Polystyrene Latex Particles Research Articles

Stable Covalently Photo-Crosslinked Poly(Ionic Liquid) Membrane with Gradient Pore Size.

Porous polyelectrolyte membranes stable in a highly ionic environment are obtained by covalent crosslinking of an imidazolium-based poly(ionic liquid). The crosslinking reaction involves the UV light-induced thiol-ene (click) chemistry, and the phase separation, occurring during the crosslinking step, generates a fully interconnected porous structure in the membrane. The porosity is on the order of the micrometer scale and the membrane shows a gradient of pore size across the membrane cross-section. The membrane can separate polystyrene latex particles of different size and undergoes actuation in contact with acetone due to the asymmetric porous structure.

Salt induced polystyrene latex flocs investigated by neutron scattering

Studies with a model system consisting of polystyrene latex particles showed that the protein from seeds of Moringa trees adsorbs to the surface and causes flocculation as unusually dense aggregates. In this study, electrolytes sodium chloride (NaCl), ferric chloride (FeCl3) and aluminium sulfate (Al2(SO4)3) have been used to aggregate model polystyrene particles. The study augments previous work using neutron scattering on the flocculation of polystyrene latex with protein from seeds of Moringa trees that had indicated higher floc dimension, df, values as the concentration of particles increased. The measurements were made using ultra small-angle neutron scattering. Generally the fractal dimension, and thus the floc density, increased with particle concentration and salt concentration. Flocculation was apparent at much lower concentrations of FeCl3 and Al2(SO4)3 than of NaCl. The values of df were found not to simply scale with ionic strength for the three electrolytes studied with FeCl3 being the most effective flocculating agent.

Electrically conducting polymeric microspheres comprised of sulfonated polystyrene cores coated with poly(3,4-ethylenedioxythiophene)

Oxidative chemical polymerization of 3,4-ethylenedioxythiophene was carried with 5.8-μm sulfonated polystyrene latex particles as template. Polymerization led to formation of poly(3,4-ethylenedioxythiophene) distributed over the surface of template particles. Increase in initial monomer concentration resulted in the change of poly(3,4-ethylenedioxythiophene) morphology from isolated clusters to continuous 0.2–0.5-μm-thick surface shells. Structure of poly(3,4-ethylenedioxythiophene) coatings had crucial influence on the surface charge and macroscopic electrical conductivity of composite latex particles.

Nanoparticle removal and exhaust gas cleaning using gas-liquid interfacial nonthermal plasma

We investigate the removal of air pollutants containing nanoparticles with a wet-type plasma reactor that generates a gas-liquid interfacial nonthermal plasma. To evaluate the performance of this reactor, we prepare a simulated exhaust gas using polystyrene latex particles, as well as gas cylinders of synthesized air and mixed gas of nitric oxide (NO) and sulfur dioxide (SO2). We achieve a partial collection efficiency of more than 99% for nanoparticles. Moreover, we obtain removal efficiencies exceeding 99% and 81% for SO2 and NOx, respectively. We confirm that the proposed reactor is useful for the simultaneous removal of nanoparticles, NOx, and SOx.

Monitoring the film formation process of polystyrene/poly acrylamide (PS/PAAm) composite films annealed by IR heating

In this study, UV‐visible (UVV) technique was used to probe the evolution of optical transmission during the film formation from composites of polystyrene (PS) latex particles and poly acrylamide (PAAm) films annealed by the infrared radiative heating (IRH) and convectional heating. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. It was shown that the activation energy for the void closure processes of viscous flow from the composite films decreased considerably in IRH annealing technique. It was observed that IRH heating speeds up the film formation process and the decrease the required energy. POLYM. ENG. SCI., 58:353–360, 2018. © 2017 Society of Plastics Engineers

Highly Enriched, Controllable, Continuous Aerosol Sampling Using Inertial Microfluidics and Its Application to Real-Time Detection of Airborne Bacteria.

We report a novel microfluidic technique for sampling of aerosols into liquids. The two-phase fluid, sampling air and collecting liquid, forms a stratified flow in the curved microchannel. By passing fluids through the curved region, the particles are transferred from air into the liquid phase by the particle centrifugal and drag forces. This microfluidic-based aerosol-into-liquid sampling system, called the MicroSampler, is driven by particle inertial differences. To evaluate the physical particle collection efficiency of the MicroSampler, we used standard polystyrene-latex (PSL) particles ranging in size from 0.6 to 2.1 μm and measured particle concentrations upstream and downstream of the MicroSampler with an aerodynamic particle sizer. The cutoff diameter of particle collection was selected controlling the air flow velocity (microfluidic air flow of 0.6 L/min showed a particle collection efficiency of ∼98% at a particle diameter of 1 μm), and continuous enriched particle sampling was possible for real-time postprocessing application. With regard to biological collection efficiency, the MicroSampler showed superior microbial recovery (Staphylococcus epidermidis) compared to the conventional BioSampler technique. These results indicate that our MicroSampler can be used as a portable, cost-effective, simple, and continuous airborne microorganism collector for applications in real-time bioaerosol detection.

Design and development of an Electrostatic Screen Battery for Emission Control (ESBEC)

Current diesel particulate filters (DPFs) can effectively capture the exhaust particles, but they add to engine backpressure and accumulate particles during their operation, which results in the need to regenerate the DPFs by burning off the collected particles periodically. This regeneration results in aerosol emissions, especially in the 10–30 nm size range and contributes to ultrafine particle pollution. In this research, we designed and developed a prototype of a novel diesel exhaust control device: the Electrostatic Screen Battery for Emissions Control (ESBEC). The device features high particle collection efficiency without adding to the exhaust backpressure and without the need for thermal regeneration of the collected particles. The ESBEC consists of a series of metal mesh screens coated with a superhydrophobic substance and an integrated carbon fiber ionizer to charge the incoming particles. Multiple pairs of screens (e.g., 5 pairs) are arranged in a battery, in which one screen of each pair is supplied with high voltage, and the other is grounded, producing electrostatic field produced across the screens. The application of a superhydrophobic coating onto the screens allows easy removal of the collected particles using liquid without the need for thermal regeneration. The current prototypes of the device were tested with fluorescent polystyrene latex (PSL) particles of 0.2 and 1.2µm in size and at 25 and 105L/min sampling flow rates. The average collection efficiency was ~87% for 0.2µm and ~95% for 1.2µm PSL particles. In addition, the ESBEC was tested with actual diesel exhaust particles; here its performance was verified by visually inspecting deposition of particles on an after-filter with the device ON and OFF. In the next stages of this work, the ESBEC will be challenged with diesel exhaust at different mass concentrations and for different collection time periods.

Laboratory evaluation of nanoparticle penetration efficiency in a cylindrical counter flow denuder for non-specific removal of trace gases

ABSTRACTThis article presents a cylindrical counter-current flow diffusion denuder with high efficiency penetration of nanoparticles, for non-specific removal of trace gases from an air flow. The denuder was designed to exchange gases in the sample flow by diffusion to the purge flow across a cylindrical microporous glass tube. Laboratory test results indicated that removal efficiencies of gases increased with a lower sample flow rate and a higher sample to purge flow rate ratio. Additionally, the pore size of the microporous glass did not affect gas removal efficiency and particle penetration following optimization of sample and purge flow rate conditions. Significantly high particle penetration was obtained for the counter flow denuder technique (94% penetration for 20 nm of polystyrene latex particle [PSL]) that agreed with theoretical estimation attributed to diffusion loss.Copyright © 2017 American Association for Aerosol Research

A comparison of facemask and respirator filtration test methods

ABSTRACTNIOSH published a Federal Register Notice to explore the possibility of incorporating FDA required filtration tests for surgical masks (SMs) in the 42 CFR Part 84 respirator certification process. There have been no published studies comparing the filtration efficiency test methods used for NIOSH certification of N95 filtering facepiece respirators (N95 FFRs) with those used by the FDA for clearance of SMs. To address this issue, filtration efficiencies of “N95 FFRs” including six N95 FFR models and three surgical N95 FFR models, and three SM models were measured using the NIOSH NaCl aerosol test method, and FDA required particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) methods, and viral filtration efficiency (VFE) method. Five samples of each model were tested using each method. Both PFE and BFE tests were done using unneutralized particles as per FDA guidance document. PFE was measured using 0.1 µm size polystyrene latex particles and BFE with ∼3.0 µm size particles containing Staphylococcus aureus bacteria. VFE was obtained using ∼3.0 µm size particles containing phiX 174 as the challenge virus and Escherichia coli as the host. Results showed that the efficiencies measured by the NIOSH NaCl method for “N95 FFRs” were from 98.15–99.68% compared to 99.74–99.99% for PFE, 99.62–99.9% for BFE, and 99.8–99.9% for VFE methods. Efficiencies by the NIOSH NaCl method were significantly (p = <0.05) lower than the other methods. SMs showed lower efficiencies (54.72–88.40%) than “N95 FFRs” measured by the NIOSH NaCl method, while PFE, BFE, and VFE methods produced no significant difference. The above results show that the NIOSH NaCl method is relatively conservative and is able to identify poorly performing filtration devices. The higher efficiencies obtained using PFE, BFE and VFE methods show that adding these supplemental particle penetration methods will not improve respirator certification.

Amphiphilic Block Copolymers as Stabilizers in Emulsion Polymerization: Effects of the Anchoring Block Molecular Weight Dispersity on Stabilization Performance

Poly(sodium acrylate)-b-polystyrene block copolymers were employed as stabilizers in the emulsion polymerization of styrene. Previous work by our group has shown that the molecular weight dispersity of the stabilizing block is an important design parameter of block copolymer stabilizers; herein, the molecular weight dispersity of the anchoring polystyrene block, ĐPS, was investigated. Stabilization performance was evaluated by the critical aggregation concentration, aggregation number, and surface activity of the block copolymers and the size, distribution, and zeta potential of the polystyrene latex particles. It was observed that ĐPS had a strong effect on aggregation number, which led to a change in the number of latex particles in the seeded emulsion polymerization of styrene. Surface activity decreased with increasing ĐPS due to a greater diversity of copolymer compositions, supporting the idea that copolymers of different composition play different roles in the stabilization of an emulsion. The perf...

Liquid filtration of nanoparticles through track-etched membrane filters under unfavorable and different ionic strength conditions: Experiments and modeling

Nanoparticle deposition experiments under unfavorable conditions were conducted experimentally and theoretically. The 0.2 and 0.4µm rated track-etched membrane filters were challenged with 60, 100, 147, 220, 350 and 494nm polystyrene latex (PSL) particles with different ionic strengths ranging from 0.005 to 0.05M. The capillary tube model, with replacing the viscosity of air to water, was used to estimate the initial efficiency, or the transport efficiency of the particles to the filter surface, which was corrected in a second step by allowing the detachment of the nanoparticles according to the sum of adhesive and hydrodynamic torques. The adhesive torques were derived from surface interactions accessed by the extended DLVO theory. Calculation results showed that the adhesive torque of a particle located in the calculated primary minimum was slightly larger than the hydrodynamic torque, resulting in particle deposition. However, experimental data clearly indicated that detachment occurred. This could only be explained by the presence of additional hydration forces, leading to a larger separation which became relevant at high ionic strengths. By including hydration into our theoretical framework, experiment and theory were in very good agreement under all different ionic strength conditions. The findings allow a basic understanding of surface interactions between nanoparticles and membranes in micro- and ultra-filtration applications for drinking water production, wastewater treatment and particle free water production in industries.

Particle Zeta Potentials Remain Finite in Saturated Salt Solutions.

The zeta potential of a particle characterizes its motion in an electric field and is often thought to be negligible at high ionic strength (several moles per liter) due to thinning of the electrical double layer (EDL). Here, we describe zeta potential measurements on polystyrene latex (PSL) particles at monovalent salt concentrations up to saturation (∼5 M NaCl) using electrophoresis in sinusoidal electric fields and high-speed video microscopy. Our measurements reveal that the zeta potential remains finite at even the highest concentrations. Moreover, we find that the zeta potentials of sulfated PSL particles continue to obey the classical Gouy-Chapman model up to saturation despite significant violations in the model's underlying assumptions. By contrast, amidine-functionalized PSL particles exhibit qualitatively different behaviors such as zero zeta potentials at high concentrations of NaCl and KCl and even charge inversion in KBr solutions. The experimental results are reproduced and explained by Monte Carlo simulations of a simple lattice model of the EDL that accounts for effects due to ion size and ion-ion correlations. At high salt conditions, the model suggests that quantitative changes in the magnitude of surface charge can result in qualitative changes in the zeta potential-most notably, charge inversion of highly charged surfaces. These findings have important implications for electrokinetic phenomena such as diffusiophoresis within salty environments such as oceans, geological reservoirs, and living organisms.

Assessment of indoor bioaerosols using a lab-made virtual impactor

ABSTRACTTo assess indoor bioaerosols, a virtual impactor having 1 µm cutoff diameter was designed, fabricated, and evaluated with computational fluid dynamics simulation and also with laboratory test using polystyrene latex particles. Two other cutoff diameters of 635 nm and 1.5 µm were obtained by changing the inlet flow rate and the ratio of minor channel-to-inlet flow rates. In field test, the virtual impactor was operated with varying cutoff diameter and field-emission scanning electron microscope (FE-SEM) analysis was performed for each cutoff diameter to observe morphologies of indoor aerosol particles sampled at the major and minor outlet channels. Particles were sampled at both outlet channels using the SKC Button Aerosol sampler and subsequently cultured. By colony counting, it was found that 56% of cultured fungal particles and 63% of cultured bacterial particles had aerodynamic sizes smaller than 1 µm. MALDI-TOF analysis and visual inspection of culture samples were used to identify indoor bact...

On the effect of thermophoretic force, gravitational force, and particle–particle interactions in field-flow fractionation

ABSTRACTThe theoretical calculations confirmed that the gravitational force cannot be neglected in all field-flow fractionation techniques separating nanometer-sized colloidal particles whenever particle diameter is approximately 200 nm and larger. Particle–particle repulsive interactions, mostly electrostatic repulsions, influence substantially concentration distribution established by any effective field acting across the fractionation channel, as confirmed explicitly for thermophoretic force generated by temperature gradient in microthermal field-flow fractionation. The ionic strength of the carrier liquid causes the screening of the electrostatic double layer around the dispersed particles and thus influences the retention. The attractive particle–particle forces occur when the zeta potential of the particles approaches to 0 mV, the electrostatic repulsions are screened, and the aggregation of the particles is observed. The pH influences differently the size and zeta potential of the plain polystyrene latex particles and of the particles modified on the surface by the groups –COOH and –NH2. The role of a detergent in carrier liquid is non-negligible, as demonstrated by its presence or absence in carrier liquid.

Synthesis of Covalently Cross-Linked Colloidosomes from Peroxidized Pickering Emulsions

A new approach to the formation of cross-linked colloidosomes was developed on the basis of Pickering emulsions that were stabilized exclusively by peroxidized colloidal particles. Free radical polymerization and a soft template technique were used to convert droplets of a Pickering emulsion into colloidosomes. The peroxidized latex particles were synthesized in the emulsion polymerization process using amphiphilic polyperoxide copolymers poly(2-tert-butylperoxy-2-methyl-5-hexen-3-ine-co-maleic acid) (PM-1-MAc) or poly[N-(tert-butylperoxymethyl)acrylamide]-co-maleic acid (PM-2-MAc), which were applied as both initiators and surfactants (inisurfs). The polymerization in the presence of the inisurfs results in latexes with a controllable amount of peroxide and carboxyl groups at the particle surface. Peroxidized polystyrene latex particles with a covalently grafted layer of inisurf PM-1-MAc or PM-2-MAc were used as Pickering stabilizers to form Pickering emulsions. A mixture of styrene and/or butyl acrylate with divinylbenzene and hexadecane was applied as a template for the synthesis of colloidosomes. Peroxidized latex particles located at the interface are involved in the radical reactions of colloidosomes formation. As a result, covalently cross-linked colloidosomes were obtained. It was demonstrated that the structure of the synthesized (using peroxidized latex particles) colloidosomes depends on the amount of functional groups and pH during the synthesis. Therefore, the size and morphology of colloidosomes can be controlled by latex particle surface properties.

Laser Doppler Electrophoresis and electro-osmotic flow mapping: A novel methodology for the determination of membrane surface zeta potential

A novel technique employing an Uzigirs dip cell arrangement is used in conjunction with Laser Doppler Electrophoresis for the determination of the surface zeta potential for a UF, NF, and RO membrane. To the authors best knowledge this is the first study employing Laser Doppler Electrophoresis and Electro-osmotic Flow Mapping for membrane surface charge determination. High correlation of the regression fit (R2>0.95) for a carboxylated polystyrene latex particle electrophoretic mobility was achieved at low electrolyte concentrations (1mM and 10mM NaCl), but the reliability and accuracy of the extrapolated zeta potential values were problematic at higher concentration due to high measurement uncertainty (>10% in some cases). Changes in the applied electric field increased the phase resolution of 50mM NaCl electrolyte solutions between 0.5–2.0V. However, the effects of Joule heating at higher voltages compromised 50mM NaCl sample integrity. When compared with the established Tangential Streaming Potential method, Laser Doppler Electrophoresis measurements provided similar zeta potential values and trends indicating that this new methodology can indeed be employed for membrane characterization purposes; however, further research needs to be conducted in order to optimize this new technique and set appropriate operating limits.

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

In aerosol research, differential mobility analyzer (DMA) is widely used for particle size distribution measurements. In general polystyrene latex (PSL) particle size standards are used to calibrate the DMAs. However, these standards are expensive, and their shelf-life is limited. Therefore in this work, we have used PSL particle standard of sizes 60 and 100nm (SRM® 1964 and SRM® 1963a, respectively) and checked their performance within and after the shelf-life period for 3 consecutive years (2013 – 2015) using a calibrated DMA (i.e., long-DMA, TSI 3081). Also the size results are compared using a reference DMA (i.e., nano-DMA, TSI 3085). Using both long- and nano-DMA, the detail results of standard particle size measurements and involved uncertainties are discussed in this paper. We observed a continuous increase in the count mean diameter (CMD) calculated from the size distribution of each standard particle size with the progress of time. Particle size measured for PSL 60 and 100nm using long-DMA are (56.01±5.56)nm and (92.86±10.81)nm in 2013, (56.37±5.66)nm and (93.71±10.44)nm in 2014, and (57.42±5.84)nm and (94.79±9.68)nm in 2015, respectively. Whereas, these results when nano-DMA was used are (56.82±4.32)nm and (94.62±9.46)nm in 2014, and (58.08±4.98)nm and (95.15±9.12)nm in 2015, respectively. Uncertainty results show that the components which contribute significantly in total uncertainty (at k=2) in CMD measurements are DMA sheath flow rate, DMA calibration, difference in certified and measured diameter, and variation in the ambient temperature and pressure. The size measurement results obtained from long-DMA and nano-DMA agreed well. Based on the measurement results, we suggest that the increasing trend of particle sizes (CMDs) with the progress of time from 2013 to 2015 is possibly because of the coating of contaminant residues (present in the standard liquid suspension) on the surface of the PSL particles which is further observed by high resolution tunnelling electron microscope (HRTEM) images of particles. Particles standards are stable and well characterized more than two years even after their shelf-life within the uncertainty limits. Size performance results for PSL 60nm using calibrated long- and reference nano-DMA show good agreement with the size value given in the certificate, however standard PSL 100nm size is found to be underestimated by ~7%.

In situ charge neutralization-controlled particle coagulation and its effects on the particle size distribution in the one-step emulsion polymerization

A novel approach to prepare sub-200nm, narrowly dispersed polystyrene latex particles is proposed for the emulsion polymerization of a ca. 40wt% solid-content solution. The presented method exploits the cationic comonomer methacryloxyethyltrimethyl ammonium chloride (MATMAC) or the initiator 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AIBA) to generate cationic oligomeric radicals shielded the negatively charged surfactant molecules adsorbed on the particles surface, further induced particle coagulation by in situ charge neutralization. By adjusting the types and amounts of the comonomer, the extent of the in situ charge neutralization is controlled. In consequence, the extent of the particle coagulation is controlled, resulting in the production of large-size latex particles. The particle coagulation induced by in situ charge neutralization occurs at the particle nucleation stage, which extends the times of particle completive growth and reversible coagulation, and therefore, narrowed the width of the particle size distribution of the ultimate latex particles. The resulting colloidal latexes containing 40wt% solid content are very stable by presenting the absolute value of zeta potentials larger than 40mV. This approach is likely to be used for large-scale industrial productions of narrowly dispersed polymer particles.

Effective diffusivity of colloidal particle multilayers

We have studied, both theoretically and experimentally, the effective diffusivity of colloidal particle multilayers. We have synthesized the multilayers of 0.8μm polystyrene latex particles, according to the layer-by-layer technique. We have measured their limiting diffusion current, using cyclic voltammetry with rotating disk electrode, to determine the equivalent thickness of stagnant solution layer. Next, we have performed mass measurements of each film to determine its mean surface coverage. From these measurements, we have calculated thickness of the multilayers. We have also presented results of our numerical simulations of multilayer adsorption of hard monodisperse spheres, using the extended random sequential adsorption model. We have generated five multilayers mimicking those obtained experimentally. Then, we have analyzed their porosity, tortuosity, and effective diffusivity as functions of the distance from the adsorption surface. We have shown that variation in effective diffusivity within our multilayers has negligible effect on the concentration profile of species diffusing through the supported membranes. We have also compared the thickness of the multilayers, determined experimentally and theoretically. We have found a good agreement between the experiments and numerical simulations.

Solution properties of poly(N-methylethylene imine), a highly hydrophilic polycation

Poly(N-methylethylene imine) (PMEI) has a wide solubility similar to poly(ethylene oxide) and a high protonation capacity similar to poly(ethylene imine). In addition, PMEI forms aggregates with negatively charged macromolecules, such as polystyrene latex particles, and acts as either a flocculant or a dispersant depending on the environment. An aqueous solution containing the as-synthesized PMEI (weight-average molecular weight: 26 kDa) exhibited an LCST of 116 °C, and a toluene solution exhibited a UCST of 36 °C. Therefore, PMEI is expected to be used as a highly hydrophilic polycation for various applications.