A Novel Route to Prepare Cationic Polystyrene Latex Particles with Monodispersity

Performance check of particle size standards within and after shelf-life using differential mobility analyzer

Surface-active properties of copolymers of N,N-dimethylacrylamide (DMA) with n-alkylsubstituted acrylamides, namely as n-butylacrylamide (NBA), n-hexylacrylamide (NHA), n-octylacrylamide (NOA), n-dodecylacrylamide (NDA), and their adsorption onto polystyrene (PS) latex particles were studied at 25°C in water. Surface tension lowering (Δγ) at a concentration of 0.1 g dL−1, where adsorption at air-water interface is close to saturation, increased with the content of N-alkylacrylamide units for respective copolymers containing different N-alkylacrylamide units. The dependence was stronger for copolymers with N-alkylacrylamides bearing the higher alkyl group. The amount of adsorption (Ws) onto PS particles at saturation also increased with the content of N-alkylacrylamide units in the copolymers. Ws linearly increased with Δγ for copolymers with NBA and those with lower contents of NHA and NOA which do not form intramolecular hydrophobic microdomains, whereas copolymers of NDA and those with higher contents of NHA and NOA, which form the microdomains, exhibited large Ws but a small increase with Δγ. Ws were lower and also slightly increased with Δγ for polymers of DMA, N-acryloylpyrrolidine (APR) and N-isopropylacrylamide (IPA). It was deduced that the adsorptions of polymers and copolymers used here at air-water and PS particle-water interfaces are mainly governed by their overall hydrophobicity and that of their alkyl groups of n-alkylacrylamide units, respectively.

Singularly narrow size distributions of 200 nm polystyrene latex spheres determined by high resolution mobility analysis

We describe a newly constructed annular-type differential mobility analyzer (DMA) with an effective electrode length of 60 cm, which is longer than that of our original DMA (40 cm length). This long DMA was developed to extend the classification size of particles measuring up to 1.5 μm. As an application of this DMA, the mean diameters and standard deviations were determined for six samples of monodisperse polystyrene latex (PSL) particles ranging from 0.94 to 1.27 μm in nominal diameter. These PSL particles suspended in double-distilled water were aerosolized by a glass nebulizer and then introduced into the DMA. The mean diameters and standard deviations of these PSL particles were calculated by Ehara's method and compared with the nominal diameters and uncertainties. There was good correlation between the nominal diameters of these samples—particularly for recently certified samples—and the measured diameters. Classification of aerosol particles more than 1 micrometer in diameter using this DMA will be useful for many purposes.

Three-component interpenetrating polymer networks (IPNs) comprising polyurethane (PUR), poly(n-butyl methacrylate) (PBMA), and polystyrene (PS) latex particles were prepared in a modified one-shot synthesis. The hydroxy-functionlized and unmodified polystyrene latex particles were synthesized via a seeded emulsion polymerization. The incorporation of hydroxyethyl methacrylate into the latex particles was confirmed via diffuse reflectance infrared analysis and modulated-temperature differential scanning calorimetry. The IPNs were characterized by dynamic mechanical thermal analysis, tensile testing, hardness measurements, and transmission electron microscopy. The three-component materials exhibited higher values for the Young's modulus and the Shore A hardness and for the dynamic storage modulus in the higher temperature range from 80 to 140°C than did the PUR/PBMA IPN alone. The latex particles with the hydroxyl functionality exhibited a better miscibility with the microheterogeneous PUR/PBMA IPN than did unfunctionalized PS latex particles, and, therefore, resulted in materials with better damping properties in the temperature range between 80 and 140°C. Transmission electron micrographs confirmed the imporved miscibility of the functionalized latex particles. The latex particles were not, however, dispersed on an individual level but formed agglomerates of between 2 and 20 μm. © 1996 John Wiley & Sons, Inc.

Interfacial physicochemical properties of functionalized conducting polypyrrole particles

A single-beam gradient force trap or an optical laser tweezer has been a powerful tool to accurately measure pico-newton to femto-newton forces in a variety of fields, such as biology, colloid/polymer physics, and rheology. When an appropriate refractive index mismatch between an object and a medium is provided, the laser beam can hold the object of which its size ranges from a few nanometers to tens of micrometer scale. The optical trapping mechanism depends on the relative length scale between an object and the wavelength of a light. In the Rayleigh regime where the diameter of the object is smaller than the wavelength of the light ( ), the trap stiffness increases with the particle size, as the number of rays incident on the particle increases. On the contrary, all rays hit an object in the ray optics regime ( ) such that Ashkin expected the trapping force to be independent of its size without quantitative calculations. Similarly, Wright et al. predicted that the size dependence on the axial and radial trapping forces are negligible in the ray optics regime, based on calculating the dimensionless efficiency of the optical trapping force for a single ray. Using the generalized LorenzMie theory, Lock also suggested that the trapping force in the axial direction does not change with the particle size. However, Simmons et al. reported the experimental results in which the trap stiffness for dielectric particles decreases as the size increases when the particle size is larger than the wavelength of a light. More recently, Mazolli et al. used an explicit partial-wave representation to extend the force expression from the Rayleigh regime (i.e., electromagnetic force model) to the GOA. In the ray optics regime, they reported that the trap stiffness is inversely proportional to the particle radius. Tlusty et al. also calculated the trapping force of highly localized fields on dielectric particles in which the trapping force in the ray optics regime decreases as their size increases. In this communication, we aim to address such contradiction, regarding the dependence of the optical trapping force on the particle size in the ray optics regime. Based on the GOA, we analytically calculate the optical trapping force with varying the particle size. Then, we compare the analytical calculations to the drag experiments in which a particle trapped by the laser tweezers is subjected to the Stokes drag force. We also provide a schematic explanation, based on drawing the ray propagation and finding the magnitude of the momentum change. Before we report our results, experimental materials and method are briefly described. We use polystyrene (PS, Interfacial Dynamics Corporation) latex particles with different radii, a=1.4, 1.7, and 3.7 μm. The refractive index of these particles is np=1.57. In order to obtain the trap stiffness (κt), which is the ratio of the Stokes drag force (Fs=6πaηu) to the lateral displacement (∆y) from the center of the particle, it is held in the aqueous phase (refractive index, nm=1.326) by the laser tweezers, and subjected to drag forces by translating the microscope stage at several constant velocities between u=3 and 7 μm/s. The viscosity of the aqueous solution is η=1 cP. We use particle tracking to measure the particle displacement during applying the Stokes flow around the particle. A movie captured on a CCD camera (Hitachi KP-M1) is saved at a frame rate of 29.97 frames/s. The digitized image sequences are imported to image processing software (ImageJ) to find the particle displacement (∆y) from the equilibrium position in the optical trap. The laser tweezer apparatus is constructed around the inverted microscope. The laser is generated by a 4-Watt CW Nd:YAG laser (λ0=1,064 nm, Coherent Compass 1064-400M). A water immersion objective (63×, NA 1.2, Zeiss C-Apochromat) is used to provide a high convergence angle (φmax), which is a maximum half angle of the conelike laser beam, given by φmax=sin(NA/nm)≈64.5. We refer the reader to Pantina and Furst for a more detailed description of the laser tweezer setup. In order to quantitatively calculate the optical trapping force in the ray optics regime, we consider the first reflection and the successive refractions of a single incident ray with power (P) hitting a dielectric spherical particle, the dimensionless efficiency (Q) of the trapping force is given by,

Steady state fluorescence (SSF) and photon transmission (PT) techniques were used for studying film formation from TiO 2 and Al 2 O 3 covered polystyrene (PS) latex particles. These films were annealed at elevated temperatures in 10 min time intervals above glass transition (T g ) temperature of polystyrene. Fluorescence emission, I p and transmitted photon, I tr intensities were measured after each annealing step to monitor the stages of film formation. Films present dramatic increase in both I tr and I p above the certain onset temperature called minimum film forming temperature, T 0 . Dissolution of annealed PS film, with high TiO 2 content presented a nice, ordered nano-sized ceramic structure, which may predict the construction of nano-layer photonic crystals. It was observed that latex particles are encapsulated above a critical Al 2 O 3 content of 33 wt% which corresponds to the critical occupation probability of p c =0.33 at which the film obey the site-percolation model with a critical exponent of 0.45.

Two-phase latex particles consisting of mainly polystyrene (PS) and polyisoprene (PI) in ratios varying from 70∶30 to 20∶80 were prepared using different polymerization techniques. Methacrylic acid (MAA) was used in small amounts as a comonomer. The latexes had narrow size distributions, and showed different particle morphologies depending on the monomer composition and the polymerization conditions used. In most cases the latexes were filmforming at room temperature. Particle size distributions and average particle sizes of the latexes have been determined using different particle sizing methods. Size determination by TEM was performed after staining with osmium tetroxide (OsO4) or uranyl acetate (UAc). The staining methods showed no significant differences in particle size averages and particle size distributions when the ratio between the PI and PS phase did not exceed 50∶50. At higher phase ratios OsO4 staining was preferred. The glass transition temperature of the PI phase increased after OsO4 staining, which prevented deformation of the latex particles. Particle morphologies for the heterogeneous latex particles were also determined after OsO4 staining. Particle sizes measured by TEM were generally smaller than the corresponding sizes measured by quasielastic light scattering (QELS). The difference in the measured diameters increased with increasing PI and PMAA content in the latex particles. The larger sizes observed by QELS are results of the presence of an immobilized water layer surrounding the particles in the aqueous environment, water absorption and swelling due to the presence of carboxylic acid groups, and adsorption of soluble carboxylated polymers forming a hydrophilic corona around the particles. By TEM the hard sphere diameters of dehydrated particles are measured.

Adsorption of polystyrene–poly(4-vinylpyridine) diblock copolymer on the assembled latex film

We report the effect of graphene oxide (GO) on film formation and morphological properties of GO-doped polystyrene (PS) latex nanocomposite (PS latex/GO) films using UV-visible absorption spectroscopy and scanning electron microscopy (SEM). PS latex particles were synthesized through emulsion polymerization technique and then nanocomposite blends, each containing different concentrations of GO ranging from 0 wt% to 70 wt%, were obtained. Prepared blends were deposited on glass plates via drop-casting method, and coated substrates were annealed at different temperatures between 100 °C and 250 °C. At each annealing temperature, transmitted light intensity of nanocomposite films was recorded. Void closure and Prager-Tirrell models were employed to interpret the film formation behavior. Activation energy of viscous flow (ΔH) decreased from 21.80 kcal·mol-1 to 5.91 kcal·mol-1 when the amount of GO content increased in film composition. However, activation energy of interdiffusion (ΔE) varied between 1.08 kcal·mol-1 and 6.94 kcal·mol-1 without any trend upon the addition of GO nanofillers. SEM images of films agreed well with calculated activation energies. Although the interdiffusion process of GO-doped latex films remained unaffected by added GO nanofillers, optical transparency of the films enhanced up to 92.5%, demonstrating that thermally resistant and highly transparent GO-rich nanocomposite films can be fabricated.

The laser-induced fluorescence technique has been used to measure primary biological aerosol particles (PBAPs) in the atmosphere because of its ability to classify the origins of particles based on the combination of excitation and detection wavelengths. However, information on the fluorescence intensity related to the amounts of fluorescent compounds in airborne particles measured by this method is limited. Therefore, in this study, the scattered and fluorescent signals from fluorescent polystyrene latex (PSL) particles were observed simultaneously through laser-induced fluorescence. The ratio of the fluorescence to scattered signal intensities from individual particles was found to be almost equal for particles of the same size. Consequently, mixed-size fluorescent particles can be observed separately by simultaneously measuring the fluorescence and scattered signals from individual particles. Mie theory was used to calculate relative scattered signal intensities. Incorporating ratios of fluorescence to scattered signal and relative scattered signal intensities, relative fluorescence intensities were obtained. These results suggest that the relative fluorescence intensities are almost linear with respect to the square of the particle size.

The structural change of a filter cake and its effect on permeation flux in crossflow filtration of a suspension containing particles different in size were studied. A suspension containing yeast cells (5 μm in average diameter) and polystyrene latex particles (0.5 μm) with different compositions was used as a model. The change in the structure of the filter cake formed on the membrane surface was observed by using a scanning electron microscope. When the pore size was smaller than the latex particle size, a yeast cell layer containing latex particles was formed on the membrane at the initial stage of filtration. Then, the yeast cell layer was replaced by the latex particle layer. The increase of the circulation flow rate decreased the amount of the filter cake to increase the permeation flux in this case. On the other hand, when the membrane pore size was larger than the latex particle size, a yeast cell layer was first formed on the membrane surface followed by deposition of latex particles on it. The permeation flux was relatively higher than the former case. However, the permeation flux slightly increased with the increase of the circulation flow rate although the weight of the filter cake decreased in the latter case. Thus, a small amount of the latex particles in the cell suspension considerably decreased the permeation flux in crossflow filtration of the suspension. In addition the dependence of the permeation flux on the circulation flow rate was proved to be different whether the small particles were smaller than the membrane pores. These findings including the structure of the filter cakes will be helpful to understand the permeation behaviors in the crossflow filtration of microbial broths which usually contain small particles.

Particle removal from patterned wafers and trenches presents a tremendous challenge in semiconductor manufacturing. In this paper, the removal of 0.3 and polystyrene latex (PSL) particles from high-aspect-ratio deep trenches is investigated. An experimental, analytical, and computational study of the removal of submicrometer particles at different depths inside the trench is presented. Red fluorescent polystyrene latex (PSL) particles were used to verify particle removal. The particles are counted using scanning fluorescent microscopy. A single-wafer megasonic tank is used for the particle removal. The results show that once a particle is removed from the walls or the bottom of a trench, the vortices and circulation zones keep the particles in the trench for a few minutes before eventually moving the particle out of the trench. The experimental results show that the time required for complete removal of particles from the bottom of the trench takes a much longer time than particles on the surface. This has been also verified and explained by physical modeling of the cleaning process. The removal efficiency and cleaning time are reported at different trench depths.

We report the preparation of hollow spherical polypyrrole balls (HSPBs) by two different approaches. In the first approach, core‐shell conductive balls, CSCBs, were prepared with poly(styrene) as core and polypyrrole (PPy) as shell by in situ polymerization of pyrrole in the presence of polystyrene (PS) latex particles. In the other approach, CSCBs were obtained by in situ copolymerization of pyrrole in the presence of PS(F) with hydrophilic groups like anhydride, boronic acid, carboxylic acid, or sulfonic acid, and then HSPBs were obtained by the removal of PS or PS(F) core from CSCBs. TEM images reveal the spherical morphology for HSPBs prepared from PS(F). The conductivity of CSCBs and HSPBs was in the range of 0.20–0.90 S/cm2.