Diameter Of Latex Particles Research Articles

Isothermal emulsion polymerization of n‐butyl methacrylate with KPS and redox initiators: Nucleation

ABSTRACTNucleation is a very important stage of emulsion polymerization due to its significant influence on the latex particle diameter, particle diameter distribution, and molecular weight. In this study, we evaluated the effect of thermal and redox initiators on the nucleation and reaction kinetics with a model emulsion system comprised of n‐butyl methacrylate, sodium lauryl sulfate, water, initiators, and other additives. Our previous study has demonstrated that a micellar nucleation mechanism plays a role in both initiator systems. In the present study, we further explored secondary nucleation using these two types of initiator systems, that is, homogeneous nucleation, which exists in the redox‐initiated process, and micellar nucleation which is the main nucleation mechanism for the thermal‐initiated system. The investigation also illustrates that coagulative nucleation in the redox‐initiated emulsion system results in a greater extent of monodispersed particle diameter distributions, much smaller particle diameters, and lower molecular weights for the final latex. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48275.

Optical corral using a standing-wave Bessel beam

Here we create a series of optical corrals and calculate their potential energy profile. A standing-wave Bessel beam is used to form traps in 1D (along the optical axis) and corrals in 2D, in planes perpendicular to the optical axis at the antinodal regions of the standing waves. These optical corrals are formed by an axicon-generated Bessel beam that is retro-reflected back onto itself. We report on Mie calculations of the 2D optical corrals and then compare the resulting probability distributions to those observed for latex particles of diameters 100, 200, and 300 nm. The experimental radial probability density function of tracked particles closely mimics the theoretical optical structure of a Bessel standing-wave corral. The Bessel standing-wave corrals we have characterized are being developed to measure rotational diffusion and torques on micro- and nanorods to help understand microfluidic behavior. The maximum forces on our small beads in the diffraction-free central zone of the Bessel beam standing wave are F||=0.5 pN and F⊥=0.1 pN.

Preparation of novel film-forming armoured latexes using silica nanoparticles as a pickering emulsion stabiliser

HypothesisFilm-forming polymer latex particles of diameter <300 nm can be prepared in the complete absence of surfactants, stabilised in part by silica nanoparticles through a Pickering type emulsion polymerisation. Control of the silica wettability through modulation of reaction pH or by reaction of the nanoparticles with a hydrophobic silane results in silica-covered latex particles. ExperimentsThe oil-in-water polymerisation process used methyl methacrylate (MMA) and n-butyl acrylate (BA) as co-monomers, potassium persulphate (KPS) as an initiator and a commercially available colloidal nano-silica (Ludox®-TM40). It was found that pH control before polymerisation using methacrylic acid (MAA) facilitated the formation of armoured latexes, and mechanistic features of this process are discussed. An alternative, more robust protocol was developed whereby addition of vinyltriethoxysilane (VTES) to control wettability resulted in latexes completely armoured in colloidal nano-silica. The latexes were characterised using SEM, cryo-TEM and AFM imaging techniques. The mechanism behind the adsorption was investigated through surface pressure and contact angle measurements to understand the factors that influence this irreversible adsorption. FindingsResults indicate that nanoparticle attachment (but intriguingly not latex size) is dependent on particle wettability, providing new insight into the formation of nanoparticle-armoured latexes, along with opportunities for further development of diversely functionalized inorganic/organic polymer composite particles.

Surface functionalization of rubber latex nanoparticles with sulfidosilane moieties

ABSTRACTPolybutadiene latex particles were functionalized with bis[3‐(triethoxysilyl) propyl] tetrasulfide (TESPT) in the presence of zinc oxide as an activator and ethanol as a co‐solvent. The success of this reaction was confirmed both by the peaks attributed to Si‐O groups at 1085 and 1110 cm−1 and C‐S bond at 630 cm−1 which appeared after reaction in Attenuated Fourier Transform Infrared (ATR‐FTIR) Spectra and also by increasing in the particle size diameter of latex particles (from 95 to 127 nm) in Dynamic Light Scattering analysis. X‐ray Diffraction results also showed changes in crystalline structure of the modified particles (as a strong decrease in the intensity of peak at 2θ=19.54). The effect of reactant concentration in a constant amount of TESPT (by varying the water and ethanol content), reaction time, activator size (micro and nanoparticles), and pH (≈7, 8.5) were investigated on degree of grafting (obtained from thermogravimetric analysis and ATR‐FTIR spectra), particle size diameter, cross‐link density, and swelling ratio of the samples. The amounts of silane grafting and cross‐link density of polymer particles were increased by an increase in the reaction time. The highest grafting degree was observed at low concentration of TESPT. Silane functionalization was also improved in a slight basic condition (pH=8.5) rather than neutral pH. The grafting reaction took place such as sulfur pre‐vulcanization and the possible mechanism of this reaction was discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43268.

Encapsulation of Amylase in Colloidosomes

Aqueous core colloidosomes encapsulating the enzyme amylase were manufactured with a shell comprising polymer latex particles of diameter 153 nm. The colloidosomes were sealed with calcium carbonate by precipitation between an inner phase of Na2CO3 and an outer phase of CaCl2. This seal allowed the retention of small molecules, such as dyes, as well as larger enzyme molecules, for several months. The encapsulated material could be released by dissolution of the CaCO3 with acid, upon a large dilution in water, or by applying a sufficient shear. The degree of release could be controlled since the greater the mass of CaCO3 precipitated onto the colloidosome shell, the greater the dilution or shear required to achieve release. The calcium carbonate seal protected encapsulated amylase from the detrimental effects of components in a liquid laundry detergent for several months so that, on triggered release, the enzyme retained its high activity.

Direct measurements of forces between different charged colloidal particles and their prediction by the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO)

Force measurements between three types of latex particles of diameters down to 1 μm with sulfate and carboxyl surface functionalities were carried out with the multi-particle colloidal probe technique. The experiments were performed in monovalent electrolyte up to concentrations of about 5 mM. The force profiles could be quantified with the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) by invoking non-retarded van der Waals forces and the Poisson-Boltzmann description of double layer forces within the constant regulation approximation. The forces measured in the symmetric systems were used to extract particle and surface properties, namely, the Hamaker constant, surface potentials, and regulation parameters. The regulation parameter is found to be independent of solution composition. With these values at hand, the DLVO theory is capable to accurately predict the measured forces in the asymmetric systems down to distances of 2-3 nm without adjustable parameters. This success indicates that DLVO theory is highly reliable to quantify interaction forces in such systems. However, charge regulation effects are found to be important, and they must be considered to obtain correct description of the forces. The use of the classical constant charge or constant potential boundary conditions may lead to erroneous results. To make reliable predictions of the force profiles, the surface potentials must be extracted from direct force measurements too. For highly charged surfaces, the commonly used electrophoresis techniques are found to yield incorrect estimates of this quantity.

Probing the Influence of the Particle in Single Particle Tracking Measurements on Lipids

We present a systematic study of the influence of the nanoparticle used as a probe in Single Particle Tracking experiments with a supported lipid bilayer as a model system. Quantum Dots, 40 nm and 200 nm diameter fluorescent latex spheres, and 40 nm diameter gold colloids were attached to headgroup-labeled lipid molecules in the bilayer by means of an antibody. The percentage of the particle's surface covered with antibody was also varied. We argue that the best estimate of the diffusion coefficient is derived from the first two points of the particle's mean square displacement. The accuracy of this estimate is equivalent to a more rigorous analysis based on the cumulated probability function. We show that, under optimal conditions, Quantum Dots and also 40 nm latex beads have a negligible influence on the lipid diffusion. The diffusion coefficient of gold colloids and 200 nm diameter latex particles was systematically reduced 2- to 3-fold compared to the reference value obtained by Fluorescence Recovery After Photobleaching. Unexpectedly, the diffusion coefficient of Quantum Dots and 40 nm latex beads depended on the percentage of the nanoparticle's surface covered with antibody: at very low percentage the perturbation to the lipid diffusion due to the particle increased. We speculate that in this regime subtle details of antibody binding to the nanoparticle become important.In an alternative system using particles tethered with 30 or 90 bp DNA strands, particles attached with the longer tether showed the highest diffusion coefficient. We propose that the proximity of the nanoparticle to the membrane may modify lipid dynamics.ReferenceP. Mascalchi et al. 2012. Probing the influence of the particle in Single Particle Tracking measurements of lipid diffusion. Soft Matter, 2012,8, 4462-4470.

Probing the influence of the particle in Single Particle Tracking measurements of lipid diffusion

We present a systematic study of the influence of the nanoparticle used as a probe in Single Particle Tracking experiments with a supported lipid bilayer as a model system. Quantum Dots, 40 nm and 200 nm diameter fluorescent latex spheres, and 40 nm diameter gold colloids were attached to headgroup-labeled lipid molecules in the bilayer by means of an antibody. The percentage of the particle's surface covered with antibody was also varied. We made the choice to extract the diffusion coefficient from the first two points of the mean square displacement of the particle after demonstrating that the accuracy of this method is equivalent to a more rigorous but less prevalent analysis based on the cumulated probability function. We show that, under optimal conditions, Quantum Dots and also 40 nm latex beads have a negligible influence on the lipid diffusion, whereas the diffusion coefficient of gold colloids and 200 nm diameter latex particles was systematically reduced 2- to 3-fold compared to the reference value obtained by Fluorescence Recovery After Photobleaching. Interestingly, the diffusion coefficient of Quantum Dots and 40 nm latex beads depended on the percentage of the surface of the nanoparticle covered with antibody in an unexpected manner: at very low percentage the perturbation to the lipid diffusion due to the particle increased. We speculate that in this regime subtle details of antibody binding to the nanoparticle become important.

Semi-Continuous Emulsion Copolymerization of Styrene-Butyl Acrylate with Methacrylic Acid: Screening Design of Experiments

A fractional factorial screening design of experiments was conducted to identify the effects of five variables, i.e., styrene/butyl acrylate ratio, methacrylic acid content, pH, emulsifier content, and chain transfer agent content on various product properties in the monomer-starved semi-batch emulsion copolymerization of styrene/butyl acrylate. The impact of these variables on the methacrylic acid (MAA) distribution in the latex, the average latex particle diameter, the molecular weight and distribution of the polymer products, the glass transition temperature (Tg) of the polymer, and the coating adhesion to a plastic substrate was studied.

Semi‐Continuous Emulsion Copolymerization of Styrene‐Butyl Acrylate with Methacrylic Acid: Box‐Behnken Design of Experiments

AbstractA three‐factor three‐level Box‐Behnken design was conducted to study the semi‐continuous emulsion copolymerization of styrene (St)/butyl acrylate (BA) with methacrylic acid (MAA). The effects of St/BA ratio, MAA content, and pH on the carboxylic acid distribution in the latex, the polymer glass transition temperature (Tg), the average latex particle diameter, the molecular weight and distribution of the polymer products, and the coating adhesion to a polycarbonate substrate were investigated. The experimental results showed how the pH affected the distribution of MAA in the polymer particles. Regression analysis revealed how the St/BA ratio, MAA content, and pH influence the copolymer Tg, the latex particle size, the number‐average molecular weight Mn as well as the weight‐average molecular weight Mw. An empirical model to correlate the pull‐off adhesion of the latex coating to a polycarbonate substrate was developed.

Carboxylic acid-functionalized, core–shell polystyrene@polypyrrole microspheres as platforms for the attachment of CdS nanoparticles

Polypyrrole-coated polystyrene latex particles bearing N-carboxyl functional groups (PS@PPyCOOH) were prepared by the in-situ copolymerization of pyrrole (Py) and the active carboxyl-functionalized pyrrole (PyCOOH) in the presence of 390 nm diameter-sized polystyrene (PS) latex particles. Uncoated PS particles were prepared by emulsion polymerization of styrene. The initial comonomer fractions (in mol%) were 25/75, 50/50, 75/25 and 100/0 for pyrrole and PyCOOH, respectively. The PS@PPyCOOH x particles, where x stands for the initial molar fraction of PyCOOH ( x = 0, 25, 50 or 75%), were characterized in terms of particle size, surface morphology, chemical composition and electrochemical redox activity using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), FTIR, TGA and cyclic voltammetry respectively. TEM showed an increase of the latex particle diameter after coating by the conducting polymer layer, from 390 nm for uncoated PS to 430 nm for PS@PPyCOOH 50 particles, allowing an estimation of the PPyCOOH shell thickness to 20 nm. FTIR and XPS detected PyCOOH repeat units at the surface of the latex particles, indicating that this monomer had indeed copolymerized with pyrrole. The core–shell structure of the PS@PPyCOOH x particles was confirmed by etching the polystyrene core in THF, leading to the formation of hollow conducting polymer capsules. Positively charged CdS nanoparticles were electrostatically assembled onto the surface of PS@PPyCOOH 50 particles, as a function of pH. It was found that, contrarily to unfunctionalized PPy-coated latex particles, PS@PPyCOOH 50 particles could be evenly decorated with stabilized CdS nanoparticles, at pH 5. The films of the PS@PPyCOOH@CdS-coated ITO electrodes are shown to be electroactive and electrochemically stable.

Preparation and characterization of fluorinated acrylate copolymer latexes by miniemulsion polymerization under microwave irradiation

Abstract Fluoroacrylate copolymer miniemulsion was prepared by miniemulsion polymerization under microwave irradiation. The composition of the copolymer was determined by FTIR, DSC, 1H NMR and 19F NMR. The morphology, size, and size distribution of the latex particles as well as changes in the size during polymerization were characterized by TEM and photon correlation spectroscopy (PCS). The effects of kinetic parameters on the polymerization were evaluated. The particle size of latex underwent almost no change during microwave irradiation polymerization. The diameters of latex particles prepared by microwave irradiation were smaller and more monodispersed than those prepared by conventional heating and the latex had good centrifugal stability. Polymerization under microwave irradiation had a higher reaction rate and higher conversion than traditional heating. By using 10 wt% fluoromonomer, the surface energy of the latex film could be reduced from 27.24 mJ/m2 (latex film of fluorine-free) to 17.59 mJ/m2 and the decomposition temperature increased by 25 °C.

Homodyne and heterodyne X-ray photon correlation spectroscopy: latex particles and elastomers

In a coherent X-ray small-angle experiment, heterodyning between the scattering amplitudes of two samples is obtained by stacking a static reference and a fluctuating sample. Results of homodyne and heterodyne measurements are compared in the case of 98 nm diameter latex particles in glycerol. The method is also used for the study of the slow relaxation process of carbon-black-filled ethylene–propylene elastomers corresponding to the relaxation of the carbon black skeleton after a 100% elongation. On the scale of the 10 µm coherent beam, heterodyning is used to separate fluctuations from long-term flowing of the sample. We show that this flow can be observed for about 10 h, with velocities of the order of nanometres per second. Random fluctuations are dominant in the speckle changes only for large q values (q > 2 × 10−2 Å−1) and after a long relaxation time.

Synthesis and performance characteristics of a water‐based polyacrylate microemulsion for UHMWPE fiber adhesive coating

AbstractThe water‐based polyacrylate microemulsion for ultrahigh molecular weight polyethylene (UHMWPE) fibers adhesive coating was synthesized by the emulsion polymerization of methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (AA), and hydroxyethyl acrylate (HEA) in the presence of a composite of sodium lauryl sulfate (SLS), OP‐10, and n‐octyl alcohol (NOA) as the emulsifier. The effects of the mass fraction of emulsifier and the reaction time on the properties of emulsion and its membrane were investigated. When m(BA) : m(MMA) : m(AA) : m(HEA) was 50 : 50 : 3 : 10 (wt ratio) and the mass fraction of emulsifier was 13 wt % and the reaction time was 3 h at 80°C, the latex particle diameter was 30 nm tested by transmission electron microscope (TEM). The Fourier transform infrared (FTIR) spectrometer and differential scanning calorimeter (DSC) were used to characterize the chemical structure and the glass transition temperature (Tg) of microemulsion membrane. The application results showed that this microemulsion was an ideal adhesive coating for UHMWPE fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Synthesis and characterization of fluoropolymer modified polyacrylate in emulsion polymerization

AbstractA novel method to produce fluorine‐containing polyacrylate emulsion is presented. It is prepared by the copolymerization of n‐methyl methacrylate, n‐styrene, n‐butyl acrylate, and α‐methacrylic acid in the presence of swollen particles of PTFE. The structure and properties of the polymers are characterized by GPC, PSD, SEM, and XPS. The number‐average molar mass (Mn) 51,332, and the polydispersity 5.8688 are obtained. The mean diameter of latex particles is 300nm. Scanning electron microscopy reveals that particles of the emulsion are well dispersed. Meanwhile, the F1S content of the surface on the latex membrane is 8.99%. It is shown that the method of mixing micron and nanometer‐sized particles should be made the next step of research. It is also proved that inertia polymers can be used in emulsion property modification. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 558–562, 2006

Concentrated emulsion polymerization of methyl methacrylate/butyl acrylate initiated by a redox system

AbstractStable concentrated emulsions of methyl methacrylate/butyl acrylate were prepared with sodium dodecyl sulfate and cetyl alcohol as the compound surfactant and poly(vinyl alcohol) as the major reinforcer of the liquid film. With a redox system based on benzoyl peroxide/N,N′‐dimethyl phenylamine introduced into the concentrated emulsions, polymer particles with different shapes and sizes were obtained by initiation of the polymerization at low temperatures. We investigated the kinetic behaviors of concentrated emulsion polymerization and drew linear regression diagrams of its time–conversion curves in a constant rate phase (conversions ranged from 20 to 70%), and the experimental results show that the variation of the concentrations of the compound surfactant and initiator, the categories of reinforcers of the liquid film, the temperatures, and so on were responsible for the polymerization stability and the polymerization rate. Finally, the kinetics equation and activation energy of the initiator were obtained. The particle size and distribution of particle diameters of latex particles were determined by photon correlation spectroscopy. The determination results reveal that concentrations of the compound surfactant, polymerization temperatures, and so on affected the shape and size of the polymer particles greatly. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1695–1701, 2005

Non-contact nanoparticle removal with laser induced plasma pulses

Nanoscale substrate cleanliness is an essential requirement in a variety of nanotechnologyapplications. The proposed particle removal technique based on pressure shock wavesdue to laser induced plasma is of interest in various nano/micro-manufacturingapplications in which the minimum feature size is reducing rapidly. Any removalmethod adopted in a manufacturing process must be on the same shrinking featurereduction curve since, for device reliability, the minimum tolerable foreign particle sizeon a substrate depends on the minimum feature size on a nano/microsystem ordevice. In the current study, the transient pressure fields exerted on a surfacewith nanosecond pulse laser generated plasma shock waves are measured using apolyvinylidene difluoride film (PVDF)-based line transducer that was designedand tested for this particular measurement task. Using the pressure data, thecorresponding diameters of latex particles that can be removed at these pressure levelsare then calculated. It has been shown that latex particles as small as 60 nm indiameter can be removed from silicon surfaces using the nanosecond pulsed laser.Experimental removal data supporting these predictions are also included and discussed.

Ultrasonic Trap To Monitor Morphology and Stability of Developing Microparticle Aggregates

Aggregation and flocculation of latex particles have been examined in an ultrasonic standing wave trap that draws microparticles from suspensions into a light-microscope prefocused central region of the pressure node plane. The ultrasound chamber had a single half-wavelength path length (λ/ 2 = 0.25 mm) at its resonant frequency of 3.17 MHz. The full course of aggregate growth, in water or in 10 mM CaCl 2 , of 25 μm diameter latex particles was monitored by video microscopy. The particles formed two-dimensional aggregates in the nodal plane. Particles suspended in deionized water joined the aggregate both as single particles and as clusters. Incoming particles rolled over particles at the edge of the aggregate. The aggregate then adjusted its internal order to maintain a regular array of particles in apparent close contact. In contrast, particles in salt solutions interacted strongly on contact so that the aggregates grew as dendritic structures. The perimeter fractal dimensions of 1.15 and 1.59 in water and in salt, respectively, were typical of transport-limited and reaction-limited aggregation. When the ultrasonic exposure was terminated, the compact, low fractal dimension flocs disaggregated as they sedimented while the dendritic aggregates remained intact. It is shown that at surface separations of the order of 10 nm the acoustic particle interaction forces (dependent on the separation of centers of mass) are small compared to the van der Waals and electrostatic interaction forces (dependent on surface- surface separation) that normally control microparticle aggregation. It is concluded that the ultrasound did not significantly influence the net interactions that determine aggregate morphology and stability and that the ultrasonic trap technique holds promise for elucidating patterns of aggregate growth.

Sonochemical production of fluorescent and phosphorescent latex particles.

A novel method for producing nanosized polymer latex particles doped with fluorescent and phosphorescent solutes is described. Methyl methacrylate monomer (10 wt %) containing either pyrene, 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DMDP), or 1-bromonaphthalene was ultrasonically dispersed in water and simultaneously polymerized to produce approximately 60 nm diameter latex particles. A fluorescence spectroscopic examination of the latex dispersion containing either pyrene or DMDP showed that the solutes were not covalently bound to the polymer and that they were embedded in a highly viscous environment possessing a low polarity (dielectric constant on the order of 2). The fluorescence lifetime of the pyrene in the core of the poly(MMA) latex was found to be 520 ns, irrespective of the oxygen concentration in the dispersion. Room-temperature phosphorescence was observed from 1-bromonaphthalene, with a lifetime of 2.0 ms in an argon atmosphere. In the presence of air, phosphorescence was still observable although with a partially reduced emission intensity.

Bioencapsulation in Artemia: II. Influences of the particle concentration in the enrichment process

Available information about bioencapsulation in Artemia indicates that there is no agreement about the food concentrations to fulfill this objective. In this study, experiments with 15 different concentrations of 5 μm diameter latex particles were made. The behavior of different size classes of animals analyzed is shown with results stating that their feeding behavior is a function of size. An increase in the percentage of filled digestive tracts of individuals occurs when the concentration of particles in the medium increases. Concentrations higher than 12 500 particles/ml allow filling of the digestive tract in individuals of up to 3.2 mm size in 1 h of treatment. Concentrations of 200 000 and 400 000 particles/ml allow the total filling of the digestive tract of individuals of up to 5.6 mm long in 1 h. For individuals larger than 5.6 mm, the highest concentrations of particle are those that allow the filling of the digestive tract most efficiently.