Solutions Of Polystyrene In Toluene Research Articles

Temperature dependence of the diffusion, thermodiffusion and Soret coefficient of a dilute polystyrene/toluene solution as measured by means of a transient holographic grating technique

We have measured diffusion, thermodiffusion and Soret coefficients of a dilute solution of polystyrene in toluene by means of the transient holographic grating technique of thermal diffusion forced Rayleigh scattering over a temperature range from 10 to 50 °C. The results show a systematic deviation from optical beam deflection measurements over a narrower temperature interval of the order of ten percent but the identical temperature dependence. A comparison with previous measurements from our laboratory, new control measurements and literature data does not lead to a clear conclusion about the correct values. From the diffusion coefficient a temperature independent hydrodynamic radius is obtained. Both the Soret coefficient and the viscosity-scaled thermodiffusion coefficient ηDT, for which a universal value has been reported in the case of asymmetric systems with large solute entities, decrease with temperature.

МАГНИТО-СОРБЦИОННАЯ ДЕАСФАЛЬТИЗАЦИЯ НЕФТЯНЫХ ФРАКЦИЙ

The article uses a magneto-sorption method for extracting asphaltenes from petroleum fractions using nanosized magnetite. Factors affecting the sorption separation of asphaltenes from toluene were evaluated using model systems prepared by dissolving asphaltenes isolated from superviscous oil from the Ashalchinskoye field (Tatarstan). It was found that the presence of polar compounds has the greatest effect on the sorption of asphaltenes from toluene solutions. Benzoic acid or isopropyl alcohol was used to evaluate the effect of acids and polar compounds. To study the effect of solution viscosity on asphaltene adsorption, model solutions of polystyrene in toluene with different viscosities were prepared by adding different amounts of polymer. Two types of sorbents were investigated: magnetite powder and suspensions of magnetite, modified with oleic acid, in toluene and n-pentane. The efficiency of using magnetite suspensions in comparison with its powder for sorption of asphaltenes is shown: for a suspension in toluene sorption increases 5 times, and in n-pentane, sorption increases 14 times. The influence of a magnetic field (0.5 T) on the increase in the sorption of asphaltenes from light oil feedstock was revealed: for a suspension in n-pentane, sorption increases from 220 ± 25 to 313 ± 38 g/g of adsorbent). The increase in sorption in the samples that passed through the magnetic installation is explained by the greater availability of asphaltenes due to the destruction of some of their clusters.

Spectral Characteristics of Mechanochemically Prepared Perovskite CH3NH3PbBr3 Nanoparticles Passivated by Amines with Different Alkyl Chain Length

We are the first to establish that the introduction of a small amount of passivating amine (Am) during the preparation of CH3NH3PbBr3 (MAPbBr3) (MA/Am = 0.7) leads to the formation of pseudo-2D nanoparticles of this hybrid perovskite, the number of layers in which decreases going from oleylamine to hexylamine. The use of a solution of polystyrene in toluene yields more homogeneous in size stabilized MAPbBr3 nanoparticles and alters the number of layers in them. The resultant MAPbBr3 dispersions and films have strong photoluminescence (PL), whose maximum is shifted toward higher energies in comparison with a powder of this hybrid perovskite due to a quantum size effect. Dispersions and films of MAPbBr3 prepared using oleylamine have the highest PL quantum yield (about 90%) due to the formation of 2D nanoparticles with ≥ 4 layers. An advantage of the MAPbBr3 samples prepared using hexylamine is increased color purity of the PL.

The Fractal Dimensions of Carbon-Black-Filled Polymers and Elastomers. Part 1. Materials and Methods of Investigation, and Morphology

Methods for preparing specimens and for processing the results obtained are described. Carbon black of grades T1 and KhS-72, monodispersed polystyrene (molecular weight 200 kDa), polyethylene, polybutadiene rubber, polyisoprene rubber, styrene butadiene elastomer, and butyl rubber were investigated. Two methods were used to prepare filled specimens. In the first case (model systems), the filler and polymer were mixed via a 1–5% solution of polystyrene in toluene. The carbon black content in the suspensions was varied in the range 1–60 wt%. After mixing, the specimens were subjected to ultrasound treatment on a UZDM-2T disperser (44 kHz) for ~10 min. In the second case, sulphur vulcanisates were obtained by the standard procedure. The morphology was studied by transmission electron microscopy (EM-301 electron microscope, Japan) using thin films or etching in high-frequency oxygen discharge plasma on a vacuum reactor (Edwards, UK). A procedure for processing electron micrographs with the aim of obtaining information about local and global fractal dimensions of particle aggregates is described.

Improvement of the mode I interlaminar fracture toughness of glass fiber/epoxy composites using polystyrene electrospun nanofibres

In this paper, the polystyrene nanofiber (PSnF) with diameter in range 40–80 nm were fabricated using electrospinning technique from solution of polystyrene in toluene and used as an effective filler for glass fiber reinforced epoxy composite materials (GF/EP) with contents in range from 0 to 0.1 wt%. GF/EP composites with absence and presence of PSnF were characterized by different techniques, namely; mode I interlaminar fracture toughness, tensile testing and scanning electron microscope. The bonding between GF and EP were also accessed by interfacial shear strength test (IFSS). The obtained results indicated that at 0.07 wt% of PSnF incorporation in epoxy matrix the stress intensity factor (KIC), initiation and propagation interlaminar fracture toughness in mode I were improved by 42.2% from 0.631 to 0.839 MPa m1/2, and 43% from 389.82 to 512.09 J/m2 and 47% from 401.38 to 545.34 J/m2, respectively, when compared to pristine epoxy resin as well as pristine composite material. The scanning electron microscopy (SEM) observation pointed out that fibers pull out during initiation delamination accounting for fracture toughness improvement the fracture surface of GF/EP.

Surface Modified Ni Nanoparticles Produced by the Electrical Explosion of Wire

Spherical nickel nanoparticles were prepared by the electrical explosion of wire. The as-prepared nanoparticles were modified immediately after fabrication at room temperature in order to provide tunable surface properties with focus on the development of composites filled with nanoparticles. Following liquid modificators were used: hexane, toluene and the solution of polystyrene in toluene. In one case the surface modification by carbon was made in gas phase as a result of hydrocarbon injection. The average size of the nanoparticles was about 50 nm and unit cell parameters were close to 0.351 nm. Detailed characterization was done by X-ray diffraction, transmission electron microscopy, and magnetization measurements. Sphericity was also checked using microwave resonant absorption.

In situ modification of Fe and Ni magnetic nanopowders produced by the electrical explosion of wire

Iron and nickel spherical magnetic nanoparticles (MNPs) with mean diameter 50–80 nm were prepared by the electric explosion of wire. The advantage of this method is that it provides a very high production rate up to 200 g/h and requires low energy consumption of 25 kW h/kg. The as-prepared MNPs were modified in situ in hexane, toluene, chloroform, and the solutions of polystyrene in toluene, in an inert atmosphere at room temperature in order to provide both the stability at ambient conditions and tunable surface properties. Hexane was an inert liquid for Fe and Ni MNPs. In the case of toluene the surface of as-prepared Fe or Ni MNPs acted as a catalyst for the condensation reaction of aromatic organic compounds forming irregular polycyclic structures. The treatment with toluene led to the deposition of carbon and formation of “hair-like” ordered structures on the surface of the MNPs. Chloroform chemically interacted with Fe MNPs, forming FeCl2. The treatment of MNPs with the solution of polystyrene in toluene resulted in the adsorption of polymer and the formation of 3–6 nm polymeric coatings on the surface. The obtained magnetic properties (like the magnetization value for Ni MNPs up to 52 emu/g and Fe MNPs up to 179 emu/g) at room temperature make these MNPs competitive candidates for nanocomposites for microwave and other technological applications.

Active surface modification for iron nanopowders produced by wire electrical explosion

The surface modification of metal iron nanopowders produced by wire electrical explosion (WEE) followed by immediate treatment with hexane, toluene, chloroform, and polymer solutions in hexane and toluene is investigated. It has been shown the nanopowders produced in the inert gas environment are shown to interact due to their active surface both with liquid media and with modifiers dissolved in them. X-ray diffraction and thermal analysis, including mass spectrometry, show that hexane is an inert liquid medium in respect to iron nanopowders, toluene treatment causes carbon deposition into the nanoparticle surface layers, and chloroform chemically interacts with iron nanoparticles with a high yield of FeCl2. Thermal analysis and transmission electron microscopy show that treating nanopowders with an oleic acid (OA) solution in hexane and isoprene rubber and polystyrene solutions in toluene results in the formation of a polymeric coating with a thickness of 3–6 nm at the nanoparticle surface. The polymer amount adsorbed at the surface reaches 0.4 mg/m2 depending on the polymer concentration in the solution. The deposited polymer layer has a loose structure formed by macromolecules adsorbed within the ball conformation.

Transient cage formation around hot gold colloids dispersed in polymer solutions

Gold colloids dispersed in dilute to concentrated polymer solutions can efficiently be heated by laser irradiation and act as almost pointlike heat sources. In systems with positive Soret coefficients S(T) of the polymer, such as solutions of polystyrene in toluene, the polymer can almost entirely be removed from the particle surface. The colloid attracts the solvent and a transient cage of low viscosity and dramatically enhanced mobility is formed, which follows the motion of the particle with a certain retardation. Based on a complete parameterization of S(T)(M, c, T), we analyze in detail the stationary temperature, concentration, and viscosity profiles. Depending on the polymer molar mass and concentration on the distance to the glass transition temperature, the negative or positive feedback-loops are established that lead to either attenuation or self-amplification of the polymer depletion.

Dielectric response as a function of viscosity for two crude oils with different conductivities

Dielectric properties and viscosities of two different crude oils (labelled E and N) and solutions of them diluted in toluene or heptane were measured by frequency domain spectroscopy and rheology, respectively. Crude oils E and N diluted with toluene show a linear trend when plotting conductivity as a function of 1/viscosity. The crude oils diluted with the same amount of heptane show a lower conductivity than those in toluene. These results indicate that the conductivity of crude oil solutions is governed by the aggregation state of the asphaltenes more than their quantity in the crude, since asphaltenes are known to be in a more aggregated state in heptane than in toluene. In order to vary the viscosity while keeping the asphaltene concentration and solvation status constant, conductivity measurements of both crude oils diluted with solutions of polystyrene in toluene were performed. For the results obtained for the polystyrene modified systems, the proportionality between conductivity and 1/viscosity is not valid for low viscosities.

Zinc-8-hydroxyquinoline intercalated in calcium bentonite: A promising DO sensor

Zn(II) and 8-hydroxyquinoline were made to react in an in situ solid−solid reaction in the interlayer space of Ca-bentonite from Thailand, resulting in [Zn(8-hydroxyquinoline) 2] 2+, the well known –Znq 2. X-ray diffraction patterns showed that the interlayer space of the bentonite increased from 1.56 to 1.67 nm on going from Zn(II)-bentonite to Znq 2-bentonite, which confirmed the intercalation of Znq 2 in bentonite. The intercalated Znq 2-bentonite compound was mixed with a solution of polystyrene in toluene and coated as a film on a polystyrene sheet. The fluorescence intensity of Znq 2-bentonite film was measured in the presence of dissolved oxygen (DO). It was found that the fluorescence intensity of the film decreased as dissolved oxygen increased, which is a promising result for developing an optical dissolved oxygen sensor (DO sensor). The fluorescence quenching by oxygen followed the Stern–Volmer plot.

Critical assessment of diffusion coefficients in semidilute to concentrated solutions of polystyrene in toluene

We have measured collective diffusion coefficients of dilute, semidilute, and concentrated solutions of polystyrene in toluene up to a polymer concentration of 0.832 mass fractions at T=25 degrees C. The three employed experimental techniques of photon correlation spectroscopy, thermal diffusion forced Rayleigh scattering, and optical beam deflection cover four orders of magnitude with respect to their characteristic diffusion lengths (200 nm-2.9 mm), corresponding to more than 8 decades of the diffusion time constants. Contrary to existing literature data, which suggest a length scale dependent anomalous diffusion at high concentrations, all our techniques yield identical diffusion coefficients and purely Fickian diffusion, irrespective of their characteristic length scale.

Swelling behavior of polystyrene networks in some aliphatic esters and linear polystyrene solutions

Polystyrene networks were synthesized by free radical polymerization of styrene in the presence of dibenzoyl peroxide as an initiator, divinylbenzene as a crosslinker at 50 °C in toluene under nitrogen atmosphere. The swelling behavior of the synthesized polystyrene networks were studied at different temperatures in methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, tert-butyl acetate, and isopentyl acetate. Equations were given for the variation of the polymer-solvent interaction parameter, χ12, as a function of reciprocal absolute temperature in the temperature range from 25 to 75 °C. Polystyrene networks were swollen in linear polystyrene solutions in toluene of different concentrations. Linear polystyrene samples were almost monodisperse and of high molecular weight. The equilibrium swelling degrees were evaluated using the Flory-Rehner theory. The relation of volume swelling ratio, qv, to the volume fraction of the linear polymer in solution, φ, was evaluated and characterized by interaction parameter of crosslinked polystyrene with linear polystyrene, χ23. The parameter χ23 was found around zero as expected from mixtures of similar chemical structures by extrapolating the values of χ23 at tested concentrations to zero solvent concentration.

Vitrification of polymer solutions as a function of solvent quality, analyzed via vapor pressures

Vapor pressures (headspace sampling in combination with gas chromatography) and glass transition temperatures [differential scanning calorimetry (DSC)] have been measured for solutions of polystyrene (PS) in either toluene (TL) (10-70 degrees C) or cyclohexane (CH) (32-60 degrees C) from moderately concentrated solutions up to the pure polymer. As long as the mixtures are liquid, the vapor pressure of TL (good solvent) is considerably lower than that of CH (theta solvent) under other identical conditions. These differences vanish upon the vitrification of the solutions. For TL the isothermal liquid-solid transition induced by an increase of polymer concentration takes place within a finite composition interval at constant vapor pressure; with CH this phenomenon is either absent or too insignificant to be detected. For PS solutions in TL the DSC traces look as usual, whereas these curves may become bimodal for solutions in CH. The implications of the vitrification of the polymer solutions for the determination of Flory-Huggins interaction parameters from vapor pressure data are discussed. A comparison of the results for TL/PS with recently published data on the same system demonstrates that the experimental method employed for the determination of vapor pressures plays an important role at high polymer concentrations and low temperatures.

Collective and thermal diffusion in dilute, semidilute, and concentrated solutions of polystyrene in toluene

Collective mass diffusion (D), thermal diffusion (DT), and Soret coefficients (ST) have been determined for solutions of polystyrene in toluene ranging from dilute (10−4 g/cm3) to concentrated (0.9 g/cm3) by a transient holographic grating technique and photon correlation spectroscopy (collective diffusion only). The molar mass range of the polymer was between 4.75 and 4060 kg/mol. With a slight exception at intermediate concentrations, DT is molar mass independent over the entire concentration range. Above a polymer concentration of C≈0.2 g/cm3 the rising glass transition temperature of the solution leads to a rapid slowing down of both mass and thermal diffusion (Ludwig Soret effect) and the structure relaxation enters the experimental time window. Both D and DT are governed by the same microscopic local viscosity ηeff, which increases dramatically at Tg. It cancels out in ST=DT/D. As a consequence, ST is completely insensitive to the glass transition and shows concentration-dependent scaling as expected for a fictive polymer solution with concentration-independent local friction. Where available, results are compared with literature data.

Diffusion and thermal diffusion of semidilute to concentrated solutions of polystyrene in toluene in the vicinity of the glass transition.

The approaching glass transition in polystyrene/toluene solutions leads to a sharp decay of both the collective diffusion coefficient D and the thermal diffusion coefficient D(T) at concentrations above 0.2 g/cm(3). The Soret coefficient S(T) = D(T)/D follows power-law scaling from semidilute to concentrated and is not influenced by the slowing down of the dynamics associated with the glass transition. Both D and D(T) are governed by the same friction coefficient. The scaling behavior of S(T) with concentration on approach of the glass transition is compared to the divergence of S(T) near a consolute critical point.

Light scattering from nonequilibrium concentration fluctuations in a polymer solution

We have performed light-scattering measurements in dilute and semidilute polymer solutions of polystyrene in toluene when subjected to stationary temperature gradients. Five solutions with concentrations below and one solution with a concentration above the overlap concentration were investigated. The experiments confirm the presence of long-range nonequilibrium concentration fluctuations which are proportional to (∇T)2/k4, where ∇T is the applied temperature gradient and k is the wave number of the fluctuations. In addition, we demonstrate that the strength of the nonequilibrium concentration fluctuations, observed in the dilute and semidilute solution regime, agrees with theoretical values calculated from fluctuating hydrodynamics. Further theoretical and experimental work will be needed to understand nonequilibrium fluctuations in polymer solutions at higher concentrations.

High-pressure viscosity of polystyrene solutions in toluene + carbon dioxide binary mixtures

High-pressure viscosity of polystyrene (Mw = 50,000, Mw/Mn ≤ 1.06) solutions in toluene and in mixtures of toluene + carbon dioxide was measured using a falling cylinder-type viscometer at 320, 340, and 360 K, and up to 35 MPa. Solutions with polystyrene concentrations of 3, 5, and 7 wt % were investigated. Carbon dioxide levels in the range from 0 to 14.7 wt % were evaluated. Viscosity was observed to vary linearly with pressure at the temperatures and polymer concentrations investigated. Viscosity of the polymer solutions decreased as the concentration of carbon dioxide in the mixture was increased. The largest viscosity reduction was observed at the lowest temperature and at the highest concentration of polymer. The viscosity of the solutions was correlated with the solution density for different compositions. It was found that solutions of the same density have different viscosities, depending upon the carbon dioxide concentration in the mixture. The solutions with the higher carbon dioxide content display the lower viscosities at a given density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 306–315, 2000

Viscosity Reduction of Polystyrene Solutions in Toluene with Supercritical Carbon Dioxide

Viscosity Reduction of Polystyrene Solutions in Toluene with Supercritical Carbon Dioxide

Measurement of the thermal activity of dielectric liquids with an accuracy of ∼ 104

A method of measuring small (∼ 10−4) relative changes in the thermal activity of liquids is developed. A theoretical substantiation of its accuracy is given based on an investigation of the factors responsible for errors in the experiment. Results of experiments on a study of the temperature dependence of the thermal activity of a solution of polystyrene in toluene are reported.