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Results for “Polystyrenes”

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PubMed1997

[Sodium polystyrene sulfonate (Resonium A) as possible cause of rectal blood loss].

A 67-year-old man underwent laparotomy for a ruptured aneurysm of the abdominal aorta. Postoperatively he was treated with haemodialysis because of perioperatively developed acute renal failure. Hyperkalaemia was temporarily treated with sodium polystyrene sulfonate (Resonium A) after which he lost blood per rectum. A hemicolectomy was necessary because of intractable blood loss due to ulceration of the colon. This complication is related to uraemia and the use of sodium polystyrene sulfonate with or without sorbitol.

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PubMed2005

Polystyrene-supported organotin dichloride as a recyclable catalyst in lactone ring-opening polymerization: assessment and catalysis monitoring by high-resolution magic-angle-spinning NMR spectroscopy.

Dialkyltin dichloride grafted to a cross-linked polystyrene, with the formula [P-H]((1-t))[P-(CH2)nSnBuCl2]t (P=[CH2CH(pC6H4)], t=the degree of functionalization, and n=6 or 11), is investigated as a recyclable catalyst in the ring-opening polymerization (ROP) of epsilon-caprolactone (CL). It is demonstrated that high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy is an invaluable tool to characterize completely the supported catalyst. The 2D 1H-13C HSQC HR-MAS spectrum, in particular, allowed extensive assignment of the 1H and 13C resonances, as well as accurate measurement of the (n)J((1)H-(117/119)Sn) and (n)J((13)C-(117/119)Sn) coupling constants. 1H and 119Sn HR-MAS NMR spectroscopy is presented as a monitoring tool for catalytic processes based on organotin compounds, particularly for the investigation of the extent to which polymerization residues are observable in situ in the material pores and for the assessment of the chemical integrity and recycling conditions of the grafted catalyst. From polymerization experiments with CL, initiated by n-propanol and with [P-H]((1-t))[P-(CH2)nSnBuCl2]t of various compositions as the supported catalyst, it appears that a partial 'burst' of the polystyrene support occurs when the length of the alkyl spacer is limited to n=6, as a result of polymer chains growing within the pores of the support. However, extension of the length of the aliphatic polymethylene spacer from 6 to 11 carbon atoms preserves the support integrity and allows the production of catalyst-deprived poly(epsilon-caprolactone) (PCL) oligomers. A preliminary attempt to recycle the heterogeneous catalyst has shown that very good reproducibility can be obtained, in terms of both catalyst activity and molecular-weight parameters of the as-recovered PCL polyester chains.

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PubMed2007

An efficient hybrid, nanostructured, epoxidation catalyst: titanium silsesquioxane-polystyrene copolymer supported on SBA-15.

A novel interfacial hybrid epoxidation catalyst was designed with a new immobilization method for homogeneous catalysts by coating an inorganic support with an organic polymer film containing active sites. The titanium silsesquioxane (TiPOSS) complex, which contains a single-site titanium active center, was immobilized successfully by in-situ copolymerization on a mesoporous SBA-15-supported polystyrene polymer. The resulting hybrid materials exhibit attractive textural properties (highly ordered mesostructure, large specific surface area (>380 m2 g-1) and pore volume (>or==0.46 cm3 g-1)), and high activity in the epoxidation of alkenes. In the epoxidation of cyclooctene with tert-butyl hydrogen peroxide (TBHP), the hybrid catalysts have rate constants comparable with that of their homogeneous counterpart, and can be recycled at least seven times. They can also catalyze the epoxidation of cyclooctene with aqueous H2O2 as the oxidant. In two-phase reaction media, the catalysts show much higher activity than their homogeneous counterpart due to the hydrophobic environment around the active centers. They behave as interfacial catalysts due to their multifunctionality, that is, the hydrophobicity of polystyrene and the polyhedral oligomeric silsesquioxanes (POSS), and the hydrophilicity of the silica and the mesoporous structure. Combination of the immobilization of homogeneous catalysts on two conventional supports, inorganic solid and organic polymer, is demonstrated to achieve novel heterogeneous catalytic ensembles with the merits of attractive textural properties, tunable surface properties, and optimized environments around the active sites.

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PubMed2001

Copper(I) chloride: a simple salt for enhancement of polystyrene cationization in matrix-assisted laser desorption/ionization mass spectrometry.

The possibility of using copper(I) chloride as a doping salt to enhance the cationization of polystyrene in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was investigated. It was shown that copper(I) chloride possesses sufficient solubility in tetrahydrofuran. The parameters of the MALDI mass spectra of different polystyrene samples, such as the number-average (M(n)) and mass-average (M(w)) molecular mass values, obtained by copper(I) cationization were compared with those obtained by means of silver(I) cationization, and good agreement was found. It was also shown that application of copper(I) chloride as a doping salt, and dithranol as a matrix, ensured good MALDI mass spectra of the sample spots even after storage for 1 month.

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PubMed1996

Magnetohydrodynamic Aggregation of Cholesterol and Polystyrene Latex Suspensions

The aggregation state of flowing (0.49 m s-1 linear velocity) colloidal dispersions of polystyrene latex microspheres (certified particle diameter of 156 ± 6 nm; measured diameter, 156 ± 3 nm at pH 5.3 in 50 mM NaCl) in NaCl solution and cholesterol (measured diameter, 533 ± 9 nm at pH 5.3), stabilized in NaCl solution by sodium taurodeoxycholate, was studied using photon correlation spectroscopy. For cholesterol suspensions having electrolyte concentrations close to the critical coagulation concentration (50 mM NaCl), pronounced aggregation was observed after 15 to 30 min of recirculation in the presence of an orthogonally applied magnetic field (2.0, 1.0 and 0.15 T). In all experiments with cholesterol, aggregation was followed by a period of deaggregation, after which aggregation again occurred. Comparable effects were not observed when cholesterol suspensions were recirculated in the absence of the magnetic field or when the suspensions were exposed to an equivalent magnetic field in the absence of flow. For cholesterol suspensions, the increase in particle size was most pronounced at 0.15 and 1.0 T rather than at 2.0 T. Aggregation effects were also observed when suspensions of polystyrene latex in 200 mM NaCl were made to flow through a 1.0-T field. In both systems, the magnetic aggregation does not appear to involve direct interaction between the field and the solid phase, but is interpreted in terms of orthokinetic effects involving magnetohydrodynamic changes in the flow profile resulting from the presence of the transverse field.

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PubMed1996

Adsorption of Poly(butyl methacrylate) and Its Mixtures with Polystyrene from Solutions: Adsorption Kinetics and Structure of Adsorption Layers

Using IR spectroscopy of attenuated total inner reflectance (ATIR) the adsorption kinetics and structure of the adsorption layer of poly(butyl methacrylate) on the Ge surface from solutions in CCl4 of pure polymer and its mixtures with polystyrene have been investigated. It was shown that at the first stage of adsorption of poly(butyl methacrylate) from diluted solution, a layer of high connectivity of macromolecules with Ge surface is formed. The diffusion coefficient of macromolecules on this part of the kinetic curve corresponds to that for the glassy state. With increasing adsorption, the fraction of bonded segments diminishes and macromolecules in the adsorption layer become more mobile. On this part of the kinetic curve there is observed a sharp increase in both the diffusion coefficient of macromolecules and the adsorption rate. On transition from diluted to semidiluted solutions the mechanism of adsorption changes. The coefficient of diffusion of macromolecules coincides with that for reptation movement of macromolecules in the entanglement network. It was shown that introduction of polystyrene into solutions affects the adsorption value and structure of the adsorption layer. This effect is supposed to be connected to possible changes in combinatorial entropy of the system.

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PubMed1998

Water Wettability and Zeta-Potential of Polystyrene Surface Modified by Ne or Na Implantation

A study has been made of the modification of the wettability and the surface potential of polystyrene by ion bombardment and implantation. Substrates used were polystyrene (PS) dishes. Ne bombardment and Naion implantation were performed at energies of 50 and 150 keV with fluences between 1 x 10(14) to 1 x 10(17) ions/cm2. The surface potential was examined by measurements of zeta-potential and the wettability was examined by the contact angle of water. The contact angle of water and the zeta-potential are found to change, depending on ion species and fluences. Two kinds of relationships between the contact angle of water and the zeta-potential are found, classified by region A and region B. From XPS results, region A means that PS surfaces modified by radiation effects of Ne-bombardment or Na-implantation have new functional groups and amorphous carbon. In region B, Na implanted PS surfaces with a high fluence show not only new functional groups and amorphous carbon but also Na atoms with chemical bonding states. Copyright 1998 Academic Press. Copyright 1998Academic Press

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PubMed1998

Structure and Extent of Adsorbed Gelatin on Acrylic Latex and Polystyrene Colloidal Particles.

The extent and structure of the adsorbed layer of gelatin onto colloidal particles is measured using dynamic light scattering, small-angle neutron scattering, and dilution viscometry. Adsorption isotherms are measured using solution depletion of fluorescein-5-isothiocyanate tagged gelatin. The results show that the adsorbed gelatin layer at saturation on acrylic-based latex (pH 6.5, 0.01 M sodium acetate) has approximately twice the average density of the free gelatin in solution, while for the adsorption onto polystyrene latex (pH 8.7, deionized water), it has nearly the same average density. The energetics of gelatin affinity is calculated from the temperature dependence of the adsorption equilibrium constant. It was found that the enthalpy of adsorption of a net negatively charged gelatin onto a negatively charged surface is favorable. An additional, favorable entropy of adsorption is measured for the polystyrene latex, for which hydrophobic interactions are important. Selective, competitive adsorption of nonionic and anionic surfactants confirms the specific source of the adsorption interactions. Copyright 1998 Academic Press.

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PubMed1999

Surface Electrical Properties of Polystyrene Latex.

The surface electrical properties of a polystyrene latex have been studied with several experimental methods. Previous studies by other authors have shown discrepancies between the surface potential and the surface charge density determined by different methods. This work is an attempt to produce more experimental data for the discussion concerning these discrepancies. Both electrophoretic mobility and electrical conductivity methods have been used. Also, gel permeation chromatography has been used to estimate the number of endgroups on the latex particle that carry charged surface groups. Synthesis and cleaning methods of polystyrene latex are also discussed. Calculations on a Poisson-Boltzmann level of approximation have been performed in an attempt to connect the quantities determined with dynamic (electrophoresis and static conductivity) methods and static (titration) methods. The discrepancies can be explained by introducing a pH- and electrolyte-dependent surface structure such as the hairy layer model. A Stern layer conductance model can also to some extent explain these discrepancies, but this model contains several parameters not directly attainable by experiments. This means that a unique set of parameters cannot be determined without further studies on several latex systems. Copyright 1999 Academic Press.

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PubMed2000

Effects of Cosolvents and pH on Protein Adsorption on Polystyrene Latex: A Dynamic Light Scattering Study.

Dynamic light scattering was used to study the adsorption of two proteins with different surface properties (IgG and HSA) on negatively charged polystyrene latex. The proteins were adsorbed from water and from water/methanol and water/glycerol mixtures at various pH. Some striking differences between the adsorption behaviors of the proteins were observed. Whereas the thickness of the adsorbed layer of HSA was extremely sensitive to pH and solvent composition, that of IgG was not. IgG mainly showed an end-on orientation on polystyrene whereas several different surface orientations are suggested for HSA under different conditions. The addition of methanol inhibited the adsorption of HSA on the latex, but it did not affect the adsorption of IgG. In contrast, the addition of glycerol increased the thickness of the adsorbed layers of both proteins. So, the orientation of IgG on the latex is insensitive to pH but is a function of the kind of solvent whereas both pH and solvent strongly affect the adsorption of HSA. This is a puzzling result since both cosolvents should equally affect the adsorption of both proteins if the dominant forces for adsorption are the same. Therefore, we concluded that, whereas hydrophobic interactions are the dominant force in the adsorption behavior of HSA, van der Waals forces are the main forces involved in the attachment of IgG to the lattices. Copyright 2000 Academic Press.

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PubMed2000

Iron Compounds as Coatings on Polystyrene Latex and as Hollow Spheres.

Sub-micrometer-sized anionic polystyrene latices have been coated with uniform layers of iron compounds by aging, at elevated temperature, dispersions of the polymer colloid in the presence of aqueous solutions of ferric chloride, urea, hydrochloric acid, and polyvinylpyrrolidone. The thickness of the deposited layers could be altered by suitable adjustment of the reactant concentrations, and they could also be increased by further aging of the coated particles in the presence of aqueous solutions of ferric chloride. Hollow colloidal spheres of iron compounds were obtained by calcination of the so-coated polystyrene latices at elevated temperature in air. Different chemical compositions of hollow colloidal spheres were obtained by heating them in hydrogen. Copyright 2000 Academic Press.

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PubMed2001

Effects of Serum on the Kinetics of CHO Attachment to Ultraviolet-Ozone Modified Polystyrene Surfaces.

Attachment kinetics of Chinese hamster ovarian (CHO) cells were investigated on ultraviolet-ozone oxidized polystyrene (UVO-PS) dishes in the presence and absence of serum. The surface chemistry of UVO-PS has been extensively characterized. Although cells attached rapidly to the oxidized dishes with serum present it was found that serum actually inhibits the rate of attachment. Spreading of attached cells was favored by the presence of serum. It is suggested that the increased quantity of hydrophilic carboxyl groups on longer exposed UVO-PS leads to a change in the protein layer adsorbed from serum and also a higher affinity of the surface for extracellular proteins secreted by the attached cells. The UVO-PS surfaces present a new way of producing tissue culture grade polystyrene (TCPS) in a highly controllable method, which would ensure greater consistency in TCPS surfaces. Copyright 2001 Academic Press.

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PubMed2001

Heteroflocculation of Sulfate Polystyrene Latex and Anticarsia gemmatalis Nucleopolyhedrovirus as a Model System for Studying Sunlight Protection.

Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus widely used as a pest control agent. Data on field persistence of this microbial insecticide reveal that sunlight is the most destructive of the environmental factors. The introduction of a physical barrier to protect the baculovirus from sunlight has been proposed. In the present work we report on the coating of a baculovirus surface with a uniform layer of smaller particles. The coating was carried out at pH 3, a condition where the baculovirus surface becomes positively charged and can be covered by sulfate polystyrene latex particles. The heteroflocculation was assessed by isotherm measurements and scanning electron microscopy. High-affinity isotherms were obtained for the two sizes of latex used, and the number of latex particles bound per baculovirus was not affected when pH was changed back to neutral range (5<pH<7). Two cycles of centrifugation and washing with deionized water did not wash the sulfate polystyrene from the polyhedron surface. Copyright 2001 Academic Press.

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PubMed1992

Styrene migration from general-purpose and high-impact polystyrene into food-simulating solvents.

General-purpose and high-impact polystyrenes (GPPS and HIPS, respectively) are used in many food-contact applications for the packaging of aqueous-based, fatty and dry foods. The correlation of residual styrene concentrations in polystyrene with styrene migration into food-stimulating solvents is of interest in order to predict the potential exposure of consumers to styrene from food-packaging applications. Studies of the migration of styrene into 8% ethanol and cooking oil from a GPPS and a HIPS polymer, each containing three different residual styrene levels, have been completed at temperatures ranging from 70 to 180 degrees F (21 to 82 degrees C). The results showed that the amount of styrene migrating from both polymers into cooking oil was proportional to the square root of the time of exposure, and the total amount of styrene migrating was proportional to the residual levels of styrene in the polymers. The calculated diffusion coefficients were found to be independent of the residual levels of styrene in a given polymer at a given temperature. While the partition equilibrium was not approached when the polymers were exposed to cooking oil, it was observed in the 8%-ethanol exposure studies. The calculated partition coefficients between the polymers and 8% ethanol appeared to be independent of the residual levels of styrene in the polymers at a given temperature. Linear relationships were observed between the logs of the diffusion and partition coefficients and the inverse of the absolute temperature of exposure.

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PubMed2005

Surface characterization of cotton coated by a thin film of polystyrene with and without a cross-linking agent.

Thin polystyrene film coated on cotton was successfully formed by admicellar polymerization. Divinylbenzene (DVB) was used as a cross-linking agent to form networked polystyrene to improve film coverage. A wettability test and XPS analysis were used to characterize the coated surface. The optimum amount of DVB was around 1%. At this amount, the film coverage was most complete, as judged by the reduction of the O1s signal in XPS analysis.

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PubMed2006

Dependence of the broad frequency dielectric spectra of colloidal polystyrene particle suspensions on the difference between the counterion and co-ion diffusion coefficients.

Dielectric properties of four suspensions of spherical polystyrene particles were measured at 25 degrees C over a broad frequency range extending from 100 Hz to 10 MHz, using a HP 4192 A Impedance Analyzer. The instrument was coupled to a cell with parallel platinum black electrodes and variable spacing, and the quadrupole calibration method was used. The aqueous electrolyte solutions were prepared using equal concentrations of NaCl, KCl, NaAc, or KAc, so that the calculated Debye screening length and Zeta potential remained constant, while the conductivity changed. The polystyrene particles used (Interfacial Dynamics Corp., surfactant-free white sulfate latex) have a diameter of 1 micron and a surface charge density that is independent of the pH. The dielectric spectra were described using the Nettelblad-Niklasson expression combined with a Debye type high-frequency term and analyzed using the Shilov-Dukhin theory and numerical results. The theoretical prediction that the low-frequency dispersion parameters are determined by the co-ion diffusion coefficient was experimentally confirmed. This also allowed to justify an alternative definition of the characteristic time of the low-frequency dispersion. On the contrary, the prediction that the high-frequency dispersion parameters are determined by the diffusion coefficient of counterions could not be confirmed, possibly due to experimental problems. However, the zeta-potential values deduced from high-frequency data were compatible with values deduced from electrophoretic mobility measurements.

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PubMed2006

Filtration application from recycled expanded polystyrene.

Water-in-oil emulsion with drop size less than 100 mum is difficult to separate. Coalescence filtration is economical and effective for separation of secondary dispersions. Coalescence performance depends on flow rate, bed depth, fiber surface properties, and drop size. The amount of surface area of the fibers directly affects the efficiency. A new recycling method was investigated in the previous work in which polystyrene (PS) sub-mum fibers were electro-spun from recycled expanded polystyrene (EPS). These fibers are mixed with micro glass fibers to modify the glass fiber filter media. The filter media are tested in the separation of water droplets from an emulsion of water droplets in oil. The experimental results in this work show that adding nanofibers to conventional micron sized fibrous filter media improves the separation efficiency of the filter media but also increases the pressure drop. An optimum in the performance occurs (significant increase in efficiency with minimal increase in pressure drop) with the addition of about 4% by mass of 500 nm diameter PS nanofibers to glass fibers for the filters.

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PubMed2003

Void closure and interdiffusion processes during latex film formation from surfactant-free polystyrene particles: a fluorescence study.

This study reports a steady state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex particles. The latex films were prepared from pyrene (P)-labeled PS particles at room temperature and annealed at elevated temperatures for 5-, 10-, 20-, and 30-min time intervals above the glass transition (T(g)) temperature of polystyrene. During the annealing processes, the transparency of the film changed considerably. Scattered light (I(sc)) and fluorescence intensity (I(0P)) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of latex films were monitored using photon transmission intensity, I(tr). Scanning electron microscopy (SEM) was used to detect variation in the physical structure of annealed films. Onset temperature for film formation, T(0), void closure, T(v), and healing temperatures, T(h), were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were modeled and related activation energies were determined.

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