Facile method to prepare monodisperse polystyrene particles by hydrothermal process

The seeded batch dispersion polymerization with or without monomer absorption was compared with the batch polymerization and delayed addition by batch polymerization, to prepare the highly crosslinked, monodispersed polystyrene (PS) particles. The seeded batch polymerization was carried out under the variation of styrene (in second stage)/styrene (in PS seed) (St/St) ratio, divinylbenzene (DVB) concentration, and polymerization temperature using 1.9-μm monodispersed PS seed particles. The experimental results imply that the seeded batch process is more efficient method that could avoid the sensitive particle nucleation step in the presence of the crosslinker than the batch and delayed addition processes. Without monomer absorption, 2.3-μm uniform crosslinked PS particles with 7 wt % of the DVB were prepared in 1/1 (St/St) ratio. In comparison, with the monomer absorption, monodispersed and smooth-surfaced PS particles containing 20 wt % of the DVB were formed. A total of 5% weight loss of the crosslinked PS particles determined by TGA occurred from 353.8 to 374.8°C, and the degree of swellability in toluene decreased from 150 to 104.5% with increasing the DVB concentration from 5 to 20 wt % because of the increase of the crosslink density of the particles. The seeded polymerization, especially through monomer absorption procedure, is a novel way to obtain highly crosslinked, monodispersed PS particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Streaming currents, streaming potentials and conductances of concentrated dispersions of negatively-charged, monodisperse polystyrene particles. Effect

The purpose of this study was to develop monodispersed polystyrene particles as certified reference materials in accordance with the ISO 17034: 2016 and the ISO Guide 35. It can play a significant role especially during the COVID-19 pandemic since several covering items such as filtering facepiece respirators or medical masks must be investigated for the quality of operation by various sizes of polystyrene. The polystyrene particles were prepared in-house by National Nanotechnology Center (NANOTEC) using polymerization of styrene. Each batch was preliminary check for distribution, aggregation and averaged size by using dynamic light scattering. Then polystyrene particles were prepared to 1% solid suspension in deionized water for homogeneity testing, stability assessment and characterization using transmission electron microscope with ImageJ software. The 100 nm polystyrene as an example has been successfully synthesized fulfilled the criteria of size deviation from nominal value less than ± 10 nm and polydispersity index less than 0.05. Then, the particle size of polystyrene was statistically analyzed for screening test with the results of the coefficient of variation less than 10%. Stability assessment consisting of short-term stability testing with three different temperatures and long-term stability testing within 6 months observed was carried out. The results of short-term and long-term stability were presented within the maximum acceptable. The homogeneity tests for within bottle standard deviation and between bottle standard deviation were performed with randomly sampling. The results of homogeneity tests satisfied the criteria and therefore assigned the value as the certify value. Consequently, the certify value of 105.5 ± 4.6 nm of monodispersed polystyrene particles has been successfully developed as Thailand reference materials which were similar level of quality and accuracy to the standard commercial products.

New strategies for synthesis of Janus particles are of essential importance in the advancement of material science and technology. However, it remains a great challenge to synthesize uniform Janus particles with controllable topological and chemical anisotropy. To overcome this challenge, we have recently developed a general emulsion interfacial polymerization approach. This approach can be applicable to a wide variety of vinyl monomers, including positively charged, neutrally charged, and negatively charged monomers. Different from the traditional seed swelling emulsion polymerization that usually involved using cross-linked polystyrene (PS) particles as seeds to produce Janus particles, we preloaded non-cross-linked PS particles in the emulsion system to construct an interfacial polymerization system. However, the role of these non-cross-linked PS particles in the emulsion interfacial polymerization is unclear. In this work, we revealed the role of non-cross-linked PS particles preloaded in emulsion int...

The effect of size of crosslinked monodisperse spherical polymer particles on the steady shear and dynamic rheology of filled poly(methyl methacrylate) (PMMA) composites was studied for PMMA and polystyrene (PS) particles in the range from 0.1 to 1.3 micron particle size. For PMMA matrices filled with crosslinked PS particles, reduction in filler size increases non‐Newtonian behavior. Particle size effects on the rheology of filled PMMA were much less pronounced for PMMA filler. The rate of growth of steady shear viscosity with aging time was much larger for PMMA filled with PS particles than with PMMA particles. The apparent yield stress of filled PMMA composites was estimated from Casson plots. The yield stress was negligible for PMMA filler but increased with decreasing particle size for PS filler. We suggest that PS particles are rejected by the PMMA matrix and form clusters, causing large enhancements in viscosity and moduli. Polym. Eng. Sci. 44:452–462, 2004. © 2004 Society of Plastics Engineers.

Synthesis of non-spherical polymer particles using the activated swelling method

Preparation and antibacterial activities of hollow silica–Ag spheres

A novel "giant" surfactant was used for the synthesis of walnut-like polystyrene particles with dual-size roughness surfaces by a facile "one-pot" emulsion polymerization. Specifically, the "giant" surfactant was obtained by grafting monomethoxy poly(ethylene glycol) (MPEG) chains onto a poly(4-vinylbenzyl chloride) bulb of polystyrene dumbbell-shaped particles. Using the novel "giant" surfactant as an emulsifier, nearly monodisperse walnut-like polystyrene particles with tunable sizes were prepared by emulsion polymerization. After removal of the hydrophilic MPEG chains, the particulate films exhibited a superhydrophobic property with a static water contact angle as high as 151°. This work indicates that emulsion polymerization with "giant" surfactants can be a facile approach for fabrication of walnut-like polymeric particles and superhydrophobic particulate films.

라텍스 블렌딩 기법을 이용하여 폴리스티렌(PS)/다중벽 탄소나노튜브(MWCNT) 나노복합재료를 제조하여 나노튜브 길이에 따른 나노복합재료의 유변학적 특성을 고찰하였다. 나노복합재료 제조에 사용된 단분산 PS 입자는 무유화제 유화중합으로 제조하였고 NWCNT는 불순물 제거와 분산성 향상을 위해 표면개질 과정을 거친 후 사용하였다. 최종적인 나노복합재료는 단분산 PS 입자와 개질한 MWCNT를 초음파 교반조에서 분산시킨 후 동결건조 과정을 거쳐 제조하였다. 나노복합재료의 MWCNT 함량과 나노튜브 길이에 따른 유변학적 특성은 소진폭 진동 전단유동을 부과시켜 평가하였다. 본 연구에서 고찰한 PS/MWCNT 나노복합재료는 MWCNT의 함량이 증가할수록, 나노튜브 길이가 길수록 유변물성 향상 효과가 뚜렷하였다. 이는 MWCNT 함량이 증가할수록 나노복합재료의 유변학적 특성이 액체적 특성에서 점차 고체적 특성으로 변화하기 때문이며. 나노튜브 길이가 길수록 네트워크 구조를 달성하는 임계 농도가 직아 지지 때문인 것으로 판단된다.

Novel materials with a periodic structure have recently been intensively studied for various photonic and photocatalytic applications due to an efficient light harvesting ability. Here, inverse opal titania (IOT) has been investigated for possible enhancement of photocatalytic activity. The IOT films were prepared on a glass support from silica and polystyrene (PS) opals by sandwich-vacuum-assisted infiltration and co-assembly methods, respectively. The reference sample was prepared by the same method (the latter) but with PS particles of different sizes, and thus without photonic feature. The modification of preparation conditions was performed to prepare the films with a high quality and different photonic properties, i.e., photonic bandgap (PBG) and slow photons’ wavelengths. The morphology and optical properties were characterized by scanning electron microscopy (SEM) and UV/vis spectroscopy, respectively. The photocatalytic activity was evaluated (also in dependence on the irradiation angle) for oxidative decomposition of acetaldehyde gas under irradiation with blue LED by measuring the rate of evolved carbon dioxide (CO2). It has been found that PBG wavelength depends on the size of particles forming opal, the void diameter of IOT, and irradiation angle, as expected from Bragg’s law. The highest activity (more than two-fold enhancement in the comparison to the reference) has been achieved for the IOT sample of 226-nm void diameter and PBG wavelengths at 403 nm, prepared from almost monodisperse PS particles of 252-nm diameter. Interestingly, significant decrease in activity (five times lower than reference) has been obtained for the IOT sample of also high quality but with 195-nm voids, and thus PBG at 375 nm (prohibited light). Accordingly, it has been proposed that the perfect tunning of photonic properties (here the blue-edge slow-photon effect) with bandgap energy of photocatalyst (e.g., absorption of anatase) results in the improved photocatalytic performance.

Recently, the authors reported that micron-sized monodispersed cross-linked polymer particles having a single hollow in the inside were produced by seeded polymerization for the dispersion of (toluene/divinylbenzene)-swollen polystyrene (PS) particles prepared utilizing the dynamic swelling method which the authors had proposed. In this article, the particles at various conversions of the seeded polymerization were observed with an optical microscope in detail. From the obtained results, the formation mechanism of the hollow structure is suggested as follows. As seeded polymerization proceeds, polydivinylbenzene (PDVB) molecules precipitated in the swollen particle are trapped near the interface and gradually pile at the inner surface, which results in a cross-linked PDVB shell. PS which dissolves in the swollen particles is repelled gradually to the inside. After the completion of the polymerization, toluene in the hollow evaporates by drying, and PS clings to the inner wall of the shell uniformly.

We report a facile method for preparation of polystyrene (PS) particles with spherical, raspberry-like, and hollow flower-like structures by single-step non-surfactant self-templating polymerization of styrene in ethanol–water mixtures. PS particles with diverse morphologies could be easily obtained by simply adjusting the volume ratios of the styrene/water/ethanol mixture and initiator-ethanol–water mixture. By decreasing this ratio, the particles with spherical, raspberry-like, and hollow flower-like structures were obtained in sequence. The wettability of the coatings changing from hydrophilicity to hydrophobicity was easily tuned by the PS particles with different roughnesses. A competitive mechanism of interfacial polymerization and exudation was proposed to interpret the formation of PS particles with diverse morphologies.

We use Fourier-Bessel Image Decomposition (FBID) of microscopy images to investigate the size, refractive index and 3-dimensional position of individual colloidal microspheres. With measurements of monodisperse polystyrene and poly(methyl methacrylate) particles we achieve a resolution of 1% in size and 0.2% in refractive index for a single image which is sufficient for accurate in situ characterization of polydisperse colloids. Also the binding of avidin molecules to individual biotinylated polystyrene particles is resolved. Finally, the FBID method offers a straightforward approach to 3-dimensional out-of-focus tracking. Here, the z-position of a freely diffusing particle is calculated by applying the statistics of Brownian motion to its set of Fourier-Bessel coefficients.

A facile and novel approach to prepare monodisperse polystyrene (PS) particles having a "cylindrical" shape was discovered. Spherical PS particles prepared by dispersion polymerization were stirred in a polyvinylpyrrolidone (PVP) aqueous solution for several hours using a magnetic stirrer at room temperature. In the presence of PVP, the spherical PS particles deformed into cylindrical shapes following stirring; however, the particles did not deform in the absence of PVP. The deformation rate of the particles was affected by the molecular weight of the dissolved PVP. This stirring method is not only highly efficient and high yielding, but also applicable to other materials such as polymethyl methacrylate. Moreover, the cylindrical particles were successfully applied as particulate surfactants in a Pickering emulsion system, which exhibited excellent stability in comparison to a system using spherical particles as a surfactant. In the first case, the emulsion was left standing for more than 4 months.

Dispersion polymerization of styrene (S) and vinylbenzyltrimethylammonium chloride (VBA) was conducted in an ethanol-water medium using an aromatic poly(amic acid) (PAA) as the stabilizer. When equimolar amounts of VBA and the carboxylic acid of PAA were used, monodisperse particles with high PAA content were obtained quantitatively. The imidization of PAA on the particles proceeded with acetic anhydride and N,N-dimethylaminopyridine to form core-shell PS-polyimide particles.