PMMA Particle Size Research Articles

Tuning thin film thickness and porosity with Layer‐by‐layer submicronic particles assembly

Porous NiO films were prepared using Layer‐by‐Layer assembly of submicronic β‐Ni(OH)2 nanoplatelets and size‐controlled poly(methyl methacrylate) (PMMA) particles. β‐Ni(OH)2/PMMA thin films were elaborated using different PMMA particle sizes and concentrations. The elaborated films were then heated at a temperature of 325°C in air for one hour to form porous NiO films by calcining β‐Ni(OH)2 nanoplatelets. PMMA polymeric particles were also calcined during this process, leading to film porosity. Thermal treatment experiments clearly showed a relationship between PMMA particle size and film properties i.e., porosity and thickness. NiO films exhibited huge pores, around 1 µm, and matter loss after calcination when PMMA particles with a diameter of 190 ± 43 nm were employed. Partial collapsing of the films was also denoted. Experiments were then carried out by decreasing PMMA particle size (100 ± 19 nm) leading to cohesive NiO films. Finally, the specific surface area (SSA) of the NiO films prepared with PMMA particles of 100 nm was determined by adsorption‐desorption of nitrogen gas using the BET (Brunauer–Emmet–Teller) method. This showed an increase in SSA with PMMA particle concentration.

Influence of PMMA particle size control on the transmittance of PMMA/tempo-oxidized cellulose composites

Cellulose is a class of biopolymers that prominently contributes to developing lightweight, eco-friendly, and biodegradable plastics. Among them, nanofibrillated cellulose (NFC) is one of the most interesting due to its mechanical behavior. Mixing it with synthetic plastic such as poly(methyl methacrylate) (PMMA) reduces synthetic polymer usage, agro-industrial residue and develops fiber-reinforced composites. NFC was prepared from residual biomass and oxidized with TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical). Herein, NFC was incorporated (25, 50 and 75 wt%) in a colloidal emulsion of PMMA, with PMMA particle size control (50 and 175 nm). The investigation of this system on the PMMA/NFC transparency was addressed here. FTIR and SEM demonstrated effective incorporation of NFC and interaction with the PMMA. The increment of NFC increased the water contact angle and improved film transparency. Paired with PMMA particle size control, particularly at 50 nm, this favored composite transparency, becoming close to or even greater than pure NFC.Graphical abstract

3D‐printed alumina‐based ceramics with spatially resolved porosity

AbstractThe interest on porous ceramics has increased in the last years with the developments in additive manufacturing methods, enabling design of components with complex geometries for membranes, filters, catalytic converters, or biostructures. In this study, porous alumina samples were produced by using different concentrations of poly(methyl methacrylate) (PMMA) as pore‐forming agent (PFA) in a photocurable slurry via vat photopolymerization (VPP). The effect of layer thickness, PMMA particle size, and sintering temperature on the mechanical properties and microstructural features of the samples was investigated as a function of PMMA concentration. It is shown that the mechanical properties of 3D‐printed porous alumina are comparable with those fabricated by conventional processes. The Young modulus, fracture toughness as well as the biaxial strength decreased with increasing weight concentration of PFA (resulting in an increased total porosity). Specially using smaller PMMA particles has a positive effect, resulting in higher Young's modulus as well as fracture toughness. The feasibility of VPP for fabricating novel parts with more complex porosity regions is explored by printing multi‐material samples and porosity‐graded architectures. The counterbalance effect between porosity and mechanical properties may be optimized by tailoring material composition and processing parameters.

Exploiting the tuneable density of scCO2 to improve particle size control for dispersion polymerisations in the presence of poly(dimethyl siloxane) stabilisers

The dispersion polymerisation of methyl methacrylate (MMA) is a widely employed method for producing discrete, spherical PMMA particles from traditional solvents, which cover a broad particle size range. With environmental impact becoming an ever more widespread concern, there is increasing demand for greener solvents with advantageous characteristics. Supercritical carbon dioxide (scCO2) offers the potential of a greener solvent for dispersion polymerisations, with uniquely tuneable solvent properties and the ability to avoid energy and cost intensive drying steps. In this work, the tuneable density of scCO2 was exploited to influence the solubility of poly(dimethyl siloxane) stabilisers in the dispersion polymerisation of methyl methacrylate as a proof-of-concept. By varying the reactor pressure at the start of polymerisation, the final particle size was altered, without the need for cosolvent systems used in traditional solvents. Finally, this additional particle size control mechanism was exploited to achieve a PMMA particle size range far beyond what was previously attainable with this stabiliser. Thus, further enhancing the potential use of scCO2 as a green solvent for industrial polymer production.

Development of lignin‐based carbon foam for use as an FRP sandwich core material

AbstractSandwich‐structure materials consist of a high‐strength skin material and a lightweight core material. The advantages of sandwich structures are known to include excellent mechanical properties and low weight, the latter of which is the result of a lightweight core. However, soft‐core members such as plastic foam materials have low rigidity and therefore may not exhibit adequate functionality when used in sandwich structures. This research sought to reduce environmental impact and to facilitate sustainable development by developing a method for fabricating high‐strength carbon foam using alkali lignin for use as an FRP sandwich core and enhancing the mechanical properties of the carbon foam with short glass fiber. PMMA particles decomposed at high temperatures to leave gaps, creating carbon foam with a closed structure. The relationship between PMMA particle size and foam pore size was investigated by observing cross‐sections of the foam.

Effects of the Particle Size and Agglomeration on the Minimum Explosible Concentration and Flame Propagation Velocity in Dust Clouds

The flame propagation behavior and the effect of particle agglomeration are examined by changing the size of PMMA particles in laboratory-scale experiments. PMMA particles having a very narrow size distribution are used. We show that the minimum explosible concentration increases as the particle size decreases. On the other hand, the flame propagation velocity also increases as the particle size decreases. Therefore, the minimum explosible concentration and the flame propagation velocity show the opposite dependences on the particle size. It is considered that the minimum explosible concentration is strongly affected by the interparticle distance; meanwhile, the flame propagation velocity strongly depends on the specific surface area. It has to be emphasized that the severity of the explosion can be serious for very fine particles, although the minimum explosible concentration is fairly high.

Preparation of cross-linked poly(methyl methacrylate) microspheres using an asymmetric cross-linker via dispersion polymerization and its application in light diffusers

Cross-linked poly(methyl methacrylate) (PMMA) microspheres have been successfully prepared by using the asymmetric cross-linker allyl methacrylate (AMA) via dispersion polymerization. The influence of the AMA amount and polymerization process on the PMMA particle size and morphology has been studied thoroughly. It was found that micron-sized, cross-linked PMMA particles with narrow size distributions could be obtained by a semi-continuous process with the asymmetric cross-linker AMA. The obtained micron-sized, cross-linked PMMA particles could be further used as a light diffusion agent in a polycarbonate matrix, and their light diffusion properties were significantly enhanced by increasing the gel content in the cross-linked particles. Moreover, the influence of the polymerization process, cross-linker content in PMMA and PMMA content in the polycarbonate matrix on light diffusion was carefully investigated. The results showed that the PMMA particles containing 5.0 wt% AMA, obtained by semi-continuous polymerization, had a higher haze and gel content and exhibited a better light diffusion effect than did the other particles.

Modification of the sedimentation method for PMMA photonic crystal coatings

The high technological applications promised by the three-dimensional photonic crystal materials increase the attractiveness of the subject day by day. In this study, it is aimed to obtain regularly arranged photonic crystal coatings in large areas and relatively in a shorter time by modifying the sedimentation technique that is used in the production of direct and indirect photonic crystals. In addition, parameters such as the amount of initiator and temperature in PMMA sphere production were investigated for the colors of the photonic crystal coatings and the effect on the size, morphology, and arrangement of PMMA spheres were scrutinized in details. Consequently, regular arrayed photonic crystal coatings were produced in large areas in a shorter time by the heat triggered the sedimentation method. The resulting color was strongly related to PMMA particle size while the clarity and vividness of color were related to the regular arrangement.

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.

Electrically Conductive Graphene/Poly(methyl methacrylate) Composites with Ultra‐Low Percolation Threshold by Electrostatic Self‐Assembly in Aqueous Medium

Thermally reduced graphene modified with cationic ammonium ions (AAG)—affording a stable dispersion in water—self‐assembles well by electrostatic interaction on the surface of anionic poly(methyl methacrylate) (PMMA) particles of various sizes, by simple mixing in water. An interconnected 3D electrically conductive network of AAG is effectively generated in the composite when the self‐assembled composite is compression molded. The AAG network becomes wide‐meshed and electrical conduction is improved when the PMMA particle size increases, exhibiting a percolation threshold of electrical conductivity as low as 0.06 vol%. In contrast, the protection of PMMA from oxidation by air is more effective when the network is fine‐meshed. image

Morphogical and swelling properties of porous hydrogels based on poly(hydroxyethyl methacrylate) and chitosan modulated by ice-templating process and porogen leaching

A comparative evaluation of the morphological and swelling properties corresponding to the porous poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels and to the chitosan (CS) hydrogels was developed in this paper. The porous structure of hydrogels based on PHEMA or CS was tailored by ice-templating process and porogen leaching. Poly(methylmethacrylate) (PMMA), as fractionated particles, was used as polymer porogen. The influence of the average size of the fractionated PMMA particles on the internal morphology and swelling properties of the hydrogels was followed. The average pore diameter of PHEMA cryogels increased from 10 ± 2 μm up to 22 ± 5 μm with the increase of the size of the fractionated PMMA particles from below 32 μm up to 50–90 μm. On the other hand, in the case of CS cryogels prepared in the presence of the PMMA particles with different sizes, pores with an average size of 74 ± 6 μm, irrespective of the size of PMMA particles were formed, strong changes being observed in the morphology of the pore walls, these being less compact and, therefore, more accessible for the diffusion of low molecular weight species. Hydrogels based on PHEMA or CS with microchanneled structures arranged along the freezing direction, were generated by unidirectional freezing. The swelling measurements showed that the cryogels prepared in the presence of PMMA particles attained the equilibrium swelling much faster than those prepared without PMMA.

Effect of hydrogen peroxide on the UCST behavior of PMMA in the modified dispersion polymerization

The effect of hydrogen peroxide on the formation of molecular weight of poly(methyl methacrylate) (PMMA) in the modified dispersion polymerization using a co-solvent of methanol/water and methanol/hydrogen peroxide aqueous solution was studied. The variables included the molecular weight upon the concentration of initiator and hydrogen peroxide, solubility upon molecular weight and temperature, particle size upon cooling rate, and reversible temperature responsive behavior upon thermal history. The relationship between the temperature and PMMA particle size showed reversible temperature-responsive behavior upon the heating and cooling processes. As a result, hydrogen peroxide was confirmed to act as a co-initiator in reducing the molecular weight of PMMA, a good co-solvent with methanol by improving the solubility and inducing the upper critical solution temperature behavior, and a stabilizer in forming stable particles upon cooling. Open image in new window

Preparation of poly(methyl methacrylate) by ATRP using initiators for continuous activator regeneration (ICAR) in ionic liquid/microemulsions

In this study, we reported the synthesis of poly(methyl methacrylate) (PMMA) polymers via initiators for continuous activator regeneration atom transfer radical polymerization using CCl4 as initiator, FeCl3·6H2O/hexamethylene tetramine as catalyst complex, and 2,2′-azobis(isobutyronitrile) (AIBN) as reducing agent. The polymerization was conducted at 60 °C in the ionic liquid based microemulsion with hexadecyl trimethyl ammonium bromide (CTAB) as surfactant. Kinetics experimental results showed that the polymerization proceeded in a controlled/‘living’ process. The effects of the molar ratio of [CCl4]/[FeCl3·6H2O], the concentration of AIBN, temperature and the concentration of CTAB on the polymerization was investigated. The effect of CTAB concentration on the resulting PMMA particle size was also investigated. The obtained polymer was characterized by proton nuclear magnetic resonance and gel permeation chromatography. The living characteristics were demonstrated by chain extension experiment.

Preparation of monodisperse poly(methyl methacrylate) microspheres: effect of reaction parameters on particle formation, and optical performances of its diffusive agent application

A 3.84 um monodisperse poly(methyl methacrylate) (PMMA) microsphere was prepared by dispersion polymerization in methanol (MeOH)/water (H2O) media. 2,2′-azobis(isobutyronitrile) (AIBN) and poly(acrylic acid) (PAA) were utilized as initiator and steric stabilizer, respectively. The effects of the PAA stabilizer, AIBN initiator, H2O solvent and MMA monomer on PMMA particle size and size distribution were reviewed in the first section. The optical properties including total transmittance (T%) and transmittance haze (H%) were performed when the monodisperse PMMA microsphere was applied as a diffusive agent. The result was examined in terms of total interface area in system, and to compare with the performance of three polystyrene (PSt) microspheres with 1.10 um, 3.13 um and 5.21 um in diameter under the same condition.

1601 分散系レオロジーのモデル化と工学的応用(OS16-1 非ニュートン流体の流動現象,オーガナイズドセッション)

A thixotropy model was developed for the highly loaded and agglomerative suspensions. As the industrial application, this suspension model was applied for the spin coating process to predict the cluster size of PMMA particles. Spin coating process of PMMA particle suspension was experimentally investigated. Comparison of model predictions with experimental results indicated that good correlations between the model prediction for dispersion characteristics and the optical characteristics of coated film were obtained.

Growth processes of poly methylmethacrylate particles investigated by atomic force microscopy

The growth processes of poly methylmethacrylate (PMMA) particles prepared by soap-free emulsion polymerization at a reaction temperature 70°C are observed using scanning electron microscopy and atomic force microscopy to clarify the growth mechanisms at the molecular scale. Here, the use of a cationic initiator, V-50, enables us to synthesize positively charged PMMA, which then adsorbs electrostatically on the negatively charged mica plate with molecular scale smoothness. As a result, the following results are found. If the monomer concentration is high, PMMA particle size increases with increasing initiator concentration, otherwise particle size decreases with increasing initiator concentration. In the former case, the growth mechanism is very similar to that of the polystyrene particles we proposed; in the latter case, the phenomenon is thought to follow the LaMer diagram.

Preparation of a large Mesoporous CeO2 with crystalline walls using PMMA colloidal crystal templates

Inverse opals of crystalline CeO2 were synthesized by using close-packed poly(methyl methacrylate) (PMMA) latex spheres of various sizes as templates, resulting in pore sizes, which could be scaled down even to the mesopore region (30–40 nm). The latex spheres were synthesized by emulsion polymerization, and the PMMA particle size could be substantially decreased by addition of sodium dodecyl sulfate (SDS) as surfactant. Owing to the larger pore wall thickness, the CeO2 with large mesopores preserves an intact porosity to higher temperatures than previously reported mesoporous CeO2 obtained from surfactant templates. The porosity and crystallinity were studied by microscopic techniques, wide angle X-ray diffraction (XRD), N2 sorption, and Hg porosimetry. The evolution of crystallinity (crystallite size and lattice parameters) was determined for different annealing temperatures by means of Rietveld refinements of the XRD data. Thereby, our study allowed getting general insights into the crystallization behavior of sol–gel derived porous CeO2 frameworks.

Dispersion polymerization of MMA in supercritical CO 2 in the presence of poly(poly(ethylene glycol) methacrylate- co-1H,1H,2H,2H-perfluorooctylmethacrylate)

Various random copolymers of poly(poly(ethylene glycol) methacrylate- co-1H,1H,2H,2H-perfluorooctylmethacrylate) (p(PEGMA- co-FOMA)) with different poly(ethylene glycol) (PEG) chain length ( M n = 300, 475, and 1100) and different FOMA content have been synthesized in supercritical carbon dioxide (scCO 2) via free-radical polymerization. The copolymers containing above 50 wt% FOMA could be used as a stabilizer for the polymerization of methyl methacrylate (MMA) in scCO 2. For PEGMA (300) and PEGMA (475) copolymers, the copolymeric stabilizer with 67–69 wt% FOMA content was shown to be optimal to produce micrometer-size spherical PMMA powder. The size of pendant PEG group and the composition of copolymer as well as the concentration of MMA affected on the size of PMMA particles and the stability of PMMA latexes in CO 2.

Fabrication of hydroxyapatite ceramics with controlled pore characteristics by slip casting

Porous hydroxyapatite (HAp) ceramics with controlled pore characteristics were fabricated using slip casting method by mixing PMMA with HAp powder. The optimum conditions of HAp slip for slip casting was achieved by employing various experimental techniques, zeta potential and sedimentation, as a function of pH of the slips in the pH range of 4-12. HAp suspensions displayed an absolute maximum in zeta potential values and a minimum in sedimentation height at pH 11.5. The optimal amount of dispersant for the HAp suspensions was found at 1.0 wt% according to the viscosity of 25 vol% HAp slurry. The rheological behaviour of HAp slurry displays a shear-thinning behavior without thixotropy, which is needed in slip casting processing. The pore characteristics of sintered porous hydroxyapatite bioceramics can be controlled by added PMMA particle size and volume. The obtained ceramics exhibit higher strength than those obtained by dry pressing.

Dispersion polymerization of methyl methacrylate in supercritical carbon dioxide: Influence of helium concentration on particle size and particle size distribution

Dispersion polymerizations of methyl methacrylate utilizing poly(1,1,-dihydroperfluorooctyl acrylate) as a steric stabilizer in supercritical carbon dioxide (CO2) were carried out in the presence of helium. Particle size and particle size distribution were found to be dependent on the amount of inert helium present. Particle sizes ranging from 1.64 to 2.66 μm were obtained with various amounts of helium. Solvatochromic investigations using 9-(α-perfluoroheptyl-β,β-dicyanovinyl)julolidine indicated that the solvent strength of CO2 decreases with increasing helium concentration. This effect was confirmed by calculations of Hildebrand solubility parameters. Dispersion polymerization results indicate that PMMA particle size can be attenuated by the amount of helium present in supercritical CO2. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2009–2013, 1997