Polar Polyethylene Research Articles

Constituents, Enantiomeric Content, and ChE Inhibitory Activity of the Essential Oil from Hypericum laricifolium Juss. Aerial Parts Collected in Ecuador.

The physical properties, chemical composition, enantiomer distribution, and cholinesterase (ChE) inhibitory activity were determined for a steam-distilled essential oil (EO), with a yield of 0.15 ± 0.05 % (w/w), from H. laricifolium aerial parts, collected in southern Ecuador. The oil qualitative and quantitative analyses were performed by GC-EIMS and GC-FID techniques, using two capillary columns containing a non-polar 5%-phenyl-methylpolysiloxane and a polar polyethylene glycol stationary phase, respectively. The main constituents (>10%) detected on the two columns were, respectively, limonene (24.29, 23.16%), (E)-β-ocimene (21.89, 27.15%), and (Z)-β-ocimene (12.88, 16.03%). The EO enantioselective analysis was carried out using a column based on 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin. Two mixtures of chiral monoterpenes were detected containing (1R,5R)-(+)-α-pinene (ee = 83.68%), and (S)-(-)-limonene (ee = 88.30%) as the major enantiomers. This finding led to some hypotheses about the existence in the plant of two enantioselective biosynthetic pathways. Finally, the EO exhibited selective inhibitory effects in vitro against butyrylcholinesterase (BuChE) (IC50 = 36.80 ± 2.40 µg/mL), which were about three times greater than against acetylcholinesterase (IC50 = 106.10 ± 20.20). Thus, the EO from Ecuadorian H. laricifolium is an interesting candidate for investigating the mechanism of the selective inhibition of BuChE and for discovering novel drugs to manage the progression of Alzheimer's disease.

Evaluation of Gas Chromatography Columns with Radially Elongated Pillars as Second-Dimension Columns in Comprehensive Two-Dimensional Gas Chromatography.

The present study investigated the use of a dedicated gas chromatography (GC) column (L = 70 cm, 75 μm deep, and 6.195 mm wide) with radially elongated pillars (REPs) as the second column in a comprehensive two-dimensional gas chromatography (GC × μGC) system. Three stationary phases [apolar polydimethylsiloxane (PDMS), medium polar room-temperature ionic liquid (RTIL) based on monocationic phosphonium, and polar polyethylene glycol (PEG-1000)] have been coated using the static method at constant pressure or using an original vacuum pressure program (VPP) from 400 to 4 mbar. The best efficiency reached up to N = 62,000 theoretical plates for a film thickness of 47 nm at 100 °C for an iso-octane peak (k = 0.16) at an optimal flow rate of 4.8 mL/min. The use of the VPP improved the efficiency by approximately 15%. Efficiencies up to 28,000 and 47,000 were obtained for PEG-1000 and RTIL, respectively. A temperature-programmed separation of a mixture of 11 volatile compounds on a PDMS-coated chip was obtained in less than 36 s. The PDMS-, PEG-1000-, and RTIL-coated chips were tested as the second column using a microfluidic reverse fill/flush flow modulator in a GC × μGC system. The REP columns were highly compatible with the operating conditions in terms of flow rate and with more than 30,000 plates for the iso-octane peak. Moreover, a commercial solvent called white spirit containing alkanes and aromatic compounds was injected in three sets of columns in normal and reverse modes, demonstrating the great potential of the chip as a second-dimension separation column.

Branched Tertiary Amines from Aldehydes and α-Olefins by Combined Multiphase Tandem Reactions.

This study presents the transformation of olefins to branched amines by combining a hydroformylation/aldol condensation tandem reaction with the reductive amination in a combined multiphase system that can be recycled 9 times. The products are branched amines that are precursors for surfactants. Since the multiphase hydrofomylation/aldol condensation system has already been studied, the first step was to develop the partial hydrogenation of unsaturated aldehydes together with a subsequent reductive amination. The rhodium/phosphine catalyst is immobilized in a polar polyethylene phase which separates from the product phase after the reaction. Reaction and catalyst recycling are demonstrated by the conversion of the C14 -aldehyde 2-pentylnonenal with the dimethylamine surrogate dimethylammonium dimethylcarbamate to the corresponding tertiary amine with yields up to 88 % and an average rhodium leaching of less than 0.1 % per recycling run. Furthermore, the positive influence of a Bronsted acid and carbon monoxide on the selectivity are discussed. Finally, the two PEG based systems have been merged in one recycling approach, by using the product phase of the hydroformylation aldol condensation reaction for the reductive amination reaction. The yields are stable during a nine recycling runs and the leaching low with 0.09 % over the two recycling stages.

Environmentally friendly water-soluble epoxy emulsions nano sphere improved the interfacial performance of high modulus carbon fiber reinforced epoxy composites based on robust van der Waals force

High modulus carbon fibers (CFs) are widely desirable in aerospace, robotics, etc. However, their high degree of graphite microcrystalline structure leads to poor interfacial properties with host matrices, deteriorating the mechanical properties of carbon fiber reinforced polymer composites (CFRPs). Here, to improve interfacial properties of CFRPs, we present to construct a uniform and continuous active sizing nanolayer on the surface of CFs via synthetic water-based epoxy (WEP) emulsion nanospheres with strong van der Waals force. The WEP emulsions were prepared by introducing polar polyethylene glycols into epoxy resin chain. The modified CFRPs showed robust interfacial properties, improving by 25% over the untreated counterparts. Moreover, the proposed method can retain monofilament tensile strength of fibers and protect CFs from being destroyed during processing at industrial scales. This work opens an avenue toward the development of materials with superior interfacial performance for various inert high modulus fibers.

Cation–dipole interaction that creates ordered ion channels in an anion exchange membrane for fastOH−conduction

AbstractPrecise control over polyelectrolyte architecture, engineered for self‐assembly of ion‐conducting channels, is of fundamental and technological importance to many fields, for example, fuel cells and redox flow batteries and electrodialysis. Building on recent advances with the supramolecular chemistry, we introduce inter/intra‐molecular cation–dipole interactions between pendent quaternary ammoniums cations and polar polyethylene glycol grafts in an anion‐exchange membrane (AEM). Such interactions lead to desirable, ordered ion‐conducting pathways when in the membrane form. Comparison of the results of molecular dynamics simulation with1H NMR and nano‐scale microscopy analyses show that the cation–dipole interactions enhance self‐assembly and the formation of interconnected ionic network domains, providing three‐dimensional pathways for both water and ion transport. The resultant AEM exhibits high OH−conductivity (49 mS cm−1at 30°C) and a completive peak power density of 622 mW cm−2at 70°C when tested in a H2/O2single‐cell alkaline membrane fuel cell.

Ligand-Regulated Uptake of Dipolar-Aromatic Guests by Hydrophobically Assembled Suprasphere Hosts.

The selective uptake of guests by capsules, cages, and containers, and porous solid-state materials such as zeolites and metal-organic frameworks (MOFs), is generally controlled by pore sizeand by the dimensions and chemical properties of interior host domains. For soluble and solid-state structures, however, few options are available for modifying their outer pores to impart chemoselectivity to the uptake of similarly sized guests. We now show that by using alkane-coated gold cores as structural building units (SBUs) for the hydrophobic self-assembly of water-soluble suprasphere hosts, ligand exchange can be used to tailor the chemical properties at the pores that provide access to their interiors. For polar polyethylene glycol functionalized ligands, occupancies after equal times increase linearly with the dipole moments of chloro-, nitro- dichloro-, and dinitro- (o-, m-, and p-) benzene guests. Selectivity is reversed, however, upon incorporation of hydrophobic ligands. The findings demonstrate how self-assembled gold-core SBUs, with replaceable ligands, inherently provide for rationally introducing finely tuned and quantitatively predictable chemoselectivity to host-guest chemistry in water.

Blending ultrahigh‐molecular‐weight polyethylene and poly(ethylene/10‐undecen‐1‐ol) in one nascent particle

ABSTRACTUltrahigh‐molecular‐weight polyethylene (UHMWPE)/polar polyethylene (PE) composites were blended in one nascent particle by in situ polymerization with a hybrid catalyst. Polystyrene‐coated SiO2 particles were used to support the hybrid catalyst. Fe(acac)3/2,6‐bis[1‐(2‐isopropylanilinoethyl)] was supported on SiO2 for the synthesis of UHMWPE, whereas [PhNC(CH3)CHC(Ph)O]VCl2 was immobilized on a polystyrene layer to prepare a copolymer of ethylene and 10‐undecen‐1‐ol (polar PE). Importantly, the core part of the supports (the polystyrene layer) exhibited pronounced transfer resistance to 10‐undecen‐1‐ol; this provided an opportunity to keep the inside iron active sites away from the poisoning of 10‐undecen‐1‐ol. Therefore, UHMWPE was simultaneously synthesized with polar PE by in situ polymerization. Interestingly, the morphological results show that UHMWPE and the polar PE were successfully blended in one nascent polymer. This improved the miscibility of the composites, where most of the chains were difficult to crystallize because of the strong interactions between the PE chains and polar chains. The blends showed an extremely low crystallinity, that is, 9.9%. Finally, the hydrophilic properties of the polymer composites were examined. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46652.

Sol-gel-based SPME fiber as a reliable sampling technique for studying biogenic volatile organic compounds released from Clostridium tetani.

A novel and efficient headspace solid-phase microextraction (HS-SPME) method, followed by gas chromatography mass spectrometry (GC-MS), was developed to study volatile organic compounds (VOCs) emerging from microorganisms. Two homemade SPME fibers, a semi-polar poly (dimethylsiloxane) (PDMS) fiber, and a polar polyethylene glycol (PEG) fiber, along with two commercial fibers (PDMS and PDMS/DVB) were used to collect VOCs emerging from Clostridium tetani which was cultured in different media. The adsorbed VOCs were desorbed and identified, in vitro, using GC-MS. The adsorption efficiency was improved by optimizing the time duration of adsorption and desorption. About 50 components were identified by the proposed method. The main detected compounds appeared to be sulfur containing compounds such as butanethioic acid S-methyl ester, dimethyl trisulfide, and dimethyl tetrasulfide. These volatile sulfur containing compounds are derived from amino acids containing the sulfur element, which probably coexist in the mentioned bacterium or are added to the culture media. The developed HS-SPME-GC-MS method allowed the determination of the chemical fingerprint of Clostridium tetani volatile constituents, and thus provides a new, simple, and reliable tool for studying the growth of microorganisms. Graphical abstract Investigation of biogenic VOCs released from Clostridium tetani using SPME-GC-MS.

Phase Transfer and Surface Functionalization of Hydrophobic Nanoparticle using Amphiphilic Poly(amino acid).

Functionalization of nanoparticles with chemical and biochemical is essential for their biomedical and other application. However, most of the high quality nanoparticles are hydrophobic in nature due to surfactant capping and their conversion into water-soluble functional nanoparticle via appropriate coating and conjugation chemistry is extremely critical issue. Here we report amphiphilic poly(amino acid)-based one-pot coating and conjugation approach that can transform hydrophobic nanoparticle into water-soluble nanoparticle functionalized with primary amine, thiol, and biomolecule. We have designed amphiphilic polyaspartimide that can anchor hydrophobic nanoparticle through octadecyl groups, leaving the polar polyethylene glycol and aspartimide groups exposed outwards. The aspartimide group is then reacted with primary amine containing chemical/biomolecule with the formation of water-soluble functional nanoparticle. This approach has been extended to different hydrophobic nanoparticles and biomolecules. The present approach has advantages over existing approaches as coating and functionalization can be performed in one pot and functional nanoparticles have <12 nm hydrodynamic size, high colloidal stability, and biocompartibility. This developed approach can be used to derive biocompatible nanobioconjugates for various biomedical applications.

Sensing performance of dielectric sensor in mixed melting polymer pellets for waste plastic separation

Physical value of dielectric properties among relative permittivity, dielectric loss and loss tangent of mixed melting polymer pellets were measured under temperature variance condition and measurement frequency from 0.5MHz to 5MHz in order to develop a real-time non-intrusive measurement technique for high performance waste plastic separation. Various volume fractions of non-polar polyethylene (PE) and polar polyethylene terephthalate (PET) were used as the mixed polymer pellets. As the results, with the volume fractions of PET from 0.05 to 0.22, as the temperature is increased up to melting point temperature and above mold temperature, the relative permittivity is decreased as the temperature is increased. However over melting temperature up to the mold temperature, the relative permittivity is slightly increased as the temperature is increased. On the other hand, the dielectric loss and loss tangent are not affected by the temperature variance, and the dielectric loss and loss tangent are increased as the measurement frequency is increased. As the conclusions, at molding temperature 180°C (453K), the highest sensitivity of dielectric property is the relative permittivity. Meanwhile, the highest linearity relationship between PET volume fraction and predicted relative permittivity is achieved at the measurement frequency of 5MHz. From relative permittivity measurement in these conditions, the performance to distinguish PET volume fraction 0.05 from PE volume fraction 0.95 is achieved in the mixed melting polymer pellets. Therefore, the relative permittivity measurement for waste plastic separation has a possibility to achieve the high purity recycled plastics as compared with conventional methods.

No Swelling Here: Polar Polyethylene by Direct Insertion Polymerization

No Swelling Here: Polar Polyethylene by Direct Insertion Polymerization

Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

Biomineralization of hydroxyapatite (Ca10(PO4)6(OH)2) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 × 10−3 to 3.1 × 10−3 OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

Few Layer Graphene Matrix for Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

We present the employment of few layer graphene (FLG) as a matrix for the analysis of low molecular weight polymeric compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The practicality of FLG as a matrix for MALDI experiments is demonstrated by analyzing low molecular weight polymers, polar polyethylene glycol (PEG) of 1000 Da and nonpolar polymethylmethacrylate (PMMA) of 650 Da. The high quality MS spectra without low-mass interference signals without any further sampling procedure were acquired.

Effects of Additives on Water Solubilization Capacity and Intermicellar Interaction in Heptane/Hexanol/Tritonx-100/Water Microemulsion

The water solubilization capacity (W0) of microemulsion system determines its physicochemical properties and interior structures. In this study, the effects of different kinds of additives such as inorganic salt, nonaqueous polar solvent, organic salt, amino acid, and polyethylene glycols (PEG series) on the water solubilization behavior of heptane/hexanol/TritonX-100/water microemulsion system have been studied in detail. The influence mechanism of every additive on W0 has also been proposed and discussed. Furthermore, the droplet size distribution and the interaction among the droplets have been investigated by dynamic light scattering technique with the presence of additives. The result shows that the hydrodynamic diameter of microemulsion droplet and the attractive interaction between the droplets increase with the increase of the water content and the additive concentration. This work presents a facile method to adjust the structure parameters and the interface strength of microemulsion system by adding additive to the system, and to direct the applications of microemulsion system in nanomaterials preparation and drug controlled release.

Enantiomeric separation and quantification of ephedrine-type alkaloids in herbal materials by comprehensive two-dimensional gas chromatography

The separation of ephedrine-type alkaloids and their enantiomers in raw herbs and commercial herbal products was investigated by carrying out enantioselective separation in the first-dimension column (containing β-cyclodextrin as the chiral selector) of a comprehensive two-dimensional gas chromatography (GC × GC) system, whereas a polar polyethylene glycol capillary column was used for separation in the second dimension. Naturally occurring ephedrine-type alkaloids and their synthetic analogues (enantiomeric counterparts) were adequately resolved from each other, as well as from potential interference species in the sample matrix using GC × GC, whereas single column GC analysis was unable to separate all the alkaloids of interest. Detection limits in the order of 0.1–1.3 μg/mL and linearity of calibration with R 2 ≥ 0.999 over approximately the range of 0.5–100 μg/mL for the quantitative determination of various ephedrine-type alkaloids were obtained. The commercial herbal products tested contained mostly (−)-ephedrine, (+)-pseudoephedrine, (−)- N-methylephedrine and (−)-norephedrine, with concentrations in the range of 40–2100, 0–1300, 15–300 and 0–30 μg/g of the product, respectively, and repeatability of analysis was generally in the range of 1–5%. The present GC × GC method is effective and useful for the determination of the dosage levels of the principle ephedrine-type alkaloids in commercial health supplements and complex raw herb formulations, as well the differentiation of ephedrine-containing products that were derived from natural plant or synthetic sources, e.g., simply by visualizing the presence or absence of the enantiomeric pairs of (±) ephedrine and (±)- N-methylephedrine in the GC × GC chromatograms.

Importance of Debye and Keesom Interactions in Separating m-Xylene and p-Xylene in GC-MS Analysis Utilizing PEG Stationary Phase

In electron impact gas chromatography (GC)-mass spectrometry analysis of a complex mixture, such as gasoline, two coeluting solutes can be distinguished if each has a unique major ion. The boiling-point difference between m-xylene and p-xylene, which also has identical major ions (mz-1: 91 and 106 Da), is 0.77 degrees C. These cannot be separated even on a crossed-linked polydimethylsiloxane capillary column, which has a minimum of 5000 plates/m. They are separated on a crossed-linked polar polyethylene glycol (PEG) capillary column. GC separation on a stationary phase depends on the relative strengths of solute-solute, stationary phase-stationary phase, and solute-stationary phase interactions. Although the calculated molar electronic polarization and refractivity factor of Lorenz-Lorentz equation for m-xylene and p-xylene are nearly equal because of its greater dipole moment difference (0.30 and 0.02), the calculated orientation polarization of m-xylene is 80 times greater than p-xylene. This implies the dipole reinforcement through inductive polarization by the hydroxyl of PEG stationary phase molecules is greater on m-xylene than p-xylene. In addition, as the permanent dipole moment of m-xylene is 15 times greater than p-xylene, m-xylene has a stronger Keesom interaction with PEG. In order for m-xylene and p-xylene to solvate in PEG, analytes must overcome the PEG-PEG Keesom/hydrogen bonding interaction forces. Physical and chemical parameters indicate that compared with p-xylene, m-xylene has a greater Debye-Keesom interaction tendency with PEG molecules. This is supported by the 0.12-min. retention-time difference between them.

Chromium-mediated aldol and homoaldol reactions on solid support directed towards an iterative polyol strategy

Chromium-Reformatsky and chromium-homoaldol reactions run under neutral and mild reaction conditions. They are highly chemoselective, tolerant towards most common functional groups, and are not prone to retroaldol reactions. Initial studies directed to transfer these homogeneous chromium-mediated solution-phase reactions to solid phase are presented. The main objective was to develop a methodology to aid a combinatorial iterative strategy to polyols (polyketides) on solid phase. A general reactivity problem was observed with polystyrene based resins compared to the solution-phase reactions, independent if the electrophilic (aldehyde) or nucleophilic (bromide) end of the polyol chain was supported to the resin. A complicated penetration, or loss of the polar solvent environment after penetration into the resin, might be responsible for the reduced reactivity. Application of either a soluble polystyrene resin or a polystyrene resin with a polar polyethylene glycol tether resulted in improved yields.

Evaluation of polar ethylene copolymers as fire retardant nanocomposite matrices

A range of nanocomposite materials was prepared under high shear based on polar polyethylene (PE) copolymer matrices. An organically modified bentonite was used as the smectite clay, with intercalation shown to occur in the presence of poly(ethylene- co-methyl acrylate) (EMA), poly(ethylene- co-vinyl acetate) (EVA), poly(ethylene- co-methyl acrylate- co-acrylic acid) (EMAAA) and poly(ethylene- g-maleic anhydride) as evidenced by small angle X-ray scattering measurements. The thermal stability and flame retardant properties of the polymer–clay composites were measured by thermogravimetry and cone calorimetry, with significant improvements in the heat-release rates and thermal stability of all systems. Enhanced char formation was shown to be responsible for reducing degradation under oxidative conditions.

Thermal degradation studies of different polar polyethylene copolymers

AbstractThe thermal degradation of different polar polyethylene copolymers, ethylene/methylacrylate (EMA), ethylene/ethylacrylate (EEA), ethylene/butylacrylate (EBA), ethylene/methylmethacrylate (EMMA), and ethylene/hydroxyethylmethacrylate (EHEMA), was studied by using thermogravimetric analysis (TGA), infrared analysis (FTIR), and size exclusion chromatography (SEC). Weight loss measurements of the different copolymers were performed at 333°C by using a nitrogen atmosphere in a TGA instrument. The samples thus aged were then characterized with the help of FTIR and SEC. Degradation reactions, such as ester pyrolysis, chain scission, and gelation, were investigated. EBA, EEA, and EHEMA undergo ester pyrolysis, which is affected by the structure of the ester moiety. EHEMA reacts additionally by transesterification and thus forms crosslinks. EMA and EMMA do not react by ester pyrolysis. It is concluded that the reaction products formed during ester pyrolysis support chain scission, and therefore, these reactions are observed more for EBA and EEA than for EMA and EMMA. Finally, the rate of chain scission is higher for EMMA than for EMA. This is explained as being due to an initiation of chain scission at the α—C—C bond, in which formed radicals are stabilized by the additional methyl group in EMMA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1465–1473, 2002; DOI 10.1002/app.10510

Composite polymer electrolytes using surface-modified fumed silicas: conductivity and rheology

We report results from our studies on composite polymer electrolytes based on novel surface-modified fumed silicas. The electrolytes were prepared by dispersing fumed silica in a matrix formed by methyl-capped polyethylene glycol and lithium salt. Silicas with widely different surface chemistries were synthesized in order to study the effects of surface modification, with the attached surface groups ranging from non-polar alkyl moieties (C1 or C8) to polar polyethylene oxide (PEO) oligomers (MW∼200). We find, rather surprisingly, that the conductivity is independent of the type of surface group present on the silica. Moreover, the conductivity decreases only slightly on addition of fumed silica, even at high weight fraction of solids. In contrast, the rheological properties of the composites are strongly affected by both the silica surface chemistry and weight fraction. Dynamic rheology measurements reveal that fumed silicas with silanol and octyl coverage both flocculate into gels (networks). The resulting materials are mechanically stable, with the elastic modulus of the gel being strongly dependent upon weight fraction of solids. The PEO-modified silica, in contrast, gives rise to a low-viscosity suspension where the silica units exist as distinct, non-interacting species. The findings of this study have significant implications for future work on composite electrolytes, in that we can tailor the mechanical properties of the system without affecting the electrochemical behavior.