Number Average Particle Diameter Research Articles

Polymeric nanoparticles for selective protein recognition by using thiol-ene miniemulsion photopolymerization

The fabrication of molecularly imprinted nanoparticles (MIP-NPs) specific for myoglobin by using thiol-ene photopolymerization in miniemulsion was described. Allyl derivatives of phenylalanine as a functional monomer was synthesized and copolymerized with acrylic monomers via miniemulsion polymerization to produce NIP-NPs with approximately 74 nm number average particle diameter. FTIR and 1H-NMR analysis confirmed the synthesis of functional monomer. MIP-NPs were prepared in the existence of myoglobin as a template protein. Morphological investigations exhibited that the particle size of the MIP-NPs, increased compared to the corresponding NIPs and the mean particle diameter by number was measured as 141 nm with narrow distribution. NIP-NPs that were polymerized without myoglobin were found to have less affinity to the target protein. In addition, the rebinding ability of MIP-NPs was much bigger than that of the corresponding NIPs. ELISA results showed that MIPs interact particularly with the myoglobin and show little affinity for BSA in competitive binding experiments.HighlightsAllyl N,N-diallyl phenylalaninate was synthesized as a functional monomer.Imprinted nanoparticles were prepared by using thiol-ene photopolymerization in miniemulsion.The nanoparticles were 141 nm with narrow size distribution.The imprinted nanoparticles showed selectivity toward myoglobin.

Semiconducting polypyrrole@TiO2 pure anatase nanoparticles for photodegradation of reactive red 120 azo dye

In the recent years, the development of new and efficient materials for photocatalytic processes has been of growing interest for applications in wastewater treatment. In this sense, TiCl4 stabilized with H2SO4 was precipitated with ammonium hydroxide in the presence of sodium dodecyl sulfate and calcined to obtain thermally stable TiO2 nanoparticles, which were subsequently coated with semiconducting polypyrrole (PPy) by chemical oxidation resulting in a composite of TiO2@PPy. TiO2 and TiO2@PPy composite were characterized by SEM, Raman, XRD, UV/Vis–NIR, FTIR and TGA. It was observed that TiO2 consisted of spherical nanoparticles with number-average particle diameter of 19.2 nm and polydispersity index in sizes of 1.2, whereas TiO2@PPy composite consisted of agglomerated spherical PPy nanoparticles of number-average diameter of 182.4 nm coating TiO2 nanoparticles. The calculated optical bandgap of TiO2 was 3.07 eV, and it was demonstrated by the Rietveld refinement method of the XRD spectrum and from the Raman analysis that synthesized TiO2 corresponds to highly pure rhombic anatase crystal structure. TiO2@PPy composite was tested in the photodegradation of the reactive red 120 azo dye in aqueous solutions under visible light irradiation. It was observed that photodegradation rate increased with decreasing the initial dye concentration and increasing the composite load. Almost 100% of dye removal was achieved after 45 min of reaction for 20 mg L−1 of initial dye concentration and 1.0 g L−1 of composite load.

Model construction of particle size in dynamic vulcanization of PVDF/SR blends—matching degree between crosslinking and shearing rates

Abstract Peroxide-induced dynamic vulcanization of poly (vinylidene fluoride)/silicone rubber (PVDF/SR) blends was studied in this paper. We controlled the size of rubber particles by changing the rotor speed, and discussed the influence of shearing on the particle diameter and the particle diameter polydispersity (dp). The size of SR particle was confirmed to be decreased with increasing the rotor speed. However, a good matching degree of shearing and crosslinking rate helped the SR phase to achieve a uniform crosslinking, as well as a narrow dp. In this particular PVDF/SR system, the suitable rotor speed was found to be 90 rpm, at which the dp reached a minimum of 1.1981 and 1.1614 for the P9S1 and the P7S3, respectively. At last, we discussed the influences of the macroscopic breaking energy (Edk) and the coalescence (P) on the number-average particle diameter (Dn) of the SR. This work is thus devoted to construct a model for predicting the particle size in dynamic vulcanization of PVDF/SR blends.

Heating of polyacrylamide ferrogel by alternating magnetic field

Ferrogel based on polacryamide network with embedded maghemite nanoparticles with mean number average particle diameter 12nm was synthesized by radical polymerization in water-based ferrofluid. The network structure of ferrogel was characterized by Flory–Rehner theory and it was shown that the embedded particles were substantially larger than the mesh size. It prevented the translational movement of particles in the ferrogel. The immobilization of particles was confirmed by dynamic light scattering. The adhesion of macromolecular chains to the particles was determined by calorimetry using thermochemical cycle. The enthalpy of interfacial adhesion was found several orders of magnitude higher than the energy of dipoles in typically applied magnetic fields. Despite the differenve in the mobility of particles in ferrofluid and ferrogel the comparative study of their heating in alternating magnetic field, however, revealed their close similarity. In both cases it was goverened by superposing of Neel and Brownian relaxation mechanisms.

Comparing Heat-treated Silica Particle with Silica Particles for the Ability to Induce Superoxide Release from Rat Alveolar Macrophages

Crystalline silica can devitrify with the formation of cristobalite and other crystalline silica species when exposed to prolonged high temperatures, which is of potential concern because crystalline silica is classified as carcinogenic. Silica particles activate macrophages to release oxidants, which contribute to inflammation and injury in the lower respiratory tract. Our aim was to compare silica particles with heat-treated silica particles for their ability to induce superoxide release from rat alveolar macrophages. We estimated the ability of four types of silica particle samples and heat-treated silica particles with different number average particle diameter to induce lucigenin-dependent chemiluminescence (CL) from macrophages based on the number of silica particles. A strong positive correlation was observed between particle diameter and the ability to induce CL in both the silica and heat-treated silica samples. Moreover, the ability of heat-treated silica samples to induce CL was approximately 43% of that of the silica samples. These results suggest that heat-treated silica reduces superoxide release from macrophages, and that the heat-treated reduces the biological effects of silica.

Orifice jamming of fluid-driven granular flow

The three-dimensional jamming of neutrally buoyant monodisperse, bidisperse, and tridisperse mixtures of particles flowing through a restriction under fluid flow has been studied. During the transient initial accumulation of particles at the restriction, a low probability of a jamming event is observed, followed by a transition to a steady-state flowing backlog of particles, where the jamming probability per particle reaches a constant. Analogous to the steady-state flow in gravity-driven jams, this results in a geometric distribution describing the number of particles that discharge prior to a jamming event. We develop new models to describe the transition from an accumulation to a steady-state flow, and the jamming probability after the transition has occurred. Predictions of the behavior of the geometric distribution see the log-probability of a jam occurring proportionally to (R(2)(2)-1), where R(2) is the ratio of opening diameter to the second moment number average particle diameter. This behavior is demonstrated to apply to more general restriction shapes, and collapses for all mixture compositions for the restriction sizes tested.

무유화중합에 의한 단분산 Submicron 크기의 고분자 미립자의 제조

음이온개시제인 <TEX>$K_2S_2O_8$</TEX> (KPS)와 양이온개시제인 2,2' azobis(2-methyl-propionamidine) dihydrochloride (AIBA)를 이용하여 MMA와 BMA 단량체간의 무유화공중합을 성공적으로 수행하여 PSD가 1.002~1.008인 단분산성이 우수한 poly(BMA-co-MMA)와 PBMA 라텍스들을 제조하였다. 실험결과, 160~494 nm 범위의 수평균입자경과 (1.25~7.55) <TEX>${\times}10^4$</TEX> 범위의 수평균분자량을 나타내었다. MMA/BMA 유화중합에 따르는 중합속도와 단량체 및 개시제 농도, DVB/EGDMA 가교제 농도, 중합온도 변화에 따르는 수평균입자경과 수평균분자량의 영향을 조사하였다. MMA/BMA 단량체 중 MMA 농도가 증가함에 따라 중합속도가 증가하였으며 일반적으로 이들 라텍스의 평균입자경과 평균분자량은 MMA/BMA 단량체중량비, 단량체량, 개시제량, 중합온도에 따라 쉽게 조절됨을 발견하였다. Narrowly dispersed poly(BMA-co-MMA) and PBMA latices (PSD : 1.002~1.008) were synthesized successfully by surfactant-free emulsion polymerization with 2,2' azobis(2-methyl-propionamidine) dihydrochloride (AIBA) and <TEX>$K_2S_2O_8$</TEX> (KPS). The number average particle diameter and the number average molecule weight were found to be 160~494 nm and (1.25~7.55) <TEX>${\times}10^4$</TEX>, respectively. The influences of BMA/MMA ratio, monomer and initiator concentrations, addition of DVB/EGDMA crosslink agent, and polymerization temperature on the polymerization rates and on the particle size and molecular weight were studied. The rate of polymerization increased with increasing MMA concentration in BMA/MMA weight ratio. The particle diameter as well as the polymer molecular weight could be controlled easily by controlling the BMA/MMA weight ratio, monomer concentration, AIBA and KPS concentration, and polymerization temperature.

Individual dose and exposure of Italian children to ultrafine particles

Time–activity patterns and the airborne pollutant concentrations encountered by children each day are an important determinant of individual exposure to airborne particles. This is demonstrated in this work by using hand-held devices to measure the real-time individual exposure of more than 100 children aged 8–11years to particle number concentrations and average particle diameter, as well as alveolar and tracheobronchial deposited surface area concentration. A GPS-logger and activity diaries were also used to give explanation to the measurement results. Children were divided in three sample groups: two groups comprised of urban schools (school time from 8:30am to 1:30pm) with lunch and dinner at home, and the third group of a rural school with only dinner at home. The mean individual exposure to particle number concentration was found to differ between the three groups, ranging from 6.2×104part.cm−3 for children attending one urban school to 1.6×104part.cm−3 for the rural school. The corresponding daily alveolar deposited surface area dose varied from about 1.7×103mm2 for urban schools to 6.0×102mm2 for the rural school. For all of the children monitored, the lowest particle number concentrations are found during sleeping time and the highest were found during eating time. With regard to alveolar deposited surface area dose, a child's home was the major contributor (about 70%), with school contributing about 17% for urban schools and 27% for the rural school. An important contribution arises from the cooking/eating time spent at home, which accounted for approximately 20% of overall exposure, corresponding to more than 200mm2. These activities represent the highest dose received per time unit, with very high values also encountered by children with a fireplace at home, as well as those that spend considerable time stuck in traffic jams.

Design of polyglycidol-containing microspheres for biomedical applications

AbstractThe paper presents a short review on the synthesis, characterisation and selected medical applications of poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) (P(S/PGL)) microspheres. The soap-free emulsion-polymerisation of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer (PGL) in water yielded core-shell microspheres with a low particle-diameter dispersity (ratio of the weight average particle diameter and the number average particle diameter). The interfacial fraction of PGL units, estimated by XPS, was in the range of 0–42 mole % depending on the concentration of the macromonomer in the polymerisation feed. The studies of adsorption of model proteins showed that the surface fraction of adsorbed protein was significantly reduced when the PGL interfacial fraction was higher than 40 mole %. The P(S/PGL) particles with covalently immobilised proteins were used for the preparation of photonic crystal assemblies suitable for applications in optical biosensors and the medical diagnostic test for the detection of Helicobacter pylori antibodies in the blood serum.

The Sintering of Supported Pd Automotive Catalysts

AbstractThis work is directed at investigating the contribution of metal particle sintering to catalyst deactivation in close‐coupled automotive catalysts that are aged at elevated temperatures. We focus on the evolution of metal particle sizes in Pd/Al2O3 under conditions typically used for accelerated aging of automotive exhaust catalysts (10 mol % H2O at 900 °C). By using multiple analytical techniques (transmission electron microscopy, X‐ray diffraction, chemisorption, and CO oxidation) we can determine the role of support surface area collapse (encapsulation) versus metal particle sintering. The final dispersion (% metal atoms exposed) after sintering for 96 h ranged from 1.94 to 0.86 % for metal loadings ranging from 0.1 to 7.0 wt % (a 70‐fold variation). Thus, it appears that metal loading (over the range studied) has only a limited effect on the final dispersion in the sintered catalyst. The sintering kinetics were found to obey a relationship dn−${d{{n\hfill \atop 0\hfill}}}$=kt for which the exponent n is approximately 2.0 and d is the number average particle diameter at time t. This relationship and the fact that metal particle size continues to grow with time are both consistent with Ostwald ripening as the dominant mechanism. Furthermore, no limiting (equilibrium) particle size was achieved within the sintering times studied here (up to 200 h). These results have important implications for the design of thermally stable automotive catalysts.

Characterization of Novel pH-Sensitive Polymeric Micelles Prepared by the Self-Assembly of Amphiphilic Block Copolymer with Poly-4-vinylpyridine Block Synthesized by Mechanochemical Solid-State Polymerization

We fabricated novel pH-sensitive polymeric micelles consisting of amphiphilic block copolymer containing pyridyl groups as side chains in the hydrophobic block. The number average particle diameter of the polymeric micelles at pH 7 was approximately 200 nm. A decrease in pH resulted in deformation of the polymeric micelles over a very narrow pH range (between pH 5.7 and 5.6). Interestingly, micellization and demicellization occurred reversibly in this narrow pH range. Polymeric micelles incorporating 5-fluorouracil (5FU) were also prepared. Decreasing the pH of this polymeric micelle solution from 7 to 5.5 resulted in the rapid release of 5FU at pH 5.6; the drug was completely released within 30 min. These results suggest that deformation of the polymeric micelles caused the rapid release of 5FU.

Synthesis of monodisperse poly(styrene-co-divinyl benzene) microspheres by precipitation polymerization in acetonitrile and n-butanol mixture

AbstractNarrow disperse poly(styrene-co-divinylbenzene) microspheres were prepared by precipitation polymerization using acetonitrile/n-butanol mixture as the reaction medium and 2,2’-azobis(2-methylpropionitrile) (AIBN) as initiator. The resulting particles have smooth surfaces due to the absence of any additional stabilizer. Effects of the reaction parameters such as n-butanol fraction in the reaction medium, monomer and initiator concentration, and divinylbenzene content were investigated. It was found that the particle size increased with an increasing concentration of monomer and initiator, while the uniformity was kept constant. The number-average particle diameter ranged from 2.36 to 1.63 μm and decreased with an increasing divinylbenzene concentration. In addition, the uniformity was enhanced as the concentration of divinylbenzene increased. On the basis of the DSC and TGA data, the microspheres prepared by the precipitation polymerization possessed a highly crosslinked structure and the thermal stability improved with the DVB concentration.

Architecture of polymer particles composed of brush structure at surfaces and construction of colloidal crystals

The synthesis of polymer particles is reported, which are composed of (1) a spherical colloidal core particle, (2) encapsulation of such seed particles with the inimer 4-vinylbenzyl N,N-diethyldithiocarbamate (VBDC) providing the formation of a hyperbranched structure by a living radical mechanism, and followed by (3) a grafted polymer brush prepared by photo-induced atom transfer radical polymerization (ATRP). The particle sizes (number-average particle diameter D n = 190–300 nm) were controlled by varying the temperature and size distributions were extremely narrow ( D w/ D n = ca. 1.0001). By variation of the particle size, the brilliant color could be varied throughout the visible spectrum. The morphology of the core–shell particles and the properties of corresponding film were characterized by Fourier transform infrared (FT-IR), dynamic light scattering (DLS), reflection spectrum measurements, and scanning electron microscopy (SEM).

Facile Access to Hydroxy‐Functional Core–Shell Microspheres via Grafting of Ethylene Oxide by Anionic Ring‐Opening Polymerization

We present a facile access route to hydroxy-functional narrow disperse microspheres of well-defined grafting density (GD). Ethylene oxide has been grafted from highly crosslinked poly(divinyl benzene) microspheres by anionic ring-opening polymerization using sec-butyllithium as activator together with the phosphazene base t-BuP(4) . Initially, core microspheres have been prepared by precipitation polymerization utilizing divinyl benzene (DVB, 80 wt.-%). The grafting of poly(ethylene oxide) (PEO) from the surface resulted in the formation of functional core-shell microspheres with hydroxy-terminal end groups. The number average particle diameter of the grafted microspheres was 3.6 µm and the particle weight increased by 5.7%. The microspheres were characterized by SEM, FT-IR spectroscopy, elemental analysis, and fluorescence microscopy. The surface GD (determined via two methods) was 1.65 ± 0.06 and 2.09 ± 0.08 chains · nm(-2) , respectively.

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization

Seeded emulsion polymerization was used to prepare magnetic polymeric composite nanoparticles (MPCNPs) with the aim to successfully encapsulate magnetite particles and to improve particle size distribution (PSD). Microscopical morphology and number-average diameter of hydrophilic magnetite particles (HMPs), magnetic seed latex nanoparticles (MSLNPs) and MPCNPs were observed and analyzed by transmission electron microscope (TEM). Weight-average diameter and PSD of MSLNPs and MPCNPs were also analyzed by TEM. Magnetic properties of MPCNPs were investigated by Vibrating Sample Magnetometry (VSM). The results showed that the encapsulation of magnetite particles was not complete by conventional emulsion polymerization but very successful by seeded emulsion polymerization, the resulted MPCNPs were nanoparticles with much narrower PSD than that of MSLNPs, and exhibited superparamagnetism and possessed a certain level of magnetic response.

Polymerization of methyl methacrylate in carbon dioxide using glycidyl methacrylate linked reactive stabilizer: Effect of pressure, reaction time, and mixing

Using glycidyl methacrylate-linked poly(dimethylsiloxane), methyl methacrylate was polymerized in supercritical CO . The effects of CO pressure, reaction time, and mixing on the yield, molecular weight, and molec- ular weight distribution (MWD) of the poly(methyl methacrylate) (PMMA) products were investigated. The shape, number average particle diameter, and particle size distribution (PSD) of the PMMA were characterized. Between 69 and 483 bar, the yield and molar mass of the PMMA products showed a trend of increasing with increasing CO pressure. However, the yield leveled off at around 345 bar and the particle diameter of the PMMA increased until the pressure reached 345 bar and decreased thereafter. With increasing pressure, MWD became more uniform while PSD was unaffected. As the reaction time was extended at 207 bar, the particle diameter of PMMA decreased at 0.48 ± 0.03% AIBN, but increased at 0.25% AIBN. Mixing the reactant mixture increased the PMMA yield by 18.6% and 9.3% at 138 and 207 bar, respectively.

Continuous emulsion copolymerization of acrylonitrile and butadiene: Computer simulation study for improving the rubber quality and increasing production

This theoretical article investigates an industrial emulsion copolymerization of acrylonitrile (A) and butadiene (B), for the production of grades BJLT and AJLT of a nitrile rubber (NBR). The simulated process involves a train of eight continuous stirred-tank reactors operating at 10 °C. The product quality is determined by its molecular structure (average copolymer composition, average molecular weights, and average level of branching), and by its final latex characteristics (number particle concentration and number-average particle diameter). The mathematical model by Vega et al. [Vega, J. R., Gugliotta, L. M., Bielsa, R. O., Brandolini, M. C., & Meira, G. R. (1997). Emulsion copolymerization of acrylonitrile and butadiene, mathematical model of an industrial reactor. Industrial and Engineering Chemistry Research, 36, 1328] for the semibatch process was extended to investigate three alternative steady-state (SS) operations of a continuous reactor train. When all the reagents are fed into the first reactor (Normal SS), then a deteriorated quality compared with respect to the equivalent batch process is produced (with increased polydispersities and degrees of branching). This can be improved by admitting intermediate feeds of A and chain transfer agent (CTA) along the train. If in addition, constant B feeds are admitted, then it is possible to eliminate the compositional drift, to generate predetermined profiles of the average molecular weights, and to increase the rubber production by over 10% with respect to the Normal SS. The best improvements were observed for grade AJLT.

Preparation and application of nanoscale microemulsion as binder for fabric inkjet printing

To obtain a nanoscale binder suitable for pigment-based inkjet ink printing on fabrics, a polymer microemulsion with a high content of soft monomer of butyl acrylate (BA) was synthesized via a modified microemulsion polymerization method, where N-methylolacrylamide (NMA) served as the cross-linking monomer and monododecyl maleate (MDM) as the copolymerizable surfactant. The effects of the functional monomers (NMA, MDM), the weight ratios of monomers, and the solid contents on the microemulsion properties were investigated by TEM, DSC, particle size analyzing, and fabric inkjet printing. The results indicated that the microemulsion had a number-average particle diameter less than 50 nm and with narrow particle size distribution. It was also found that the glass transition temperatures ( T g) of the film formed from the microemulsion could be lower than −30 °C. Fabric inkjet printing application of the pigment-based inks formulated with the as-considered optimum microemulsion as a binder and commercial pigment dispersions demonstrated excellent printability of the inks, and good colour fastnesses and softness of the printed fabrics.

Catalytic Insertion Polymerization of Norbornene in Miniemulsion

The catalytic insertion polymerization of norbornene (NB) was implemented under miniemulsion conditions. Using sodium dodecyl sulfate (SDS) as surfactant and hexadecane as hydrophobe, the insertion polymerization was initiated by multicomponent catalysts generated in situ by reacting allylpalladium chloride dimer, [(eta(3)-allyl)Pd(Cl)](2), with a desired phosphine ligand and then activating the resulting procatalyst with a salt of noncoordinating anion, typically the lithium salt of tetrakis(pentafluorophenyl)borate (Li[B(C6F5)(4)]center dot 2.5Et(2)O). By choosing either an organo-soluble (tricyclohoxylphosphine) or a water-soluble phosphine ligand (tris(3-sulfonatophenyl)phosphine sodium salt), two palladium procatalysts I and II exhibiting different solubilities in water were generated and then used to polymerize NB in miniemulsion. After activation, both I and H displayed high activity and led to stable PNB latexes with good particle size control throughout the course of the reaction. Stable polynorbornene latexes with a relatively broad particle size distribution were produced. The number-average particle diameter is often below 100 nm. The nature of the surfactant and the effect of changing the concentrations of activating agent, procatalyst, and hydrophobe on the polymerization kinetics, latex stability, and particle size were investigated.

Dispersed Particle Size Distribution in Impact Modified Polypropylene

In this work ternary polypropylene (PP) rich blends with ethylene propylene terpolymers (EPDM) and LLDPE are studied. Attention is focused on the effect of different viscosity ratios (β1/4 viscosity of dispersed phase/viscosity of PP matrix) on the particles sizes and particle size distribution of the dispersed phase. The incidence of the elastomer viscosity and dispersed phase content are also analyzed. A reduction in the viscosity ratio mainly affects the weight average particle diameter (Dw) rather than the number average particle diameter (Dn).