Aqueous Solutions Of Polyethylene Oxide Research Articles

Photophysical studies of a coumarin derivative in the aqueous solution of three different classes of copolymers

In this article we have reported the modulation of spectral behavior of a hydrophilic coumarin based molecule 7-(diethylamino) coumarin-3-carboxylic acid (7-DCCA) in aqueous solution of polyethylene oxide (PEO)-polypropylene oxide (PPO) block copolymers with different structures and hydrophobicity. Linear triblock copolymer namely Pluronic (F-98, F-38, P-84), its X-shaped counterpart namely Tetronic (T-1304, T-1307) along with a reverse Pluronic (17-R4) were utilised with a temperature variation from 10 °C to 50°C and 7-DCCA was used as the probe to observe the changes in photophysical aspect. Of the studied copolymers, 10 wt% T-1307 and F-38 face difficulty in micelle formation owing to their hydrophilic nature and lower molecular weight PPO blocks. Also, 0.1 wt% 17-R4 remains as single-coils in the studied temperature range. Hence, these copolymers induce a different environment on the photophysics in 7-DCCA as compared to copolymers that form usual micelles (10 wt% T-1304, P-84, F-98). With increasing temperature, a persistent blue-shift in absorption and excitation spectra of the probe could be noticed upon addition of 10 wt% T-1304, T-1307, F-98, P-84, as well as 0.1 wt% 17-R4. The fluorescence emission maximum of the probe blue-shifted in T-1304, T-1307, F-98 and P-84 solutions whereas a red-shift was noticed in 17-R4. The fluorescence emission decays collected in the presence of T-1304, T-1307, F-38, F-98 and P-84 were fitted using tri-exponential functions while bi-exponential functions were used in the presence of 17-R4. A dip-rise-dip anisotropy decay pattern was observed for T-1307, F-38, and 17-R4 whereas, bi-exponential functions were used for T-1304, F-98 and P-84. The constitution of the copolymer along with its molecular properties helped us to correlate the obtained data.

Soy Protein Nanofibers Obtained by Solution Blow Spinning

The climate crisis, growing pollution of the environment with waste, and ubiquitous microplastics have encouraged the search for new methods and new opportunities to use natural materials in the least harmful processes. Replacing synthetic materials with raw materials is not only a matter of “fashion”, but also a necessity. Therefore, this study aimed to produce fibers from an aqueous solution containing the highest possible concentration of soy protein isolate (SPI) through solution-blowing. As the aqueous solution of SPI has no fiber-forming potential, polyethylene oxide (PEO) was used as the carrier/matrix. The rheology of the aqueous PEO solution and PEO/SPI blends (flow curves, loss modulus, and storage modulus) was then analyzed. The proportions of the PEO/SPI mixtures and the process parameters were determined on this basis. As a result of the conducted research, nanofibers were produced from water solutions of PEO/SPI with a soy protein content of up to 7.88%, with a PEO share of 1.25%. The average diameter of the obtained fibers was 225–495 nm, depending on the process parameters and SPI content—as the SPI content in the PEO/SPI mixture increased, the average fiber diameter decreased. The production of nanofibers with a high soy protein content increases their application possibilities. Firstly, due to a much larger surface area, and secondly, due to the presence of numerous functional groups in the protein structure, which can be a place of attachment for additional compounds that give the obtained nanofibers the desired properties.

The Water-Polymer Method of Hydroperforation of Oil and Gas wells

The aim of the study is to develop an efficient, innovative method of perforating oil and gas well casing strings with a high-velocity stream of polymer solution that conserves resources and energy and meets the requirements for environ- mentally friendly hydrocarbon production. New knowledge about the dynamics of polymer solutions in the model conditions of flow through the nozzles of the hydro perforator, which form a high-velocity jet, became the main scientific basis for substantiating the water-polymer method of hydro perforation of oil and gas wells. The study of the reaction of polymer solutions to tension hydrodynamic influence allowed to formulate a structural concept, the "common denominator" of which is the strong deformation effect of tension hydrodynamic field on high molecular weight coils, which, according to nonequilibrium thermodynamics, should cause a kind of high elasticity. Peculiarities of hydrodynamic behavior of aqueous polymer solutions in model conditions of flow through jet-forming nozzles are studied. The possibility of transition to a highly developed state of the tangle of polyethylene oxide macromolecules in the conditions of the inlet section of the nozzle of the hydro perforator has been experimentally proved. The mechanism of perforation of oil and gas wells by a high-velocity jet of an aqueous polymer solution has been elucidated. It is proved that the mechanism of the high cutting ability of the high-velocity jet of aqueous polymer solution is the destructive effect of the dynamic pressure of water-polymer jet "reinforced" by highly developed macromolecular chains in the inlet nozzles of the hydro perforator nozzles under the action of tensile leakage. Experimental and industrial testing of the method of perforation of wells by a high-speed jet of an aqueous solution of polyethylene oxide confirmed the practical and economic feasibility of its use.

Rheological Characterization of High-Molecular-Weight Polyethylene Oxide—An Extensive Parametric Experimental Study

Abstract A comprehensive study of the rheological characterization of the aqueous solutions of polyethylene oxide (PEO) with molecular mass of 4 × 106, 5 × 106, and 8 × 106 g/mol, respectively, named (4 miDA), (5 miDA), and (8 miDA) was conducted. A large batch of samples of 4 miDA PEO with concentrations varying from 0.1% to 3%, representing the range of dilute solutions to very high viscous hydrated gels, were tested. Steady-state shear flow and oscillatory measurements are reported. Cross, Carreau, and Carreau–Yasuda models were used to describe the shear-thinning behavior within the shear rate range (0.001 ≤ γ˙ ≤ 3000 s−1). Experimental findings were validated with published results under the same operating conditions within specified shear rate ranges (0.1 ≤ γ˙ ≤ 100 s−1). We find that the behavior of PEO under shear is highly dependent on the rheometer, material, and operating procedures. Oscillatory measurements were carried out to determine the complex properties of the PEO solutions in the frequency ω and strain amplitude γ ranges of 0.01 ≤ ω ≤ 100 rad/s and 0.01 ≤ γ ≤ 1000%, respectively. Higher magnitudes of dynamic moduli (G/ and G//), zero (η0) and infinite (η∞) shear rate viscosities, resonant frequencies (ωres), linear viscoelastic regions (LVER), and higher relaxation time constants (λ) were observed with increasing concentration and molecular weight. The rheological response of the PEO polymeric solutions was further clarified via Lissajous curves. The aim of this work is to characterize the behavior of the 4 miDA PEO prior to its use in an experimental investigation of the secondary flows of viscoelastic fluids in noncircular channels.

What determines the drop size in sprays of polymer solutions?

The effect of viscoelasticity on sprays produced from agricultural flat fan nozzles is investigated experimentally using dilute aqueous solutions of polyethylene oxide (PEO). Measurements of the droplet size distribution reveal that polymer addition to water results in the formation of overall bigger droplets with a broader size distribution. The median droplet size is found to increase linearly with the extensional relaxation time of the liquid and to be well captured by a simple empirical expression in terms of non-dimensional Weber and Deborah numbers. We show that the increase in droplet size with increasing viscoelasticity can be partly attributed to an increase of the wavelength of the flapping motion responsible for the sheet breakup, resulting in the formation of larger ligaments from which droplets are formed. We also show that droplet size distributions, rescaled by the average drop size, are well described by a compound gamma distribution with parameters n and m encoding for the ligament corrugation and the width of the ligament size distribution, respectively. These parameters are found to saturate to values n = 4 and m = 4 at sufficiently high polymer concentrations. • Viscoelasticity leads to larger droplets in sprays for agricultural flat fan nozzles. • Polymer additives can therefore be used to reduce airborne spray drift. • The median droplet size increases linearly with the extensional relaxation time. • Droplet sizes are Gamma distributed with broad drop and ligament sizes with polymers.

Perforacja odwiertów ropnych i gazowych za pomocą strumienia roztworu polimeru o dużej prędkości

ABSTRACT: The work is devoted to the development of a technological process for perforating oil and gas well casing strings by a high-velocity jet of a polymer solution. The proposed method of well perforation refers to methods for the secondary opening of productive deposits in the well by hydrojet perforation of the casing strings, annulus cement ring (stone) and rock. The new knowledge about the dynamics of polymer solutions under the conditions of flow through the jet-forming nozzles of a hydroperfora-tor, which create a high-velocity jet, became the main scientific basis for this method of hydroperforation of oil and gas well casings. The study of the reaction of polymer solutions to the hydrodynamic effect with stretching led to the formulation of a structural con-cept, the “common denominator” of which is a strong deformation effect of the hydrodynamic field on macromolecular coils, which in terms of nonequilibrium thermodynamics generates a kind of rubber-like high elasticity. The peculiarities of the hydrodynamic behaviour of aqueous solutions of polyethylene oxide (PEO) during flow under the conditions of various nozzle jets were modelled, and the regularities of the influence of the resulting dynamic structures on the efficiency of hydrojet water–polymer perforation were established. The mechanism of hydrojet water–polymer perforation of casing columns in oil and gas wells was clarified. The mecha-nism of the large destructive capacity of a high-velocity polymer solution jet is not due to the reduction of turbulent friction by small polymer additives (the Toms effect), but consists in the destructive action of the dynamic pressure of the water–polymer jet “rein-forced” by highly developed macromolecular coils and the dynamic structures formed under the action of extended flow in the inlet section of the hydroperforator nozzles. The method of perforating oil and gas well casings comprises the exact determination of the perforation zone in lowering on production tubing a hydroperforator with 2–4 jet flow-forming nozzles for directing hydrojet to the zone of perforation, sealing the inside cavity of tubing pipes and the jet operators, actuating a ball valve at the bottom of the jet operators, sealing the annulus with a self-sealing gland and supplying the working cutting fluid to the tubing – which differs in that the aqueous solution of PEO used as a working cutting fluid has a molecular weight of 6 · 106 and a concentration 0.003–0.007% by weight and a working pressure of 100–300 MPa. The PEO additives are very environmentally friendly because this polymer is not harmful to humans or the environment. Experimental and industrial testing of this method of well perforation, which was carried out during the secondary opening of a reservoir at a well in the Carpathian oil- and gas-bearing region, confirmed the practical and eco-nomic feasibility of its use.

High-efficiency casing perforation oil and gas wells

The energetic capabilities of a high-speed jet of an aqueous solution of polyethylene oxide (PEO) with varying concentration and different outflow pressures from a jetforming nozzle were investigated using the length of the forming channel in the model of the casing of an oil and gas well, cement sheath and rock layer, as well as impact of the jet force on a metal plate fixed on a physical pendulum. The experimental data made it possible to obtain a calculated dependence in a dimensionless form to determine the quality (initial sections) of jets of aqueous solutions with different concentrations and molecular weights of PEO, considering the real parameters of the jet-forming nozzles of the hydroperforator. A comprehensive study of the perforation process made it possible to substantiate the mechanism of the high destructive capacity of a high-speed jet of polymer solution. It has been established that the mechanism of the high destructive capacity of the polymer water jet is not due to the Toms effect, but caused by the destructive action of the dynamic pressure of the polymer water jet «reinforced» by strongly unfolded macromolecular chains under the action of a tensile flow in the inlet area of the jet forming nozzle of the hydroperforator. Keywords: perforator; jet nozzle; jet quality; casing; cement sheath; rock; Toms effect.

Effects of crosslinking on the physical solid-state and dissolution properties of 3D-printed theophylline tablets

Crosslinking is an established treatment to alter the physicochemical and functional properties of polymers through the creation of bonds between the polymer chains. Polymers can be crosslinked via radiation in the presence of photo-initiator. The aim of the present study was to formulate 3D-printed theophylline (THEO) tablets using polyethylene oxide (PEO) as a carrier polymer, and to study the influence of crosslinking on the drug release behavior. The tablets were 3D-printed using the aqueous solution of PEO and THEO (80:20 w/w) with a micro-extrusion-based printing setup. A photo-initiator (4-hydroxybenzophenone) was added into the printing solutions, and the injectability of the solutions was investigated prior to printing. The 3D-printed tablets were crosslinked after printing using ultraviolet (UV) or gamma-radiation, and crosslinking was verified by means of Fourier-transform infrared (FTIR) spectroscopy. The maximum injection force of aqueous printing solutions of PEO and THEO was close to that observed with the pure PEO solution. Increasing the number of printing layers in the 3D-printed tablets resulted in a slower drug release in vitro. Gamma-radiation in a nitrogen environment and UV-crosslinking made the carrier polymer (PEO) less water-soluble, but such crosslinking did not affect the release rate of the tablets. Surprisingly, even faster drug release behavior was found with the crosslinked 3D-printed tablets compared to that of non-crosslinked tablets. More research work is needed on the impact of 3D-printed tablet layering thickness and crosslinking for tailoring drug release behavior.

Hydrogen-bonded network enables semi-interpenetrating ionic conductive hydrogels with high stretchability and excellent fatigue resistance for capacitive/resistive bimodal sensors

The construction of ionic conductive hydrogels with complex deformation tolerance and excellent fatigue resistance is highly demanded yet challenging. Herein, a semi-interpenetrating ionic conductive hydrogel (SICH) is fabricated by a hydrogel-network constrained polymerization of 1-butyl-3-vinylimidazole tetrafluoroborate and acrylic acid in polyethylene oxide aqueous solution. Ascribing to the formation of a dense intermolecular hydrogen-bonded network, the SICH is capable of being stretched up to ~300%, compressed to ~85%, and recovered immediately when the external force is fully released. The SICH can readily work as a high deformation-tolerant ionic conductor for capacitive/resistive bimodal ionic sensors. The ionic sensor not only showed a wide response range to dynamic pressures (0–8 kPa) and excellent cycling stability (500 cycles) in a capacitive mode, but also demonstrated high sensitivity (gauge factor of ~1.1), excellent linear response (0–300% strain) and fast response time (80 ms) in a resistive mode. As a demonstration, a wearable bimodal SICH ionic sensor was assembled, showing high sensitivity, linearity, wide response range and great durability in detecting complex human motions including speaking and various joint bending.

Effect of polymer solutions on the propagation and structure of freely translating vortex rings

We experimentally study the propagation of vortex rings in aqueous solutions of polyethylene oxide (PEO400) and hydrolysed polyacrylamide (PAMH25). We study the canonical vortex ring as a caricature problem to the phenomenon of turbulent polymer drag reduction. PAMH25 has a similar infinite shear viscosity, ten times the zero shear viscosity and a thousand times the relaxation time of PEO400. We study the vortex rings generated by the trapezoidal motion of a piston-cylinder mechanism using PIV and PLIF at constant impulse. We see that PAMH25 drastically affects the propagation properties and the structure of the vortex ring, while PEO400 shows a behaviour similar to water. We conclude that PAMH25 retards the roll-up process of the ring, due to both the large range of plateau viscosities and large relaxation time. We surmise that the behaviour of the vortex ring observed might be used to unravel the mechanism of polymer drag reduction.

Development and Characterization of Electrospun Nanostructures Using Polyethylene Oxide: Potential Means for Incorporation of Bioactive Compounds

The development of processes for stabilization of the properties of bioactive compounds has been studied in recent years, and the use of nanotechnology is among the most discussed routes. The present work addressed the assembly of nanostructures using polyethylene oxide (PEO), the production of core-shell nanofibers (NFs) with bioactive compounds, and the evaluation of their microscopic and physical characteristics. Aqueous solutions of PEO were electrospun by varying different process and solution parameters (PEO and NaCl concentrations, feeding rate, the tip-to-collector distance (TCD), and applied voltage) in order to optimize production of nanostructures. The best condition obtained was evaluated to form core-shell NFs composed by jussara pulp as a source of anthocyanins. To assess the production of NFs with PEO and jussara pulp, feed solutions were prepared in acetate buffer (pH 4.5) with 6% PEO and 10% lyophilized jussara pulp, at a feeding rate of 150 μL·h−1 and TCD of 15 cm using an applied voltage of 10 kV to form core-shell NFs. The results revealed the formation of core-shell NFs with a diameter of 126.5 ± 50.0 nm. The outcomes achieved represent a crucial step in the application of anthocyanins in food systems as pigments, establishing a basis for further research on the incorporation of nanomaterials into foodstuff.

Polyethylene oxide-assisted dispersion of graphene nanoplatelets in poly(lactic acid) with enhanced mechanical properties and crystallization ability

Abstract Polyethylene oxide (PEO) was introduced to improve the dispersion of graphene nanoplatelets (GNPs) in poly (lactic acid) (PLA) matrix. GNPs were dispersed into PEO aqueous solution and freeze-dried to form PEO/GNPs masterbatch, followed by melt-mixed with PLA to prepare the nanocomposites. Three grades of PEO with different molecular weights were evaluated. It is found that adding very low loading of PEO (1 wt%) enhances the dispersion of GNPs in PLA matrix, resulting in remarkable improvement in elongation at break of PLA/GNPs without obviously sacrificing its modulus and tensile strength. Meanwhile, PEO reveals a synergistic effect with GNPs in promoting PLA crystallization. Moreover, GNPs enhances significantly the thermal stability of PLA, while further addition of PEO does not apparent compromise this effect. In addition, PEO with low molecular weight presents the best effect in improving the properties of PLA/GNPs nanocomposites.

Properties of Mixed Aqueous Solutions of Polyethylene Oxide and Carboxymethyl Cellulose with Different Degrees of Ionization and of Composite Films Prepared from Them

Rheological properties of mixtures of dilute and moderately concentrated aqueous solutions of carboxymethyl cellulose with various degrees of ionization and polyethylene oxide were studied. The range of compositions in which the viscosity of dilute solutions of the polymer blends shows negative deviation from the calculated additive values becomes broader in going from carboxymethyl cellulose sodium salt to partially ionized carboxymethyl cellulose. In concentrated mixed polymer solutions, the deviation of the viscosity from the additive values is always positive. Film composite materials were prepared, and their structural organization and compatibility of the polymers in the solid state were studied by dynamic mechanical analysis and X-ray diffraction analysis. Carboxymethyl cellulose with various degrees of ionization is incompatible with polyethylene oxide in the composite films obtained, and no new mixed structures are formed. Polyethylene oxide behaves as an interstructural plasticizer of the cellulose ether.

Synthesis and characterization of polyethylene oxide (PEO)—N,N-dimethylacrylamide (DMA) hydrogel by gamma radiation

Novel polyethylene oxide (PEO)/N,N-dimethylacrylamide (DMA) blend hydrogel (PD hydrogel) has been prepared by applying gamma radiation on aqueous mixture of PEO and DMA. Different concentrations of DMA have been blended with aqueous solution of PEO and then gamma radiation of different doses was applied to form the hydrogels. The synthesized hydrogels were characterized using Fourier transform infrared-attenuated total reflection spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM). The effect of different radiation doses, concentration of monomers on the properties of prepared hydrogel (PD hydrogel), such as gel content, swelling behavior, and mechanical properties (Tensile strength) was investigated thoroughly. Results showed that hydrogels were formed at the experimental conditions without the use of any external cross-linker. All the prepared hydrogels showed a significantly larger swelling ratio and improved mechanical strength.

CaBER vs ROJER—Different time scales for the thinning of a weakly elastic jet

In this paper, we demonstrate that the capillary thinning dynamics of a weakly viscoelastic jet follow a different timescale than a liquid bridge of the same fluid between two stationary surfaces for similar geometrical scales. The thinning in the latter case observed with capillary breakup extensional rheometry (or CaBER) follows a well established scaling of the radius with time for an elasto-capillary (EC) balance of R∼exp⁡(−t/3λ). However, for the thinning of the filaments between droplets in a jet, it was so far just assumed that the same scaling law holds. In this paper, we experimentally demonstrate that the jet thinning in a Rayleigh–Ohnesorge jetting extensional rheometer (or ROJER) follows a different scaling of R∼exp⁡(−t/2λ). This is demonstrated by a direct comparison of the thinning dynamics of weakly viscoelastic (Oh<0.01) aqueous solutions of polyethylene oxide in the two experimental setups, covering a wide range of jetting velocities or Weber numbers of 1–70. We demonstrate outgoing from a momentum balance that includes inertia and elasticity that this difference in scaling is due to a constant axial tension in the jet arising from the constant creation rate of new surface at the nozzle. Numerical simulations using the FENE-P model support this theory and demonstrate that in the exponential thinning regime of the jet the elastic stresses are indeed balanced by the axial tension (rather than by capillary pressure as in the EC balance regime of the CaBER experiment). It is readily shown from the reduced stress balance that this axial-elastic balance regime in the ROJER experiment leads to a faster exponential thinning, following the new scaling of R∼exp⁡(−t/2λ) that was experimentally observed. Furthermore, we observe both in experiment and simulation that a jet thinning does not exhibit a self-similar structure of the corner region where the thinning filament connects to the drop as it is generally observed for a filament with an axial tension decaying with the filament radius as in the CaBER. The resulting difference of 50% in extensional relaxation time λ extracted from ROJER experiments might require one to revisit previously reported ROJER experiments and is required for the correct evaluation of future jetting rheometry experiments.

Studies on the Interaction Between Polyethylene Oxide and Cationic Gemini/Conventional Surfactants

The interactions of two gemini surfactants (16-s-16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) in water and in aqueous solutions of polyethylene oxide (PEO, molecular weight = 100,000) having concentrations of 0.1–0.75 wt.% have been investigated at different temperatures using surface tension, viscosity and scanning electron microscopy (SEM) techniques. The results indicate that there is interaction between PEO and CTAB/gemini surfactants. The driving force which is responsible for the interaction is supposed to be the minimization of interfacial force between the non-polar polymer parts and the solvent water by association. It is observed that critical micellization concentration (cmc) values increase with temperature. It was observed that cmc values for geminis are very small as compared to CTAB. Viscosity increases with increase in polymer concentration and is higher in case of geminis. Dense micellar arrangement is seen for geminis than cationic CTAB as evident from SEM images. The result shows that the interaction of geminis is much higher than its conventional surfactant with PEO.

Thermodynamic properties of aqueous PEO–PPO–PEO micelles of varying hydrophilicity with added cisplatin determined by differential scanning calorimetry

Differential scanning calorimetry was performed on a series of aqueous solutions of polyethylene oxide–polypropylene oxide–polyethylene oxide, PEO–PPO–PEO (L101, P104, P105, and F108), amphiphiles in the low concentration regime (0–2 % mass v−1) to resolve the critical micelle concentrations of the neat polymers. Work was done from 2 to 10 % mass v−1 (in 2 % mass v−1 increments) amphiphilic copolymer concentrations and co-formulated with cisplatin concentrations (0–0.1 % mass v−1 in 0.02 % mass v−1 increments) to resolve any deviation in the enthalpy of micelle formation. Enthalpy–entropy compensation plots for each neat copolymer and each amphiphile solution mixed with cisplatin were obtained. Two types of behaviors were observed: a drug-influenced compensation temperature profile (P104) and a drug-invariant behavior (L101, P05, and F108) where the change in compensation temperature was <1 °C. Only neat P104 was found to be profoundly influenced by the presence of cisplatin that must reorganize the core–shell interface between the hydrophobic and hydrophilic regions of the micelle. Adding cisplatin lowered Tcompensation from 302.1 to 288.8 K for Pluronic P104.

Non-monotonic temperature response of polymer mediated interactions.

In a recent publication, Feng et al. [Feng et al., Nat. Mater., 2015, 14, 61] reported a very interesting re-entrant solidification behaviour of colloidal particles in an aqueous solution containing polyethylene oxide (PEO). In this system, a crystalline colloidal phase, which is present at low temperatures, melts to a homogeneous fluid upon increasing the temperature. Further raising the temperature, however, eventually gives rise to a flocculated colloidal phase. Feng et al. proposed that the low-temperature crystalline phase is caused by polymer depletion while, at higher temperature, an increased attraction between polymers and particles leads to bridging attractions, and colloidal flocculation. The intermediate temperature regime sees the colloidal interactions dominated by charge repulsion, giving rise to a fluid phase. In the model by Feng et al., polymers are treated as hard spheres, which interact with the colloids via a phenomenological, temperature dependent potential. In this work, we develop a more detailed polymer density functional treatment, based on a model for aqueous PEO solutions that was originally developed by Karlström [Karlström, J. Phys. Chem., 1985, 89, 4962] for bulk solutions. In this model, monomers are assumed to be in either of two classes of states, labelled A and B, where B is more solvophobic than A. On the other hand, the degeneracy of the B states exceed that of A, causing the population of solvophobic monomers to increase with temperature. If the colloidal particles are also solvophobic, then this model displays the same qualitative temperature response as was observed by Feng et al. That is, at low temperatures, A type monomers predominate and one observes depletion interactions, whereas polymer bridging dominates at higher temperatures, due to the attraction between B-type monomers and the colloidal surface. Interestingly, the intermediate temperature regime is characterized by a polymer mediated interaction between colloids which is repulsive. That is, according to our model the homogeneous fluid phase would form even in the absence of repulsive electrostatic interactions. We emphasize that our model does not rely upon any temperature-dependent interactions. Furthermore, all possible polymer configurations are accounted for, subject to a mean-field Boltzmann weight. Finally, we show that interactions between colloids, mediated by neutral non-grafted polymers, generally follow the trend: attraction ⇒ repulsion (or vanishing interaction) ⇒ attraction as the surface affinity toward monomers proceeds from repulsive to attractive.

Carbon nanotubes in electrospun polyethylene oxide nanofibres: A potential route to conducting nanofibres

Polyethylene oxide solution containing multi-walled carbon nanotubes have been electrospun onto a rotating collector to produce highly aligned arrays of electrospun nanofibers ranging in diameters from (200 – 360) nanometres. The addition of a surfactant (Triton X-100) is highly effective in dispersing carbon nanotube within an aqueous solution of polyethylene oxide and the resulting mixture can be electrospun without excessive clumping to produce nanofibers containing high loadings of nanotubes; in this case up to 5% wt thereby providing an effective route to electrically conductive nanofibres.

Colloidal behavior of aqueous montmorillonite suspensions in the presence of non-ionic polymer

In this paper we characterized at first, the rheological behavior of the bentonite suspensions and the aqueous solutions of polyethylene oxide (PEO), then we were investigated the influence of this polymer in a water-based drilling fluid model (6% of bentonite suspension). The objective is to exhibit how the non ionic polymer with molecular weight 6×103 g/mol. of varying concentration mass (0.7%, 1%, 2% et 3%) significantly alter the rheological properties (yield stress, viscosity, loss and elastic modulus) of the bentonite suspensions. The rheological measurements made in simple shear and in dynamic on the mixture (water-bentonite-PEO), showed rheological properties of bentonite suspensions both in the presence and absence of non-ionic polymer. The PEO presents an affinity for the bentonite particles slowing down their kinetic aggregation. The analysis by X-rays diffraction also allowed understanding the structure of this mixture. It had revealed the intercalation between of the clay platelets on one hand, and the links bridges assured by the chains of polymer between bentonite particles beyond a critical concentration in PEO on the other hand. The Herschel- Bulkley rheological model is used for the correlation of our experimental results.