Showing papers on "Polystyrene published in 1999"
TL;DR: In this article, the enzyme horseradish peroxidase (HRP) was used to polymerize aniline in the presence of a polyanionic template, sulfonated polystyrene.
Abstract: A novel strategy for the enzymatic synthesis of a water-soluble, conducting polyaniline (PANI)/sulfonated polystyrene (SPS) complex is presented. The enzyme horseradish peroxidase (HRP) is used to polymerize aniline in the presence of a polyanionic template, sulfonated polystyrene. The synthesis is simple, and the conditions are mild in that the polymerization may be carried out in a 4.3 pH buffered aqueous solution, with a stoichiometric amount of hydrogen peroxide and a catalytic amount of enzyme. UV−visible absorption, FTIR, GPC, elemental analysis, and conductivity measurements all confirm that the electroactive form of PANI, similar to that which is traditionally chemically synthesized, is formed and complexed to the SPS. The reversible redox activity of the polyaniline displays a unique hysteresis loop with pH change. Cyclic voltammetry studies show only one set of redox peaks over the potential range of −0.2 to 1.2V, which suggests that the PANI/SPS complex is oxidatively more stable. The conductiv...
469 citations
TL;DR: In this paper, the formation of crew-cut aggregates of various structures prepared from polystyrene-b-poly(acrylic acid) diblock copolymers in DMF/water mixtures is explored.
Abstract: Thermodynamic vs kinetic aspects of the formation of crew-cut aggregates of various structures prepared from polystyrene-b-poly(acrylic acid) diblock copolymers in DMF/water mixtures are explored. In particular, the reversibility of the transitions between the crew-cut aggregates of various morphologies is studied by “jumps” in the polymer or ion concentration at various water contents. The aggregates are prepared by two different methods: micellization is induced either by the addition of water to polymer/DMF solutions or by the direct dissolution of the polymer in DMF/water mixtures. It is shown that as the polymer concentration increases, the morphology of the aggregates changes from spheres to rodlike micelles, to interconnected rods, and then to bilayers. As the water content increases, the boundaries for the formation of the different morphologies move toward lower polymer concentrations. The thermodynamic vs kinetic control of the morphology depends largely on the water content and the method of a...
390 citations
TL;DR: In this paper, the authors reported the preparation of macroporous polymer membranes with regular voids and the characterization of their diffractive optical properties using a colloidal crystal template of silica microspheres; the air between the spheres can be replaced by monomers that can be subsequently polymerized.
Abstract: The fabrication of polymeric materials with ordered submicron-sized void structures is potentially valuable for many separation technologies as well as for emerging optical applications. This paper reports the preparation of macroporous polymer membranes with regular voids and the characterization of their diffractive optical properties. These materials are made using a colloidal crystal template of silica microspheres; the air between the spheres can be replaced by monomers that can be subsequently polymerized. The use of silica microspheres as templates makes it possible to employ chemical rather than thermal methods for template removal. For this reason, polymers as diverse as polyurethane and polystyrene can be used to create free- standing macroporous films, with thickness ranging from 0.5 to 50 Im. Scanning electron microscopy of these samples indicates a well-formed porous structure consisting of voids ranging in diameter from 200 to 400 nm. These large cavities are not isolated, but rather interconnected by a network of monodisperse smaller pores (d ) 50-130 nm) whose size can be controlled by varying the polymerization temperature. These membranes exhibit striking optical properties due to the periodic arrangement of air spheres in the polymer medium. Normal-incidence transmission measurements of these samples are compared to a theoretical model based on a scalar wave approximation. This model assumes an ordered structure of close-packed, three-dimensional air spheres. The good agreement between theory and experiment provides additional evidence of the long-range order of these samples.
377 citations
TL;DR: In this paper, a self-assembled monolayer (SAM) of biphenyllithium moieties on gold substrates is used to initiate anionic polymerization of styrene.
Abstract: A synthetic concept of preparing dense polymer brushes on planar surfaces is described, in which a self-assembled monolayer (SAM) of biphenyllithium moieties on gold substrates is used to initiate anionic polymerization of styrene. The thickness of the resulting dry polystyrene brush, as estimated by ellipsometry and atomic force microscopy (AFM), is 18 ± 0.2 nm. These techniques also reveal a smooth, homogeneous polymer surface throughout the entire substrate on the macroscopic, as well as on the microscopic, scale, with a roughness of 0.3−0.5 nm (rms). On the basis of results from in situ swelling experiments, monitored by ellipsometry, a polymerization degree of N = 382 and a grafting density of approximately 7−8 chains/Rg2, or 3.2−3.6 nm2/chain, were calculated with use of mean-field theory. Polarized external reflection (ER) FTIR spectra of the grafted layer confirm highly stretched preferentially oriented polystyrene chains. Upon annealing, spin-coated polystyrene films dewet immediately the brush s...
358 citations
TL;DR: In this article, a solution of the desired polymer within the pores of microporous template membranes was used as the templates for polymer microtubules and nanofibrils with diameters as small as 30 nm.
Abstract: Polymeric microtubules and nanofibrils have been prepared by depositing a solution of the desired polymer within the pores of microporous template membranes. Both microporous alumina and track-etched polyester membranes were used as the templates. Tubules and fibrils composed of polystyrene, poly(2,6-dimethyl-1,4-phenylene oxide), poly(vinylidene fluoride), poly(methyl methacrylate), poly(bisphenol A carbonate), and poly(lactic acid) have been prepared. Nanofibrils with diameters as small as 30 nm have been achieved. A concentric tubular composite microstructure consisting of an outer microtubule of polystyrene surrounding an inner microwire of polypyrrole has also been fabricated.
291 citations
TL;DR: In this article, the pyrolysis of mixed-plastic waste has been proposed as a means of recycling to produce petrochemical feedstock, and the interaction of the main plastic types in plastic mixtures is significant in predicting the likely yield and composition of products from different plastic mixture.
Abstract: The pyrolysis of mixed-plastic waste has been proposed as a means of recycling to produce petrochemical feedstock. The interaction of the main plastic types in plastic mixtures is significant in predicting the likely yield and composition of products from different plastic mixtures. The six main plastics in municipal solid waste are high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), poly(vinyl chloride) (PVC), and poly(ethylene terephthalate) (PET). Each of the plastics was pyrolyzed individually in a fixed-bed reactor heated at 25 °C min-1 to a final temperature of 700 °C. Polystyrene was then mixed with each of the other five plastics in a ratio of 1:1 and pyrolyzed in the fixed-bed reactor under the same pyrolysis conditions. The yield and composition of the derived oil/wax and gases was determined. The main gases produced from the individual plastics were hydrogen, methane, ethane, ethene, propane, propene, butane, and butene and for the PET plasti...
276 citations
265 citations
TL;DR: In this paper, a brush-like monolayers composed of two different polymers, polystyrene and poly(2-vinylpyridine), are grafted by radical polymerization on the surface of silicon wafers.
Abstract: Polymer coatings of brushlike monolayers composed of two different polymers, polystyrene and poly(2-vinylpyridine), are grafted by radical polymerization on the surface of silicon wafers. Thickness, grafting density, molecular weight of grafted chains, and the composition of the coatings were regulated by grafting time, monomer concentration, and additional initiator in solution. A typical dry film thickness is between 10 and 100 nm, and the molecular weights of the components range from 100 to 300 kg/mol. The fabricated coatings turn out to be sensitive to the composition of the environment. For instance after exposition to toluene the layer becomes hydrophobic and the top of the layer is covered by polystyrene. After exposition to HCl the layer becomes hydrophilic with polyvinylpyridine in the upper layer. This reconstruction of the polymer layer was observed with contact angle and X-ray photoelectron spectroscopy measurements. The composition of the top layer in different media is controlled by the com...
227 citations
TL;DR: In this article, a range of monodisperse nanospheres was obtained by emulsifier-free dispersion copolymerization of styrene with a surface-grafted poly(N-isopropylacrylamide) macromonomer.
Abstract: Well-dispersed platinum colloids have been prepared on polystyrene nanospheres with surface-grafted poly(N-isopropylacrylamide) (PNIPAAm) via the reduction of PtCl62- by ethanol. A range of monodisperse nanospheres was obtained by emulsifier-free dispersion copolymerization of styrene with a PNIPAAm macromonomer. The surface compositions of the polystyrene nanospheres before and after immobilization of Pt colloids have been investigated by X-ray photoelectron spectroscopy. Peak fitting of the C 1s core-line spectra provides evidence for the presence of PNIPAAm chains at the surface of polystyrene nanospheres. These immobilized Pt colloids were found to be active and stable heterogeneous catalysts for the hydrogenation of allyl alcohol in water. Both the particle size and activity of platinum colloids showed a marked dependence on the level of surface PNIPAAm. The average diameter of an immobilized Pt colloid is 15.0 A and largely unchanged after seven cycles in hydrogenation, as confirmed by TEM. The immo...
191 citations
TL;DR: Saricci et al. as mentioned in this paper presented efficiency data of solar cells based on a soluble derivative of p-phenylene vinylene (PPV), poly [2-methoxy, 5-(3′,7′-dimethyl-octyloxy)]-p-phenylon vinylene, and a highly soluble methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), embedded into a conventional polymer, polystyrene (PS).
Abstract: Bulk donor–acceptor heterojunctions between conjugated polymers and fullerene derivatives have been utilized successfully for photovoltaic devices showing monochromatic energy conversion efficiencies above 1%. The photovoltaic response of these devices is based on the ultrafast, photoinduced electron transfer from the conjugated polymer to the fullerene [N. S. Sariciftci and A. J. Heeger, Handbook of Organic Conductive Molecules and Polymers, (Wiley, New York, 1997), pp. 413–455]. In this work we present efficiency data of solar cells based on a soluble derivative of p-phenylene vinylene (PPV), poly [2-methoxy, 5-(3′,7′-dimethyl-octyloxy)]-p-phenylene vinylene (MDMO-PPV), and a highly soluble methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), embedded into a conventional polymer, polystyrene (PS). By the blending of the optimized donor–acceptor components into the conventional polymer matrix, the percolation threshold for photovoltaic response of the three component systems is found to be determined by percolation of the methanofullerene in the polymer matrix. We present current/voltage data of PS–MDMO-PPV–PCBM devices with various PS concentrations as well as photoinduced absorption studies in the infrared [(PIA) Fourier transform infrared] and light induced electron spin resonance studies on the electron transfer in these composites. At low light intensities, the monochromatic power conversion efficiency ηe and the photon carrier collection efficiency ηc of the PS free device are calculated with 1.5% and 18%, respectively.
172 citations
TL;DR: Closed cell foams of broad molecular weight distribution commercial polystyrene samples, prepared by expansion of supercritical-CO2-swollen specimens, exhibit cell diameters that are ∼3−10 times (1) larger than those of open-cell foams as discussed by the authors.
Abstract: Closed cell foams of broad molecular weight distribution commercial polystyrene samples, prepared by expansion of supercritical-CO2-swollen specimens, exhibit cell diameters that are ∼3−10 times (1...
TL;DR: In this article, a polystyrene−poly(ethylene oxide) containing diblock copolymer, when spread at the air/water interface, spontaneously forms surface aggregates.
Abstract: A polystyrene−poly(ethylene oxide) containing diblock copolymer, when spread at the air/water interface, spontaneously forms surface aggregates. This surface aggregation is shown to be neither compression-induced, associated with micellization in the spreading solvent, nor induced by the Langmuir−Blodgett film transfer process. We have previously found that such two-dimensional surface aggregation occurs for diblock copolymers with a polystyrene block and a hydrophilic block of quaternized poly(vinylpyridine), poly(tert-butyl acrylate), poly(n-butyl acrylate), or poly(dimethylsiloxane). The phenomenon has also been observed in films of polystyrene−poly(methyl methacrylate) by Rice and co-workers.1 Indeed, whenever an appropriate imaging technique has been used, phase-separated domains with 30−100 nm length scales have been observed, when amphiphilic diblock copolymers are spread at the air/water interface and transferred to solid substrates at appreciable surface pressures. We therefore believe that the f...
TL;DR: In this article, the authors used Extended-DLVO theory to determine the median detaching pH for deionized water, and solutions of 0.01 and 0.1 M NaCl.
Abstract: Detachment of polystyrene latex colloids was studied in a model porous media system comprised of a packed column of glass beads. The polystyrene colloids were attached and subsequently detached from the glass beads by varying solution pH and ionic strength. It was found that classical-DLVO theory could not predict detaching conditions. Extended-DLVO theory was used to determine the median detaching pH for deionized water, and solutions of 0.01 and 0.1 M NaCl. Although both the colloids and porous media were macroscopically homogeneous, detachment was observed at a variety of pH values. The pH distribution of detachment and the energy distribution of the interaction between the polystyrene latex colloids and the glass beads followed gamma distributions. This work has provided a technique to quantitatively predict the aqueous chemistry changes that induce colloid detachment in porous media.
TL;DR: In this paper, a cascade of well-s stirred reactors is used to perform stepwise pyrolysis of mixtures of poly(vinyl chloride), polystyrene and polyethylene, where the different components of the mixture are pyrolysed at different temperatures.
TL;DR: In this paper, a polyelectrolyte brush was prepared on silicon blocks in two steps: first, they graft polystyrene (PS) chains terminated by a trichlorosilane group, and then, they convert the grafted PS to poly(s...
Abstract: We have prepared polyelectrolyte brushes on silicon blocks in two steps: first, we graft polystyrene (PS) chains terminated by a trichlorosilane group, and then, we convert the grafted PS to poly(s...
TL;DR: Rhenium(V) iododioxobis(triphenylphosphine) [ReO2I(PPh3)2] proved an effective metal catalyst for living radical polymerization of styrene in conjunction with alkyl iodide as an initiator as discussed by the authors.
Abstract: Rhenium(V) iododioxobis(triphenylphosphine) [ReO2I(PPh3)2] proved an effective metal catalyst for living radical polymerization of styrene in conjunction with alkyl iodide as an initiator [R−I: CH3CH(Ph)I, (CH3)2C(CO2Et)I, and CH3CH(CO2Et)I] in the presence of Al(Oi-Pr)3 Compared to RuCl2(PPh3)3, the group 7 complex was highly effective for styrene, so as to induce the living polymerization even at 30 °C to yield well-controlled polystyrene, with Mn up to ∼4 × 104 and very narrow molecular weight distributions (MWDs) (Mw/Mn = 119) The polystyrene thus obtained possessed one initiator moiety (R) at the α-end and one iodine atom at the ω-end, both from the initiator R−I, which indicates that the polymerization proceeds via activation of the C−I terminal, derived from R−I, by the Re(V) complex Addition of methanol or water did not inhibit these polymerizations, while a stable nitroxide radical (TEMPO) immediately and completely quenched them The quenching experiments thereby supported intervention o
TL;DR: In this paper, a multistage emulsion polymerization using styrene monomer, divinylbenzene crosslinking agent, and potassium persulfate initiator in the absence of emulsifier is described.
Abstract: Micron-sized monodisperse crosslinked polystyrene (PS) beads have been prepared by a multistage emulsion polymerization using styrene monomer, divinylbenzene crosslinking agent, and potassium persulfate initiator in the absence of emulsifier. In the first stage of the reaction, the lower the reaction temperature, the larger the bead size obtained. In the later stages of the reaction, the particle size is increased with the initiator concentration and monomer content. Particle nucleation of the preexisting polymer seed of 0.7–0.8 μm in diameter is prepared at 60°C, then the monodisperse crosslinked PS beads > 2 μm are synthesized up to the third stage of the reaction. As the particle size grows, the number of free radicals in the growing particles increases, and the conversion of the next stage is continuously increased. The reaction mechanism is suggested that the continuous polymerization be conducted due to the diffusion of monomer into the preexisting particles to induce spherical beads in the later stages of the reaction. Otherwise, phase separation or the formation of protrusion by the capture of free radicals will be taking place. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2259–2269, 1999
TL;DR: In this article, the double gyroid (DG) cubic phase in glassy-rubbery block copolymer systems is examined and the deformation behavior of the DG is compared to those of the sphere, cylinder, and lamellar morphologies.
Abstract: The mechanical properties of the double gyroid (DG) cubic phase in glassy−rubbery block copolymer systems are examined. The stress−strain properties of an isoprene-rich polystyrene/polyisoprene/polystyrene (SIS) triblock and a polystyrene/polyisoprene (SI) starblock DG, both comprised of two separate interpenetrating glassy networks embedded in rubbery matrices, are compared to those of the sphere, cylinder, and lamellar morphologies. This 3-dimensionally interpenetrating periodic nanocomposite is found to have superior properties over those of its classical counterparts, attributable to the morphology rather than to the volume fraction of the glassy component, the architecture of the molecule, or the molecular weight. The DG is the only polygranular/isotropic thermoplastic elastomer morphology which exhibits necking and drawing and which requires considerably higher stresses for deformation up to 200% strain than any of the three classical microdomain morphologies. The deformation behavior of the DG is f...
TL;DR: In this article, the morphology of ternary polystyrene/styrene-butadiene rubber/polyethylene (PS/SBR/PE) blends has been investigated in the limits of a constant content of the major component (PS; 75 ¼ ) while changing the weight ratio of the two minor constitutive polymers.
TL;DR: In this article, polystyrene resins containing flexible tetrahydrofuran derived cross-linkers are presented, which render the resins more organic solvent-like and thus impart increased swelling/solvation characteristics.
TL;DR: In this paper, a series of polymacromonomer samples (F15) consisting only of polystyrene and having a fixed side chain length of 15 styrene residues have been prepared and studied by static light scattering in cyclohexane at different temperatures and in toluene at 15 °C.
Abstract: A series of polymacromonomer samples (F15) consisting only of polystyrene and having a fixed side chain length of 15 styrene residues have been prepared and studied by static light scattering in cyclohexane at different temperatures and in toluene at 15 °C. The measurement has also been made on polymacromonomer samples (F33) of the same kind but with 33 side chain residues in toluene. The second virial coefficient for the F15 polymer in cyclohexane vanishes at 34.5 °C, the Θ temperature for linear polystyrene, as was previously found to be the case for the F33 polymer. Analysis of the measured mean-square radii of gyration based on the wormlike chain with or without excluded volume shows that, while the contour length per main-chain residue is insensitive to the side chain length, the Kuhn segment length λ -1 (or more generally the stiffness parameter in the helical wormlike chain) under the Θ condition remarkably increases with increasing side chain length and that the λ -1 values (16 and 36 nm) for the polymacromonomers F15 and F33 in toluene, a good solvent, are about 1.6 times as large as those in the Θ solvent. Thus, it is concluded that, in addition to the high segment density around the main chain, repulsions between the main chain and side chain and between neighboring side chains play an important role in the high stiffness of polymacromonomers.
TL;DR: In this paper, the effects of dynamic crosslinking using sulphur, peroxide and mixed systems on morphology and mechanical properties of natural rubber and polystyrene blends have also been studied.
TL;DR: In this article, a poly(n-butyl methacrylate) has been polymerized in bulk at 130 °C in the presence of given amounts of a nitroxide stable free radical (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) using either a low molar mass alkoxyamine initiator (2,2.6, 6, 6-TTE) or a TEMPO-capped polystyrene macroinitiator.
Abstract: n-Butyl methacrylate has been polymerized in bulk at 130 °C in the presence of given amounts of a nitroxide stable free radical (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) using either a low molar mass alkoxyamine initiator (2,2,6,6-tetramethyl-1-(1-phenethyloxy)piperidine) or a TEMPO-capped polystyrene macroinitiator. Complete consumption of both initiators was always observed. In contrast, very low final monomer conversions were found. Proton NMR spectroscopy and MALDI-TOF mass spectrometry were used for investigation of the polymer structure. They showed that the formed poly(n-butyl methacrylate) had the attached initiator at one end and that a block copolymer was synthesized when the polystyrene macroinitiator was used. The other terminal functionality of the polymer was not a TEMPO-based alkoxyamine but a methylene unsaturation exclusively. Particularly, no saturated polymer which would also be formed by conventional disproportionation reaction between two propagating radicals could be detected. F...
TL;DR: In this article, the synthesis of nanometer scale homogeneous polystyrene and silica gel polymer hybrids utilizing ionic interactions was investigated, and the partially sulfonated poly styrene (10 mol %) was used as a s...
Abstract: We investigated the synthesis of nanometer scale homogeneous polystyrene and silica gel polymer hybrids utilizing ionic interactions. The partially sulfonated polystyrene (10 mol %) was used as a s...
TL;DR: In this article, the column performance of the hypercrosslinked polystyrene was found to be acceptable, with reduced plate height increasing very slowly as the linear velocity of the mobile phase increased to high values (up to 20-45 cm min−1).
Abstract: The mechanical rigidity, swelling properties, adsorption selectivity, and chromatographic performance of hypercrosslinked polystyrene (mainly MN-200 or Purosep-200; Purolite, UK) have been studied to evaluate the use of the material as a stationary phase for reversed-phase high-performance liquid chromatography (RPHPLC). By use of inverse size-exclusion chromatography (SEC) this adsorbent, with a high specific surface area of 1500 m2 g−1 was found to have a biporous structure with micropores of ca 1–2 nm and macropores ca 100 nm in diameter. The polymer does not change its volume significantly on changing water for organic solvents. The retention increments for methylene and phenyl groups were calculated and indicated that the mechanism of retention on the hypercrosslinked polystyrene involves π-π interactions and strong hydrophobic interactions. The column performance of the hypercrosslinked polystyrene was found to be acceptable, with reduced plate height increasing very slowly as the linear velocity of the mobile phase increased to high values (up to 20–45 cm min−1). Columns containing hypercrosslinked polystyrene were evaluated for the separation of phenols, dialkyl phthalates, and polyaromatic compounds. On-column preconcentration of trace organic compounds from aqueous media is possible. With smaller particles of hypercrosslinked polystyrene becoming available, this material can be regarded as an alternative to alkylsilica as a hydrolytically stable column-packing material for RPHPLC.
TL;DR: A new type of heterogeneous, polystyrene-bound catalyst, which has an unprecedented efficiency and stability in multiple applications, is introduced for the enantioselective catalysis of the addition of Et2Zn to PhCHO.
Abstract: A new type of heterogeneous, polystyrene-bound catalyst is introduced: A cross-linking, dendritic ligand, the TADDOL 1, is copolymerized with styrene, loaded with titanate, and used for the enantioselective catalysis of the addition of Et2Zn to PhCHO. The polymer-bound catalyst has an unprecedented efficiency and stability in multiple applications.
TL;DR: In this paper, a 1.8 μm diameter poly(vinylpyrrolidone)-stabilized polystyrene (PS) latex has been coated with poly(3,4-ethylenedioxythiophene) [PEDOT], an organic conducting polymer which exhibits good environmental stability.
Abstract: A 1.8 μm diameter poly(N-vinylpyrrolidone)-stabilized polystyrene (PS) latex has been coated with poly(3,4-ethylenedioxythiophene) [PEDOT], an organic conducting polymer which exhibits good environmental stability. Despite its limited solubility, EDOT was successfully polymerized in aqueous solution using iron(III) tris(p-toluenesulfonate) at 85 °C. The PEDOT loading was easily controlled by simply varying the latex concentration, and hence the surface area available for deposition. Thus, a series of PEDOT-coated latexes was obtained with PEDOT loadings varying from 4.9 to 38.0 wt %. Pressed-pellet conductivity measurements on these composites indicated a percolation threshold of ca. 5 vol %, with a conductivity plateau of 0.43 S cm-1 obtained at the highest PEDOT loading. Scanning electron microscopy (SEM) studies revealed that a PEDOT subphase was present in addition to the coated particles at high PEDOT loadings, whereas at lower loadings (<12 wt %) only particles with relatively smooth, uniform PEDOT ...
TL;DR: In this paper, the degradation of polystyrene plastics containing cassava starch and graft copolymers was investigated by outdoor exposure, soil burial testing, UV irradiation, and the resistance of the plastic to bacteria.