Volume Of Toluene Research Articles

Surface modification of bacterial cellulose aerogels by ARGET ATRP.

Bacterial cellulose (BC) aerogels have received more and more attention due to their renewability, biodegradability and other excellent properties in recent years. Modification of BC aerogels using different methods would expand their applications. However, many problems exist for these modifications, such as a low grafting ratio, the larger dosage of metal catalyst required and so on. Activator regeneration by electron transfer (ARGET) for atom transfer radical polymerization (ATRP) is a novel ATRP method which could significantly reduce the amount of metal catalyst required and achieve a high grafting ratio. Novel nanostructured BC aerogels containing epoxy groups were prepared by the ARGET ATRP method. BC aerogels were functionalized with initiating sites by reaction with 2-bromoisobutyryl bromide (BiBBr), and followed by ARGET ATRP reaction with glycidyl methacrylate (GMA) which was catalyzed by copper(II) bromide (CuBr2) and N,N,N',N,'N"-pentamethyldiethylenetriamine (PMDETA), and then reduced by vitamin C. BC aerogels containing epoxy groups (BC-g-PGMA) were obtained after freeze-drying. The influence factors of the solvent ratio of N,N-dimethyl formamide (DMF)/toluene, monomer concentration, the concentration of CuBr2, the molar ratio of vitamin C (Vc)/CuBr2,reaction temperature and time on the grafting ratio were investigated. The results showed that the optimal DMF and toluene volume ratio was 2:1, the optimal monomer and CuBr2 concentration were 2 mol/l and 1.5 mmol/l. The optimal molar ratio of PMDETA/CuBr2 and Vc/CuBr2 were 4:1 and 1:1. The optimal reaction temperature and time were 60°C and 9 h. Scanning electron microscopy (SEM) images showed that GMA was strongly adhered onto the surface and inside of the BC pellicle. GMA was self-grown on the BC surface and achieved the high grafting ratio of 1052.7% under optimal conditions. The BC-g-PGMA aerogels containing the epoxy groups will provide wider application prospects in drug release, enzyme fixed, functional materials and other fields.

Online coupling of fully automatic in-syringe dispersive liquid-liquid microextraction with oxidative back-extraction to inductively coupled plasma spectrometry for sample clean-up in elemental analysis: A proof of concept

A proof of concept of a novel automatic sample cleanup approach for metal assays in troublesome matrixes as a front-end sample pre-treatment to inductively coupled plasma optical emission spectroscopy – ICP-OES – is herein presented. Target metals, namely, copper, lead, and cadmium were complexed in-system quantitatively using ammonium pyrrolidine dithiocarbamate (APDC) and transferred into a minute volume of toluene as extractant employing lab-in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction (LIS-MSA-DLLME). After discharge of the sample, the analytes were back-extracted into nitric acid and injected on-line into ICP-OES. To promote and expedite this process in-syringe, advantage was taken from oxidative decomposition of the chelate by potassium iodate, reported in this article for the first time.Experimental conditions for LIS-MSA-DLLME were optimized by Box-Benkhen multivariate analysis using the geometric mean of analyte recoveries as the desirability function. Times of extraction and back-extraction of 300s and 100s, respectively, pH 5.5 at 30mmol/L acetate, 300µL of extraction solvent, and 600µmol/L of APDC were finally applied. Online interfacing to ICP-OES for back-extract analysis yielded average repeatabilities for Cd, Cu, and Pb of 2.9%, 3.5%, and 3.5% with limits of detections (3s) of 1.9, 1.4, and 5.6ng/mL, respectively. Oxidative back-extraction was proven reliable for the determination of metal species in coastal seawater, surrogate digestive fluids and soil leachates with recovery values for Cd, Cu, and Pb ranging from 90% to 118%, 68% to 104%, and 86% to 112%, respectively.

Microencapsulation of TOMAC by suspension polymerisation: Process optimisation

The optimisation process for the synthesis of microcapsules containing trioctylmethylammonium chloride (TOMAC), a selective extractant agent for the removal of mercury from wastewaters, by the suspension copolymerisation of styrene (St) and divinylbenzene (DVB) was studied. The influence of the diluent, mass ratio of the suspending agents (arabic gum –AG– and polivinylalcohol –PVA–), TOMAC:diluent volume ratio and weight percentage of DVB respect to the monomers mixture (% DVB) on the encapsulation process and the physical properties of the resulting microcapsules were investigated.It was found that using heptane as diluent led to non-spherical microcapsules with poor reaction yield and conversion of the monomers. Nevertheless, when toluene was used these properties were improved. Furthermore, for a TOMAC:toluene ratio of 1:3 spherical beads were obtained. The combined use of the suspending agents was more appropriate than using them separately, due to the latex product and the low conversion of the monomers for AG and PVA, respectively. The increase of the % DVB from 18.8 to 50% enhanced the mechanical resistance of the polymeric shell, increasing the reaction yield up to an 84.7% and maintaining the TOMAC encapsulation (36.0%) and the sphericity of the microcapsules. The obtained particle size (40μm) indicated that the main application of this material will be in fluidised beds or in perfectly mixed reactors. On the basis of the experimental results, a AG:PVA mass ratio of 1:1, a TOMAC:toluene volume ratio of 1:3 and 50% DVB were established as the best conditions to produce this kind of microcapsules, enabling its reproduction on a pilot scale plant. In addition, the high values of the distribution coefficient for mercury removal confirm the success of this optimisation process.

Sooting tendency and particle size distributions of n-heptane/toluene mixtures burned in a wick-fed diffusion flame

The sooting characteristics of binary mixtures of n-heptane and toluene and a commercial gasoline were studied. The experiment involves the non-premixed combustion of the fuel in wick-fed burner. The particle size distributions (PSDs) of soot were measured at the tip of flames of different heights, using a differential mobility spectrometer (DMS). Transmission electron microscopy (TEM) was used to investigate the morphology of the particles formed. Pure n-heptane and toluene were studied along with blends of 10%, 30%, and 50% by volume of toluene in n-heptane. The addition of toluene to heptane shifts the PSD to larger diameters. As toluene is added to n-heptane the dependence of soot particle size on flame height changes from resembling a paraffinic to resembling an aromatic fuel in a non-linear fashion. A tolerance to toluene addition at the lowest flow rates was found, where particles were not detected. A commercial gasoline with approximately 44% by mass of aromatics was also analysed. The smoke point and PSDs are similar to the mixture 50% toluene 50% n-heptane, but the mean aggregate mobility size, number of particles and primary particle size formed by the gasoline are smaller.

Synthesis of pure iron nanoparticles at liquid–liquid interface using pulsed plasma

Pure α-Fe nanoparticles with ≤10 nm size were synthesized using a simple method—pulsed plasma in liquid. This is the first time that pure metallic nanoparticles were prepared by arc discharge method using water–toluene interface as a medium. Several experiments made evident that toluene–water ratio in emulsion influences the purity and size of Fe nanoparticles. The purity of the nanoparticles gradually increased from 48 to 98 %, while particle size decreased from 21 to 9.5 nm with smaller toluene volume fraction (from 40 to 5 %) in the microemulsions. Finally, toluene:water with 95:5 (%) ratio was found to be the most appropriate medium for pure Fe nanoparticle formation. Lattice parameters of the obtained Fe samples calculated from XRD found to be larger (a = 0.2927 nm) than those previously reported Fe (a(BCC-Fe) = 0.2866 nm). HRTEM showed spherical-shaped Fe nanoparticles with partial aggregation. Vibrating sample magnetometer indicated superparamagnetic properties of particles with high-saturation magnetization (Ms = 125 emu g−1) at room temperature.

Mesoporous titania/tungstophosphoric acid composites: suitable synthesis of flavones

Mesoporous TiO2/H3PW12O40 composites were synthesized by sol–gel reactions using urea as a low-cost template, and adding tungstophosphoric acid (TPA) at the same time as the template. The TPA concentration was varied in order to obtain TPA contents of 0, 10, and 20 (w/w) in the solid. The samples presented mesopores with a diameter higher than 3.0 nm. The specific surface area of the solids decreased with both the increase of the TPA content and the calcination temperature. From Fourier transform infrared and 31P magic angle spinning-nuclear magnetic resonance studies it was observed that the main heteropolyoxometallate species present in the composites is the [PW12O40]3− anion, which was partially transformed into the [P2W21O71]6− and [PW11O39]7− anions during the synthesis and drying step. The X-ray diffraction patterns of the modified samples only exhibited the characteristic peaks of the anatase phase of titanium oxide. The point of zero charge decreased with both the increase of TPA content in the solids and the calcination temperature. The materials were found to be efficient and recyclable catalysts for the synthesis of a series of flavones. The reaction was carried out in different reaction media: heterogeneous and solvent-free conditions. The solvent-free conditions represent the best green conditions. Initially, we optimize the reaction condition to obtain 6-chloroflavone by direct reaction of the cyclodehydration of 1-(2-hydroxy-5-chlorophenyl)-3-phenyl-1,3-propanodione in the presence of a catalytic amount of mesoporous titania modified with tungstophosphoric acid catalyst. Reactions were performed in two conditions: low volume of toluene, at 110 °C, typically 24 h, and solvent-free at the same temperature, 1 h. In all cases the product (6-chloroflavone) was obtained with high selectivity. Conversions up to 76 and 92 % were obtained respectively, using the supported catalyst (TiTPA10). Optimal reaction conditions were applied to the preparation of six substituted flavones in both conditions. Open image in new window

A Rapid Procedure for the Determination of C60 and C70 Fullerenes in Soil and Sediments by Ultrasound-assisted Extraction and HPLC-UV

In this work, a rapid and sensitive method, based on ultrasound-assisted extraction of samples with a small volume of toluene, has been developed for the quantification of C60 and C70 fullerenes in soil and sediments. Good extraction efficiencies were obtained at all of the fortification levels studied (200, 100, 20 and 2 ng/g), which ranged from 72 to 104%. An important effect of the extraction temperature was observed on C60 recoveries, and an acceptable decrease in the recovery rates was observed in aged samples. In the case of wet samples, the extraction can be done by percolating a small volume of acetonitrile before extraction. The extraction yields of the developed method for the extraction of C60 and C70 from soil were compared with those obtained by pressurized liquid extraction. Finally, analyses of fullerenes in agricultural and industrial soils and sediments were carried out, but no fullerene residues were found.

Efficient and suitable preparation of N-sulfonyl-1,2,3,4-tetrahydroisoquinolines and ring analogues using recyclable H6P2W18O62·24H2O/SiO2 catalyst

Abstract Silica gel-supported H6P2W18O62·24H2O is an efficient and recyclable catalyst for the synthesis of biologically important molecules. Several substituted N-sulfonyl-1,2,3,4-tetrahydroisoquinolines and ring analogues can be prepared in very good yields and purity by direct reaction of N-aralkylsulfonamides and sym-trioxane by a Pictet-Spengler reaction in the presence of a catalytic amount of silica gel-supported H6P2W18O62·24H2O. Reactions were performed in a low volume of toluene, at 70 °C and for a short time, typically 15 to 30 min. The title heterocyclic compounds were prepared in very good yields (60%–95%) using the described procedure results in a clean and useful alternative, which has the advantages of a greener methodology with operative simplicity, use of a reusable and non-corrosive solid catalyst, soft reaction conditions, low reaction times, and good yields.

Optimization and characteristics of preparing chitosan microspheres using response surface methodology

AbstractIn this study, response surface methodology (RSM) was employed to optimize preparation of chitosan microspheres (CMs). Firstly, Plackett–Burman design (PBD) was applied to screen out the factors, which influence preparation of CMs significantly. The results showed that the concentration of chitosan and acetic acid as well as the volume of toluene were the key factors. Then, steepest ascent experiment and Box–Behnken design were introduced to optimize the levels of the key factors. As a result, the appropriate conditions of preparing CMs were chosen as follows: 2% (w/v) chitosan, 1.7% (v/v) acetic acid, 7 mL span‐80, 488 mL toluene, 1100 rpm, 60 min (emulsification time), 10 mL formaldehyde, and 60 min (crosslinking time). Also, the morphology, size particle, and FTIR spectra of CMs were studied by scanning electron microscopy, small angle laser light scattering, and FTIR spectrometer. Results showed that CMs had quite smooth surface spherical and sharp size distribution, which indicated that the CMs were successfully prepared by W/O emulsification crosslinking method using RSM. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Optimized solvent-exchange synthesis method for C60 colloidal dispersions

An existing solvent exchange method used to produce aqueous suspensions of fullerene C60 aggregates (nC60) using the solvents toluene, tetrahydrofuran, acetone, and water, has been optimized for producing 75nm diameter particles. Numerous synthesis parameters were evaluated for their effects on colloid yield and particle size distribution. Varying the relative volumes used of the intermediate solvents relative to the initial toluene volume allowed the controlled tuning of the resulting particle size up to a diameter of 210nm. The resulting suspensions produced 10–20ppm concentrations and reduced the residual organic solvents to less than the detection limit of 1ppm.

Matrix-assisted laser desorption/ionization mass spectrometry for quantitative determination of β-blocker drugs in one-drop of human serum sample

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been applied for the quantitative determination of β-blocker drugs in one-drop of human serum samples using drop-to-drop solvent microextraction (DDSME) as a preconcentrating probe. The optimum experimental conditions for β-blocker drugs were investigated and 1.8μL volume of toluene for 10min extraction time with the 5% addition of NaCl under pH 11.0 was found to be the best conditions for the separation and preconcentration of drugs from 30μL of serum sample from a patient with high blood pressure. The optimized methodologies for DDSME/MALDI-MS analyses exhibited a good linearity with intra- and inter day precision value of 8.5–10.5% and 9.4–12.6%, respectively. The proposed DDSME/MALDI-MS offers a very simple, rapid and low-cost technique for the determination of β-blocker drugs in one drop of serum sample. The reported method has been successfully applied for the determination of propranolol and nadolol in small volume of serum sample from patient suffering from high blood pressure. In future, this technique could be applied for pharmacokinetic and clinical studies.

A new way to prepare tin oxide precursor polymeric gels

Transparent tin oxide gels are elaborated in the isopropoxide/toluene/isopropanol system. The gelation occurs at room temperature without any acid or base additions. The formation of the SnO2 precursor gels polymeric network is evidenced by Fourier transform infrared spectroscopy. The gelation time is studied as a function of the complexing ratio R = [acac]/[Sn(OR)4], the hydrolysis ratio W = [H2O]/[Sn(OR)4], the concentration of tin oxide precursor C = [Sn(OR)4], and the volume fraction of toluene P = (toluene volume) / (total solvent volume).

High‐Yield Synthesis of Silver Nanoparticles by Precipitation in a High‐Aqueous Phase Content Reverse Microemulsion

Silver nanoparticles were precipitated at 70°C in a reverse microemulsion containing a high concentration of 0.5 M silver nitrate aqueous solution, toluene as organic phase, and a mixture of surfactants sodium bis (2‐ethylhexyl) sulfosuccinate/sodium dodecyl sulfate (2/1, w/w). Nanoparticles were characterized by X‐ray diffraction, atomic absorption spectroscopy, and high‐resolution transmission electron microscopy. In spite of the high‐water/surfactant molar ratio and concentration of silver nitrate solution used in this study, characterizations demonstrated that nanoparticles were silver crystals (purity >99%) with 8.6–8.8 nm in average diameter and 2.9–4.7 nm in standard deviation. It is proposed that slow dosing rate of aqueous solution of precipitating agent and the small molecular volume of toluene attenuated both particle aggregation and polydispersity widening. Experimental yield of silver nanoparticles obtained in this study was much higher than theoretical yields calculated from available data in the literature on preparation of silver nanoparticles in reverse microemulsions.

Interaction Forces between Asphaltene Surfaces in Organic Solvents

The colloidal interactions between asphaltene surfaces in heptol, a mixture of n-heptane and toluene, were studied for the first time by colloidal force measurements using an atomic force microscope (AFM). Asphaltenes were deposited on silica wafers and silica spheres using the Langmuir-Blodgett upstroke technique. The results showed that the ratio of toluene to heptane can significantly change solvent quality in terms of the ability to solubilize asphaltenes and hence the nature and the magnitude of the interaction forces between asphaltene surfaces. In pure toluene, there is a steric long-range repulsion which can be well fitted by the scaling theory of polymer brushes. As toluene volume fraction in heptol (Phi(T)) is gradually decreased from Phi(T) = 1 (pure toluene) to Phi(T) = 0 (pure n-heptane), the steric repulsion reduced and changed to weak attraction when Phi(T) < 0.2. The attraction in heptane can be fitted by van der Waals forces alone which are thus believed to promote asphaltene aggregation, leading to asphaltene precipitation. The results obtained in this study provide an insight into interactions that determine asphaltene behavior in an organic medium and hence in crude oils.

15-Deoxyspergualin Primarily Targets the Trafficking of Apicoplast Proteins in Plasmodium falciparum

15-Deoxyspergualin, an immunosuppressant with tumoricidal and antimalarial properties, has been implicated in the inhibition of a diverse array of cellular processes including polyamine synthesis and protein synthesis. Endeavoring to identify the mechanism of antimalarial action of this molecule, we examined its effect on Plasmodium falciparum protein synthesis, polyamine biosynthesis, and transport. 15-Deoxyspergualin stalled protein synthesis in P. falciparum through Hsp70 sequestration and subsequent phosphorylation of the eukaryotic initiation factor eIF2alpha. However, protein synthesis inhibition as well as polyamine depletion were invoked only by high micromolar concentrations of 15-deoxyspergualin, in contrast to the submicromolar concentrations sufficient to inhibit parasite growth. Further investigations demonstrated that 15-deoxyspergualin in the malaria parasite primarily targets the hitherto underexplored process of trafficking of nucleus-encoded proteins to the apicoplast. Our finding that 15-deoxyspergualin kills the malaria parasite by interfering with targeting of nucleus-encoded proteins to the apicoplast not only exposes a chink in the armor of the malaria parasite, but also reveals new realms in our endeavors to study this intriguing biological process.

Application of microwave-assisted extraction to the analysis of PCBs and CBzs in fly ash from municipal solid waste incinerators

Polychlorinated biphenyls (PCBs) and chlorobenzenes (CBzs) are two classes of dioxin precursors formed in municipal solid waste incinerators (MSWIs) producing negative health effects similar to those of dioxins. Reducing the analytical time required for determining the concentrations of these compounds in MSWIs is important for quickly evaluating their importance and associated health risks. In the present study, microwave-assisted extraction (MAE) is compared with traditional Soxhlet extraction (SE) to determine the extraction efficiencies attained for PCB and CBz analysis. The efficiencies of MAE are compared with those of SE under various experimental conditions, using fly ash spiked with standards. Water is used as a safe and environmentally friendly solvent in MAE for PCB and CBz analyses and MAE has high extraction efficiency for spiked fly ash compared with that of SE. Furthermore, the extraction time and organic solvent consumption are reduced with MAE compared with SE. The optimum conditions for MAE established in this study are using a 30-ml volume of toluene/acetone (1/1) or a 15-ml volume of toluene, samples with less than 60% water content (WC), and an irradiation time of 15min.

Trypanosoma brucei Glycoproteins Contain Novel Giant Poly-N-acetyllactosamine Carbohydrate Chains

The flagellar pocket of the bloodstream form of the African sleeping sickness parasite Trypanosoma brucei contains material that binds the beta-d-galactose-specific lectin ricin (Brickman, M. J., and Balber, A. E. (1990) J. Protozool. 37, 219-224). Glycoproteins were solubilized from bloodstream form T. brucei cells in 8 M urea and 3% SDS and purified by ricin affinity chromatography. Essentially all binding of ricin to these glycoproteins was abrogated by treatment with peptide N-glycosidase, showing that the ricin ligands are attached to glycoproteins via N-glycosidic linkages to asparagine residues. Glycans released by peptide N-glycosidase were resolved by Bio-Gel P-4 gel filtration into two fractions: a low molecular mass mannose-rich fraction and a high molecular mass galactose and N-acetylglucosamine-rich fraction. The latter fraction was further separated by high pH anion exchange chromatography and analyzed by gas chromatography mass spectrometry, one- and two-dimensional NMR, electrospray mass spectrometry, and methylation linkage analysis. The high molecular mass ricin-binding N-glycans are based on a conventional Manalpha1-3(Manalpha1-6)Manbeta1-4-GlcNAcbeta1-4GlcNAc core structure and contain poly-N-acetyllactosamine chains. A significant proportion of these structures are extremely large and of unusual structure. They contain an average of 54 N-acetyllactosamine (Galbeta1-4GlcNAc) repeats per glycan, linked mostly by -4GlcNAcbeta1-6Galbeta1-interrepeat linkages, with an average of one -4GlcNAcbeta1-3(-4GlcNAcbeta1-6)Galbeta1- branch point in every six repeats. These structures, which also bind tomato lectin, are twice the size reported for the largest mammalian poly-N-acetyllactosamine N-linked glycans and also differ in their preponderance of -4GlcNAcbeta1-6Galbeta1- over -4GlcNacbeta1-3Galbeta1- interrepeat linkages. Molecular modeling suggests that -4GlcNAcbeta1-6Galbeta1- interrepeat linkages produce relatively compact structures that may give these giant N-linked glycans unique physicochemical properties. Fluorescence microscopy using fluorescein isothiocyanatericin indicates that ricin ligands are located mainly in the flagellar pocket and in the endosomal/lysosomal system of the trypanosome.

Chiral Bis(amino alcohol)oxalamide Gelators—Gelation Properties and Supramolecular Organization: Racemate versus Pure Enantiomer Gelation

Four new chiral bis(amino alcohol)oxalamides (1-4: amino alcohol=leucinol, valinol, phenylglycinol, and phenylalaninol, respectively) have been prepared as low-molecular-weight organic gelators. Their gelation properties towards various organic solvents and mixtures were determined and these were then compared to related bis(amino acid) oxalamide gelators. Spectroscopic (FTIR, (1)H NMR) and X-ray diffraction studies revealed that the primary organization motif of (S,S)-1 and racemate 1 (rac-1) in lipophilic solvents involved the formation of inverse bilayers. The X-ray crystal structure of (S,S)-1 also shows this type of bilayer organization. The crystal structure of rac-2 reveals meso bilayers of hydrogen-bonded aggregates. Within the bilayers formed, the gelator molecules are connected by cooperative hydrogen bonding between oxalamide units and OH groups, while the interbilayer interactions are realized through lipophilic interactions between the iBu groups of leucinol. Oxalamide meso-1 lacks any gelation ability and crystallizes in monolayers. In dichloromethane rac-1 forms an unstable gel; this is prone to crystallization as a result of the formation of symmetrical meso bilayers. In contrast, in aromatic solvents rac-1 forms stable gels; this indicates that enantiomeric bilayers are formed. Oxalamide rac-1 is capable of gelling a volume of toluene three times larger than (S,S)-1. A tranmission electron microscopy investigation of rac-1 and (S,S)-1 toluene gels reveals the presence of thinner fibers in the former gel, and, hence, a more compact network that is capable of immobilizing a larger volume of the solvent. The self-assembly of these types of gelator molecules into bilayers and subsequent formation of fibrous aggregates can be explained by considering the strength and direction of aggregate forces (supramolecular vectors) in three-dimensional space.

Effects of petroleum resins on asphaltene aggregation and water-in-oil emulsion formation

Abstract Asphaltenes from four crude oils were fractionated by precipitation in mixtures of heptane and toluene. Solubility profiles generated in the presence of resins (1:1 mass ratio) indicated the onset of asphaltene precipitation occurred at lower toluene volume fractions (0.1–0.2) than without resins. Small-angle neutron scattering (SANS) was performed on solutions of asphaltene fractions in mixtures of heptane and toluene with added resins to determine aggregate sizes. Water-in-oil emulsions of asphaltene–resin solutions were prepared and separated by a centrifuge method to determine the vol.% water resolved. In general, the addition of resins to asphaltenes reduced the aggregate size by disrupting the π–π and polar bonding interactions between asphaltene monomers. Interaction of resins with asphaltenic aggregates rendered the aggregates less interfacially active and thus reduced emulsion stability. The smallest aggregate sizes observed and the weakest emulsion stability at high resin to asphaltene (R/A) ratios presumably corresponded to asphaltenic monomers or small oligomers strongly interacting with resin molecules. It was often observed that, in the absence of resins, the more polar or higher molecular weight asphaltenes were insoluble in solutions of heptane and toluene. The addition of resins dissolved these insolubles and aggregate size by SANS increased until the solubility limit was reached. This corresponded approximately to the point of maximum emulsion stability. Asphaltene chemistry plays a vital role in dictating emulsion stability. The most polar species typically required significantly higher resin concentrations to disrupt asphaltene interactions and completely destabilize emulsions. Aggregation and film formation are likely driven by polar heteroatom interactions, such as hydrogen bonding, which allow asphaltenes to absorb, consolidate, and form cohesive films at the oil–water interface.

Characterization of nano-structured poly(ε-caprolactone) nonwoven mats via electrospinning

Nano-structured poly(ε-caprolactone) (PCL) nonwoven mats were prepared by electrospinning process. In this study, three types of solution were used. One dissolved in only methylene chloride (MC), the second dissolved in mixture of MC and N, N-dimethylformamide (DMF), the third dissolved in mixture of MC and toluene. MC, toluene and DMF are a good, poor, and nonsolvent for PCL, respectively. For the MC only, electrospun fibers had very regular diameter of about 5500 nm, but electrospinng is not facilitated. For the mixture of MC and DMF, electrospinning is certainly enhanced as well as fiber diameter decreased dramatically as increasing DMF volume fraction. It was due to high electric properties of solution such as dielectric constant and conductivity. Whereas, as increasing toluene volume fraction, electrospinning is strictly restricted due to very high viscosity and low conductivity. As the results, it has regarded that solution properties is one of the important parameter in electrospinning. Properties such as conductivity, surface tension, viscosity and dielectric constant of the PCL solutions prepared from three types of solvent system were studied. The morphology, crystallinity and mechanical properties of electrospun PCL nonwoven mats were characterized by scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and universal testing method (UTM), respectively.