Room temperature synthesis of water-repellent polystyrene nanocomposite coating

A stable superhydrophobic polystyrene nanocomposite coating was fabricated by means of a very simple and easy method. The coating was characterized by scanning electron microscopy and X-ray photoelectron spectrum. The wettability of the products was also investigated. By adding the surface-modified SiO₂ nanoparticles, the wettability of the coating changed to water-repellent superhydrophobic, not only for pure water, but also for a wide pH range of corrosive liquids. The influence of the drying temperature and SiO₂ content on the wettability of the nanocomposite coating was also investigated. It was found that both factors had little or no significant effect on the wetting behavior of the coating surface.     

Comparison of the cytotoxic effect of polystyrene latex nanoparticles on planktonic cells and bacterial biofilms

The cytotoxic effect of positively charged polystyrene latex nanoparticles (PSL NPs) was compared between planktonic bacterial cells and bacterial biofilms using confocal laser scanning microscopy, atomic force microscopy, and a colony counting method. Pseudomonas fluorescens, which is commonly used in biofilm studies, was employed as the model bacteria. We found that the negatively charged bacterial surface of the planktonic cells was almost completely covered with positively charged PSL NPs, leading to cell death, as indicated by the NP concentration being greater than that required to achieve single layer coverage. In addition, the relationship between surface coverage and cell viability of P. fluorescens cells correlated well with the findings in other bacterial cells (Escherichia coli and Lactococcus lactis). However, most of the bacterial cells that formed the biofilm were viable despite the positively charged PSL NPs being highly toxic to planktonic bacterial cells. This indicated that bacterial cells embedded in the biofilm were protected by self-produced extracellular polymeric substances (EPS) that provide resistance to antibacterial agents. In conclusion, mature biofilms covered with EPS exhibit resistance to NP toxicity as well as antibacterial agents.     

Fabrication of grating-like polystyrene latex monolayer structure as three-dimensional calibration standards for scanning probe microscope

This paper illuminates the preparation of grating-like polystyrene latex monolayer structure, which can minimize the effects of the size deviation of spheres and the defect transfer on the accuracy as calibration samples for microscopes. The latex films are grown on freshly cleaved mica substrates by vertical deposition method. The concentration dependence of the structure and the topography of latex films is characterized by optical microscope, ultraviolet--visible transmission spectrum and scanning probe microscope. The origination of such a grating-like structure is also discussed.     

Measurement of filtration efficiency of Nuclepore filters challenged with polystyrene latex nanoparticles: experiments and modeling

Membrane filtration has been demonstrated to be effective for the removal of liquid-borne nanoparticles (NPs). Such technique can be applied to purify and disinfect drinking water as well as remove NPs in highly pure chemicals used in the industries. This study aims to study the filtration process of a model membrane filter, the Nuclepore filter. Experiments were carried out using standard filtration tools and the nanoparticle tracking analysis (NTA) technique was used to measure particle (50–500 nm) concentration upstream and downstream of the filter to determine the filtration efficiency. The NTA technique has been calibrated using 150-nm polystyrene latex particles to determine its accuracy of particle concentration measurement. Measurements were found reliable within a certain concentration limit (about 10⁸–10¹⁰ particles/cm³), which is dependent on the camera settings during the measurement. Experimental results are comparable with previously published data obtained using the aerosolization method, validating the capability of the NTA technique. The capillary tube model modified from that developed for aerosol filtration was found to be useful to represent the experimental results, when a sticking coefficient of 0.15 is incorporated. This suggests that only 15% of the particle collisions with the filter results in successful attachment. The small sticking coefficient found can be explained by the unfavorable surface interactions between the particles and the filter medium.     

The impact of polystyrene resins in solid-phase organic synthesis

Summary A major objective of the DIVERSOMER^® technology is to provide pure and characterized compounds for biological testing in order to prevent false negatives in our libraries. On several occasions, analysis of the final products by¹H-NMR and MS, has revealed by-products from the polystyrene solid support. Subsequently, three alternative methods were studied to remove polystyrene by-products; (i) prewashing of the resin prior to execution of the synthesis; (ii) pretreatment of the resin with the cleavage conditions consistent with the solid-phase synthesis reaction scheme; and (iii) parallel purification.     

Fluorescence of polystyrene microspheres during photochemical synthesis of gold nanoparticles

The results of investigation of the fluorescence of carboxylated polystyrene microspheres in the process of photochemical synthesis of gold nanoparticles are presented. The introduction of an aqueous solution of hydrogen tetrachloroaurate (III) into an unirradiated polymer dispersion causes a decay of the excimer fluorescence in polystyrene at 335 nm. UV irradiation (λ_exc = 254 nm) of polystyrene dispersions in the presence of AuCl ₄ ^? ions leads to the formation of metal particles, which occurs after an induction period and affects the polystyrene fluorescence.     

Film formation from latex: Hindered initial interdiffusion of constrained polystyrene chains characterized by small-angle neutron scattering

Bulk polystyrene film samples were made from a 50% deuterated latex with a molecular weight of 5.85 × 10⁶ g/mol and 38 nm particle diameter. Because of the high molecular weight and small particle size, these chains are constrained in dimensions by a factor of four. Mildly molded (compacted to full density) samples were annealed for increasing time periods and their small-angle neutron scattering (SANS) patterns recorded. The radii of gyration increase with time as segmental diffusion proceeds during film formation. The initial diffusion was hindered, as shown by a slower than expected relaxation of the chains. Residual interfacial effects were postulated to be the main cause. Chain interdiffusion between latexes of about 110 Å is sufficient to develop a tough, coherent film.     

Ultrasonic enhancing amorphization during synthesis of calcium phosphate

Amorphous calcium phosphate (ACP) has great application potential in biomaterials field due to its non-cytotoxicity, high bioactivity, good cytocompatibility, and so on. The results of this research demonstrated that ultrasonic obviously enhanced amorphization during synthesis of calcium phosphate. The ACP phase was relatively ideal when the solvent of Ca(NO₃)₂·4H₂O was ethanol and the solvent of (NH₄)₂HPO₄ was a mixture of water and ethanol, under ultrasonic. In-situ crystallization of ACP could be observed by HRTEM. The mechanism on the effects of ultrasonic on amorphization of the synthesized calcium phosphate was discussed. It was suggested that ultrasonic synthesis might be a facile method to prepare pure and safe ACP related biomaterials.     

Ultrasonic monitoring of zeolite synthesis in real time

Variations of the phase and amplitude of a transmitted ultrasonic wave package were monitored in real time during the synthesis of zeolite A and zeolite X. For both materials, characteristic changes of the measured attenuation and the sound velocity of ultrasonic waves traveling in the reaction fluid were observed, correlating with the processes of gel formation and zeolite crystallization, respectively. Aging effects of the reaction fluids are demonstrated. The observation of the onset of the zeolite crystallization was verified with ex-situ X-ray diffraction (XRD) measurements.     

超声化学法制备纳米WO3掺杂聚苯乙烯及其表征

 为了满足惯性约束聚变和电磁内爆实验对靶材料的需求，以W(CO)_{5/sub>为原料，利用超声化学法在线制备纳米WO3/sub>掺杂聚苯乙烯。所得样品用TEM，XPS，FTIR和TG进行了表征。测试结果表明，钨元素主要以WO3/sub>的形态存在，WO3/sub>粒径分布为20~50 nm，WO3/sub>微粒被聚苯乙烯完全包覆，掺杂后聚苯乙烯的热稳定性提高了70 ℃。在此基础上，对超声化学法的反应机理进行了探讨。研究表明：纳米WO3/sub>与聚苯乙烯分子链有一定的化学键结合，纳米WO3/sub>在聚苯乙烯基体中分布均匀。}     

超声化学法制备纳米WO3掺杂聚苯乙烯及其表征

为了满足惯性约束聚变和电磁内爆实验对靶材料的需求,以W(CO)5/sub>为原料,利用超声化学法在线制备纳米WO3/sub>掺杂聚苯乙烯。所得样品用TEM,XPS,FTIR和TG进行了表征。测试结果表明,钨元素主要以WO3/sub>的形态存在,WO3/sub>粒径分布为20~50 nm,WO3/sub>微粒被聚苯乙烯完全包覆,掺杂后聚苯乙烯的热稳定性提高了70 ℃。在此基础上,对超声化学法的反应机理进行了探讨。研究表明：纳米WO3/sub>与聚苯乙烯分子链有一定的化学键结合,纳米WO3/sub>在聚苯乙烯基体中分布均匀。     

Ultrasonic early detection of the initiation of a ductile tearing at very low temperature

The possibility of performing early ultrasonic detection of the initiation of ductile tearing in a three point bending test specimen had been demonstrated for temperatures between room temperature and -140 degrees C.     

Ultrasonic pretreatment for hydrothermal synthesis of SAPO-34 nanocrystals

Synthesis of SAPO-34 nanocrystals which has been recently considered as a challenging task was successfully performed by sonochemical method using TEAOH as structure directing agent (SDA). The products were characterized by XRD, SEM, EDX, BET and TGA. The average crystal size of the final product prepared sonochemically is 50 nm that is much smaller than that of synthesized under hydrothermal condition and the morphology of the crystals changes from uniform spherical nanoparticles to spherical aggregates of cube type SAPO-34 crystals respectively. In the case of sample synthesized sonochemically with aid of hydrothermal condition, the surface area is significantly upper than that of obtained by the conventional static hydrothermal technology with almost the same crystallinity. SAPO-34 framework synthesized by just ultrasonic treatment is unstable and a significant part of SAPO-34 nanocrystals is transformed to the dense phase of AlPO₄ structure, i.e., Cristobalite. Contrary to hydrothermal method that at least 24 h of the synthesis time is required to obtain fully crystalline SAPO-34, sonochemical-assisted hydrothermal synthesis of samples leads to form fully crystalline SAPO-34 crystals taking only 1.5 h. In a sonochemical process, a huge density of energy for crystallization is provided by the collapse of bubbles which formed by ultrasonic waves. The fact that small SONO-SAPO-34 crystals could be prepared by the sonochemical method suggests a high nucleation density in the early stages of synthesis and slow crystal growth after nucleation.     

Ultrasonic synthesis of hydroxyapatite in non-cavitation and cavitation modes

The size control of materials is of great importance in research and technology because materials of different size and shape have different properties and applications.This paper focuses on the synthesis of hydroxyapatite in ultrasound fields of different frequencies and intensities with the aim to find the conditions which allow control of the particles size. The results are evaluated by X-ray diffraction, Transmission Electron Microscopy, morphological and sedimentation analyses. It is shown that the hydroxyapatite particles synthesized at low intensity non-cavitation regime of ultrasound have smaller size than those prepared at high intensity cavitation regime. The explanation of observed results is based on the idea of formation of vortices at the interface between phosphoric acid and calcium hydroxide solution where the nucleation of hydroxyapatite particles is taken place. Smaller vortices formed at high frequency non-cavitation ultrasound regime provide smaller nucleation sites and smaller resulting particles, compared to vortices and particles obtained without ultrasound. Discovered method has a potential of industrial application of ultrasound for the controlled synthesis of nanoparticles.     

Ultrasonic irradiation effects on electrochemical synthesis of ZnO nanostructures

In the present article, electrochemical synthesis of ZnO nanostructures in presence of ultrasonic irradiation is investigated. The ultrasonic bath use for synthesis is calibrated using hydrophone method so that its frequency and acoustic power were obtained. From the results of the experimentation the role of ultrasonic irradiation in synthesis of ZnO nanoparticles is discussed. Diameter of the ZnO nanoparticles produced in the electrolyte was compared and investigated in absence and presence of the ultrasonic irradiation utilizing UV–visible photo-spectrometer. Then electrodeposited ZnO layer on the ITO glass as cathode’s surface in absence and presence of the ultrasonic irradiation were studied by UV–visible photo-spectrometer and field emission scanning electron microscopy (FE-SEM) and the results were compared. FE-SEM micrographs show, higher growth of nanosheets on the cathode electrode in presence of ultrasonic irradiation. Experiment shows synthesis of ZnO nanoparticles in presence of the ultrasonic irradiation happen 10 times faster.     

A rapid synthesis of nanofibrillar cellulose/polystyrene composite via ultrasonic treatment

A new method of the synthesis of nanofibrillar cellulose/polystyrene composite based on ultrasonic treatment of styrene emulsion in cellulose-water solution was elaborated. A new approach does not require additional heating and proposes a significantly faster synthesis (15 min, 45 °C) of the target composite compared to the methods described previously. A comprehensive analysis did not reveal any significant differences between mechanical, physical and biodegradable properties of the composite obtained by ultrasonic method and that one obtained by conventional thermal method, which requires much higher temperature (above 75 °C) and reaction duration (from 3 h).     

Ultrasonic studies on polystyrene/styrene butadiene rubber polymer blends filled with glass fiber and talc

The compatibility of solid blends: PS/SBR, PS/SBR filled with glass fiber and PS/SBR filled with talc were studied using ultrasonic pulse echo technique. Measurements were carried out at room temperature (298 K) and a frequency of 3 MHz. The ultrasonic velocity for the compressional wave and that for shear wave have been measured to obtain the elastic moduli data by knowing of density. The variation of ultrasonic wave velocities and elastic moduli with weight percent of the blend was found to be linear in PS/SBR blend, indicating some degree of compatibility but the drawback of elastic moduli indicate incompatibility of the system blend, while it deviates from linearity in blends of PS/SBR filled with glass fiber and talc but the increase in elastic moduli indicates that there is an increase in degree of compatibility between PS and SBR due to adding of glass fiber or talc. The ultrasonic absorptions for longitudinal wave in the temperature range from 298 to 423 K in the studied system were measured using ultrasonic pulse echo technique. Typical results showing the temperature dependence of the ultrasonic absorption at frequencies of 1, 2, 3 and 5 MHz are illustrated for all samples of the different compositions. The study of compositional and temperature dependence of the ultrasonic absorption in the present studied blends reveals the same behavior of the compatibility degree of the blends. Density data of the blends confirmed the ultrasonic results. Also the correlation between hardness and elastic moduli for the present blend systems has been studied.     

Ultrasonic waves induce rapid zeolite synthesis in a seawater solution

The synthesis of zeolites from fly ash was performed through a low-temperature hydrothermal process with seawater. Compared with the results obtained using the same hydrothermal method but in the absence of sonication, the application of an ultrasonic pre-treatment to the conventional hydrothermal process with seawater reduces the crystallization temperature below that observed when hydrothermal synthesis is performed using distilled water.     

Absence of scaling for the intermediate scattering function of a hard-sphere suspension: static and dynamic x-ray scattering from concentrated polystyrene latex spheres

X-ray photon correlation spectroscopy and small-angle scattering measurements are presented of the dynamics and structure of concentrated suspensions of charge-stabilized polystyrene latex spheres dispersed in glycerol, for volume fractions from 3% to 52%. The static structures of the suspensions show essentially hard-sphere behavior, and the short-time dynamics shows good agreement with predictions for the wave-vector-dependent collective diffusion coefficient. However, the intermediate scattering function is found to violate a scaling behavior found previously for a sterically stabilized hard-sphere suspension.     

Ultrasonic pretreatment for lipase-catalyed synthesis of phytosterol esters with different acyl donors

This study is focused on the enzymatic esterification of phytosterols with different acyl donors to produce the corresponding phytosterol esters catalyzed by Canadia sp. 99-125 lipase under ultrasound irradiation. An ultrasonic frequency of 35 kHz, power of 200 W and time of 1h was determined to guarantee satisfactory degree of esterification and lipase activity. The influence of temperature, substrates concentration and molar ratio was investigated subsequently. The optimum production was achieved in isooctane system at 60°C with phytosterol concentration of 150 μmol/mL and phytosterol to fatty acid molar ratio of 1:1.5, resulting in a phytosterol esters conversion of above 85.7% in short reaction time (8h). Phytosterols esters could also be converted in high yields to the corresponding long-chain acyl esters via transesterification with triacylglycerols (above 90.3%) under ultrasound irradiation. In optimum conditions, the overall esterification reaction rate using the ultrasonic pretreatment process was above 2-fold than that of mechanical stirring process without damage the lipase activity.