Cationic Polystyrene Research Articles

Polystyrene nanoparticles as a flotation collector: A molecular dynamics study

Nanoparticles have significant potential as new candidates for generating new types of flotation reagents with unique performance for wettability design and control. Hence, this study explores the wettability of a glass surface covered with polystyrene nanoparticles at various surface coverage percentage using molecular dynamics simulations. To investigate wettability on the bare and coated glass surface, the dynamics of water molecules, contact angle, density distribution profile, and hydrogen bonding patterns are analyzed as substrate wettability indicators. The results reveal that both unrelaxed and relaxed forms of glass surface tolerate a strong asymmetric distribution of surface energy in general, due to charge accumulation on the surface leading the surface to strong hydrophilic behavior. However, unlike chemical collectors, partial covering of glass surface with cationic polystyrene nanoparticles up to 10% reduces the surface tension to a favorable level of hydrophobicity for flotation.

Antimicrobial activities of low molecular weight polymers synthesized through soap-free emulsion polymerization

To evaluate the influence of low molecular weight polymers synthesized through soap-free emulsion polymerization on the indicator microorganism, Micrococcus luteus, methyl methacrylate (MMA) and styrene were polymerized by using various initiators. The MMA polymer colloid was not toxic to M. luteus. High volumes of polystyrene were continuously synthesized, and low-molecular weight polystyrenes were removed from the suspension to the supernatant. During the bioassay test, as the molecular weight of the cationic polystyrene in the supernatant decreased, the inhibition zone against M. luteus grew larger. Low molecular weight cationic polystyrene was toxic to M. luteus. Hence, the supernatant containing low molecular weight cationic polystyrenes (particularly those with molecular weights below 1000 g/mol) obtained from soap-free emulsion polymerization should be treated carefully prior to its discharge to the environment. Moreover, such supernatants should be treated with more care if they are to be discharged into seas or rivers. One solution to reduce the toxicity of the supernatant against M. luteus is the addition of N-vinylacetamide monomers during polymerization.

Cationic polystyrene nanoparticle and the sea urchin immune system: biocorona formation, cell toxicity, and multixenobiotic resistance phenotype

In order to assess the impact of nanoplastics on marine species, polystyrene nanoparticles (PS NPs) have been largely used as model particles. Here we studied the effects of 50 nm amino-modified PS-NH2 on Mediterranean sea urchin Paracentrotus lividus immune system cells (coelomocytes) in the presence of celomic fluid (CF) and at different NP concentrations (1, 5, 10, and 25 μg mL−1) and experimental conditions (absence or presence of EDTA). PS-NH2 acquired a protein corona once incubated with CF, dominated by the toposome precursor protein (TPP). In short-term cultures, a significant concentration- and time-dependent decrease in lysosomal membrane stability and apoptotic-like nuclear alterations were observed in phagocytes upon exposure to PS-NH2 (10 and 25 µg mL−1) in CF but they resulted abolished in the presence of EDTA confirming the role of TPP in triggering PS-NH2-coelomocytes interaction and toxicity. PS-NH2 did not alter MXR phenotype but the observed dose-dependent decrease in calcein accumulation suggests the ability of PS-NH2 to affect pump’s efflux activity. Overall results encourage additional studies on positively charged nanoplastics, since the observed effects on sea urchin coelomocytes as well as the TPP corona formation might represent a first step for addressing their impact on sensitive marine species.

Effect of low levels of lipid oxidation on the curvature, dynamics, and permeability of lipid bilayers and their interactions with cationic nanoparticles

Lipid bilayers composed of saturated and unsaturated lipids, oxidized lipids, and cholesterol at concentrations of 0–18 mol% oxidized lipid were simulated, showing that the presence of oxidized lipid increases bilayer disorder, curvature, and lateral dynamics at low oxidized-lipid concentrations of 18 mol% or less. The aldehyde terminal of a shortened oxidized-lipid tail tends to interact with water and thus bends toward the bilayer-water interface, in agreement with previous experiments and simulations. In particular, water molecules pass through the oxidized bilayer without pore formation, implying passive permeability. A single nanoparticle, which consists of 300 polystyrene (PS) chains with cationic terminals, added to this bilayer simulation induces negative bilayer curvature and inserts to the bilayer, regardless of the oxidized-lipid concentration. Hydrophobic monomers and cationic terminals of the PS particle interact respectively with lipid tails and headgroups, leading to the wrapping of either lipid monolayer or bilayer along the particle surface. These results indicate that lipid oxidation increases membrane curvature and permeability even at such a low concentration of oxidized lipid, which supports the experimental observations regarding the passive permeability of oxidized bilayer, and also that oxidized lipids of low concentration do not significantly influence the insertion of a cationic PS particle to the bilayer.

A facile synthesis of hollow TiO2 photocatalyst with high amount of carbon exhibiting efficient visible-light photocatalytic performance

ABSTRACTA facile approach was developed for the synthesis of hollow TiO2 photocatalyst with a high amount of carbon (C/TiO2). The method mainly includes the following steps: the preparation of cationic polystyrene spheres (CPSs), deposition of TiO2 precursor, and the pyrolysis of CPS in an N2 atmosphere at 450 °C (close system). The structure and morphology of C/N-TiO2 were characterized by using TEM, XRD, XPS, and UV-Vis spectroscopy. The results confirm that the carbon is coated on the surface of the photocatalysts, substantially enhancing the visible-light harvesting and accelerating the separation of the photo-generated electrons/holes. Interestingly, the formed C/TiO2 effectively narrows the bandgap of TiO2, manifesting excellent photocatalytic activities for degradation of MB and Rh B under visible-light irradiation than commercial P25. Therefore, our findings demonstrate that C/TiO2 is a more promising candidate as visible-light photocatalysts for potential applications.

On the Size‐Determining Role of the Comonomer in the Nucleation and Growth of Cationic Polystyrene Latex via Emulsion Polymerization

AbstractThe formation of positively charged polystyrene latex particles via the surfactant‐free emulsion polymerization of styrene with cationic initiator is investigated. Using the comonomer (vinylbenzyl)trimethyl‐ammonium chloride (VBTMAC) it is shown that the particle size can be tuned rather precisely between above 350 nm and below 70 nm. The simple functional dependence of the particle size on the inverse cube root of the comonomer concentration leads to propose, with reasonable assumptions, that VBTMAC comonomer addition allows the separation of nucleation and growth for this reaction. Thereby the comonomer concentration determines the nucleation rate and number of particles produced, while the styrene amount determines by how much the nucleated particles grow. Support for this model is obtained through zeta potential measurements at different pH values. The latter confirmed that the surface density of cationic groups resulting from the comonomer relative to that of groups resulting from the initiator decreases with decreasing comonomer concentration.

Effect of wall thickness of hollow TiO2 spheres on properties of polyacrylate film: Thermal insulation, UV-shielding and mechanical property

Hollow TiO2 spheres were fabricated by calcining the polystyrene-titania composite microspheres prepared via a sol-gel process of titanium tetrabutoxide (TBT) using cationic polystyrene (PS) spheres as template. The wall thickness of hollow TiO2 spheres was finely tuned between 13 nm and 94 nm by varying the amount of titania precursor from 0.43 wt% to 1.25 wt% based on polystyrene latex during the coating process. The thermal insulation, UV-shielding, and mechanical properties of polyacrylate (PA) film were obviously enhanced by introducing hollow TiO2 spheres via physical blending method. Moreover, these properties exhibit a trend of first good and then become worse with the wall thickness of hollow TiO2 spheres increasing. When the wall thickness of hollow TiO2 spheres is 43 nm, the properties of polyacrylate/hollow TiO2 composite film are optimum.

High photocatalytic activity of hierarchical SiO2@C-doped TiO2 hollow spheres in UV and visible light towards degradation of rhodamine B

Ongoing research activities are targeted to explore high photocatalytic activity of TiO2-based photocatalysts for the degradation of environmental contaminants under UV and visible light irradiation. In this work, we devise a facile, cost-effective technique to in situ synthesize hierarchical SiO2@C-doped TiO2 (SCT) hollow spheres for the first time. This strategy mainly contains the preparation of monodisperse cationic polystyrene spheres (CPS), sequential deposition of inner SiO2, the preparation of the sandwich-like CPS@SiO2@CPS particles, and formation of outer TiO2. After the one-step removal of CPS templates by calcination at 450°C, hierarchical SiO2@C-doped TiO2 hollow spheres are in situ prepared. The morphology, hierarchical structure, and properties of SCT photocatalyst were characterized by TEM. SEM, STEM Mapping, BET, XRD, UV–vis spectroscopy, and XPS. Results strongly confirm the carbon doping in the outer TiO2 lattice of SCT hollow spheres. When the as-synthesized SCT hollow spheres were employed as a photocatalyst for the degradation of Rhodamine B under visible-light and ultraviolet irradiation, the SCT photocatalyst exhibits a higher photocatalytic activity than commercial P25, effectively overcoming the limitations of poorer UV activity for many previous reported TiO2-based photocatalysts due to doping.

Mineral-mineral particle collisions during flotation remove adsorbed nanoparticle flotation collectors

Flotation of 43μm diameter, hydrophilic glass beads with hydrophobic cationic polystyrene nanoparticle flotation collectors revealed that bead-bead collisions during conditioning and flotation caused the irreversible abrasion of the adsorbed nanoparticles. The abraded particles were present in the suspension as large aggregates. Nanoparticle abrasion explains why small polystyrene particles are more effective than larger ones, and why, much higher dosages of larger nanoparticles are required for the same flotation performance. These behaviors also were demonstrated with a phenomenological model of the abrasion dynamics.

Low-cost synthesis of hollow mesoporous silica spheres and its application in the removal of aromatic volatiles

In the paper, hollow mesoporous silica (HMS) spheres were prepared by an environment-friendly and low-cost method using cheap sodium silicate as silica precursor and inexpensive cationic polystyrene spheres as interior templates. Hollow structure with uniform size were characterized by TEM and SEM images. Nitrogen adsorption-desorption isotherm was used to confirm mesoporous structure with BET surface area of 424m2/g and narrow pore size distribution. TG-IR was utilized to investigate the influence of HMS spheres on the removal of aromatic volatiles. The as-prepared HMS spheres exhibited high removal ability of aromatic volatiles, mainly attributed to interior hollow for facilitating aggregation of aromatic volatiles to smoke particles and external mesoporous for strongly adsorbing aromatic volatiles.

Cationic Polystyrene Resolves Nonalcoholic Steatohepatitis, Obesity, and Metabolic Disorders by Promoting Eubiosis of Gut Microbiota and Decreasing Endotoxemia.

A pandemic of metabolic diseases, consisting of type 2 diabetes, nonalcoholic fatty liver disease, and obesity, has imposed critical challenges for societies worldwide, prompting investigation of underlying mechanisms and exploration of low-cost and effective treatment. In this report, we demonstrate that metabolic disorders in mice generated by feeding with a high-fat diet without dietary vitamin D can be prevented by oral administration of polycationic amine resin. Oral administration of cholestyramine, but not the control uncharged polystyrene, was able to sequester negatively charged bacterial endotoxin in the gut, leading to 1) reduced plasma endotoxin levels, 2) resolved systemic inflammation and hepatic steatohepatitis, and 3) improved insulin sensitivity. Gut dysbiosis, characterized as an increase of the phylum Firmicutes and a decrease of Bacteroidetes and Akkermansia muciniphila, was fully corrected by cholestyramine, indicating that the negatively charged components in the gut are critical for the dysbiosis. Furthermore, fecal bacteria transplant, derived from cholestyramine-treated animals, was sufficient to antagonize the metabolic disorders of the recipient mice. These results indicate that the negatively charged components produced by dysbiosis are critical for biogenesis of metabolic disorders and also show a potential application of cationic polystyrene to treat metabolic disorders through promoting gut eubiosis.

Tu1941 - Cationic Polystyrene Resolves Nonalcoholic Steatohepatitis (NASH), Obesity,and Metabolic Disorders in an Animal Model by Promoting Eubiosis of Gut Microbiota and Decreasing Endotoxemia

Tu1941 - Cationic Polystyrene Resolves Nonalcoholic Steatohepatitis (NASH), Obesity,and Metabolic Disorders in an Animal Model by Promoting Eubiosis of Gut Microbiota and Decreasing Endotoxemia

In situ synthesis of carbon-doped TiO2 single-crystal nanorods with a remarkably photocatalytic efficiency

Incorporating dopants into the TiO2 single crystals lattice is a big challenge because single crystal has a high crystallinity and the nucleation and growth of TiO2 single crystals is readily subjected to the interference of the dose of dopant precursors. Here, we propose an in situ synthetic strategy for the construct of carbon-doped TiO2 single crystal nanorods using CPS/TiO2 as the precursors of TiO2 nanorods and carbon source via a facile hydrothermal route. This technique involves the preparation of cationic polystyrene spheres (CPS), sequential deposition of TiO2 precursor, hydrothermal reaction, and the pyrolysis of CPS in a N2 atmosphere at 450°C. The morphology and structure of as-prepared C-TiO2 single crystal nanorods were characterized by TEM, SEM, STEM Mapping, XRD, UV–vis spectroscopy, and XPS. All results confirm the carbon doping in the as-prepared TiO2 single crystal nanorods. As a result of unique microstructure, the resulting TiO2 exhibits remarkably visible-light photocatalytic efficiency for the degradation of organic pollutants including methylene blue (MB), Rhodamine B (RhB) and p-nitrophenol (PNP). Therefore, the current study provides a new insight for incorporating dopants into the TiO2 single crystals lattice.

Role of Acetone in the Formation of Highly Dispersed Cationic Polystyrene Nanoparticles

Abstract A modified emulsion polymerisation synthesis route for preparing highly dispersed cationic polystyrene (PS) nanoparticles is reported. The combined use of 2,2′-azobis[2-(2-imidazolin- 2-yl)propane] di-hydrochloride (VA-044) as the initiator and acetone/water as the solvent medium afforded successful synthesis of cationic PS particles as small as 31 nm in diameter. A formation mechanism for the preparation of PS nanoparticles was proposed, whereby the occurrence of rapid acetone diffusion caused spontaneous rupture of emulsion droplets into smaller droplets. Additionally, acetone helped to reduce the surface tension and increase the solubility of styrene, thus inhibiting aggregation and coagulation among the particles. In contrast, VA-044 initiator could effectively regulate the stability of the PS nanoparticles including both the surface charge and size. Other reaction parameters i.e. VA-044 concentration and reaction time were examined to establish the optimum polymerisation conditions.

Growth Kinetics in Layer-by-Layer Assemblies of Organic Nanoparticles and Polyelectrolytes.

The growth rates of layer-by-layer (LbL) assemblies of polyelectrolytes (PEs) with oppositely charged polystyrene (PS) nanoparticles (NPs) as a function of molecular weight (MW) of the PEs, ionic strength of the media, and NP size and charge are systematically investigated. To optimize LbL growth, the effects of suspension concentration, pH of the media, and deposition time on the growth rate of multilayers are assessed. Both linear and exponential growth behaviors are observed and, under optimal conditions, films of up to around 1 μm thick can readily be assembled after 10 or so bilayers have been deposited. For many of the cases studied, an intermediate MW of PE leads to the fastest film buildup, for both cationic poly(ethyleneimine) deposited alternately with anionic PS NPs and for anionic poly(acrylic acid) deposited alternately with cationic PS NPs. The existence of an optimal MW suggests that growth rate is determined by a balance of thermodynamic factors, including density of polymer bridges between particles, and kinetic factors, specifically the diffusivity of polymer in the film. The optimal MW, however, is very sensitive to the materials used. Moreover, depending on the MW of the PE, increasing salinity could increase or decrease the growth kinetics. Finally, the surface morphology of the films is characterized with AFM and SEM to reveal that the roughness increases less than linearly with film thickness.

Characterization of Heterocoagulation with Oppositely Charged Polymer Colloid Particles through Online Tracking of Light Transmittance.

Heterocoagulation of colloid particles with opposite surface charge has been used for the preparation of composite microspheres with specifically designed suprastructure, such as those with raspberry-like surface morphology and core-shell microspheres, which are difficult to achieve through other techniques. Here we report our investigation on the heterocoagulation of cationic polystyrene (PS) particles with anionic poly(methyl methacrylate) (PMMA) particles by a novel technique, i.e., by following online the evolution of the light transmittance in the process with practically no disturbance of the dispersion and no post-treatment for the samples. Different heterocoagulations were conducted with PS and PMMA latexes with different latex mixing regimes and different particle sizes for both latexes. The evolution of the light transmittance in all of these processes, mainly with addition of anionic latex to cationic latex, was followed online. By combining TEM to detect the morphology of the composite microspheres formed and light scattering to follow the size evolution in the heterocoagulation, this work gives a clear picture of the heterocoagulation process. In addition, a set of mathematical equations are established in order to estimate the number ratio of the particles with opposite charge and the surface coverage percent of the large primary particle with the small ones. Results show that the particle size plays a key role in the process. The mechanism of the heterocoagulation process is discussed.

Synthesis, characterization and performance of a novel phosphate-modified fluid loss additive useful in oil well cementing

A phosphate-modified terpolymer comprising of 2-acrylamido-2-tert-butyl sulfonic acid (ATBS), N,N-dimethyl acrylamide (NNDMA) and 2-(methacryloxy)ethyl phosphate (MEP) was synthesized by aqueous free radical copolymerization and evaluated as fluid loss additive (FLA) in oil well cement. Successful incorporation of MEP was confirmed via1H NMR spectroscopy, and molecular properties of the terpolymer were determined using size exclusion chromatography. It was found that the presence of phosphate anchor groups along the polymer backbone enhances the FLA's performance in cement slurries at high temperatures (up to 140 °C) and in sea water when compared with commonly used ATBS-co-NNDMA or its counterpart composed of ATBS, NNDMA and 2-(methacryloxy)ethanol which bears a hydroxyl instead of the phosphate functionality. The phosphate-modified FLA also revealed better effectiveness and robustness when combined with acetone–formaldehyde–sulfite (AFS) dispersant or ATBS-co-acrylic acid retarder. Adsorption measurements suggest that the superior fluid loss performance is owed to higher adsorption of the phosphated FLA. Measurements of the adsorbed layer thickness on cationic polystyrene particles indicate that the phosphated FLA adsorbs in a train-like conformation which results from the strong affinity of the phosphate anchor groups to the positively charged surface.

Interactions of cationic polystyrene nanoparticles with marine bivalve hemocytes in a physiological environment: Role of soluble hemolymph proteins

The bivalve Mytilus galloprovincialis has proven as a suitable model invertebrate for evaluating the potential impact of nanoparticles (NPs) in the marine environment. In particular, in mussels, the immune system represents a sensitive target for different types of NPs. In environmental conditions, both NP intrinsic properties and those of the receiving medium will affect particle behavior and consequent bioavailability/uptake/toxicity. However, the evaluation of the biological effects of NPs requires additional understanding of how, once within the organism, NPs interact at the molecular level with cells in a physiological environment. In mammalian systems, different NPs associate with serum soluble components, organized into a “protein corona”, which affects particle interactions with target cells. However, no information is available so far on the interactions of NPs with biological fluids of aquatic organisms.In this work, the influence of hemolymph serum (HS) on the in vitro effects of amino modified polystyrene NPs (PS-NH2) on Mytilus hemocytes was investigated. Hemocytes were incubated with PS-NH2 suspensions in HS (1, 5 and 50µg/mL) and the results were compared with those obtained in ASW medium. Cell functional parameters (lysosomal membrane stability, oxyradical production, phagocytosis) were evaluated, and morphological changes were investigated by TEM. The activation state of the signalling components involved in Mytilus immune response (p38 MAPK and PKC) was determined. The results show that in the presence of HS, PS-NH2 increased cellular damage and ROS production with respect to ASW medium. The effects were apparently mediated by disregulation of p38 MAPK signalling. The formation of a PS-NH2-protein corona in HS was investigated by centrifugation, and 1D- gel electrophoresis and nano-HPLC-ESI-MS/MS. The results identified the Putative C1q domain containing protein (MgC1q6) as the only component of the PS-NH2 hard protein corona in Mytilus hemolymph. These data represent the first evidence for the formation of a NP bio-corona in aquatic organisms and underline the importance of the recognizable biological identity of NPs in physiological exposure medium when testing their potential impact environmental model organisms. Although the results obtained in vitro do not entirely reflect a realistic exposure scenario and the more complex formation of a bio-corona that is likely to occur in vivo, these data will contribute to a better understanding of the effects of NPs in marine invertebrates.

Implication of mesoporous 3-D graphene skeleton platform based on interconnected framework architecture in constructing electro-conductive flexible nanocomposites

Various polymer nanocomposites exhibiting elecro-conductivity along with flexibility were successfully fabricated by construction of the graphene-based three-dimensional (3-D) mesoporous skeleton platform derived from 3-D interconnected framework architecture constituted with two-dimensional (2-D) graphitic nanosheets, and the subsequent infiltration of polymer into pore volumes of the skeleton platform. The mesoporous 3-D skeleton platform of graphene has been easily constructed by the aggregation of graphene-coated polystyrene (PS) hybrid spheres prepared through ionic interacton between anionic graphene nanosheets and cationic PS nanospheres, and the subsequent thermal removal of polymer components, which made it possible to provide well-made pathways for electron transport as well as empty pores for the following infiltration of polymer matrix component. When a flexible polymer such as PVDF-HFP was chosen as a polymer matrix component entering into pore volumes of the graphene skeleton platform, the graphene/polymer nanocomposite tended to exhibit interesting behavior of electrical conductivity, which is comparable to that of neat graphene skeleton platform, and also maintained the initial value even under half-folding condition, evidencing excellent structural stability of the graphene skeleton. Furthermore, it was found that exchange of polymer matrix does not significantly alter the electrical conductivity of nanocomposite, confirming again the performance of 3-D graphene skeleton employing interconnected framework architecture as electron transport pathway. The ability to embed 3-D graphene skeleton into polymer matrix is a great opportunity to impart high electrical and mechanical properties to polymer composite formulation. Open image in new window

Enhanced supercapacitor performances using C-doped porous TiO2 electrodes

Considerable efforts have been paid to develop electrochemical capacitors with energy storage capability in order to meet the demands of multifunctional electronics. Here we report a facile method to fabricate C-doped porous anatase TiO2. This technique involves the preparation of monodisperse cationic polystyrene nanoparticles (CPN), following sequential deposition of tetrabutylorthotitanate (TBT), and directly carbonizing of CPN. Interestingly, during the process of carbonizing CPN, a phase transition of TiO2 will be happened and whist C-doped porous anatase TiO2 is in situ formed. When this porous C-doped TiO2 is used as electrode material to prepare electrochemical capacitor, it manifests a higher capacitance than the commercial P25, effectively broadening it potential for many practical applications.