳液,研究了乳化剂加入量以及加料速率对核壳乳液聚合的影响,并推导了核及壳乳液聚合阶段所需乳化剂量的计算公式.研究表明,当种子、核、壳乳液聚合阶段单体量分别为12g、50g和50g,种子乳液聚合阶段加入的乳化剂量为0.44g时,控制核、壳乳液聚合阶段乳化剂的加入量分别在0.64～2.07g及0.04～2.12g之间,且预乳化单体的滴加速度低于2.3g/min时,可以防止二次成核及新乳胶粒子的形成,制得粒径分布窄、核/壳结构明显的乳胶粒子.利用透射电镜(TEM)对所制备的核壳结构乳胶粒子的结构形态进行了验证,试验结果与理论预测结果一致.