Janus Particles Synthesis by Emulsion Interfacial Polymerization: Polystyrene as Seed or Beyond?

A facile method to prepare monodisperse polystyrene (PS)/cross-linked PS particles was studied by combining hydrothermal process with dispersion polymerisation. Compared to traditional dispersion polymerisation, in this way the polymerisation of styrene in ethanol–water media could be carried out in a relatively wide ethanol/water ratio range from 10/90 to 70/30, consequently monodisperse particles from 160 to 1300 nm in size were generated at 80°C. It implies that the monodisperse PS particles could be acquired simply and the significant change in PS particle size could be adjusted by only varying the ethanol/water ratio. The phenomenon could be inferred that the hydrothermal process improved the solubility of the monomer in the media under a higher reaction pressure, which enabled this method to expand the ethanol/water ratio range for traditional dispersion polymerisation. Furthermore, the monodisperse cross-linked PS particles could also be obtained even at the cross-linking agent being up to 2% without addition of stabiliser through this method. Not using stabiliser could enlarge the application range of the cross-linked monodisperse PS particles. The formation process of the particles was detected using scanning electron microscopy. The particle morphology transformation along with hydrothermal reaction in the early stage was demonstrated, that is, the initial irregular particles in different size congregated gradually to form monodisperse particles.

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

In order to explore the antimicrobic materials, new strategies for synthesis of particles were paid more and more attention as it was crucial to the advancement of material technology and environmental. In this work, we provided a strategy for construction of novel hollow‐carved microspheres (HCMs) by a simple method of emulsion interfacial polymerization (EIP). Firstly, using sodium p‐styrene sulfonate (SSS) and styrene (St) as hydrophilic/hydrophobic and rigid comonomers, diallyl dimethylammonium chloride (DMA) as cationic cross‐linking monomer, azobisisobutyronitrile (AIBN) as initiator, hexane as a pore‐forming agent, the HCMs were synthesized by EIP. Then, the quaternized HCMs (QHCMs) was prepared by quaternization of hydrophilic sodium sulfonate groups (SO3Na). The composition and micromorphology of the obtained microspheres were characterized by FT‐IR, XPS, EDS, DLS, SEM, and TEM. The antibacterial properties of QHCMs were tested against Escherichia coli and Staphylococcus aureus. At a concentration of 320 μg/ml QHCMs, the bacteriostatic activities of S. aureus and E. coli decreased by more than 91.7% and 86.4%, respectively, which was confirmed by the colony forming units and regeneration curves. In summary, a novel antibacterial polymer material was successfully synthesized by EIP and quaternization, which could be widely used in coating materials to reduce bacterial infection.

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.

The compressional instability of particle-laden air/water interfaces is investigated with plain and surface-anisotropic (Janus) particles. We hypothesize that the amphiphilic nature of Janus particles leads to both anisotropic particle-particle and particle-interface interactions that can yield particle films with unique collapse mechanisms. Analysis of Langmuir isotherms and microstructural characterization of the homogeneous polystyrene particle films during compression reveal an interfacial buckling instability followed by folding, which is in good agreement with predictions from classical elasticity theory. In contrast, Janus particle films exhibit a different behavior during compression, where the collapse mode occurs through the subduction of the Janus particle film. Our results suggest that particle-laden films comprised of surface-anisotropic particles can be engineered to evolve new material properties.

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.

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

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

Anisotropic particles have a wide range of applications in materials science such as emulsion stabilization, oil-water separation, and catalysis due to their asymmetric structure and properties. Nevertheless, designing and synthesizing large quantities of anisotropic particles with controlled morphologies continue to present considerable challenges. In this study, we successfully synthesized anisotropic microspheres using a soap-free seed emulsion polymerization method. This approach combines the benefits of seed emulsion polymerization with emulsion interfacial polymerization. By varying the concentrations of dissolved polymeric monomers, 3-methacryloyloxypropyltrimethoxysilane (MPS), and the initiator of potassium persulfate (KPS), different shapes of bowl, cap, and three-sided concave particles were obtained in surfactant-free aqueous solutions, simplifying the post-treatment process. The cap particles are Janus particles with good emulsion stability to toluene/water emulsions over 30 days. The catalytic degradation of 4-nitrophenol (4-NP) was investigated after loading silver nanoparticles on the surface of the particles by in situ deposition. The anisotropic particles obtained in this work have potential applications in emulsion stabilization and catalysis.

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.

We report the fabrication of large area, thin asymmetric free-standing two-dimensional (2-D) photonic crystals. We fabricate large area 2-D close-packed monodisperse polystyrene (PS) particle monolayers at air/water interfaces by using our needle tip flow method. We then layer tetraethyl orthosilicate (TEOS) onto the 2-D array to form a thin TEOS layer on the 2-D particle array on water. The hemispheres of PS particles located within the TEOS phase swell such that the adjacent particle hemispheres fuse. After TEOS evaporation, we obtain a free-standing connected photonic crystal film of hemispheres that efficiently diffracts light. The other side of the photonic crystal film consists of a fused connecting thin, flat sheet. Reactive ion etching (RIE) of the asymmetric films forms unusual, rough particle 2-D arrays and 2-D flower-like arrays. Mechanical abrasion allows one to separate the resulting novel Janus particles.

In this work, biocompatible and biodegradable chitosan microcapsules are successfully prepared in abundance and easily via using carboxylfunctionalized polystyrene (PS) particles as core template and the chitosan crosslinked with gultaraldehyde as the shell. Firstly, the monodisperse functionalized PS particles are made by emulsifier-free emulsion polymerization. The structure and morphology of the carboxyl-functionalized PS particles are characterized by FTIR, FESEM and TEM. Secondly, microcapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized PS particles and by removing the core template. The microcapsules are characterized by FESEM and TEM. The results revealed that the latex particles are removed by exposure to solvent and the microcapsules exhibited the hollow structure. This work confirmed that the microcapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized PS particles and by removing the core template.

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.

Named after the two-faced Roman god, Janus particles (JPs) are defined by their distinct dual chemical compositions on a single particle. Research on micron-sized JPs has yielded remarkable insights, showcasing their unique assembly behaviors both in bulk and at interfaces. However, significant challenges persist, particularly in the synthesis of smaller (<500 nm) JPs, which remains complex and difficult to scale up. To date, there has been no commercial success with JPs. Recently, seeded synthesis methods, such as emulsion polymerization that is already employed in industrial-scale manufacturing, have shown great promise. These methods enable the production of high-quality JPs with different sizes, morphologies, and functionalities. This advancement has inspired more efforts in exploring JP applications across various fields, including emulsion stabilization, drug delivery, electronic devices, and coatings. This review provides a comprehensive overview of the recent progress in the synthesis and application of polymeric JPs, with an emphasis on the seeded synthesis approach. It discusses the underlying reaction mechanisms and explores different strategies for controlling JP morphology. Serving as a roadmap, this review aims to guide the design of novel functional JPs and their potential future applications. The successful implementation of JPs will require careful consideration and a deep understanding of both synthesis and applications, as these are indeed two sides of the same coin.

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