PMMA Particles Research Articles

Rapid Synthesis of Poly(methyl methacrylate) Particles with High Molecular Weight by Soap‐Free Emulsion Polymerization Using Water‐in‐Oil Slug Flow

AbstractA flow process for the production of poly(methyl methacrylate) (PMMA) particles is proposed by soap‐free emulsion polymerization using a water‐in‐oil (W/O) slug flow in a microreactor. Thin oil films generated around the dispersed aqueous phase of the W/O slug prevent the prepared particles from adhesion to the microchannel wall, enabling the continuous production of PMMA particles without clogging. The effects of the linear flow rate of the slug flow and the addition of ethanol in the dispersed aqueous phase on the polymerization are evaluated. It is found that increasing the linear flow rate of the slug flow or the addition of ethanol in the dispersed aqueous phase results in PMMA particles with high molecular weight (≈1500 kg mol−1) in 20 min reaction time. It is believed that this process would be a promising way to prepare polymer particles with high molecular weight in a short reaction time.

Photocatalytically Active Amorphous and Crystalline TiO2 Prepared by Atomic Layer Deposition

In this work, the photocatalytic properties of amorphous and crystalline TiO2 deposited on oxide and polymer nanoparticles by atomic layer deposition (ALD) were studied. Beside TiO2, as reference, both ALD grown amorphous Al2O3 and crystalline ZnO layers were also examined. When choosing the carrier, the priority was that it had no effect on the photocatalytic activity of TiO2; therefore the oxide layers were deposited on SiO2 and poly(methyl-methacrylate) (PMMA) nanoparticles. The amorphous SiO2 particles were synthetized by the Stöber method, while the PMMA particles were prepared by emulsion polymerization. Both the bare and core/shell composite nanoparticles were investigated by SEM-EDX, TEM, FT-IR, and XRD. Finally, the photocatalytic activity of PMMA, SiO2 and the core/shell nanoparticles was measured by the decomposition of methylene orange, monitored by UV-Vis spectroscopy. Based on the results, the SiO2 was uniformly coated with the deposited oxide films, while in the case of the PMMA a contiguous web-like polymer/TiO2 matrix was formed. During the photocatalytic reactions, the amorphous Al2O3 was not active, while the crystalline ZnO and TiO2 showed good photocatalytic activity. The amorphous TiO2 deposited by ALD on the SiO2 and PMMA nanoparticles had smaller, but a clearly detectable photocatalytic effect on the photodegradation of methylene orange.

Impact of spatial harmonic waves on dielectric particles displacement in standing and traveling wave electric fields

The purpose of this work is to investigate the effect of spatial harmonic waves on dielectric particles displacement process using standing and traveling electric wave electric conveyors. This investigation is divided into two main parts. The first one is an experimental study, where the efficiency of conveyors for the displacement of micrometer sized PMMA particles is analyzed. The second part consists of a numerical and theoretical study in which the spatial electric potential distribution and the consequences on the spatial harmonics on particles displacement are investigated. The results show that the displacement efficiency and the particles direction depend basically on the particles size, the charge to mass ratio, the applied voltage and the frequency. In the standing wave conveyor, the particles move toward both right and left directions. In the traveling wave conveyor, at high voltage, low frequency, small particles or high charge to mass ratio conditions particles move toward the traveling wave direction. In the case of low applied voltage, high frequency or if the particles have a low charge to mass ratio, some particles move toward the opposite direction because of the backward harmonic wave that appears near to the surface. The magnitude of the harmonic waves depends on the levitation height of particles; it can be controlled by varying the number of phases, the gap spacing or the thickness of electrodes or by adding a dielectric barrier over the surface.

A centrifugal magnetic levitation approach for high-reliability density measurement

Magnetic levitation (MagLev) of diamagnetic materials in a paramagnetic medium under a magnetic field gradient provides an effective tool to measure the densities of samples. In this study, a centrifugal magnetic levitation approach for high-reliability density measurement is presented. Based on the balance of the magnetic forces, centrifugal forces and gravities, densities of several different samples can be obtained by measuring the equilibrium positions without knowing the mass or volume. Different from the static MagLev configuration, the magnified centrifugal acceleration is simply controllable, which not only facilitates the improvement of measurement sensitivity, but also provides flexibility and reliability. The performance of the proposed measurement method is investigated in the aspects of accuracy, reliability and sensitivity. Experiments with different diamagnetic materials are carried out, and measurement uncertainties are evaluated. To demonstrate the potential for quality control of plastic products, several PMMA particles in the same batch are levitated and separated. The proposed method is well balanced in accuracy and flexibility, which has prospects for broad applications in density-based detection and separation, especially for plastic products of arbitrary shapes.

Size-controlled synthesis of polymer hollow nanoparticles using emulsion templates prepared by tandem acoustic emulsification

We have developed a new emulsion template method for the synthesis of poly(methylmethacrylate) (PMMA) hollow nanoparticles with different sizes. This synthetic method involves sequential ultrasonic irradiation (20 kHz → 500 kHz → 1.6 MHz → 2.4 MHz → 5.0 MHz) for acoustic emulsification of a water-insoluble fluorous solvent such as perfluoromethylcyclohexane (PFMCH) in an aqueous medium, followed by monomer (methylmethacrylate (MMA)) adsorption on the surface of the PFMCH emulsion droplets and photopolymerization of the adsorbed MMA in the obtained emulsion solution. Since the size of the PFMCH droplet templates can be tuned according to the number of steps of tandem acoustic emulsification, the obtained PMMA particle size can also be controlled. The subsequent removal of the core fluorous solvent by the heat treatment yielded size-controlled PMMA hollow nanoparticles and monodisperse PMMA hollow nanoparticles of different sizes. Furthermore, we confirmed that the substances could go in or go out of the hollow particles through the shells. Such a nice permeability is important for applications such as nanoreactors and drug delivery systems.

Synthesis of monodisperse, re-dispersable polymer particles by one-step high solid emulsion polymerization in the presence of reactive surfactant

In this study, monodispersed and re-dispersed poly (methyl methacrylate) (PMMA) particles were prepared by high solid content (50 wt%) macroemulsion polymerization using commercial macromonomer (Emulsogen APS 100) as a reactive surfactant (surfmer). Highly monodispersed, re-dispersed PMMA particles with sizes around 300 nm were obtained using this process. The effect of recipe composition including surfmer content, monomer/water ratio and electrolyte concentration on particle formation and growth were also investigated. Compared to classical macroemulsion polymerization theory, the formation of particles was found different. The number of formed particles firstly increased to a maximum value, then rapidly decreased to reach a constant value stabilized at around 1/5 of the maximum particle number. The particle coagulation theory was used to explain the process of particle formation and growth. The relationship between polymer particle size distribution and particle coagulation was also examined and the results were discussed. The proposed method would probably find applications in industrial production of monodisperse particles.

Direct measurement of electrostatic interactions between poly(methyl methacrylate) microspheres with optical laser tweezers.

In this study, we measured the force of electrostatic interactions between poly(methyl methacrylate) (PMMA) particles dispersed in organic solvent mixtures of cyclohexyl bromide (CHB) and n-decane. Optical laser tweezers were employed to directly measure interactive forces between paired PMMA particles in a CHB medium that contained n-decane in various volume ratios. CHB, having a moderate dielectric constant, provided an environment with a high charge storage capacity. The addition of n-decane lowered the effective refractive index of the medium, which increased the optical trapping efficiency. We also fabricated microscope flow cells with a commonly used UV-curable adhesive and quantified the effects of dissolved adhesive compounds through interactive force measurements and nuclear magnetic resonance analysis. In addition, we studied the impact of CHB dissociation into H+ and Br- ions, which could screen electrostatic interactions.

PMMA particles coated with chitosan-silver nanoparticles as a dual antibacterial modifier for natural rubber latex films

The antibacterial activity in sulphur prevulcanized natural rubber (SPNR) latex film was effectively improved by deposition of poly(methyl methacrylate) (PMMA) particles encircled with chitosan-coated silver nanoparticles (AgNPs-CS). With the focus on a green process, CS was selected as a safe reducing and stabilizing agent for the one-step synthesis of AgNPs-CS (38 nm, +40.4 mV) in an autoclave. The adsorption of small-sized AgNPs-CS directly onto rubber film did not provide an inhibitory effect on S. aureus. It also had a low antibacterial effect on E. coli. This is because of the particles becoming completely/partially submerged into the soft rubber matrix upon drying. Hence, the AgNPs-CS were fabricated as a shell surrounding a rigid PMMA core (496 nm, -30.9 mV). This was done using a heterocoagulation technique prior to coating on SPNR film. The presence of PMMA/AgNPs-CS on the surface of SPNR film effectively increased the surface roughness from ca. 44 to 150 nm. This substantially promoted the antibacterial activity against E. coli and S. aureus by way of contact killing and repelling mechanisms. The cytotoxicity on L-929 fibroblasts was also suppressed. This study would be, therefore, applicable to the development of antibacterial SPNR film with high surface roughness, low cytotoxicity. It could also be applied for other soft substrates.

Assessment of forces acting on fine particles on a traveling-wave electric field conveyor: Application to powder manipulation

The purpose of this work is to investigate the transport mechanism of fine dielectric particles using a traveling-wave electric field conveyor. In the first part of this study, an experimental bench is set up to evaluate the efficiency of particle displacement according to their size and to visualize their motion. The displacement efficiency is evaluated based on the ratio of the mass of transported particles to the total mass of particles deposited. The experimental setup allows us to measure the charge of particles as well. In the second part of this study, we discuss the experimental results based on the balance of forces exerted on particle in such a device. The particles studied are spherical PMMA particles having sizes ranging between 50 and 500 μm. The results show that the displacement efficiency and charge per mass ratio of the particles decrease as the particle diameter increases. This is explained by the dominance of the gravitational force for large particles. The balance of forces also shows that the adhesion force is dominant for small particles. Coulomb's force is predominant in a certain particle size range. It is the only repulsive force, which make it the responsible of the particles movement.

Transport and deposition of colloidal particles on a patterned membrane surface: Effect of cross-flow velocity and the size ratio of particle to surface pattern

In this study, the transport and deposition of colloidal particles onto a patterned membrane surface are analyzed by both numerical simulation and experiment. The channel Reynolds number (Re) and the size ratio of the particle to the pattern (a/h) are chosen as the major simulation parameters. With an increase in Re and a/h, the number of deposited particles decreases and the rate of permeate flux decline is reduced. Under certain specific combinations of the design parameters, the suspended particles are impeded to access the patterned membrane surface. Based on the particle trajectory analysis, it is claimed that “inaccessible zones”, where the suspended particles cannot be accessed by the flow, are formed near the patterned membrane surface, with the increase in Re and a/h. Cross-flow microfiltration experiments using a poly(methyl methacrylate) (PMMA) particle suspension are also conducted to verify the trend in particle deposition observed in simulation. As the radius of the PMMA particle increases, the number of deposited particles is reduced and the critical flux for the onset of the particle deposition is increased, which qualitatively matches well with simulation. It is found that a patterned membrane can reduce tremendous amounts of colloidal fouling by prohibiting the access of the suspended particles to the membrane surface with the appropriate choice of design parameters such as Re and a/h.

3D photonic crystals based poly (methyl methacrylate) for active photonic SERS substrates

Synthesis of 400 nm average size poly (methyl methacrylate) (PMMA) and fabrication onto surface-enhanced Raman scattering (SERS) active substrate were presented.“Bottom-up” technique was employed to fabricate SERS active substrate while PMMA suspension was obtained via surfactant-free emulsion polymerization. Morphology of fabricated PMMA photonic crystals (PMMAPc) SERS substrate was observed through scanning electron microscopy (SEM) with 20 000 magnification at 10 kV power. Photonic properties measurement was carried out using ocean optic spectrometry at range of 800 nm to 900 nm. Thermal resistivity study was measured through thermogalvanic analysis (TGA) over a range of 0 °C to 500 °C. Subsequently, enhancement percentage assessment by Raman spectroscopy provided evidence that PMMAPc SERS substrate potentiality towards Raman signal by using 4-aminothiolphenol (4-ATP) as probe molecule. Evidence from SEM supported that highly homogenous PMMA particles fabricated onto thin film brings wellordered arrangement in agreement with photonic crystals design. The proposed model was assessed experimentally using ocean optic spectrometry show a wide dip transmission at 899 nm and thermally stable up to 336 °C. Raman spectrum of 4-ATP using normal Raman analysis (without using PMMAPc SERS substrate) and using PMMAPc substrate support the results of the improvement of Raman signal upon 45 %. Low cost and large area fabrication would suggest PMMAPc as convenient yet affordable active SERS substrate for advance and fast detection.

NF-κB/let-7f-5p/IL-10 pathway involves in wear particle-induced osteolysis by inducing M1 macrophage polarization

ABSTRACTNF-κB signaling pathway shows significant influence on wear particle-induced osteolysis, and this study aims to explore the underlying mechanism and the role of let-7f-5p in this process. A mouse calvarial osteolysis model was constructed with PMMA particles, and the bone marrow-derived macrophages (BMMs) were isolated from the osteolysis area. The expression of miRNA and protein was determined by qRT-PCR and western blot, respectively. The level of cytokines was evaluated with ELISA. Recombinant plasmids were transfected into cells for the endogenous expression of related genes. Dual-luciferase reporter assay was performed to determine the interaction between let-7f-5p and IL-10 in macrophage RAW264.7 cells. M1 macrophage polarization and expression of let-7f-5p were promoted in BMMs of osteolysis mouse model, compared with that in sham group. The expression of let-7f-5p was increased in the process of M1 macrophage polarization that induced by PMMA. Let-7f-5p was involved in M1 polarization in macrophages that treated with PMMA. IL-10 was negatively regulated by let-7f-5p. NF-κB regulated the expression of IL-10 through let-7f-5p. NF-κB participated in the PMMA-induced M1 macrophage polarization through let-7f-5p. Let-7f-5p contributed to PMMA-induced osteolysis by promoting M1 polarization of macrophages. The NF-κB/let-7f-5p/IL-10 pathway induces M1 macrophage polarization, and thus contributing to wear particle-induced osteolysis.

Deterministic displacement of particles and oil droplets in a cross-flow microsieve module

Our investigation aims to apply Deterministic Lateral Displacement (DLD) to separate (deformable) particles or droplets from dispersions on industrial scale. DLD is a promising technique because it can separate particles smaller than the pores. Previous work shows how to manipulate the critical particle diameter in a sieve-based lateral displacement system by modifying the hydrodynamics. In this study, we apply this fundamental understanding of the DLD separation principle to deterministically displace particles in a cross-flow microsieve module. First, two-dimensional simulations of the fluid dynamics in this cross-flow module were performed to investigate the hydrodynamic conditions required for particle displacement. Next, these simulations were compared with the flow fields visualized in the experimental setup. In addition, high speed recordings confirmed deterministic displacement of particles and oil droplets over the microsieve surface. Last, the systems performance was evaluated by measuring the transmission of rigid PMMA particles and deformable hexadecane droplets and the particle size distribution for different operation conditions. These results clearly demonstrate that the DLD principle can be effectively applied in a cross-flow microsieve module. With this, the application of this microfluidic separation principle to separate particles or droplets (1–20 µm) from dispersions on industrial scale has become realistic.

Energy-Efficient Templating Method for the Industrial Production of Porous Carbon Particles by a Spray Pyrolysis Process Using Poly(methyl methacrylate)

Template selection is a critical step to determining an effective and efficient method for the synthesis of porous materials. We introduce the use of the low-cost poly(methyl methacrylate) (PMMA) as a template in a spray pyrolysis process for the synthesis of a porous carbon particle. Monodisperse, negatively charged, three sizes of PMMA particles are used to evaluate the porous structure formation. The highest surface area of the prepared porous carbon particle is 172 m2/g, which is double that of carbon particles produced using a polystyrene latex (PSL) template. The high surface area is attributed to the low PMMA decomposition residue and the formation of a micropore and a mesopore. The use of PMMA reduces the energy consumption for template decomposition by 32% compared with PSL. This benefit suggests an excellent potential for the use of PMMA in the scaled-up production of porous materials.

Preparation and Characterization of Poly(methyl methacrylate) Particles by Combined Dispersion and Emulsion Polymerization

Monodispersed poly(methyl methacrylate) (PMMA) nanoparticles were synthesized by combined dispersion and emulsion polymerization, using aqueous alcohol (methanol/water) as the dispersion medium. The influence of the dispersion medium ratio, stabilizer concentration, and initiator type and concentration on the colloidal stability, particle size, size distribution, and %conversion, was investigated. Submicron PMMA particles with a size of approximately 760 nm with a narrow size distribution, high conversion (91%) and good stability throughout the polymerization were obtained using a 50/50 methanol/water ratio, 1 wt% 2,2’-azobisisobutyronitrile (based on monomer), and 1 wt% polyvinylpyrrolidone (based on medium). With increasing the polarity of the dispersion medium (30/70 methanol/water ratio), the size and conversion of PMMA particles decreased to 345 nm and 72%, respectively.

Acceleration of instability during the capillary thinning process due to the addition of particles to a poly(ethylene oxide) solution

The effect of particles on the development of instability patterns during the capillary thinning process of a poly(ethylene oxide) solution has been experimentally studied in an effort to clarify the filament breakup behavior of particulate systems. We focus on breathing and formation of the first bead in particular, which as this bead initiate blistering. Changes in instability patterns due to an addition of PMMA particles are investigated by observing the evolution of a filament undergoing capillary thinning. The addition of particles accelerates breathing and the formation of the first bead. By comparing the extensional properties of a PMMA/PEO suspension to those of glycerin/PEO solutions which has the same shear viscosity, surface tension and polymer concentration, it was found that the addition of particles has little effect on the behavior of polymer chains under an extensional flow. Meanwhile, the flow becomes heterogeneous with the fluctuation of the local particle concentration, inducing rapid thinning at the neck region, which propagates throughout the filament as capillary thinning proceeds. The addition of particles also influences the position of the first bead. For a pure polymer solution and a polymer solution with a small amount of particles (∼2 wt.%), the first bead mostly appears near the upper neck. However, as the particle concentration increases to 10 wt.%, the first bead appears at random locations along the filament, with similar probabilities. The randomization of the position of the first bead is attributed to the non-uniform distribution of particles inside a thinning filament due to the fluctuation of the local particle concentration.

Characterization of poly methyl methaacrylate and reduced graphene oxide composite for application as electrolyte in dye sensitized solar cells

Quasi-solid state iodide/triiodide redox electrolyte containing reduced graphene oxide and poly (methyl methaacrylate) (RGO-PMMA) composites for the fabrication of more durable, high performance dye sensitized solar cells are prepared. The morphological analysis of prepared RGO-PMMA composites showed formation of spherical like morphologies of RGO dispersed PMMA particles with their macroscopic inter-particle networks having voids. The x ray diffraction and electrical conductivity studies showed the addition of 1 wt% of filler RGO into amorphous PMMA matrix increased the electrical conductivity of the polymer composite about three orders of magnitude from 10−7 and 10−4 S cm−1. Further, the photovoltaic current-voltage analysis of DSSCs with different RGO-PMMA composite based iodide/triiodide redox electrolytes showed the highest power conversion efficiency of 5.38% and the fill factor 0.63 for 2% RGO-PMMA electrolyte. The EIS analysis showed an increased recombination resistance (Rct2) at TiO2 electrode/dye/electrolyte interface due to the better electrical conductivity of RGO with good ionic conductivity in 2% RGO-PMMA composite based redox electrolyte boosted the generation of a high current density and fill factor in their DSSCs.

Fate of Nanoplastics in Marine Larvae: A Case Study Using Barnacles, Amphibalanus amphitrite

The exposure of nanoplastics was investigated by observing their interaction with Amphibalanus amphitrite (commonly known as acorn barnacles). Poly(methyl methacrylate) (PMMA) and fluorescent perylene tetraester (PTE) dye were used to prepare highly fluorescent nanoplastic particles. At concentrations of 25 ppm, the PMMA particles showed no detrimental impact on barnacle larvae and their microalgae feed, Tetraselmis suecica and Chaetoceros muelleri. PMMA nanoplastics were ingested and translocated inside the body of the barnacle nauplii within the first 3 h of incubation. The fluorescent PMMA particles inside the transparent nauplius were tracked using confocal fluorescence microscopy. Subsequently, the nanoplastics were fed to the barnacle nauplii under two conditions—acute and chronic exposure. The results from acute exposure show that nanoplastics persist in the body throughout stages of growth and development—from nauplius to cyprid and juvenile barnacle. Some egestion of nanoplastics was observed thr...

Electric field induced charging of colloidal particles in a nonpolar liquid

HypothesisColloidal particles in a pure nonpolar solvent are expected to be in a state of dynamic equilibrium where a particle’s charge fluctuates around a stable mean value. However, we find that PHSA-coated PMMA microparticles in dodecane gain positive charge over time. We hypothesize that this phenomenon is prompted by the high electric field (∼1 V/µm) that is applied in these measurements. Hence, we expect the reaction rate at which charge builds up on the particle to change when modifying the measurement parameters. ExperimentsSingle elementary charging and discharging events can be resolved by measuring the charge of PHSA-coated PMMA particles with optical trapping electrophoresis. With this technique, the influence of the electric field amplitude and frequency, particle size, electrode material and acquired charge can be investigated. FindingsThe rate of the charging phenomenon is proportional to the amplitude of the applied electric field and the charging stops when the voltage is switched off. We propose a reaction mechanism where the particle sheds negatively charged ions. This mechanism can account for all the experimental observations of the electric field induced charging phenomenon.

Single charging events on colloidal particles in a nonpolar liquid with surfactant

Electrical charging of colloidal particles in nonpolar liquids due to surfactant additives is investigated intensively, motivated by its importance in a variety of applications. Most methods rely on average electrophoretic mobility measurements of many particles, which provide only indirect information on the charging mechanism. In the present work, we present a method that allows us to obtain direct information on the charging mechanism, by measuring the charge fluctuations on individual particles with a precision higher than the elementary charge using optical trapping electrophoresis. We demonstrate the capabilities of the method by studying the influence of added surfactant OLOA 11000 on the charging of single colloidal PMMA particles in dodecane. The particle charge and the frequency of charging events are investigated both below and above the critical micelle concentration (CMC) and with or without applying a DC offset voltage. It is found that at least two separate charging mechanisms are present below the critical micelle concentration. One mechanism is a process where the particle is stripped from negatively charged ionic molecules. An increase in the charging frequency with increased surfactant concentration suggests a second mechanism that involves single surfactant molecules. Above the CMC, neutral inverse micelles can also be involved in the charging process.