Showing papers on "Polystyrene published in 2014"

High-Modulus, High-Conductivity Nanostructured Polymer Electrolyte Membranes via Polymerization-Induced Phase Separation

Abstract: The primary challenge in solid-state polymer electrolyte membranes (PEMs) is to enhance properties, such as modulus, toughness, and high temperature stability, without sacrificing ionic conductivity. We report a remarkably facile one-pot synthetic strategy based on polymerization-induced phase separation (PIPS) to generate nanostructured PEMs that exhibit an unprecedented combination of high modulus and ionic conductivity. Simple heating of a poly(ethylene oxide) macromolecular chain transfer agent dissolved in a mixture of ionic liquid, styrene and divinylbenzene, leads to a bicontinuous PEM comprising interpenetrating nanodomains of highly cross-linked polystyrene and poly(ethylene oxide)/ionic liquid. Ionic conductivities higher than the 1 mS/cm benchmark were achieved in samples with an elastic modulus approaching 1 GPa at room temperature. Crucially, these samples are robust solids above 100 °C, where the conductivity is significantly higher. This strategy holds tremendous potential to advance lithiu...

Preparation and characterization of magnetic porous carbon microspheres for removal of methylene blue by a heterogeneous Fenton reaction.

Abstract: High-specific-surface-area magnetic porous carbon microspheres (MPCMSs) were fabricated by annealing Fe2+-treated porous polystyrene (PS) microspheres, which were prepared using a two-step seed emulsion polymerization process. The resulting porous microspheres were then sulfonated, and Fe2+ was loaded by ion exchange, followed by annealing at 250 °C for 1 h under an ambient atmosphere to obtain the PS-250 composite. The MPCMS-500 and MPCMS-800 composites were obtained by annealing PS-250 at 500 and 800 °C for 1 h, respectively. The iron oxide in MPCMS-500 mainly existed in the form of Fe3O4, which was concluded by characterization. The MPCMS-500 carbon microspheres were used as catalysts in heterogeneous Fenton reactions to remove methylene blue (MB) from wastewater with the help of H2O2 and NH2OH. The results indicated that this catalytic system has a good performance in terms of removal of MB; it could remove 40 mg L–1 of MB within 40 min. After the reaction, the catalyst was conveniently separated from...

Core–Shell Structure of Hierarchical Quasi‐Hollow MoS2 Microspheres Encapsulated Porous Carbon as Stable Anode for Li‐Ion Batteries

Abstract: Monodisperse sulfonated polystyrene (SPS) microspheres are employed as both the template and carbon source to prepare MoS2 quasi-hollow microspheres-encapsulated porous carbon. The synthesis procedure involves the hydrothermal growth of MoS2 ultrathin nanosheets on the surface of SPS microspheres and subsequent annealing to remove SPS core. Incomplete decomposition of SPS during annealing due to the confining effect of MoS2 shells leaves residual porous carbon in the interior. When being evaluated as the anode materials of Li-ion batteries, the as-prepared C@MoS2 microspheres exhibit excellent cycling stability (95% of capacity retained after 100 cycles) and high rate behavior (560 mAh g(-1) at 5 A g(-1)).

Functionalized polystyrene nanoparticles as a platform for studying bio–nano interactions

Abstract: Nanoparticles of various shapes, sizes, and materials carrying different surface modifications have numerous technological and biomedical applications. Yet, the mechanisms by which nanoparticles interact with biological structures as well as their biological impact and hazards remain poorly investigated. Due to their large surface to volume ratio, nanoparticles usually exhibit properties that differ from those of bulk materials. Particularly, the surface chemistry of the nanoparticles is crucial for their durability and solubility in biological media as well as for their biocompatibility and biodistribution. Polystyrene does not degrade in the cellular environment and exhibits no short-term cytotoxicity. Because polystyrene nanoparticles can be easily synthesized in a wide range of sizes with distinct surface functionalizations, they are perfectly suited as model particles to study the effects of the particle surface characteristics on various biological parameters. Therefore, we have exploited polystyrene nanoparticles as a convenient platform to study bio–nano interactions. This review summarizes studies on positively and negatively charged polystyrene nanoparticles and compares them with clinically used superparamagnetic iron oxide nanoparticles.

Surface-Initiated Polymerization from Barium Titanate Nanoparticles for Hybrid Dielectric Capacitors

Abstract: A phosphonic acid is used as a surface initiator for the growth of polystyrene and polymethylmethacrylate (PMMA) from barium titanate (BTO) nanoparticles through atom transfer radical polymerization with activators regenerated by electron transfer. This results in the barium titanate cores embedded in the grafted polymer. The one-component system, PMMA-grafted-BTO, achieves a maximum extractable energy density of 2 J/cm3 at a field strength of ∼220 V/μm, which exhibits a 2-fold increase compared to that of the composite without covalent attachment or the neat polymer. Such materials have potential applications in hybrid capacitors due to the high permittivity of the nanoparticles and the high breakdown strength, mechanical flexibility, and ease of processability due to the organic polymer. The synthesis, processing, characterization, and testing of the materials in capacitors are discussed.

Encapsulated phase change materials stabilized by modified graphene oxide

Abstract: The microencapsulation of phase change materials (n-hexadecane) with double-walled shells (polystyrene/graphene oxide) was realized from Pickering emulsion templating. Graphene oxide nanosheets were modified by the polycondensate of diethanolamine and adipic acid, which can well stabilize oil-in-water (O/W) Pickering emulsions. The morphology of the double-walled shell of polymer microspheres was observed by scanning electron microscopy (SEM). The thermal and barrier properties of microcapsules were studied using differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and the flammability test. DSC results indicate that the encapsulation ratio of n-hexadecane is as high as 78%. The encapsulated phase change material has good thermal stability, owing to the existence of graphene oxide on the surface protecting the core material from leakage and evaporation. This double-walled microencapsulation of phase change materials may have potential applications in energy storage and energy saving.

Formation Mechanism of High-Density, Flattened Polymer Nanolayers Adsorbed on Planar Solids

Abstract: Thermal annealing is one of the most indispensable polymer fabrication processes and plays essential roles in controlling morphologies and properties of polymeric materials. We here report that thermal annealing also facilitates polymer adsorption from the melt on planar silicon (Si) substrates, resulting in the formation of a high-density polymer nanolayer with flattened chain confirmations. Three different homopolymers (polystyrene, poly(2-vinylpyridine), and poly(methyl methacrylate)), which have similar inherent stiffness and bulk glass transition temperature (Tg), but have different affinities with Si substrates, were chosen as models. Spin-cast films (∼50 nm in thickness) with the three polymers were prepared on cleaned Si substrates and then placed in a vacuum oven set at a temperature far above the bulk Tg. In order to monitor the polymer adsorption process at the solid-polymer melt interface during thermal annealing, we used the protocol that combines vitrification of the annealed films (via rapi...

One-step polymer screen-printing for microfluidic paper-based analytical device (μPAD) fabrication

Abstract: We report a simple, low-cost, one-step fabrication method for microfluidic paper-based analytical devices (μPAD) using only polystyrene and a patterned screen. The polystyrene solution applied through the screen penetrates through the paper, forming a three-dimensional hydrophobic barrier, defining a hydrophilic analysis zone. The optimal polystyrene concentration and paper types were first investigated. Adjusting polystyrene concentration allows for various types of paper to be used for successful device fabrication. Using an optimized polystyrene concentration with Whatman#4 filter paper, a linear relationship was found to exist between the design width and the printed width. The smallest hydrophilic channel and hydrophobic barrier that can be obtained are 670 ± 50 μm and 380 ± 40 μm, respectively. High device-to-device fabrication reproducibility was achieved yielding a relative standard deviation (%RSD) in the range of 1.12–2.54% (n = 64) of the measured diameter of the well-shaped fabricated test zones with a designed diameter of 5 and 7 mm. To demonstrate the significance of the fabricated μPAD, distance-based and well-based paper devices were constructed for the analysis of H2O2 and antioxidant activity, respectively. The analysis of H2O2 in real samples using distance-based measurement with CeO2 nanoparticles as the colorimetric agent produced the same results at 95% confidence level, as those obtained using KMnO4 titration. A proof-of-concept antioxidant activity determination based on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was also demonstrated. The results verify that the polymer screen-printing method can be used as an alternative method for μPAD fabrication.

Electromagnetic interference shielding materials derived from gelation of multiwall carbon nanotubes in polystyrene/poly(methyl methacrylate) blends.

Abstract: Blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with different surface-functionalized multiwall carbon nanotubes (MWNTs) were prepared by solution blending to design materials with tunable EMI (electromagnetic interference) shielding. Different MWNTs like pristine, amine (∼NH2), and carboxyl acid (∼COOH) functionalized were incorporated in the polymer by solution blending. The specific interaction driven localization of MWNTs in the blend during annealing was monitored using contact mode AFM (atomic force microscopy) on thin films. Surface composition of the phase separated blends was further evaluated using X-ray photoelectron spectroscopy (XPS). The localization of MWNTs in a given phase in the bulk was further supported by selective dissolution experiments. Solution-casted PS/PMMA (50/50, wt/wt) blend exhibited a cocontinuous morphology on annealing for 30 min, whereas on longer annealing times it coarsened into matrix-droplet type of morphology. Interestingly, both pristine MWNTs and N...

Polystyrene sulphonic acid resins with enhanced acid strength via macromolecular self-assembly within confined nanospace

Abstract: Tightening environmental legislation is driving the chemical industries to develop efficient solid acid catalysts to replace conventional mineral acids. Polystyrene sulphonic acid resins, as some of the most important solid acid catalysts, have been widely studied. However, the influence of the morphology on their acid strength--closely related to the catalytic activity--has seldom been reported. Herein, we demonstrate that the acid strength of polystyrene sulphonic acid resins can be adjusted through their reversible morphology transformation from aggregated to swelling state, mainly driven by the formation and breakage of hydrogen bond interactions among adjacent sulphonic acid groups within the confined nanospace of hollow silica nanospheres. The hybrid solid acid catalyst demonstrates high activity and selectivity in a series of important acid-catalysed reactions. This may offer an efficient strategy to fabricate hybrid solid acid catalysts for green chemical processes.

A Facile Method for Generating Designer Block Copolymers from Functionalized Lignin Model Compounds

Abstract: We report a versatile scheme for the synthesis of renewable homopolymers and block copolymers (BCPs) via the functionalization and subsequent controlled reversible addition–fragmentation chain transfer (RAFT) polymerization of vanillin, a possible lignin derivative. The vanillin-based homopolymers exhibit glass transition temperatures (120 °C) and degradation temperatures (≥300 °C) comparable to polystyrene, indicating that these and similar polymers may serve as suitable alternatives to petroleum-based materials. Additionally, by employing controlled polymerization techniques, a vanillin-based homopolymer was chain-extended with lauryl methacrylate, a model fatty acid-derived monomer, to generate nanostructured BCPs. As one example, these elastomeric copolymers can self-assemble into a body-centered cubic array of vanillin-based nanospheres in a poly(lauryl methacrylate) matrix, which we demonstrated via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) analysis. This work pr...

Sustainable Conversion of Mixed Plastics into Porous Carbon Nanosheets with High Performances in Uptake of Carbon Dioxide and Storage of Hydrogen

Abstract: Conversion of waste plastics into high value-added carbon nanomaterials has gained wide research interest due to the requirement of sustainable development and the ever-increasing generation of waste plastics. However, most of studies are limited to single component plastic; besides, little attention has been paid to carbon nanosheets (CNS). Herein, CNS were prepared by catalytic carbonization of mixed plastics consisting of polypropylene, polyethylene, polystyrene, poly(ethylene terephthalate), and polyvinyl chloride on organically modified montmorillonite. After KOH activation, porous CNS (PCNS) were produced. The morphology, microstructure, phase structure, textural property, surface element composition, and thermal stability of PCNS were investigated. PCNS contained randomly oriented lattice fringes and showed a layered morphology consisting of thin, leaf-like, agglomerated nanosheets ranging from hundreds of nanometers to several micrometers in length. Besides, PCNS exhibited high specific surface ar...

Interactions, structure and properties in poly(lactic acid)/thermoplastic polymer blends

Abstract: Blends were prepared from poly(lactic acid) (PLA) and three thermoplastics, polystyrene (PS), polycarbonate (PC) and poly(methyl methacrylate) (PMMA). Rheological and mechanical properties, structure and component interac- tions were determined by various methods. The results showed that the structure and properties of the blends cover a rela- tively wide range. All three blends have heterogeneous structure, but the size of the dispersed particles differs by an order of magnitude indicating dissimilar interactions for the corresponding pairs. Properties change accordingly, the blend con- taining the smallest dispersed particles has the largest tensile strength, while PLA/PS blends with the coarsest structure have the smallest. The latter blends are also very brittle. Component interactions were estimated by four different methods, the determination of the size of the dispersed particles, the calculation of the Flory-Huggins interaction parameter from sol- vent absorption, from solubility parameters, and by the quantitative evaluation of the composition dependence of tensile strength. All approaches led to the same result indicating strong interaction for the PLA/PMMA pair and weak for PLA and PS. A general correlation was established between interactions and the mechanical properties of the blends.

Modifying graphite oxide nanostructures in various media by high-energy irradiation

Abstract: The alterations of GO nanostructures after γ-ray irradiation in water, air and styrene with an absorbed dose of 200 kGy are systematically investigated. The interlayer structures of the ultimate products are confirmed to be remarkably different from each other due to the distinct changes of functional groups on single-sheets in various media. After irradiation in water, oxygen groups in graphite oxide are shown to be obviously decreased owing to the generation of reductive radicals by the decomposition of water molecules, which is reflected in the decrease of graphite oxide interlayer spacing. The interlayer distance of graphite oxide irradiated in air is found to be significantly increased, which may be attributed to the increase of the hydroxyl groups and the topological defects. However, the graphite oxide seems to be mainly exfoliated and functionalized by the intercalation of the monomers and the grafting of polystyrene chains when irradiated in styrene. It is expected that γ-ray irradiation in different media should be a promising strategy for manipulating nanostructures and properties of graphite oxide for improving its applicability in fields of composites, catalysts and sensors.

Measuring the proton conductivity of ion-exchange membranes using electrochemical impedance spectroscopy and through-plane cell.

Abstract: The role of the incorporation of conducting polymer (CP), doped with different sulfonic acid organic molecules, in polystyrene (PS) and high-impact polystyrene (HIPS) with poly(styrene-ethylene-butylene) (SEBS) triblock copolymer has been investigated. Two factors associated with this model membrane system are addressed: (i) the influence of the presence of a low concentration of doped conducting polymer and (ii) the influence of the membrane preparation method. Membrane characterization and bulk conductivity measurements allowed the conclusion that proton conductivity has been promoted by the addition of CP; the best results were achieved for PAni-CSA, in either PS/SEBS or HIPS/SEBS blends. Additionally, the water uptake only decreased with the addition of PAni-doped molecules compared to the pure copolymer, without loss of ion-exchange capacity (IEC). Electrodialysis efficiency for HIPS/SEBS (before annealing) is higher than that for HIPS/SEBS (after annealing), indicating that membrane preparation meth...

In situ atom transfer radical polymerization of styrene to in-plane functionalize graphene nanolayers: grafting through hydroxyl groups

Abstract: Graphene oxide (GO) was modified with two different amounts of 3-(trimethoxysilyl)propyl methacrylate (MPS) by a silane coupling reaction. Atom transfer radical polymerization of styrene in the presence of different amounts of MPS-modified graphene was carried out to evaluate the effect of graphene loading along with the graft density on the properties of the products. Successful attachment of MPS on the surface of GO was evaluated using Fourier transform infrared spectroscopy. Expansion of graphene interlayers by oxidation and functionalization processes was evaluated using X-ray diffraction. The ordered and disordered crystal structure of carbon in pristine and surface modified graphenes was evaluated by Raman spectroscopy. Relaxation behavior of polystyrene chains in the presence of graphene layers and also effect of graft content on the chain confinement was studied using differential scanning calorimetry. High-density nanocomposites show much increase of Tg by addition of graphene content. Morphology of graphene nanolayers after modification processes was studied by scanning electron microscopy and also transmission electron microscopy. Flat and smooth morphology of graphene nanosheets was disturbed during the oxidation and functionalization processes and consequently wrinkled sheets with curvature were obtained.

Local Segmental Dynamics and Stresses in Polystyrene–C60 Mixtures

Abstract: The polymer dynamics of homogeneous C60–polystyrene mixtures in the molten state are studied via molecular simulations using two interconnected levels of representation for polystyrene nanocomposites: (a) A coarse-grained representation, in which each polystyrene repeat unit is mapped into a single “superatom” and each fullerene is viewed as a spherical shell. Equilibration of coarse-grained polymer–nanoparticle systems at all length scales is achieved via connectivity-altering Monte Carlo simulations. (b) An atomistic representation, where both nanoparticles and polymer chains are represented in terms of united-atom forcefields. Initial configurations for atomistic molecular dynamics (MD) simulations are obtained by reverse mapping well-equilibrated coarse-grained configurations. By analyzing MD trajectories under constant energy, the segmental dynamics of polystyrene (for neat and filled systems) is characterized in terms of bond orientation time autocorrelation functions. Nanocomposite systems are foun...

Pickering emulsion-fabricated polystyrene–graphene oxide microspheres and their electrorheology

Abstract: Graphene oxide (GO) was used as a solid surfactant, and core–shell structured polystyrene (PS)–GO microspheres were fabricated using the Pickering emulsion polymerization method. The resulting electro-responsive ‘smart’ microspheres were dispersed in silicone oil and their electrorheological characteristics were measured using a rotational rheometer under an applied electric field and correlated with their dielectric properties. The GO was found to impart electro-responsive properties to the polymer composite suspension under an applied electric field.