Doping behavior of water-soluble π-conjugated polythiophenes depending on pH and interaction of the polymer with DNA

Doping behavior of two kinds of water-soluble polythiophenes (PThs) (PTh with a CH₂CH₂CH₂SO₃M substituent at the 3-position, P3(RSO₃H)Th, and poly(ethylenedioxythiophene), PEDOTh) has been investigated spectroscopically at various pH under air. The p-doped (or oxidized) state of P3(RSO₃M)Th is stable at pH=1.0, whereas at pH levels higher than 4, the polymer is undoped. To the contrary, the p-doped state of PEDOTh is stable over a pH range of 1 to 7. Mixing of PEDOTh and a DNA (poly(G-C)₂) in a Tris buffer solution leads to a change of the UV-visible spectrum and precipitation of their adduct, supporting formation of an adduct between PEDOTh and poly(G-C)₂.     

Effect of the type of polymer functional groups on the structure of its film formed on the alumina surface – Suspension stability

The effects of polymer functional group and solution pH on stability of colloidal Al₂O₃ water suspension were studied. Both the nonionic polymers: polyethylene glycol (PEG), polyethylene oxide (PEO) and the ionic ones: polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA) were used in the experiments. The following methods were applied: turbidimetry (stability measurements), spectrophotometry (determination of polymer adsorption), viscosimetry (thickness of polymer adsorption layer), potentiometric titration (solid surface charge density) and microelectrophoresis (potential zeta). It was shown that anionic polyacrylic acid is both the most effective stabilizer (at pH 9) and flocculant (at pH 3) of the alumina suspension. Its carboxyl groups have the greatest affinity for the surface active sites (the largest adsorption) of all functional groups present in the other examined polymers. The latter, i.e. hydroxyl (PEG, PEO, and PVA) and acetate (PVA) show a much lower affinity for the Al₂O₃ surface (negligible adsorption) and minimally affect the stability of the alumina-solution system.     

Effect of blend ratio on the dynamic mechanical and thermal degradation behavior of polymer–polymer composites from low density polyethylene and polyethylene terephthalate

Microfibrillar polymer–polymer composites (MFCs) based on low-density polyethylene (LDPE) and polyethylene terephthalate (PET) were prepared by cold drawing-isotropization technique. The weight percentage of PET was varied from 5 to 45 %. Microfibrils with uniform diameter distribution were obtained at 15 to 25 wt% of PET as evident from the scanning electron microscopy (SEM) results. Dynamic mechanical properties such as storage modulus (E′), loss modulus (E″) damping behavior (tan δ) were examined as a function of blend composition. The E′ values were found to be increasing up to 25 wt% of PET. An effort was made to model the storage modulus and damping characteristics of the MFCs using the classical equations used for short-fiber reinforced composites. The presence of PET microfibrils influenced the damping characteristics of the composite. The peak height at the β-transitions of loss modulus was lower for MFCs with 25 % PET, showing that they had superior damping characteristics. This phenomenon could be correlated with the PET microfibrils morphology. The thermal degradation characteristics of LDPE, neat blends and microfibrillar blends (MFBs) were compared. The determination of activation energy for thermal degradation was carried out using the Horowitz and Metzger method. The activation energy for thermal degradation of microfibrillar blends was found to be higher than that for the corresponding neat blends and MFCs. The long PET microfibrils present in MFBs could prevent the degradation and enhance the activation energy.     

Tuning the crystallite size of monoclinic ZrO_2 to reveal critical roles of surface defects on m–ZrO_2 catalyst for direct synthesis of isobutene from syngas

The effects of crystallite size on the physicochemical properties and surface defects of pure monoclinic ZrO_2 catalysts for isobutene synthesis were studied. We prepared a series of monoclinic ZrO_2 catalysts with different crystallite size by changing calcination temperature and evaluated their catalytic performance for isobutene synthesis from syngas. ZrO_2 with small crystalline size showed higher CO conversion and isobutene selectivity, while samples with large crystalline size preferred to form dimethyl ether(DME) instead of hydrocarbons, much less to isobutene. Oxygen defects(ODefects) analyzed by X-ray photoelectron spectroscopy(XPS) provided evidence that more ODefectsoccupied on the surface of ZrO_2 catalysts with smaller crystalline size. Electron paramagnetic resonance(EPR) and ultraviolet–visible diffuse reflectance(UV–vis DRS) confirmed the presence of high concentration of surface defects and Zr~(3+) on mZrO_2-5.9 sample, respectively. In situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS) analysis indicated that the adsorption strength of formed formate species on catalyst reduced as the crystalline size decreased. These results suggested that surface defects were responsible for CO activation and further influenced the adsorption strength of surface species, and thus the products distribution changed. This study provides an in-depth insight for active sites regulation of ZrO_2 catalyst in CO hydrogenation reaction.     

Effect of type of polymerization catalyst system on the degradation and stabilization of polyethylenes in the melt state—Part 4: Comparative antioxidant effectiveness on organoleptic extractables

Several polyethylene resins using Ziegler, metallocene, and Phillips catalyst technologies were examined to obtain more detailed information about the effect of different polymerization catalyst systems on the production of extractable thermo-oxidative degradation products formed during melt processing cycles. This produces volatile organoleptic components (VOCs and extractable) such as hydrocarbons, alcohols, aldehydes, ketones, and carboxylic acids. Although some of the oxidation products are in-chain bound, many are produced as free, easily extractable entities or volatile components. The purpose of this study is to identify the nature of the products by gas chromatography–mass spectrometry (GC–MS) and FTIR analysis. The identity of the VOCs formed is necessary to modify the product's quality or establish which are toxic and/or leachable with food products. The results show that the evolution of carbonyl products, nature, and quantity is influenced significantly by the polymer type and catalyst used. Over 300 organoleptics low molar mass degradation products, such as alkane, alkene, carbonyl, and alcohol functionalities were detected by GC–MS analysis coupled with FTIR analysis on hexane extractables. Certain stabilizers can control the generation of certain functionalities and inhibit others. Of importance was the discovery of the relationship between additive activity and structure and inhibition of the formation of specific types of oxidation functionalities to a particular catalyst system.     

Effect of annealing and silylation on the strength of melt-spun Ni–Mn–Ga fibres and their adhesion to epoxy

Single crystals of ferromagnetic Ni–Mn–Ga shape memory alloys show magnetic-field and stress induced twinning, leading to shape memory. Adaptive composites can thus be produced by embedding single crystalline particles or bamboo-structured Ni–Mn–Ga fibres into a polymer matrix. To guarantee a durable performance of these composites, adhesion between reinforcement phase and matrix should be quantified and optimised. The influence of annealing and surface treatment with an aminosilane of melt-spun Ni–Mn–Ga fibres on their strength and adhesion to an epoxy matrix was investigated using single fibre tension and fragmentation tests. Annealing of the melt-spun Ni–Mn–Ga fibres changed the surface from a “pimpled” to a smooth microstructure. This resulted in a reduced adhesion of the annealed fibres in comparison to the as-spun fibres embedded in an epoxy matrix. As-spun fibres exhibited an interfacial shear strength (IFSS) comparable to the shear strength of the epoxy matrix so that the silylation did not change the adhesion significantly. For the annealed fibres, the silane treatment improved the IFSS by 67%. Furthermore, the silylation increased the fracture strength of the Ni–Mn–Ga fibres due to surface flaw healing or forming of a protective surface coating.     

Study on the role of tannic acid–calcium oxide adduct as a green heat stabilizer as well as reinforcing filler in the bio-based hybrid polyvinyl chloride–thermoplastic starch polymer composite

In this study, we prepared a green heat stabilizer tannic acid–calcium oxide (TA–CaO) adduct in a green method and its efficacy was studied in a bio-based polyvinyl chloride-thermoplastic starch polymer matrix. The composite was prepared in a green pathway by melt mixing. CaO in the prepared complex also acted as a reinforcing filler in the composite. The addition of TA–CaO adduct in place of lead carbonate improved all the physical and chemical properties of the composite. The tensile strength and flexural strength improved to 102% and 127%, respectively, in comparison with similar percentage of lead carbonate and TA–CaO adduct. The composite with 15 phr loading of TA–CaO showed improved properties compared with other TA–CaO loaded composites.     

A Study on the Change in the Dielectric Properties of CR-39 Polymer Track Detector Due to α-Irradiation in the Frequency Range from 100 Hz to 100 kHz

The dielectric properties in the frequency range from 100 Hz to 100 kHz of polyallyldiglycol carbonate “CR-39” samples before and after irradiations have been investigated. The irradiations were verified with 4.84 MeV α-particles at different irradiation times. The dependence of the dielectric properties of unirradiated and irradiated samples at room temperature (25°C) and constant frequency (10 kHz) on the total number of α-particles have been studied. It was found that the CR-39 can be used as a detector for high α-particles fluxes.     

The roles of H-bonding, π-stacking,and antiparallel CO ⋯ CO interactions in the formation of a new Gd(III) coordination polymer based on pyridine-2,6-dicarboxylic acid

This study reports the synthesis of a new catenane Gd(III) complex using pyridine-2,6-dicarboxylic acid (H₂pydc) as ligand. The structure of [Gd(pydc)(Hpydc)(H₂O)₂]_n (1) was characterized by IR spectroscopy, X-ray diffraction methods and the elemental analysis to check the purity of the compound. On the basis of crystallographic data, compound 1 contains a Gd(III) metal center that is coordinated to seven oxygen atoms of two tridentate and one monodentate H₂pydc ligands and two coordinated water molecules. Other lanthanoid complexes involving this ligand are available in the literature; however, this is the first example where a combination of monoanionic (Hpydc⁻) and dianionic (pydc^2 −) forms of the ligand counterbalance the Gd^3 + metal center. The intermolecular interactions in this novel system consist of different kinds of H-bonding and π-stacking interactions in addition to antiparallel CO ⋯ CO interactions which have been analyzed using DFT calculations and the Bader's theory of “atoms in molecules”.     

Analysis and estimation/prediction of the disk stack centrifuge separation performance – Scaling from benchtop fixed rotor type to disk stack centrifuges

ABSTRACT

A mathematical model is proposed to calculate the total separation effectiveness in terms of GT for a disk stack centrifuge taking account of the variation of the centrifugal force with a position in the disk. In practice, the centrifuge ability/force is often referred as Relative Centrifugal Force (RCF) or G number, which is a multiple of the centrifugal acceleration over the gravitational acceleration. As the radial velocity varies it is important to integrate the relative centrifuge force, here in terms of the G number along the path taking account of the change in velocity. The separation effectiveness, GT is defined as an integrated product of local G number, G(x) and local residential time (dt), where dt is the time taken for the bulk fluid to traverse a distance from r to r+ dr. The GT value calculated for a disk type centrifuge can be compared with the GT value of others and compared with a bench top fixed rotor centrifuge. An industrial centrifuge would be expected to be able to deliver similar separation performance to a pilot or a lab scale one, if operated at the same/similar value of GT. This would allow the performance of a full-scale clarifier to be predicted. This model is, in essence, a simple alternative to the Sigma concept.     

Phase Equilibria in the Sodium-Acetate–Sodium-Formate–Water System at Temperatures of from 0 to–22°C and the Anti-icing Properties of Compositions Based on These Salts

Phase equilibria in sections of the phase diagram of the sodium-acetate—sodium-formate–water ternary system with component ratios of NaCH₃COO : NaHCOO varying from 3 : 1 to 1 : 3 are studied, and the anti-icing properties of the compositions based on these salts are investigated. Polythermal sections of ice crystallization and the ice-melting ability for each of the prepared compositions are calculated from the experimental data. The formulation with a 1 : 1 ratio of the considered salts has a eutectic temperature of?22°C, which is 4–6°C lower than the eutectic temperatures of systems based on the individual salts. This formulation displays a high ice-melting ability and can be recommended for use as a de-icer in airports.     

Exploring the Effects of Plant Odors,from Tree Species of Differing Host Quality,on the Response of <Emphasis Type="Italic">Lymantria dispar</Emphasis> Males to Female Sex Pheromones

A widely accepted hypothesis for host-plant selection in herbivorous insects is that ovipositing females select host-plants that maximize the survival and performance of their offspring. However, numerous studies indicate that this is not always the case for polyphagous species. Lymantria dispar is a highly polyphagous forest defoliator and has flightless females in some subspecies, resulting in a limited capacity to make host-choices. Males of other Lepidopteran species utilize a combination of sexual pheromones and plant volatiles in their mating choices and exhibit preferences among plant species. We explored the behavior of L. dispar males towards sexual pheromone in the presence and absence of plant volatiles and their ability to discriminate between two plant species with different degrees of suitability for their offspring: a suboptimal host (Pinus sylvestris), and an optimal host (Quercus robur). In no-choice wind tunnel assays, we found that rates of male success in locating a pheromone source were not altered by the presence of plant odors; however, the time spent by males searching for the pheromone source after reaching the full length of the tunnel was reduced by more than 50% in the presence of plant volatiles. In dual choice assays, males exhibited a clear preference for a combination of pheromones and plant volatiles over the pheromone alone. However, we did not find evidence of an innate ability to discriminate between the odors of optimal and suboptimal host plants. We discuss possible ecological and evolutionary explanations for these observations.     

Direct synthesis of formate from methanol oxidation on the CuPd[85∶15]{110}p(2×1) surface: induction of a new reaction pathway via a ligand effect

Thermal molecular beam studies of the oxidative dehydrogenation of methanol over the 1/4 ML and 1/2 ML oxygen predosed CuPd[85 15]{110}p(2 × 1) surfaces has been performed. Post reaction thermal desorption spectroscopy (TDS) clearly shows that during these experiments observable levels of formate are produced. This is in contrast to the results of similar experiments performed over oxidised Cu{110} surfaces which showed little formate production. It is hypothesised that the alloying in the surface region causes this new reaction pathway to appear as a consequence of a modification of the stability of one or more of the reactive intermediates produced in this reaction. It is proposed that these modifications of adsorbate stability are due to a ligand effect arising from the presence of Pd in the second layer of the selvedge.