Sacrificial functional polystyrene core template to fabricate cross-linked chitosan microcapsules

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

Ag nanoparticles were distributed onto polystyrene nanoparticle (PS-Ag) beads using two synthetic methodologies. In the first methodology, polystyrene (PS) beads were prepared via emulsion polymerization, with Ag nanoparticles subsequently loaded onto the surface of the PS beads. The polymerization of styrene was radiolytically induced in an ethanol (EtOH)/water medium, generating PS beads. Subsequently, Ag nanoparticles were loaded onto the PS beads via the reduction of Ag ions. The results from the morphological studies, using field emission transmission electron microscopy (FE-TEM), reveal the PS particles were spherical and nanosized, and the average size of the PS spherical particles decreased with increasing volume % of water in the polymerization medium. The size of the PS spherical particles increases with increasing radiation dose for the polymerization. Also, the amount of Ag nanoparticle loading could be increased by increasing the irradiation dose for the reduction of the Ag ions. In the second methodology, the polymerization of styrene and reduction of Ag ions were simultaneously performed by irradiating a solution containing styrene and Ag ions in an EtOH/water medium. Interestingly, the Ag nanoparticles were preferentially homogeneously distributed within the PS particles (not on the surface of the PS particles). Thus, Ag nanoparticles were distributed onto the surface of the PS particles using the first approach, but into the PS clusters of the particles via the second. The antimicrobial efficiency of a cloth coated with the Ag-PS composite nanoparticles was tested against bacteria, such asStaphylococcus aureus and Klebsiella pneumoniase, for 100 water washing cycles.

Kinetic and mechanistic analysis of membrane fouling in microplastics removal from water by dead-end microfiltration

In this study, the optical properties of two nano-sized polymer colloids in optical coherence tomography (OCT) were compared in vitro with respect to their potential use as contrast agents. We used two types of particles: compact hydrophobic spherical polystyrene (PS) particles and soft water-swollen nanogel (NG) particles both with grafted hydrophilic shell, both prepared at two different sizes (PS at 300 and 150 nm, NG at 300 and 200 nm). The OCT backscattering signals of the particles in a vessel-mimicking highly scattering agar/TiO2 phantom were compared on either number of particles or weight percent. Larger particles and higher concentrations produced higher OCT contrast. At each concentration tested, a markedly higher contrast was achieved by PS particles than NG particles. PS particles generated a markedly higher OCT contrast than the phantom at concentrations of at least 1 × 1010 or 0.1 % for PS 300 nm and at least 3 × 1011 particles/mL or 0.4 % for PS 150 nm. The contrast generated by NG 300 nm was above the phantom contrast at concentrations of at least 3 × 1011 particles/mL or 1 %, whereas NG 200 nm only at 4 %. At any given weight percent, the differences in OCT contrast between differently sized particles were much less evident than in the comparison based on particle number. PS 300 nm generated also a good contrast ex vivo on chicken muscle tissue. These results strongly suggest that PS spheres have strong potential as intravascular OCT contrast agent, while NG particles need further contrast enhancer for being used as OCT contrast agent.

Golf ball-like particles having a number of dimples on their spherical surfaces were prepared by a combined method of heterocoagulation between hard polymer particles and soft silicone oil droplets, polymerization of the oil droplets, and dissolution of the polymer particles with tetrahydrofuran. In the heterocoagulation, polystyrene (PSt) particles of three different sizes were employed as hard particles. Distribution of dimples formed with small-sized PSt particles was less homogeneous than that with middle-sized PSt particles (MPS). Narrowly dispersed golf ball-like particles with homogeneously distributed dimples were successfully prepared with a high number ratio of MPS to oil droplets. The employment of large-sized PSt particles in the heterocoagulation decreased the number of PSt particles required for the stabilization of the oil droplets, which created polyhedron-like particles having dimples on their surface. Additional experiments in which polymer particles with different surface affinities to the oil droplets were heterocoagulated with the droplets revealed that a high surface affinity of particles to the droplets could deeply embed the polymer particles into the droplets and form dimples with a low contact angle.

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.

Microplastics (MPs) and heavy metals are two major types of pollutants that interact with each other, but they are poorly understood. Polystyrene (PS) is one type of MPs that is often detected in aquatic environments. In this study, we examined the adsorption capacity and release rate of heavy metals with respect to different particle sizes of PS, heavy metals, initial heavy metal concentrations, and salinities. Virgin (new) PS with diameters of 20, 50, 130, and 250 μm was used in this study, and four heavy metals (lead, cadmium, copper, and zinc) were used. The results showed that larger PS particle sizes adsorbed more heavy metals even though it took longer to achieve equilibrium adsorption. An increase in heavy metal concentration caused the adsorption capacity (μg g–1) of PS particles to also increase, but the adsorption rate (%) decreased. Increased salinity of the heavy metal solution resulted in a slower adsorption time and a lower adsorption capacity and release rate from the surface of PS particles. Different heavy metals also had different adsorption capacities. Pb was consistently more highly adsorbed by MPs, followed by Cu, Zn, and Cd. Larger PS sizes released heavy metals faster than smaller PS sizes, and the amounts of heavy metals released were higher. The heavy metal with the highest release rate was Cd, followed by Pb, Cu, and Zn. Finally, our findings highlight the interactions between PS and heavy metals and strongly support that PS particles can act as vectors for heavy metals in aquatic systems.

Preparation of submicron-sized porous titanium oxide particles by the swelling process

The combined effect of polystyrene (PS) particles and triphenyltin chloride (TPTCl) to the green algae Chlorella pyrenoidosa was studied. The 96h IC50 of TPTCl to the green algae C. pyrenoidosa was 30.64μg/L. The toxicity of PS particles to C. pyrenoidosa was size-dependent, with the 96h IC50 at 9.10mg/L for 0.55μm PS but no toxicity observed for 5.0μm PS. The exposure to 0.55μm PS led to damage on structure of algal cells, which could in turn cause inhibition on photosynthesis and population growth of the green algae. TPTCl concentrations in test medium were lowered by 15-19% at presence of 0.55μm PS particles, indicating a reduced bioavailability of TPTCl. In spite of this reduced bioavailability, the presence of PS increased the toxicity of TPTCl, which might be attributed to facilitated uptake of TPTCl by the green algae after the damage of cell structure. The overall results of the present study provided important information on the effect of PS on the bioavailability and toxicity of TPTCl to phytoplankton species.

Nanometer scale particles of seed latex were successfully prepared by polymerization induced by gamma rays. By modification of the coupling agent 3‐methacryloxylpropyltrimethoxylsilane (MPS) at the surface of polystyrene (PSt) particles, polydimethylsiloxane (PDMS) was introduced outside the PSt particles and composite latex particles with a core–shell (PSt–PDMS) structure were successfully prepared. Because of the chemical bond linkage between the core and the shell, such a structure is stable. Direct evidence of the core–shell structure was observed by transmission electron microscopy (TEM). In addition the chemical bond linkage was confirmed by Fourier‐transfer infrared (FT‐IR) spectroscopy. An indirect proof of the core–shell structure was given by water absorption ratio determination of the different samples. Copyright © 2004 Society of Chemical Industry

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...

Polymeric nanoparticles have many advantages as the reinforcing filler of rubber. To investigate the mechanism of the reinforcement, nanocomposites of poly(styrene‐butadiene) rubber (SBR) filled with polystyrene (PS) particles as the reinforcing agents was prepared. Morphology and dynamical mechanical properties of PS particles‐filled SBR were investigated. It was found that the polymer chains of the elastomer could be absorbed onto the PS particles, in reminiscent to the concept of bound rubber in inorganic filler‐filled elastomeric system. The adsorbed polymer layer can form up glassy bridges between neighboring filler particles, leading to the agglomeration of the filler particles and the reinforcement of the elastomer. With higher filler content or smaller filler size, the numbers of the glassy bridges increase, and the modulus of the elastomer increases. With higher strain or higher temperature, the filler–filler interaction is disrupted and the material is softened. The study discovered the existence of bound rubber in PS particles‐filled elastomer and illustrated its influence on the dynamic mechanical properties, which could be helpful to design the polymeric nanoparticles for rubber reinforcement. POLYM. COMPOS., 38:1112–1117, 2017. © 2015 Society of Plastics Engineers

The preparation of disc-like polystyrene (PS) particles via seeded dispersion polymerization of 2-ethylhexyl methacrylate (EHMA) was previously demonstrated using a shaker with the PS particles as seeds in methanol/water medium in the presence of decane and subsequent removal of PEHMA and decane, but only under restrictive conditions. Moreover, no structural visualization of the disc-like particles by transmission electron microscope (TEM) was conducted. In this work, we revisit this synthesis using a conventional magnetic stirring apparatus, significantly broadening the range of feasible conditions (i.e., methanol/water mass ratios of 10/0-5/5, stirring rates of 80-360 rpm, and polymerization times of 2-24 h). Systematic studies reveal that disc-like morphology can be achieved even with smaller PS seed particles (>730 nm) or alternative hydrocarbons (e.g., hexadecane). Crucially, we recognize for the first time that these disc-like particles exhibit a multihollow structure with compartmentalized voids (50-300 nm), formed via phase separation between PS and decane during polymerization and subsequent decane removal. A mechanism for this unique structure is proposed based on experimental evidence. This work is expected to provide useful insights into the preparation of polymer particles with both disc-like shape and multihollow structure.

Particles under a perpendicularly applied alternating current (AC) electric field assemble into complex structures and exhibit tunable locomotion. Although they possess very similar physical properties, silica particles form two‐dimensional (2D) close‐packed crystals in deionized water, whereas polystyrene (PS) spheres repel each other. Using nanoparticle tracers, it is shown that the electrohydrodynamic (EHD) flow around silica particles is contractile, whereas it is extensile around PS particles. The Stern‐layer conductivities of PS and silica spheres are further measured experimentally and used in theoretical models to calculate the EHD flow surrounding them, which matches well with experiments. Therefore, the incorporation of Stern‐layer conductivity resolves the puzzle that EHD flow surrounding a particle with moderate zeta potentials is extensile. The impacts of zeta potential, Stern‐layer conductivity, salt concentration, and particle size on the EHD flow are examined herein. It is found that particles with high zeta potential, small diameter, or immersed in low salt concentration solutions tend to have extensile EHD flow surrounding them because the enhanced surface conductivity in the double layer makes the particles effectively more polarizable than the solvent. Herein, it is further shown that asymmetric EHD motors made from PS and silica particles exhibit behaviors that are consistent with the model predictions.

In this article, we investigate the complex drainage behavior of liquid (“dimple”) films entrapped between hydrophilic glass substrates and air bubbles in water and aqueous suspensions of polystyrene (PS) particles. The film drainage was monitored by capturing the evolution of spatial-temporal thicknesses using interferometry. Faster drainage of the entrapped film is observed in the PS colloid suspensions compared to the water. The film drainage strongly depends on the interface boundary conditions. Our experiments reveal that the air–liquid interface of the entrapped film becomes partially mobile in the PS suspensions, which results in faster drainage. The hydrophobic PS particles tend to migrate toward the air–water interface and form an ordered layer. We argue that the adsorbed layer of PS particles makes the bubble surface elastic, delaying the formation of the immobile interface.