Nonpolar Characteristics Research Articles

Nanodomain organization in ionic liquids: Implications of polarization effects in the alkyl side-chain association

The existence of domains at the nanometric scale has been observed in ionic liquids with long alkyl side chains. Experimental evidence and theoretical studies have suggested the existence of nanodomains with polar and non-polar characteristics. This evidence has been related to the capacity of ionic liquids to dissolve species within a broad range of chemical properties. Herein, we present a study of the structural features of the non-polar domain using classical molecular dynamics using a polarizable force field. The results suggest that the tail-to-tail association is stronger when a polarizable force field is used, owing to the better description of the dispersive forces between them. We propose using a polarizable force field in the simulations of ionic liquids based on classical molecular dynamics as the default method. To account for these differences, we compare the non-polarizable force field and its polarizable variant in describing the self-association of long-tailed imidazolium-based ionic liquids. Finally, a nanodomain analysis could rationalize the solute-solvent interactions brought about by ionic liquid since they strongly depend on the hydrogen-bond acidity and basicity, which are expected to operate in the polar domain.

A Ferricyanide Anion-Philic Interface Induced by Boron Species within Carbon Framework for Efficient Charge Storage in Supercapacitors.

Carbon materials with hierarchical porous structures hold great potential for redox electrolyte-enhanced supercapacitors. However, restricted by the intrinsic inert and nonpolar characteristics of carbon, the energy barrier of anchoring redox electrolytes on the pore walls is relatively high. As such, the redox process at the interface less occurs, and the rate of mass transfer is impaired, further leading to a poor electrochemical performance. Here, a ferricyanide anion-philic interface made of in situ inserted boron species into carbon rings is constructed for enhanced charge storage in supercapacitors. Profiting from the unique component-driven effects, the polar anchoring sites on the pore wall can be built to grasp the charged redox ferricyanide anion from the bulk electrolyte and promote the redox process; the dynamics process is fastened correspondingly. Especially, the boron atoms in BC2O and BCO2 units with higher positive natural bond orbital values in the carbon skeleton are pinpointed as intrinsic active sites to bind the negatively charged nitrogen atoms in the ferricyanide anion via electrostatic interaction, confirmed by density functional theoretical calculations. This will suppress the shuttle and diffusion effects of the ferricyanide anion from the surface of the electrode to the bulk electrolyte. Finally, the well-designed PC-3 with high content of BC2O and BCO2 units can reach 1099 F g-1 at 2 mV s-1, which is a more than 2-fold increase over boron-free units of carbon (428 F g-1). The work offers a novel version for designing high-performance carbon materials with unique yet reaction species-philic effects.

Versatile separation layer for separation and purification of ethanol/cyclohexane mixtures by pervaporation process

Quaternized cyclodextrin (CD) obtained by quaternization reaction of bromine-CD and N, N-Dimethylethylenediamine, are used for preparing PV membranes. Three different kinds of composite membranes are interfacially synthesized on the polyacrylonitrile substrate. The different sequences of piperazine and quaternized CD reacted with trimesoyl trichloride show a great difference in separation of polar/nonpolar mixture. The topmost layer of CD-based polyamide layer shows a higher separation factor, which can be inferred that quaternized CD played the major role during separation. Quaternized CD can integrate cavity size, polar and non-polar characteristics to achieve exceptional screening performance. PV performance of the optimal membrane at 25 °C is measured using the 5 wt% ethanol and cyclohexane mixture, exhibiting the separation factor of 66.7. PV performances of other different organic mixtures prove that nonpolar inner cavity of CD has a stronger inclusion of cyclohexane than other smaller nonpolar molecules, thus enhancing the repulsion of cyclohexane from the mixture. In summary, these outside polar quaternary ammonium salt structures of quaternized CD have a high selectivity for polar solvents. The nonpolar cavity of CD shows the inclusion ability of nonpolar solvents, especially the organic solvent with large molecular volume, which hinders their penetration and improves the separation factor.

Barbier polymerization towards synthesizing polar polyolefin analogues for polyolefin modification

A Barbier polymerization method is demonstrated to be a versatile strategy to synthesize polar polyolefin analogues (PPAs), which are further utilized as modifiers to improve the properties of non-polar polyolefins by physically introducing polar groups.

Selective area growth of in-plane InAs nanowires and nanowire networks on Si substrates by molecular-beam epitaxy

In-plane InAs nanowires and nanowire networks show great potential to be used as building blocks for electronic, optoelectronic and topological quantum devices, and all these applications are keen to grow the InAs materials directly on Si substrates since it may enable nanowire electronic and quantum devices with seamless integration with Si platform. However, almost all the in-plane InAs nanowires and nanowire networks have been realized on substrates of III–V semiconductors. Here, we demonstrate the selective area epitaxial growth of in-plane InAs nanowires and nanowire networks on Si substrates. We find that the selectivity of InAs growth on Si substrates is mainly dependent on the growth temperature, while the morphology of InAs nanowires is closely related to the V/III flux ratio. We examine the cross-sectional shapes and facets of the InAs nanowires grown along the 〈110〉, 〈100〉 and 〈112〉 orientations. Thanks to the non-polar characteristics of Si substrates, the InAs nanowires and nanowire networks exhibit superior symmetry compared to that grown on III–V substrates. The InAs nanowires and nanowire networks are zinc-blende (ZB) crystals, but there are many defects in the nanowires, such as stacking faults, twins and grain boundaries. The crystal quality of InAs nanowires and nanowire networks can be improved by increasing the growth temperature within the growth temperature window. Our work demonstrates the feasibility of selective area epitaxial growth of in-plane InAs nanowires and nanowire networks on Si substrates.

First report on ecotoxicological QSTR and i-QSTR modeling for the prediction of acute ecotoxicity of diverse organic chemicals against three protozoan species

The recent years have witnessed an upsurge of interest to assess the toxicity of organic chemicals exhibiting harmful impacts on the environment. In this investigation, we have developed regression-based quantitative structure-toxicity relationship (QSTR) models against three protozoan species (Entosiphon sulcantum, Uronema parduczi, and Chilomonas paramecium) using three sets of descriptor combinations such as ETA indices only, non-ETA descriptors only, and both ETA and non-ETA descriptors to examine the key structural features that determine the toxic properties of protozoa. The interspecies QSTR models (i-QSTRs) were also generated for efficient data gap-filling of toxicity databases. The statistical results of the validated models in terms of both internal and external validation metrics suggested that the models are statistically reliable and robust. Additionally, using these validated models, we screened the DrugBank database containing 11,300 pharmaceuticals for assessing the ecotoxicological properties. The features appearing in the models suggested that non-polar characteristics, electronegativity, hydrogen bonding, π–π, and hydrophobic interactions are responsible for chemical toxicity toward protozoan. The validated models may be utilized for the development of eco-friendly drugs & chemicals, data gap-filling of toxicity databases for regulatory purposes and research, as well as to decrease the use of toxic and hazardous chemicals in the environment.

Impact of the Polymer Backbone Structure on the Separation Properties of New Stationary Phases Based on Tricyclononenes

The main purpose of this paper is to compare the chromatographic properties of capillary columns prepared with polymers with different backbone structures and to demonstrate the possibility of polymer differentiation via inverse gas chromatography. With the use of addition and metathesis types of polymerization of tricyclononenes, two new stationary phases were prepared. The metathesis polymer contained double bonds in the polymeric backbone while the backbone of the addition polymer was fully saturated and relatively mobile. A comparison of the separation and adsorption properties of new phases with conventional gas chromatography (GC) stationary phases clearly indicated their non-polar characteristics. However, the difference in the polymer structure appeared to have very little effect on the stationary phase separation properties, so other parameters were used for polymer characterization. The thermodynamic parameters of the sorption of alkanes and aromatic compounds in both polymeric stationary phases were also very similar; however, the entropy of sorption for hydrocarbons with seven or more carbon atoms was different for the two polymers. An evaluation of the specific surface energy of the stationary phases also allowed us to discriminate the two stationary phases.

2-μm fused-core column ultra-high-performance liquid chromatography/tandem mass spectrometric determination of donepezil in human plasma: Application to a bioequivalence study

Ultra-high-performance liquid chromatography (UHPLC) hyphenated to tandem mass spectrometric methods using the dimethylpentafluorophenylpropyl stationary phase with polar and nonpolar characteristics of a 2-μm fused-core silica particle packing were evaluated to perform efficient separation for the analysis of donepezil in human plasma. The fused-core silica particle design providing the shorter diffusional mass transfer path for the analytes is less affected in resolving power by increasing mobile-phase velocity for faster chromatographic resolution between the administered compound and multiple interfering peaks from the extracted quality control, calibration standard and study samples following simple protein precipitation extraction procedures. In this work, two UHPLC-MS/MS approaches requiring 1.2 min per sample run time and neither expensive ultra-high-pressure instrumentation nor new laboratory protocols were applied and compared for determination of donepezil in human plasma at sub-nanograms per milliliter region to support a randomized, crossover bioequivalence (BE) study in which healthy volunteers each received a single oral dose of the test and reference formulations of 10 mg donepezil hydrochloride. The column performance in terms of chromatographic separation efficiency, peak asymmetry and resolution and retention time reproducibility was found to be sustainable over a thousand extracted plasma injections. The linear dynamic range was detected over a concentration range of 0.2–50 ng/mL. The intra- and inter-day assay accuracy and precision were within 15% for the analyte in individual biological fluids. Positive correlation coefficients (r) greater than 0.98 and 0.99 for donepezil concentrations in study plasma samplers measured by the proposed UHPLC-MS/MS approaches and another validated HPLC-MS/MS method were observed.

Vol4 num4-8 FE Mechanical properties prediction of CFRP considering different carbon fiber surface treatments

Reinforcement/matrix interaction is recognized as a key issue in polymeric composite materials. From the mechanical point of view, being the link between the fibres and the polymer, a proper load transfer is ensured only if a good enough interphase exists. This is particularly critical in carbon fibre (CF) composites since, due to the non-polar characteristics and chemical inertness of carbon, sometimes they exhibit weak interfacial adhesion. In this sense, various surface treatments for CFs are currently being investigated, in order to improve their interaction with the polymeric matrices: wet chemical or electrochemical methods, chemically or physically activated oxidation procedures, application of thin coatings and plasma treatments. This is precisely one of the challenges addressed in the MODCOMP project. This paper describes part of the work carried out within the mentioned project in order to estimate the improvement of properties that can be achieved through enhancements of the CF/epoxy interphases. The study covers both elastic engineering constants and strengths predictions, and it has been performed using finite element models of RVEs of UD fibres and introducing cohesive elements to take into account the interfacial failure mode. The results obtained allow identifying which range of CF/epoxy interphase properties enhancement should be achieved in order to get significant effects in the composites mechanical response.

Microgels Based on Carboxymethylpullulan Grafted with Ferulic Acid Obtained by Enzymatic Crosslinking in Emulsion for Drug Delivery Systems.

Carboxymethylpullulan (CMP) grafted with ferulic acid (FA) is crosslinked with laccase by the reverse water-in-oil emulsion technique (with sunflower oil) to obtain microgels with size from 40 to 200µm. It is demonstrated that laccase activity and dispersion time have an impact on microgels' size. Fluorescence spectroscopy of different probes (e.g., pyrene, Nile red, and curcumin) shows the nonpolar characteristics of hydrophobic microdomains formed by the FA moieties and its dimers forming the crosslinking nodes. Encapsulation and release of curcumin or lidocaine used as drug models are studied in different buffers. Curcumin is well encapsulated but retained in microgels, while lidocaine is released at 65-70% in 2 h and 30 min in buffer simulating the gastrointestinal tract and at 75-85% in 1 h in acetate buffer pH 5.6 or phosphate-buffered saline (PBS) pH 6.9.

Low threshold voltage, highly stable electroforming-free threshold switching characteristics in VOx films-based device

Threshold switching (TS) devices have evolved as one of the most promising elements in memory circuit due to their important significance in suppressing crosstalk current in the crisscross array structure. However, the issue of high threshold voltage (Vth) and low stability still restricts their potential applications. Herein, the vanadium oxide (VOx) films deposited by the pulsed laser deposition (PLD) method are adopted as the switching layer to construct the TS devices. The TS devices with Pt/VOx/Pt/PI structure exhibit non-polar, electroforming-free, and volatile TS characteristics with an ultralow Vth (+0.48 V/−0.48 V). Besides that, the TS devices also demonstrates high stability, without obviously performance degradations after 350 cycles of endurance measurements. Additionally, the transition mechanism is mainly attributed to the synergistic effect of metal-insulator transition of VO2 and oxygen vacancies. Furthermore, the nonvolatile bipolar resistance switching behaviors can be obtained by changing oxygen pressure during the deposition process for switching films. This work demonstrates that vanadium oxide film is a good candidate as switching layer for applications in the TS devices and opens an avenue for future electronics.

Effect of 2-propanol content on solute retention mechanisms determined using amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase under normal- and reversed-phase conditions

The electrostatic interactions between chiral solutes and polysaccharide (PS)-based chiral selectors are the key to achieving chiral recognition; however, PS-based sorbents, derivatized of phenyl moieties, can exhibit considerably non-polar characteristics, and they are also useful for the separation of enantiomers in the reversed-phase mode. In this study, an immobilized amylose 3,5-dimethylphenylcarbamate-based sorbent was used to investigate the balance between electrostatic interactions and solvophobic interactions, with complementary effects on solute retention behavior when the isopropanol (IPA) concentration was altered. It was proposed that in both normal- and reversed-phase modes, information on the retention mechanisms could be obtained by observing the curvature of the logarithm of the retention factor versus the logarithm of the IPA concentration, and the slope values of the curves were related to the number of displaced IPA molecules upon solute adsorption. Using the proposed model and the two-site adsorption model, the retention behaviors of pantolactone (PL) enantiomers in both normal- and reversed-phase modes were investigated. The PL−sorbent interactions were classified into four types: electrostatic/enantioselective, electrostatic/nonselective, solvophobic/enantioselective, and solvophobic/nonselective. At IPA concentrations below 50 vol.% in n-hexane, the retention behaviors of PL were dominated by electrostatic/enantioselective sites, whereas at IPA concentrations beyond 50 vol.%, the solvophobic interactions of PL−sorbent were strengthened and mostly nonselective. By contrast, in the reversed-phase mode, a reverse in the enantiomeric elution order of PL was observed at 10 vol.% IPA, and considerably different enantioselectivity behaviors were found below and above 20 vol.%, indicating an abrupt change in the sorbent molecular environment. At IPA concentrations beyond 40 vol.%, the presence of PL-sorbent electrostatic interactions enhanced chiral recognition.

Disclosure of the solvatochromism and the reversal switch in some tailor-made electron push-push anils

The impacts of a series of organic solvents, having diverse polarities on the electronic absorption spectra of some selected anils, N-benzylideneaniline, and its five derivatives with hydroxy and methoxy substituents were investigated. The absorption spectra of each of the anils displayed a cluster of absorption bands within 200–500 nm. The electronic transitions and the effect of substituents on the solvatochromism of these anils were successfully deciphered. The reversal in solvatochromism was observed in moving from the hydrogen bond acceptor to hydrogen bond donor solvents. This fact was attributed to the structural transition of the anils due to the interaction with solvents of differential polarity or due to the obscurity of anils within the solvent cage. The ET(30) values at which the reversal solvatochromic switch due to the anils appeared was controlled by the position and nature of the substituents. The early accomplishment of the reversal solvatochromism in o-OH substituted anils connoted the non-polar characteristics of these anils. By subjecting the electronic transition energies to multiple regression analysis with fourteen different solvent parameters, the multi-parametric regression models were optimized following the successive exclusion of variable technique. The linearity of the plot of the calculated electronic transition energy against corresponding observed values validated the regression models. The induced solvatochromism observed in the case of o/p-hydroxy-substituted anils in ethylene glycol medium was attributed to the formation of the corresponding conjugate acids of the anils. The solvent-solute interaction models were proposed to probe the localization site of anils in the solvents. The intramolecular H-bonding and the twisted structure of the anils due to the substituent effects were found to play the predominant role in deciding the localization sites of the anils.

Broadband Determination of Biodiesel Content in Petroleum Diesel Blends by Terahertz Time Domain Spectroscopy

The biodiesel content in petroleum diesel-biodiesel blends is determined using broadband terahertz time-domain spectroscopy. We model the spectra of the blend components based on the nonpolar characteristics of the samples. The biodiesel content in diesel is determined from the coefficients that best fit the measured spectra to the optimal linear combination of the model for each individual component (pure diesel and pure biodiesel). This method proves to be valid for real-time applications. A simpler approach based on the maximum observed dispersion is also demonstrated to be a distinctive characteristic of a given blend.

Influence of Stacking Sequence on Mechanical and Metallurgical Properties of Ramie/areca Laminates Using B4C Nano Filled Epoxy Resin

ABSTRACT The areca fibers are significantly playing a vital role in the production of activated carbon, ethanol, and enzyme, as a fuel in bio-gas and commonly used as air fresheners. Due to hydrophilic in nature of areca fibers exist nonpolar characteristics and compounding difficulties along with the matrix result an ununiform distribution of resins which increase complexity issues while laminating into the desired shape. Moreover, an uneven resin flow caused fibers to de-bond from the laminated surface that consequences low mechanical and metallurgical properties. Therefore, an attempt has been made to utilize ramie fiber as an effective compatibilizer for the areca fiber. The necessary tests, such as mechanical and metallurgical characteristics of areca/ramie fibers were analyzed by varying its stacking sequences. Moreover, B4C nanoparticles were dispersed on the fibril surfaces to understand the effects of nanoparticles on the areca/ramie fibers. The obtained results revealed that ramie fibers could be used as a better compatibilizer to retain the required shape and also to produce an adequate bonding between the fiber/matrix.

Carbon nanotubes-supported Pt catalysts for decalin dehydrogenation to release hydrogen: A comparison between nitrogen- and oxygen-surface modification

The effect of carbon nanotubes (CNT) surface chemistry on supported Pt catalytic performance in decalin dehydrogenation to release hydrogen was investigated through modifying CNT surface with nitrogen and oxygen functional groups. The results indicate that the mechanism of improving Pt dispersion is different for nitrogen and oxygen groups. Although oxygen groups can improve Pt dispersion, their electron donating feature inhibits the electron transfer from Pt to carbon support. DFT calculations have clarified the negative effect of oxygen group on decalin dehydrogenation in aspect of adsorption energy. Moreover, the abundant oxygen species on catalyst surface lead to a bad wettability of catalyst in non-polar reaction liquid, which significantly weaken the approaching of reactant onto catalyst. Therefore, the introduction of oxygen groups is unfavorable to the catalyst activity. In contrast, the highly dispersed Pt nanoparticles anchored by nitrogen groups may be one reason for the high activity of Pt supported on CNT modified with nitrogen groups. Furthermore, nitrogen groups promote the electron transfer from Pt to CNT, leading to lower Pt d-band and weaker naphthalene adsorption. Meanwhile little change happened on the non-polar characteristics of CNT during nitrogen doping treatment. Therefore, the introduction of nitrogen functional groups is conducive to the catalytic dehydrogenation.

Sulfonation and Characterization of Tert-Butyl Styrene/Styrene/Isoprene Copolymer and Polypropylene Blends for Blood Compatibility Applications.

Hydrogenated styrenic block copolymers (HSBCs) have been used in medical tubing for many years due to their high clarity, flexibility, kink resistance, and toughness. However, when it comes to blood storage applications, HSBC compounds’ market has been limited because of their high hydrophobicity, which may trigger platelet adhesion when contacting with blood. HSBC needs to be physically or chemically modified in advance to make it blood compatible; however, HSBC has strong UV/ozone resistance, thermooxidative stability, and excellent processing capability, which increases the difficulty of the chemical modification process as unsaturated dienes has been converted to saturated stable midblocks. Moreover, medical HSBC-containing compounds primarily make up with the non-polar, hydrophobic nature and benign characteristics of other common ingredients (U.S. Pharmacopeia (USP) grades of mineral oil and polypropylene), which complicates the realization of using HSBC-containing compounds in blood-contacting applications, and this explains why few studies had disclosed chemical modification for biocompatibility improvement on HSBC-containing compounds. Sulfonation has been reported as an effective way to improve the material’s blood/platelet compatibility. In this study, hydrogenated tert-butyl styrene (tBS)-styrene-isoprene block copolymers were synthesized and its blends with polypropylene and USP grades of mineral oil were selectively sulfonated by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tBS-styrene-isoprene block copolymer in the blend, sulfonated films were optimized to demonstrate sufficient physical integrity in water as well as thermal stability, hydrophilicity, and platelet compatibility.

Biomethane production by typical straw anaerobic digestion: Deep insights of material compositions and surface properties

Straws as lignocellulosic agricultural biomass have a huge amount and are widely used for biomethane production by anaerobic digestion (AD). However, the mechanism of impacts of straw composition and surface properties on biomethane production remain unclear. Here, a lab-scale AD incubation experiment was conducted and the characterization of four types of straws (corn straw, wheat straw, sweet sorghum straw, and rice straw) were also determined. The straw compositions and net cumulative methane production showed significant difference. Although the relative contents of key organic components and carbon had no significant correlation to the biomethane production (r = -0.36, P > 0.05), there existed differences of non-polar characteristics, steric hindrance effect and special surface morphology in four types of straws, indicating that the surface characteristics affected anaerobic biomethane production process. In addition, the straw matrix associating with silicon might hinder the biotransformation.

Preliminary Study of Modified Lignin Compatibility in Polypropylene‐Modified Bitumen

AbstractLignin is an amorphous biopolymer that has both polar and nonpolar characteristics which has been proven able to chemically bond bitumen and polypropylene. However, the presence of polar bond in lignin is more dominant than the nonpolar one making it less effective to bond polypropylene. Thus, lignin is modified to reduce its polar hydroxyl group by synthetizing it with prepolyurethane otherwise known as polyurethanization. This modified lignin compatibility to bond bitumen and polypropylene is then studied and compared with lignin, such is the true purpose of this research. Experiment is done through several stages ranging from sample preparation, mixing, and characterization. Hot melt mixing method is used to mix bitumen, polypropylene, and modified lignin with mass ratio of 19:1 for bitumen and polypropylene, which are mixed in 80 rpm. Mixing is done at the temperature of 180 °C for 30 min with 0.3% total weight addition of modified lignin. Characterizations are done using FT‐IR and FESEM. Result shows that modified lignin has better compatibility compared to pure lignin.

A benzene vapor sensor based on a metal-organic framework-modified quartz crystal microbalance

As one of the BTEX (benzene, toluene, ethylbenzene, xylene) from living environment, benzene has the greatest carcinogenic, anesthetic and neurotoxic effects. At the same time, due to its chemical inertness and nonpolar characteristics, benzene is also the most difficult to detect in BTEX. Herein, based on QCM (quartz crystal microbalance) platform, MOF-14, a metal-organic framework, is first employed to detect benzene vapor by the host − guest interaction of MOF with benzene molecule, as well as Lewis acid-base interaction. By comparing with other three types of MOF materials, it was found that the effect of the ligand on the adsorption is greater than that of the metal point of junction. On the other hand, the different steric hindrance effects in BTEX restrict their adsorption capacity. Thus, the MOF-14 modified QCM sensor exhibits high sensing performance to benzene vapor with a detection limit at the level of 150 ppb. Our studies also indicate that the sensor shows good selectivity to oppose various kinds of interfering gases. Even toluene has a structure similar to that of benzene, it also can be distinguished. And the measurements on repeatability and long-term stability are both approved for the excellent reliability of the MOF-14 modified QCM sensor. By using computational simulation, we explored that why benzene and toluene can be distinguished by MOF-14 modified QCM sensor. This work extended the usages of MOF based QCM for high performance benzene sensing.