PEO Surfactant Research Articles

Fabrication of TEOS/PDMS/F127 hybrid coating materials for conservation of historic stone sculptures

The present work was aimed to develop a new kind of stone conservation materials (TEOS/PDMS/F127 hybrid coating) by a facile sol–gel method for the protection of decayed sandstones of Chongqing Dazu stone sculptures in China. The hydrophobic property, surface morphology, water vapor permeability, ultraviolet aging resistance and mechanical properties were measured to evaluate the effectiveness of TEOS/PDMS/F127 hybrid coating as a stone conservation material. The results showed that the addition of hydroxyl-terminated polydimethylsiloxane (PDMS-OH) contributed to improve the hydrophobic properties and incorporation of PEO–PPO–PEO (F127) surfactant resulted in the formation of superficial protrusions with micro- and nanoscopic structures and overall alteration of surface morphology and roughness, thus preventing the coating materials from cracking. After treatment with TEOS/PDMS/F127 hybrid coating materials, the ultraviolet aging resistance and mechanical properties of stone were also improved without the obvious effects on the breathability and color of the stone, indicating promising applications of TEOS/PDMS/F127 hybrid coating materials for conservation of historic stone sculptures.

Synthesis and characterization of α-MoO3 nanobelt composite positive electrode materials for lithium battery application

α-MoO3 and PEO surfactant MoO3 nanobelts were synthesized by a solvothermal method. The morphology and nanostructure of samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Bare α-MoO3 and 12.5wt% PEO surfactant MoO3 nanobelts have an initial specific capacities of 279 and 352mAhg−1, respectively, at constant current density 30mAg−1 with potential range of 1.5–4.0V vs. Li/Li+. While MoO3 is modified by the intercalation of PEO, it is effectively shielded against electrostatic interaction between the MoO3 interlayer and Li+ ions. We reported positive material, a nanocomposite of MoO3 coated with polyethylene oxide. It presents good cycling stability due to existence of the conductive and protective polyethylene oxide coating and the nanobelt morphology of MoO3. The polyethylene oxide acts as a conducting matrix, a binder and an active material, as well as a volume change buffer agent, which holds the MoO3 particles in place during the discharge cycles. The cyclic voltammograms of the 12.5wt% PEO surfactant MoO3 nanobelt composite displayed better cyclic performance compared with pure MoO3 nanobelts. The specific capacity of the pure MoO3 nanobelts and 12.5wt% PEO surfactant MoO3 nanobelts exhibit as 199mAhg−1 and 225mAhg−1, respectively, after 9 cycles, suggesting that the stability of surfactant material is worthy.

Synthesis, structural, and electrochemical performance of V2O5 nanotubes as cathode material for lithium battery

Various vanadium oxide nanostructures are currently drawn interest for the potential applications of Li batteries, super capacitors, and electrochromic display devices. In this article, the synthesis of V2O5 nanotubes by hydrothermal method using 1-hexadecylamine (HDA) and PEO as a template and surface reactant were reported, respectively. The structural properties and electrochemical performances of these nanostructures were investigated for the application of Li batteries. Structure and morphology of the samples were investigated by XRD, FTIR, SEM, and TEM analysis. The battery with V2O5 nanotubes electrode showed initial specific capacity of 185 mAhg−1, whereas the PEO surfactant V2O5 nanotubes exhibited 142 mAhg−1. It was found that PEO surfactant V2O5 nanotubes material showed less specific capacity at initial stages but better stability was exhibited at higher cycle numbers when compared to that of V2O5 nanotubes. The cyclic performance of the PEO surfactant material seems to be improved with the role of polymeric component due to its surface reaction with V2O5 nanotubes during the hydrothermal process.

Modeling the Phase Behavior of PEO−PPO−PEO Surfactants in Carbon Dioxide Using the PC-SAFT Equation of State: Application to Dry Decontamination of Solid Substrates

The phase behavior of several commercially available poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) block copolymers (PEO−PPO−PEO or Pluronics L) in compressed carbon dioxide has been investigated within the framework of dry nuclear decontamination. For this purpose, cloud points have been measured in the pressure and temperature range from P = (10 to 40) MPa and from T = (293 to 338) K, respectively. To find a reliable method for surfactant selection, the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state (EoS) has been applied to model the experimental data. The pure-component and the respective homopolymer + CO2 binary interaction parameters have been fitted to liquid densities and to homopolymer + CO2 binary equilibrium data. The phase behavior of Pluronics L copolymers as a function of concentration, molar mass, and copolymer composition has been predicted very accurately using a constant PEO−PPO binary interaction parameter kPEO-PPO = 0.007. The PC-SAFT model was also successfully applied to Pluronics R copolymers (PPO—PEO—PPO), although a different kPEO-PPO = −0.018 was required to match the experimental data. The model predictions have shown that Pluronics L copolymers with molar mass M < 2750 g·mol−1 and a PEO mass fraction in the copolymer of less than 30 % have sufficiently low cloud-point pressures and are therefore the most suitable for the decontamination process.

EFFECTS OF NH4Cl ON THE INTERACTION BETWEEN POLY(ETHYLENE OXIDE) AND IONIC SURFACTANTS IN AQUEOUS SOLUTIONS

The interaction of poly(ethylene oxide) (PEO) with the ionic surfactants, sodium dodecylsulfate (SDS) and cetyltrimethylammonium chloride (CTAC) respectively, in aqueous solutions containing a certain concentration of NH4Cl, is studied by the viscosity measurement. It has been found that the ion-dipole interaction between PEO and ionic surfactants is changed considerably by the organic salt. For anionic surfactant of SDS, the addition of NH4Cl into solution strengthens the interaction between PEO and the headgroup of SDS. On the other hand, for cationic surfactant of CTAC, the interaction between PEO and the headgroup of CTAC is screened significantly by NH4Cl dissolved in solution. These findings may potentially be attributed to the negative property of the oxygen group of the PEO chain. In the presence of NH4Cl, the cationic ions of the organic salt bind to the oxygen group of the PEO chain so that PEO can be referred to as a pseudo-polyelectrolyte in solution.

Growth and Surface Properties of Boehmite Nanofibers and Nanotubes at Low Temperatures Using a Hydrothermal Synthesis Route

The growth of boehmite nanostructures at low temperature using a soft chemistry route with and without (PEO) surfactant is presented. Remarkably long boehmite 1D nanotubes/nanofibers were formed within a significantly short time by changing the reaction mechanism of aluminum hydroxide. By using the PEO surfactant as a templating agent, boehmite nanotubes up to 170 nm in length with internal and external diameters of 2-5 and 3-7 nm, respectively, were formed at 100 degrees C. A slightly higher temperature (120 degrees C) resulted in the formation of lath-like nanofibers with an average length of 250 nm. Using the cationic surfactant CTAB, nanotubes rather than nanofibers were formed at 120 degrees C. Without surfactant, nanotubes counted for around 20% of the entire sample. A regular interval supply of fresh boehmite precipitate resulted in a larger crystallite size distribution of nanotubes. The morphology of nanotubes was more uniform in samples without the regular addition of aluminum hydroxide. Moreover, for the same hydrothermal time, the final nanotubes for nanomaterials without a regular interval supply of fresh aluminum hydroxide precipitate were longer than those with a regular aluminum hydroxide precipitate supply, which is in contrast to previously published results. Higher Al/PEO concentrations resulted in the formation of shorter nanotubes. A detailed characterization and mechanism are presented.

Cosorption of Atrazine and a Lauryl Polyoxyethylene Oxide Nonionic Surfactant on Smectite

Commercial atrazine formulations commonly contain nonionic surfactants that serve as solubilizing and wetting agents for enhancing the stability and efficacy of the herbicide. The fate of atrazine in soils has been extensively investigated; yet, few studies have considered the effects of formulation components on the fate of atrazine in soils. In this study, we investigated the influence of the nonionic surfactant, Brij 35 (Brij), on the sorption of atrazine on Ca- and K-saturated samples of a reference smectite, Panther Creek (PC). In general, Brij concentrations of 50 and 200 mg L(-1) had little effect on atrazine sorption, but sorption was substantially inhibited by Brij concentrations of 2100 mg L(-1). For Brij concentrations of 6300 mg L(-1), atrazine sorption was intermediate between that observed for the 200 and 2100 mg L(-1) Brij systems. Brij molecules themselves were very strongly sorbed by PC, with sorption maxima exceeding 200 g kg(-1). X-ray diffraction analysis of Brij-treated PC indicated that the sorbed Brij was intercalated into interlayers of the smectite. At Brij concentrations of 2100 mg L(-1), Brij competed with atrazine for interlayer sorption sites. In contrast, at the initial Brij concentration of 6300 mg L(-1), the clay interlayers were largely filled with Brij, and excess Brij probably accumulated on external surfaces of the clay as surface micelles. We hypothesize that atrazine partitioning into surfactant micelles on external surfaces of the clay led to enhanced retention by the solid phase.

X-ray reflectivity study of acid–base post-synthesis treatments of mesoporous thin films templated by P123

Mesoporous silica thin films have been prepared through evaporation-induced self-assembly in the presence of non-ionic PEO–PPO–PEO surfactants. We investigated the effects of acid–base post-synthesis treatments on the structure of SBA-15 by immersing the samples into diluted HCl or HNO 3 solutions at ambient temperature and by exposing them to NH 3 atmosphere. The evolution of the 2D hexagonal structure was investigated by X-ray reflectivity (XR) before and after removing the surfactant from the silica matrix. XR curves analyzed were evaluated by the matrix technique to obtain the average electron density of the films, the wall thickness, the electron density of the walls.

Zinc(II)-benzoato complexes immobilised in mesoporous silica host

Mesoporous silica (MS) was synthesised using amphiphilic PEO–PPO–PEO surfactant (Pluronic F127). This chemically stable matrix composed of micropores and mesopores was used as host system for two bactericidal zinc(II) complexes of distinct structure types. The composite materials were characterised by thermogravimetry (TGA), IR spectroscopy, X-ray diffraction (XRD), N 2 adsorption, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Different loadings were achieved for the respective complexes. Their values were comparable with those obtained by incorporation of ibuprofen into MCM-41. The correlation of the results of XRD, nitrogen adsorption/desorption, X-ray structural analysis of the complexes and their interactions with the silica walls is discussed in the paper. Finally, the time dependence of the release of the complexes from the mesoporous system was investigated.

Improvement on cycling efficiency of lithium by PEO-based surfactants in cross-linked gel polymer electrolyte

The effect of poly(ethylene oxide) (PEO)-based surfactant in the gel polymer electrolyte on the cycling efficiency of lithium was investigated by means chronopotentiometry. The gel polymer electrolyte was prepared by thermal curing using bisphenol A ethoxylate diacrylate as a cross-linker. While an improvement in cycling efficiency of lithium was found for the electrolytes containing both of perfluorinated and star-shaped PEO-based surfactants, the better cycling efficiency was observed for the star-shaped surfactants than that for the perfluorinated surfactant. More than 90% of cycling efficiency of lithium was achieved for the polymer electrolyte using star-shaped PEO surfactants. The cycling efficiency of lithium in the gel polymer electrolyte containing star-shaped surfactant increased as increasing of the molecular weight of side chain. By using star-shaped PEO surfactant, the interface resistance was almost constant during the repeated cycles. The star-shaped PEO-based surfactants seem to be very effective to form stable SEI layer.

Composite natural rubber based latex particles: a novel approach

The oil resistance of natural rubber (NR) film could be effectively improved by using the heterocoagulation of large NR particle with small polychloroprene (CR) particles. In the preparation of NR/CR composite particle with a core-shell structure, a nonionic surfactant whose molecule bears poly(ethylene oxide) (PEO) was adsorbed on CR particles and allowed to form complexes between PEO and indigenous surfactant (protein–lipid) on the NR particle surface. Composite latex particle obtained was characterised by particle size, zeta potential and glass transition temperature measurements and the data indicated the presence of CR on the outer layer of composite particle. Better oil resistance of film casted from heterocoagulated latex when compared to that of NR film confirmed the NR/CR core-shell structure. The epoxidised natural rubber (ENR), crosslinked ENR and/or skim latex particles were investigated in order to replace the use of CR in the heterocoagulation process.

Photocatalysts prepared from layered clays and titanium hydrate for degradation of organic pollutants in water

Reaction between titanium hydrate sol of strong acidity and four smectite clays were utilized to create composite nanostructures of titanium dioxide (TiO 2) and silicate nanoparticles. The acidic sol solution reacts with the clay platelets and leaches out part of the magnesium or aluminum in the clay, while the sol particles hydrolyze further, yielding larger precursors of TiO 2 nanoparticles and condense on the fragmentised pieces of the leached silicate. Moreover, introducing PEO surfactants into the synthesis can significantly increase the porosity and surface area of the composite solids. The TiO 2 in the product are crystal grains of several nanometres in size. They disperse on silicate plates or are separated by silicate fragments and voids such that they are accessible to organic molecules. The mechanism of the synthesis reaction is distinguishingly different from conventional pillaring process. The composite solids provide highly effective photocatalysts for the degradation of phenol and synthetic dyes in aqueous solution.

Stability of silicon and titanium carbide suspensions in electrolyte, poly(ethylene oxide), and PEO–surfactant solutions

It has been shown that the coagulation values of counterions for SiC and TiC suspensions with particle radius from 0.5 to 5 μm obey a z 2.5–3.5 law and there is an insufficient change in the critical concentration of 1–1 electrolytes (CCE) when the surface potential of particles increases more than two times. Also, the CCE values hardly depend on the position of counterions in the lyotropic sequence. This is explained by aggregation of SiC and TiC particles at a secondary minimum, which is proved by calculations of the potential curves of interparticle interactions using the DLVO theory. The adsorption of poly(ethylene oxide) on the surfaces studied does not cause—in contradiction to dispersions with smaller particles—an unlimited growth in the stability of suspensions. This is due to the aggregation of large particles with adsorbed PEO, as in polymer-free dispersions, under barrierless conditions in which the coordinates of the secondary minimum are determined by superposition of molecular attractive forces and steric repulsive forces of adsorbed polymeric chains, without a contribution from the electric repulsion term. PEO–anionic surfactant complexes possess higher stabilizing capacity compared to the individual components of the mixture. Our results show that the adsorbed polymer layers may hinder the aggregation both in the primary and in the secondary minimum for not very large particles only, the critical size of which depends on the dispersed phase nature and the molecular mass of the polymer.

Growth of Boehmite Nanofibers by Assembling Nanoparticles with Surfactant Micelles

It is known that boehmite (AlOOH) nanofibers formed in the presence of nonionic poly(ethylene oxide) (PEO) surfactant at 373 K. A novel approach is proposed in this study for the growth of the boehmite nanofibers: when fresh aluminum hydrate precipitate was added at regular interval to initial mixture of boehmite and PEO surfactant at 373 K, the nanofibers grow from 40 to 50 nm long to over 100 nm. It is believed that the surfactant micelles play an important role in the nanofiber growth: directing the assembly of aluminum hydrate particles through hydrogen bonding with the hydroxyls on the surface of aluminum hydrate particles. Meanwhile a gradual improvement in the crystallinity of the fibers during growth is observed and attributed to the Ostwald ripening process. This approach allows us to precisely control the size and morphology of boehmite nanofibers using soft chemical methods and could be useful for low temperature, aqueous syntheses of other oxide nanomaterials with tailorable structural specificity such as size, dimension and morphology.

Novel Composites of TiO2 (Anatase) and Silicate Nanoparticles

Thermally stable composite nanostructures of titanium dioxide (anatase) and silicate nanoparticles were prepared from Laponite clay and a sol of titanium hydrate in the presence of poly(ethylene oxide) (PEO) surfactants. Laponite is a synthetic clay that readily disperses in water and exists as exfoliated silicate layers of about 1-nm thick in transparent dispersions of high pH. The acidic sol solution reacts with the clay platelets and leaches out most of the magnesium in the clay, while the sol particles hydrolyze further due to the high pH of the clay dispersion. As a result, larger precursors of TiO2 nanoparticles form and condense on the fragmentized pieces of the leached silicate. Introducing PEO surfactants into the synthesis can significantly increase the porosity and surface area of the composite solids. The TiO2 exists as anatase nanoparticles that are separated by silicate fragments and voids such that they are accessible to organic molecules. The size of the anatase particle can be tailored by manipulating the experimental parameters at various synthesis stages. Therefore, we can design and engineer composite nanostructures to achieve better performance. The composite solids exhibit superior properties as photocatalysts for the degradation of Rhodamine 6G in aqueous solution.

The Role of the Carboxylate Head Group in the Interaction of Sodium Dodecanoate with Poly(ethylene oxide) Investigated by Electrical Conductivity, Viscosity, and Aggregation Number Measurements

The binding of sodium dodecanoate (SDoD) to poly(ethylene oxide) (PEO) in aqueous solution was investigated and compared with the well-known polymer–surfactant complexes formed between PEO and sodium dodecyl sulfate (SDS). Electrical conductivity measurements indicated that the concentration ratio of bound SDoD to PEO (on monomer basis) was greater than that for the system PEO–SDS. However, the aggregation numbers of the micelles supported on the polymer chain are practically constant and similar for both surfactants at concentrations lower than the polymer saturation point. The difference in binding capability is explained in terms of a larger PEO coil expansion upon complexation of SDoD than in the case of SDS. An increase in the polymer surface favors the binding of SDoD to PEO in aqueous solution. This conclusion is supported by the results of the viscometric studies of PEO–surfactant solution.

Composite natural rubber-polychloroprene latex particles produced by the heterocoagulation technique

Composite natural rubber (NR) based latex particles were prepared using the heterocoagulation technique. A nonionic surfactant (Tween 80) whose molecules bear poly(ethylene oxide) (PEO) was adsorbed on polychloroprene (CR) latex particles and allowed to form complexes between PEO and indigenous surfactant (protein–lipid) on the NR particle surface. The heterocoagulated NR/CR–Tween particles produced were characterised by particle size, zeta-potential and glass-transition temperature measurements and the data indicated the presence of CR–Tween on the outer layer of the composite polymer particles. The results agreed well with the better oil resistance of films cast from heterocoagulated latex when compared with that of the NR film.

Interactions between Poly(ethylene oxide) and Sodium Alkylcarboxylates As Studied by Conductivity and Gel Permeation Chromatography

The interactions between PEO and sodium alkylcarboxylates (octyl, decyl, and dodecyl) have been investigated by conductivity measurements and gel permeation chromatography (GPC). Also included in the study was sodium dodecyl sulfate. From the conductivity measurements the critical aggregation concentration, ionization degree, and binding ratios were determined; the binding ratio was also determined from GPC. PEO–surfactant interactions were observed for all the studied surfactants, except sodium octanoate. For the polymer–surfactant complexes the ionization degree was in all cases observed to be about 0.2 higher than the ionization degree for the corresponding aqueous micelles. Further, the binding ratio decreased somewhat with decreasing chain length of the alkylcarboxylate. The Gibbs free energy showed that the polymer–surfactant interaction decreases with decreasing chain length of the alkylcarboxylates and is weaker for alkylcarboxylate compared to alkylsulfate of similar chain length.

Surfactant polymers designed to suppress bacterial (Staphylococcus epidermidis) adhesion on biomaterials.

We describe a series of surfactant polymers designed as surface-modifying agents for the suppression of bacterial adhesion on biomaterials. The surfactant polymers consist of a poly(vinyl amine) backbone with hydrophilic poly(ethylene oxide) (PEO) and hydrophobic hexanal (Hex) side chains (PVAm/PEO:Hex). Surface modification is accomplished by simple dip coating from aqueous solution, from which surfactant polymers undergo spontaneous surface-induced assembly on hydrophobic biomaterials. The stability of PVAm/PEO:Hex on pyrolytic graphite (HOPG) and polyethylene (PE) was demonstrated by the absence of detectable desorption under flow conditions of pure water over a 24-h period. PEO surfactant polymers with four different PEO:Hex ratios (1:1.4, 1:2.5, 1:4.6, and 1:10.7) and a dextran surfactant polymer were compared with respect to S. epidermidis adhesion under dynamic flow conditions. Suppression of S. epidermidis adhesion was achieved for all modified surfaces over the shear range 0-15 dyn/cm(2). The effectiveness depended on the surfactant polymer composition such that S. epidermidis adhesion to modified surfaces decreased significantly with increasing PEO packing density. Modified HOPG was more effective in reducing bacterial adhesion compared with the corresponding modification on PE, which we attribute to the presence of defects in surfactant polymer assembly on PE. Our results are discussed from the perspective of critical factors, such as optimal PEO packing density and hydration thickness, that contribute to the effectiveness of surfactant polymers to shield a biomaterial from adhesive bacterial interactions.

Poly(ethylene oxide)-polyelectrolyte blends: viscometric and thermal analysis behaviour

The miscibility of binary poly(ethylene oxide) (PEO) and sodium poly(4-styrene sulphonate) (PSS) or [3,6]-ionene (ION) systems, was analysed in aqueous solutions and in the solid state by viscometry and thermal analysis, respectively. Both techniques indicate partial miscibility of PEO–PSS and immiscibility of PEO–ION blends. In water solution, the partial miscibility of the PEO–PSS system is probably due to the counterion Na+ which can partially provide the driving force association in a similar manner to that observed for PEO–surfactant systems. In blend films, the PEO–polyelectrolyte interaction is also analysed in terms of the effect on the PEO crystallization observed through optical microscopy, and the results indicate compatibility between the components in the PEO–PSS system. © 2000 Society of Chemical Industry