Synthesis of monodisperse nickel‐coated polymer particles by electroless plating method utilizing functional polymeric ligands

In the electroless plating process, to omit a sensitizing process with SnCl₂, we utilized amino‐functional groups on polymer particles. At first, highly monodisperse functional polymer particles could be prepared by a two‐step seeded polymerization of styrene, divinylbenzene, and glycidyl methacrylate. Then, surface epoxy‐functional groups were converted to amino‐functional groups by treating the particles with a diamine. By using these surface amino functionalities, we tried to prepare uniformly metal‐coated monodisperse polymer particles by electroless plating method. The constituents of an electroless nickel solution bath are nickel salt, a reducing agent, suitable complexing agents, and stabilizers. And the metal thickness was simply controlled by changing the loading amount of substrate polymer particles. Morphological observation of nickel‐plated polymer particles was conducted by using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The structural composition of plated nickel was also investigated. Most of all, the function and the efficiency of the amino‐functional group of polymer particles as a polymeric ligand for metal binding was elucidated. From all observations, it was evident that in the electroless metal plating process without any sensitization step, the deposition of metal clusters on substrate particles is largely dependent upon the particle surface functionality. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3801–3808, 2006     

水相添加剂对热可膨胀聚合物微球颗粒结构和膨胀特性的影响

通过戊烷发泡剂存在下的偏氯乙烯-丙烯腈-甲基丙烯酸甲酯(VDC-AN-MMA)悬浮共聚制备包覆型热可膨胀聚合物微球,考察氯化钠、柠檬酸和重铬酸钾等水相添加剂对聚合物微球颗粒结构和热膨胀特性的影响。结果表明氯化钠、柠檬酸和重铬酸钾的添加均可起到降低聚合过程中形成难膨胀聚合物细微粒子的作用,当氯化钠添加量为4%(质量分数,基于单体,下同)、柠檬酸添加量为2.5%～5.0%、重铬酸钾添加量为0.05%～0.1%时,制备的可膨胀聚合物微球具有粒径分布窄、形态规整、聚合物对发泡剂包覆效果好等特点;加热后未膨胀聚合物微粒数目少,膨胀均匀,膨胀温度区间宽。     

A parallel plate flow cell for the investigation of the role of surfactants in the codeposition of polymer particles in nickel electroplating

A parallel plate flow cell was designed for the study of particle codeposition in metal electrodeposition. Particle deposition was visualized and recorded with a microscope/video assembly. The effects of two surfactants (anionic sodium dodecyl sulphate and cationic cetyl trimethyl ammonium bromide) on the adhesion of anionic polystyrene particles to a nickel substrate were examined. The deposition rate in laminar flow was measured as a function of the main parameters, that is, electrode potential, Ni(ii) concentration, surfactant concentration and pH. The hydrodynamic drag force applies uniformly and tangentially to the collector under laminar flow in contrast with rotating disc or impinging jet cells. No deposition is observed unless specific attractive forces carry the particles through the boundary layer. Particle attachment takes place over a limited range of surfactant/Ni(II) composition and correlates with the formation of a surface film visible under the microscope. Results discussed are based on the adsorption of SDS and CTAB on to both the electrode and the particles, an adsorption which significantly alters the interaction potential at a short distance. The cell gives interesting evidence for the occurrence of specific interactions in electrolytic codeposition. It also proves useful for observing other phenomena, such as hydrogen bubbling.     

Preparation of nickel coating on ZTA particles by electroless plating

With the aim to effectively improve the interface between ZrO₂ toughened Al₂O₃ (ZTA) particles and metal matrix, nickel was deposited on the surface of ZTA particles by electroless plating method. Formation mechanism of nickel coating and effects of the solution pH, loading capacity of ZTA particles and temperature on the nickel deposition were investigated. Microstructures, thickness and element distributions of nickel coating were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that the nickel was successfully deposited on the surface of ZTA particles by electroless plating without noticeable defects. The process of electroless nickel plating could be explained by combination of atomic hydrogen and electrochemistry theories. The interfacial nucleation of nickel is easier to form than spontaneous nucleation in the solution. Deposited Nickel has priority on the surface of ZTA particles comparing to that in solution. The optimal conditions to coat nickel on the surface of ZTA particles are: solution pH 4.7–4.8, loading capacity 15–20?g/L, and electroless plating temperature 85?°C. The ZTA particle reinforced iron matrix composites prepared by powder metallurgy could have better interfacial bonding between ZTA particle and iron matrix because of the nickel coating on the surface of ZTA particle. Nickel diffuses into the iron matrix during the sintering preparation of composite materials. The interface between ZTA particle and iron matrix presents the evidence of non-chemical bonding.     

The effect of electrically charged dielectric walls on the diffusive deposition of submicron aerosol particles

The effect of an electrical charge on a dielectric wall on the deposition of charged aerosol particles is investigated. The dielectric walls used in the deposition experiments, poly(vinyl chloride) or polytetrafluoroethylene disks, are prepared to have known uniform surface charge distributions by using a corona discharge procedure. This avoids any effects on deposition caused by nonuniformity of the surface charge. The surface charge densities are based on measurements of the surface voltage in the center of the sample. Deposition experiments using a turbulently-mixed stirred tank demonstrate that particle deposition rates to the wall decrease as the sample's thickness increases or its relative permittivity decreases, even at a constant surface voltage. The electric field over the sample wall is calculated using the surface charge density, and the convection-diffusion equations describing particle deposition by Brownian and turbulent diffusion and electric migration are solved numerically. The calculated deposition rates agree well with those measured, indicating that quantitative prediction of particle deposition is possible if the surface charge, material, thickness and the effect of adjacent walls are taken into account.     

Polymerization of MMA at the surface of inorganic submicron particles

Inorganic submicron particles, such as TiO₂, were modified with titanate coupling agents. The structure and stability of some titanates, both in solution and at the particle surface, were investigated by various methods. The modified titanium dioxide was dispersed in a solution of sodium dodecylsulphate (SDS) in water. The surfactant adsorbs at the now hydrophobic particle surface, thus creating a micellelike structure with an inorganic particle in the centre. In this system an emulsion polymerization of methyl methacrylate was carried out. Product formed at the particle surface is either physically bound by entanglement or chemically bound by covalent bonding to the titanates. In this way a core-shell morphology is obtained with an inorganic core and a polymer shell. The effects of several reaction parameters on the kinetics of the polymerization were studied. The encapsulated TiO₂ particles may offer interesting prospects in those applications where good coupling between polymer matrix and inorganic particles is necessary, such as latex paints and polymer composite materials.     

SMA polymer thin film electrodeposition on carbon particles

Electrodeposition of styrene-co-maleic anhydride (SMA) polymer, as thin films on carbon particle substrates, was carried out in a fluidized electrode bed reactor (FEBR). Feeder current, time of deposition, flow rate of anolyte (i.e., bed expansion or bed porosity), concentration of SMA in the anolyte, and pH of the anolyte were the key parameters investigated. The film characteristics were evaluated through SEM and FTIR analyses, the amounts determined by weighing. The effect of these parameters on the electrodeposition process is discussed and optimum conditions for deposition are proposed. Also, a possible mechanism for electrodeposition, particularly for the SMA–carbon system, is discussed. Furthermore, where relevant, the parameters and mechanism are compared with those for our parallel work on the ethylene-co-acrylic acid (EAA)–carbon system.     

化学镀镍-铜-磷三元合金工艺的研究

为提高化学镀镍－磷合金镀层的性能及获得多种性能的合金镀层以拓宽其应用范围。在化学镀镍－磷合金液中加入硫酸铜制得镍－铜－磷三元合金。研究了镀液中硫酸镍、次磷酸钠、柠檬酸钠、硫酸铜、稳定剂、光亮剂的含量以及pH值和温度等因素对合金镀层的外观、沉积速度及铜含量的影响。通过5％氯化钠溶液和10％硫酸溶液浸泡试验比较了所得镍－铜－磷合金镀层与镍－磷合金镀层以及前人制得的镍－磷合金镀层的耐蚀性，同时比较了上述镀层的其它性能。结果表明，所得镍－铜－磷合金镀层的耐蚀性、外观、结合力、孔隙率、沉积速度、硬度和耐磨性等性能优于镍－磷合金及前人制得的镍－铜－磷合金镀层。     

Metallization of a liquid crystal polymer by PVD using a nickel interlayer

In this paper metallization of a liquid crystal polymer (LCP) substrate by physical vapor deposition (PVD) is described. Pretreatment of LCP substrates with oxygen-containing plasma improves the adhesion strength between the PVD copper layer and substrate. When a nickel interlayer was used, the adhesion was improved further. Still higher adhesion was also achieved with appropriate bias used during deposition of the nickel interlayer by PVD. Even after 1000 cycles of thermal shock the adhesion strength of Cu/Ni on LCP pretreated with oxygen plasma was still high.     

Role of thermophoresis in the deposition of fume particles resulting from the combustion of high inorganic containing fuels with reference to kraft black liquor

Fume generation and deposition are key processes in many manufacturing operations. These include the manufacture of carbon black and silica fume. In addition to its role in these processes, fume deposition is an important phenomenon in the combustion of fuels containing inorganic compounds. One combustion process where fume deposition presents special problems is the burning of kraft black liquor. This paper presents a laboratory study of fume deposition with emphasis on the kraft recovery boiler. A unique aspect of this study was the construction of an experimental system capable of generating sodium sulfate, sodium carbonate, and sodium chloride fume particles. With this experimental system, variables such as particle size, particle gas-phase concentration, particle composition, temperatures and gas flow rates could be independently controlled. The major objectives of this study are to: (1) determine the mechanisms responsible for particle deposition within the kraft recovery furnace, (2) provide experimental data to support the hypothesis that thermophoresis is the major mechanism responsible for deposition of fume type particles, and (3) correlate the experimental results obtained in the study to deposition rates observed in operating recovery furnaces. The experimental results obtained in this study showed that thermophoresis is the dominant mechanism for fume deposition under conditions similar to those existing in the kraft furnace. This result is well supported by the experimental data. For example, thermophoresis theories accurately predict effects of the temperature, particle concentration, and particle size that were observed in this study. The experimental results obtained in this study were extrapolated to deposition in an operating kraft furnace and found to provide a reasonable prediction of boiler bank deposition. Although the study was targeted at the kraft recovery boiler, the results should be applicable to the combustion of any fuel containing a high level of inorganic material.     

金刚石表面化学镀镍沉积速度影响因素分析

研究了以硼氢化钠为还原剂的金刚石表面化学镀N i工艺,重点探讨了镀液主要工艺参数对沉积速度的影响,获得了最佳工艺条件:硼氢化钠1.0 g/L;氯化镍30 g/L;乙二胺60 g/L;温度85℃;pH值13,并用JSM-5610LV型扫描电镜观察了原始金刚石和镀覆后的形貌。     

Janus-like polymer particles prepared via internal phase separation from emulsified polymer/oil droplets

Poly(methylmethacrylate) (PMMA) and polystyrene(PS)/PMMA particles with Janus-like morphology were prepared via the internal phase separation followed by extraction of hexadecane (HD) template. The internal phase separation was triggered by evaporation of dichloromethane (DCM) from the polymer/HD/DCM-in-water emulsion droplets, which led to the formation of HD/PMMA or HD/PMMA/PS microparticles. After extraction of HD with hexane, PMMA or PS/PMMA particles with different morphologies were produced. Poly(vinyl pyrrolidone) (PVP), sodium dodecyl sulfonate (SDS) or sodium dodecyl benzylsulfate (SDBS) was chosen as the emulsifier. The morphology depended on the HD/polymer ratio and the interfacial tensions, which were adjusted by changing the type of the emulsifier and its concentration. With poly(vinyl pyrrolidone) (PVP) emulsifier, PMMA hollow spheres were observed; while with SDS emulsifier, the particles changed from bowl-like particles to hemispheres and truncated spheres with the increase of SDS content. The morphology of PS/PMMA composite particles depended on the ratio of the two polymers. Scanning electron microscopy observation, selective etching and X-ray photoelectron spectroscopy results confirmed that PMMA tended to engulf PS component. With the increase of PMMA/PS ratio, the particles changed the morphology from capped acorn to ‘ball in bowl’ morphology. Furthermore, the particle morphology was simulated via a theoretical model based on the minimum interfacial energy of the system. The simulation results agreed with the experimental observations. Our results indicate that internal phase separation is an effective method to obtain Janus-like microparticles. Via adjusting the composition of the system and the corresponding interfacial tensions, we could tailor the polymer particles with different morphologies.     

Morphology of composite polymer emulsion particles consisting of two kinds of polymers between which ionic bonding intermolecular interaction operates

The morphology of particles (I) produced by seeded emulsion copolymerization of styrene (S) and sodium p-styrene sulfonate (NaSS) with butyl acrylate (BA)-methacryloyloxyethyl-trimethylammonium chloride (QDM) copolymer particles as seed was examined in comparison with poly(butyl acrylate) (PBA)-polystyrene (PS) composite polymer emulsion particles (II). In an electron microscopic observation, it was observed that II particles had an anomalous shape and the electron densities at different points in the particle were heterogeneous, whereas I particles had an almost spherical shape and the electron densities were homogeneous. The maximum tensile strength and toughnes were much larger in II than I. The dynamic mechanical studies indicate that II film had a macroheterogeneous structure consisting of PS-rich and PBA-rich phases, whereas I film had a microheterogeneous structure. These ressults suggest that there is an effect of intermolecular interaction between polymers of different kinds on the formation of heterogeneous structure in particles consisting of two kinds of polymers.     

Coagulation of polymer emulsions on metal surfaces

Emulsions of polyethylacrylate using sodium dodecylsulfate, cetylpyridinium chloride or nonylphenol ethoxylate as anionic, cationic and nonionic emulsifiers were prepared and the polymer deposition on metal panels in presence of an acid and an oxidizing agent was studied. Homogeneous films are formed within limited concentration ranges of the reactants. Diluted hydrofluoric acid and diluted hydrogen peroxide are useful components. Instead of a chemical oxidant a potential of 250 to 500 mV or more may be applied. The iron ion content of the film was determined by atomic absorption spectroscopy. A ratio of iron to emulsifier of 4.1 : 1 was found. The distribution of iron in film cross-cuts by scanning electron microscopy using the energy dispersive technique shows a high iron concentration near the metal interface and a sharp drop towards the film surface. In the outer third of the film the ratio iron to emulsifier is nearly 1 : 1. By adding iron salt solutions to polyethylacrylate emulsions the coagulation point was determined and a ratio iron ion to emulsifier of 1 : 1.2 was found in the coagulate. Steel panels were coated as well as phosphated steel or zinc but no film formation appeared on aluminum.     

Size-dependent mechanical behavior of nanoscale polymer particles through coarse-grained molecular dynamics simulation

Anisotropic conductive adhesives (ACAs) are promising materials used for producing ultra-thin liquid-crystal displays. Because the mechanical response of polymer particles can have a significant impact in the performance of ACAs, understanding of this apparent size effect is of fundamental importance in the electronics industry. The objective of this research is to use a coarse-grained molecular dynamics model to verify and gain physical insight into the observed size dependence effect in polymer particles. In agreement with experimental studies, the results of this study clearly indicate that there is a strong size effect in spherical polymer particles with diameters approaching the nanometer length scale. The results of the simulations also clearly indicate that the source for the increases in modulus is the increase in relative surface energy for decreasing particle sizes. Finally, the actual contact conditions at the surface of the polymer nanoparticles are shown to be similar to those predicted using Hertz and perfectly plastic contact theory. As ACA thicknesses are reduced in response to reductions in polymer particle size, it is expected that the overall compressive stiffness of the ACA will increase, thus influencing the manufacturing process.     

Preparation of a Nickel Ion Containing Langmuir–Blodgett Multilayer and an Ultra-Thin Nickel Film Deposited on an Interpenetrating Polymer Network Substrate

The nickel ion containing Langmuir–Blodgett (LB) multilayer was prepared by transferring nickel acetate, spread on the surface of a sub-phase of ultra-pure water and stearic acid–chloroform mixture, onto an interpenetrating polymer network (IPN) substrate. The substrate was prepared by dip-pulling a hydrophilic silicon wafer or a glass plate into precursors, followed by solidification at room temperature, in order to create an ultra-thin and uniform surface for metal deposition. The multilayer was then converted into an ultra-thin nickel film after chemical reduction by 0.01 mol/l sodium borohydride. The surface pressure of the monolayer and dipping speed of substrate were determined by measuring the transfer coefficient. Fourier transform infrared spectroscopy (FT-IR) was used to investigate the interactions of the nickel ions with the IPN during the multilayer deposition on substrate, and the metal transformations of nickel ion in the ultra-thin film. The shifted peak location for –C=O verified the interactions between the IPN and the nickel ion and the transformation of the nickel ion by reduction. Further reduction caused the organic phase to dissolve, resulting in most of it being removed from the multilayer. The surface morphologies of the LB multilayer were detected by atomic force microscopy (AFM). Compared with the IPN, which formed a uniform and flat film, within a range of nanometers, the Ni/IPN multilayer and Ni ultra-thin film both showed some surface fluctuations, although these were still within nanometer range. The roughness of the nickel ion containing multilayer and the ultra-thin nickel film was 1.123 nm and 0.773 nm with a maximum height of 12.451 nm and 14.933 nm, respectively, which were larger than that of pure IPN substrate of 0.593 nm with the max height of 6.795 nm.     

Gas-phase synthesis of l-leucine-coated micrometer-sized salbutamol sulphate and sodium chloride particles

Coating of micrometer-sized particles of salbutamol sulphate or sodium chloride with the amino acid l-leucine in the gas phase is described. A novel method to synthesize core particles and coat them with l-leucine simultaneously was carried out in an aerosol flow reactor. The coating was prepared via temperature-induced heterogeneous nucleation of l-leucine vapor on the 0.6-1.0 µm core particles, and subsequent growth of l-leucine crystals by physical vapor deposition. The core salbutamol particles were amorphous, whereas the NaCl core particles were crystalline. The l-leucine sublimation that took place at 140-195 °C depended on the identity of the core material due to (i) molecular interaction and (ii) phase mixing. The former was dominant with salbutamol/l-leucine particles and the latter was dominant with NaCl/l-leucine particles. During the vapor deposition, l-leucine formed a discontinuous coating layer of leafy-looking crystallites, with sizes from a few nanometers to hundreds of nanometers, pointing out from the core particle surface. The l-leucine deposition properties depended on the core morphology: l-leucine crystallites were distributed more evenly on salbutamol core surfaces than on salt core surfaces, where the crystallites were localized mainly on edges. The stability of coated salbutamol particles was retained during storage under humid conditions.     

Transformation of waterborne hybrid polymer particles into films: Morphology development and modeling

Films cast from multiphase polymer particles have the potential to combine the properties of their components synergistically. The properties of the film depend on the hybrid polymer architecture and the film morphology. However, how the polymer microstructure and particle morphology are transformed during film formation to determine the film morphology is not well understood. Here, using waterborne alkyd-acrylic nanocomposite particles in a case study, it was found that phase migration leading to the formation of aggregates occurred during film formation. A coarse-grained Monte Carlo model was developed to account for the effects of polymer microstructure and particle morphology on the morphology of the film. The model was validated by comparing its predictions with the observed effects, and then used to explore combinations of polymer microstructure and particle morphology not attainable with the system used as a case study. Significantly, the compatibility of the phases was found to have a greater influence than the morphology of the particles in determining the film structure.     

Synthesis of polymer suspensions for immunochemical studies

New methods of preparing polymer suspensions of narrow particle size distribution with amino and carboxylic groups on the particle surface have been suggested. The effects of various factors on the diameter and size distribution of polymer particles, their stability, and concentration of functional groups on the particle surface were investigated. The application of such polymer suspensions for immunochemical studies was shown. © 1996 John Wiley & Sons, Inc.