Ethylene Oxide Groups Research Articles

Adsorption at air-water and oil-water interfaces and self-assembly in aqueous solution of ethoxylated polysorbate nonionic surfactants.

The Tween nonionic surfactants are ethoxylated sorbitan esters, which have 20 ethylene oxide groups attached to the sorbitan headgroup and a single alkyl chain, lauryl, palmityl, stearyl, or oleyl. They are an important class of surfactants that are extensively used in emulsion and foam stabilization and in applications associated with foods, cosmetics and pharmaceuticals. A range of ethoxylated polysorbate surfactants, with differing degrees of ethoxylation from 3 to 50 ethylene oxide groups, have been synthesized and characterized by neutron reflection, small-angle neutron scattering, and surface tension. In conjunction with different alkyl chain groups, this provides the opportunity to modify their surface properties, their self-assembly in solution, and their interaction with macromolecules, such as proteins. Adsorption at the air-water and oil-water interfaces and solution self-assembly of the range of ethoxylated polysorbate surfactants synthesized are presented and discussed.

Efficient CO2 capture by functionalized graphene oxide nanosheets as fillers to fabricate multi-permselective mixed matrix membranes.

A novel multi-permselective mixed matrix membrane (MP-MMM) is developed by incorporating versatile fillers functionalized with ethylene oxide (EO) groups and an amine carrier into a polymer matrix. The as-prepared MP-MMMs can separate CO2 efficiently because of the simultaneous enhancement of diffusivity selectivity, solubility selectivity, and reactivity selectivity. To be specific, MP-MMMs were fabricated by incorporating polyethylene glycol- and polyethylenimine-functionalized graphene oxide nanosheets (PEG-PEI-GO) into a commercial low-cost Pebax matrix. The PEG-PEI-GO plays multiple roles in enhancing membrane performance. First, the high-aspect ratio GO nanosheets in a polymer matrix increase the length of the tortuous path of gas diffusion and generate a rigidified interface between the polymer matrix and fillers, enhancing the diffusivity selectivity. Second, PEG consisting of EO groups has excellent affinity for CO2 to enhance the solubility selectivity. Third, PEI with abundant primary, secondary, and tertiary amine groups reacts reversibly with CO2 to enhance reactivity selectivity. Thus, the as-prepared MP-MMMs exhibit excellent CO2 permeability and CO2/gas selectivity. The MP-MMM doped with 10 wt % PEG-PEI-GO displays optimal gas separation performance with a CO2 permeability of 1330 Barrer, a CO2/CH4 selectivity of 45, and a CO2/N2 selectivity of 120, surpassing the upper bound lines of the Robeson study of 2008 (1 Barrer = 10(-10) cm(3) (STP) cm(-2) s(-1) cm(-1) Hg).

Amphiphile micelle structures in the protic ionic liquid ethylammonium nitrate and water.

Micelles formed by amphiphiles in a protic ionic liquid (PIL), ethylammonium nitrate (EAN), were investigated using synchrotron small-angle X-ray scattering and contrasted with those that formed in water. The amphiphiles studied were cationic hexadecyltrimethylammonium chloride (CTAC) and hexadecylpyridinium bromide (HDPB) and nonionic poly(oxyethylene) (10) oleyl ether (Brij 97) and Pluronic ethylene oxide-propylene oxide-ethylene oxide block copolymer (P123). The scattering patterns were analyzed using spherical, core-shell, and cylindrical scattering models. The apparent micelle shape and size of the surfactants and the block copolymer in the PIL have been reported. At low amphiphile concentrations (<10 wt %) spherical micelles were preferentially formed for all the amphiphiles in EAN. The micelles formed by the two cationic amphiphiles in EAN and water were similar, though different scattering models were required predominantly due to the ionic nature of EAN. The two nonionic amphiphiles formed micelles with similar core radii in water and in EAN. However, the micelle shells composed of ethylene oxide groups fitted to a significantly thicker layer in water compared to EAN. At high concentrations (>10 wt %) in EAN and water, there was a preference for cylindrical micelles for CTAC, HDPB, and Brij 97; however, the P123 micelles remained spherical.

Removal of nickel ions from aqueous solution by micellar-enhanced ultrafiltration, using mixed anionic–non-ionic surfactants

The aim of this study was to investigate the performance of single and mixed surfactants, both non-ionic and anionic, for the removal of nickel from aqueous solution using micellar-enhanced ultrafiltration (MEUF). To achieve this objective, SDS and four non-ionic surfactants with different ethylene oxide (EO) group length were utilized in this work. Furthermore, the synergistic interaction of non-ionic surfactants with SDS micelles was evaluated using β interaction parameter for TX100. The synergistic behavior of non-ionic surfactants in the SDS micelles was demonstrated, in view of the fact that the interaction parameter had a negative value. In this work, the effects of parameters such as SDS and nickel concentration, pressure and pH on the nickel rejection rate were examined in VCF=1.7 at 25°C. The optimum SDS and nickel concentration were determined 8mM and 10ppm (rejection was about 100%), respectively. It was also concluded that in the non-ionic surfactant and SDS system, the nickel rejection rate was considerably enhanced from 56% to 98%, 99%, 96% and 95%, using TX114, TX100, Brij35 and TX405, respectively for a particular concentration of SDS (i.e., 3.2mM). Furthermore, the molar mass concentration and EO group length of non-ionic surfactants in the MEUF had a considerable effect on the performance; i.e., the surfactants with lower molar mass would lead to a higher flux rate and retention.The findings of this study also revealed that as the SDS concentration was increased, the mean micelle size in the SDS and nickel solutions would also decrease accordingly.

Dynamic interfacial tensions of p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine solutions

Abstract The dynamic interfacial tensions (IFT) of four p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine C 12 BE x CB ( x =0, 1, 2, 3) have been investigated by a spinning drop interfacial tensiometer. The influence factors such as ethylene oxide group, surfactant concentration, organic base, electrolyte concentration and type are explored between C 12 BE x CB solutions and two oils including n -alkane model oil and Shengli crude oil. It is found that the n min (the minimum alkane carbon number) and IFT min increase with increase in the ethylene oxide group for n -alkane model oil systems. For Shengli crude oil, the C 12 BE x CB surfactants used alone cannot reduce the IFT to ultralow value. In order to meet the demand, the organic base, monoethanolamine (MEA), is applied together with C 12 BE x CB to form organic base/surfactant system. The results show that there exists a synergistic effect between organic alkaline MEA and C 12 BE x CB surfactant. At optimum MEA concentration (0.10 wt%) and optimum ethylene oxide group number ( x =0, 1), the IFT value becomes lower than 10 −2 mN/m. All these results show that the interfacial surfactant concentration and the surfactant molecular size are two most important factors in dominating ultralow IFT. Moreover, it is found that electrolyte concentration and type have little effects on IFT and the C 12 BE x CB surfactants exhibit good salinity resistance.

Dilational Rheological Properties of P-(n-alkyl)-benzyl Polyoxyethylene Ether Carboxybetaine at Water–Decane Interface

The dilational rheological behaviors of absorbed films of p-(n-alkyl)-benzyl polyoxyethylene ether carboxybetaine CxBE2CB (x = 8, 10, 12) at the water–decane interface have been investigated by the drop-shape analysis method. The influences of time, oscillation frequency, and bulk concentration on dilational modulus and phase angle have been expounded. The experimental results show that the phase angle of CxBE2CB (x = 10, 12) decreases with the increase of time, the slope of the log ϵ − log ω curve and phase angle of CxBE2CB (x = 10, 12) decrease in a wide concentration range. These phenomena become more and more apparent with the increase of hydrocarbon chain length and it cannot be attributed to the diffusion-exchange process between the bulk and the interface. It is reasonable to consider that ethylene oxide groups are flexible and can be compressed and expanded, just like a spring. Therefore, the compression and expansion of the ethylene oxide groups in the interfacial layer and the exchange between interface and sublayer play a more important role for CxBE2CB (x = 10, 12) adsorption film. The dependence of dilational modulus on interfacial pressure can support our provided mechanism strongly.

Dispersing Carbon Nanotubes in Aqueous Solutions of Trisiloxane‐Based Surfactants Modified by Ethoxy and Propoxy Groups

AbstractSilicone surfactants favor spreading at interfaces and siloxane has strong interaction with carbon nanotubes (CNT), thus silicone surfactant may be a good dispersant of CNT. Here, four silicone surfactants (named S1E19, S2E38, S2E16 and S1E16P8) were used to disperse CNT in aqueous solutions. The effects of surfactant structure and concentration on the ability at dispersing CNT were considered. All of the four silicone surfactants can disperse CNT in aqueous solution and the sample with 1,000 mg L−1 S1E16P8 was the best one. The hydrophilic group polyoxyethylene (PEO) and the hydrophobic groups siloxane and polypropylene (PPO) are crucial factors in the ability of dispersing CNT. S2E38 with more ethylene oxide (EO) groups has a stronger ability to disperse CNT than S2E16. The dispersion system provided by S1E19 which contains fewer siloxane and EO groups is relatively unstable and disperses less CNT. These experimental results are explained by molecular dynamics simulation. S2E38 compared with S1E19 and S2E16 has stronger interactions with CNT. The interaction energy of CNT with S1E16P8 which has a PPO moiety but fewer siloxane groups is close to that of S2E16. Furthermore, it can be concluded that these four surfactants are adsorbed on CNT mainly by van der Waals forces and the Si–O–Si chain of silicon surfactant was flexible due to the long Si–C bond and it could easily wrap onto the surface of CNT through hydrophobic and other intermolecular interactions. The hydrophilic part of PEO helped the CNT dispersed in the aqueous solution and prevented CNT from aggregating in water through steric stabilization.

High efficiency polyethylene glycol diacrylate monoliths for reversed-phase capillary liquid chromatography of small molecules

Highly cross-linked monolithic networks (i.e., polyethylene glycol diacrylate, PEGDA) synthesized from monomers containing varying ethylene oxide chain lengths were fabricated inside fused silica capillary columns for use in liquid chromatography (LC) of small molecules. Tergitol was used as a surfactant porogen in combination with other typical organic liquid porogens. Column performance was correlated with quantitative descriptors of the physical/chemical properties of the monomers and porogens using a statistical model. Solubility and viscosity values of the components were identified as important predictors of monolith morphology and efficiency. The chromatographic retention mechanism was determined to be principally reversed-phase (RP) with additional hydrogen bonding between the polar groups of the analytes and the ethylene oxide groups embedded in the monolith structure. The fabricated monolithic columns were evaluated under RPLC conditions using phenols, hydroxy benzoic acids, and alkyl parabens as test compounds. Isocratic elution of hydroxy benzoic acids at a linear velocity of 0.04cm/s using a PEGDA-700 monolith gave chromatographic peaks with little tailing (i.e., tailing factor<1.28). The chromatographic efficiency measured for a non-retained compound (uracil) using this column was 186,000plates/m when corrected for injector dead volume. High resolution gradient separations of selected pharmaceutical compounds and phenylurea herbicides were achieved in less than 18min. Optimized monoliths synthesized from all four crosslinking monomers exhibited high permeability and demonstrated little swelling or shrinking in different polarity solvents. Column preparation was highly reproducible, with relative standard deviation (RSD) values less than 2.1%, based on retention times of the phenol standards (3 different columns).

Impact of the degree of ethoxylation of the ethoxylated polysorbate nonionic surfactant on the surface self-assembly of hydrophobin-ethoxylated polysorbate surfactant mixtures.

Neutron reflectivity measurements have been used to study the surface adsorption of the polyethylene sorbitan monostearate surfactant, with degrees of ethoxylation varying from 3 to 20 ethylene oxide groups, with the globular protein hydrophobin. The surface interaction between the ethoxylated polysorbate nonionic surfactants and the hydrophobin results in self-assembly at the air-solution interface in the form of a well-defined layered surface structure. The surface interaction arises from a combination of the hydrophobic interaction between the surfactant alkyl chain and the hydrophobic patch on the surface of the hydrophobin, and the hydrophilic interaction between the ethoxylated sorbitan headgroup and the hydrophilic regions on the surface of the hydrophobin. The results presented show that varying the degree of ethoxylation of the polysorbate surfactant changes the interaction between the surfactant and the hydrophobin and the packing, and hence the evolution in the resulting surface structure. The optimal degree of ethoxylation for multilayer formation is over a broad range, from of order 6 to 17 ethylene oxide groups, and for degrees of ethoxylation of 3 and 20 only monolayer adsorption of either the surfactant or the hydrophobin is observed.

Adsorption at the biocompatible α-pinene–water interface and emulsifying properties of two eco-friendly surfactants

In this contribution, we provide an accurate characterization at the α-pinene/water interface of two commercial polyoxytheylene glycerol ester surfactants which differ in the number of ethylene oxide (EO) groups, comprising a systematic analysis of interfacial pressure isotherms, dynamic curves, interfacial rheology and emulsifying properties. Polyoxyethylene glycerol esters derived from cocoa oil are non-ionic surfactants obtained from a renewable source which fulfill the environmental and toxicological requirements to be used as eco-friendly emulsifying agents. α-Pinene is a renewable biosolvent completely insoluble in water, which could find numerous applications. Interfacial rheology and equilibrium interfacial pressure data fitted a rigorous reorientation model that assumes that the surfactant molecules, when adsorbed at the interface, can acquire two orientations. The surfactant with the highest number of EO groups (Levenol C201) turned out to be more surface active at the α-pinene/water interface. In addition, the surfactant with the lowest number of EO groups (Levenol H&B) is solubilized into the adjacent oil phase. Slightly concentrated α-pinene emulsions were obtained using both surfactants. Nevertheless, more stable α-pinene emulsions with smaller droplet sizes and lower polidispersity were obtained when Levenol C201 was used as emulsifier instead of Levenol H&B. The systematic characterization presented in this work provides important new findings on the interfacial and emulsifying properties of polyoxytheylene glycerol ester surfactants, which can be applied in the rational development of new biocompatible products.

New surfactant developments for chemical enhanced oil recovery

Abstract Recent advancements in surfactants for chemical enhanced oil recovery (EOR) are presented. For oils with a high equivalent alkane carbon number (EACN), surfactants with very large hydrophobes are needed to obtain the ultra-low interfacial tensions needed to reduce the residual oil saturation to nearly zero. The need increases at high temperature. Furthermore, these large hydrophobes need to be branched to promote formation of microemulsions with low to moderate viscosity as opposed to gels or other viscous structures that cause high surfactant retention. We show that such surfactants can be made from more than one type of hydrophobe in the form of either alkoxy sulfates or carboxylates. The carboxylates have the advantage of better stability at high temperature. Both the sulfates and carboxylates can be easily tailored to specific reservoir conditions and oils by adjusting the number of ethylene oxide (EO) or propylene oxide (PO) groups in the surfactant. A new correlation has been developed using an extensive data set taking into account the effects of PO number, EO number, temperature, brine salinity and the EACN of the oil on the optimum hydrophobe size. These new developments have enabled us to address a much wider range of conditions of oil characteristics, reservoir temperature, salinity and hardness level. Furthermore, the new surfactants are competitive in cost with previous EOR surfactants. Thus, these new developments have greatly advanced the commercial potential of chemical EOR.

Investigation on the interactions between hydrophobic anions of ionic liquids and Triton X-114 micelles in aqueous solutions

The interactions between hydrophobic anions of ionic liquids (ILs) and Triton X-114 (TX-114) micelles were studied in this work. The 1-alkyl-3-methylimidazolium based ILs with the anions bromide (Br−), tetrafluoroborate (BF4−), hexafluorophosphate (PF6−) and bis(trifluoromethylsulfonyl)imide (NTf2−) were selected to study their effects on physicochemical properties of the TX-114 micellar solution. Both the hydrophilic ILs with long alkyl (e.g., C12mimBr) and hydrophobic ILs (e.g., C4mimNTf2) significantly influenced the aggregate size and increased the absolute value of zeta potential as well as the cloud point. However, C4mimNTf2 changed the critical micellar concentration (CMC) and the aggregation number much less whereas made the micellization enthalpy decrease more obviously than C12mimBr did. It was suggested that the hydrophobic IL anions (PF6−, NTf2−) are located at the head group area of TX-114 micelles and interact with the ethylene oxide groups of TX-114 molecules. This work gives a further understanding of the interactions between IL cation/anion and micelles.

Ethanol-in-palm oil/diesel microemulsion-based biofuel: Phase behavior, viscosity, and droplet size

Increased environmental awareness and depletion of resources are driving industry to develop viable fuels from renewable resources. Vegetable oils are one alternative being considered for the production of renewable fuels. Surfactant reverse micelle microemulsions can be used as an alternative method for reducing high viscosities of vegetable oil without chemical wastes generated from the transesterification reaction. The objective of this research is to study the effects of surfactant saturation, unsaturation, and ethylene oxide groups on the phase behavior, kinematic viscosity, and microemulsion-droplet size with the goal of formulating optimized surfactant based biofuel. Four nonionic surfactants, stearyl alcohol (saturated), oleyl alcohol (unsaturated), methyl oleate (unsaturated with ester group), and Brij-010 (EO groups), were investigated in this research. It was found that the presence of methyl oleate unsaturated surfactant can greatly reduce the bulk viscosity and produce uniformly size of microemulsion droplets while use the least amount of surfactant for solubilizing ethanol-in-oil in the system. Thus, these results show that reverse micelle microemulsion can produce biofuels with desirable viscosity and fuel properties as compared to diesel.

Synthesis of polyvinyltrimethylsilane-graft-poly(ethylene glycol) copolymers and properties of gas-separating membranes formed on their basis

A method is developed for the synthesis of the graft copolymer polyvinyltrimethylsilane-graft-poly(ethylene glycol) via the interaction of a brominated polymer with the methyl ether of a low-molecular-mass poly(ethylene glycol). Graft copolymer samples containing up to 79 wt % poly(ethylene glycol) are synthesized through this method. The properties of the graft copolymers and blends formed on their basis with a specially synthesized low-molecular-mass PEG derivative with a terminal trimethylsilyl group are investigated. Physical blends are prepared in order to increase the content of ethylene oxide groups while the film-forming properties of the composite materials are preserved. As shown by structural studies, the graft copolymers are amorphous single-phase systems, while the related blends are two-phase disperse systems, in which one phase is enriched in polytrimethylvinylsilane and the other is enriched in PEG. Studies of the gas-transport behavior of the samples reveal that the introduction of PEG, in contrast to the nonselective initial polymer, results in the formation of PVTMS-based materials that are selective for CO2 in mixtures with H2.

High-performance composite membrane with enriched CO2-philic groups and improved adhesion at the interface.

A novel strategy to design a high-performance composite membrane for CO2 capture via coating a thin layer of water-swellable polymers (WSPs) onto a porous support with enriched CO2-philic groups is demonstrated in this study. First, by employing a versatile platform technique combining non-solvent-induced phase separation and surface segregation, porous support membranes with abundant CO2-philic ethylene oxide (EO) groups at the surface are successfully prepared. Second, a thin selective layer composed of Pebax MH 1657 is deposited onto the support membranes via dip coating. Because of the water-swellable characteristic of Pebax and the enriched EO groups at the interface, the composite membranes exhibit high CO2 permeance above 1000 GPU with CO2/N2 selectivity above 40 at a humidified state (25 °C and 3 bar). By tuning the content of the PEO segment at the interface, the composite membranes can show either high CO2 permeance up to 2420 GPU with moderate selectivity of 46.0 or high selectivity up to 109.6 with fairly good CO2 permeance of 1275 GPU. Moreover, enrichment of the PEO segment at the interface significantly improves interfacial adhesion, as revealed by the T-peel test and positron annihilation spectroscopy measurement. In this way, the feasibility of designing WSP-based composite membranes by enriching CO2-philic groups at the interface is validated. We hope our findings may pave a generic way to fabricate high-performance composite membranes for CO2 capture using cost-effective materials and facile methods.

Electrochromic enhancement of poly(3,4‐ethylenedioxythiophene) films functionalized with hydroxymethyl and ethylene oxide

ABSTRACT2‐((2,3‐Dihydrothieno[3,4‐b]dioxin‐2‐yl)methoxy)methyl oxirane (EDOT‐MO) was successfully synthesized by the reaction of epichlorohydrin with hydroxymethylated‐3,4‐ethylenedioxylthiophene (EDOT‐MeOH), which was synthesized via a simple four‐step sequence. Poly(hydroxymethylated‐3,4‐ethylenedioxylthiophene) (PEDOT‐MeOH) and poly(2‐((2,3‐dihydrothieno[3,4‐b]dioxin‐2‐yl)methoxy)methyl oxirane) (PEDOT‐MO) were electrosynthesized through electropolymerization of EDOT‐MeOH and EDOT‐MO, respectively. Structural, electrochemical, optical, and thermal properties of as‐formed polymers were investigated by FTIR, cyclic voltammetry, UV–vis, and thermogravimetry. Spectroelectrochemistry studies demonstrated that PEDOT‐MeOH and PEDOT‐MO could be reversibly oxidized and reduced accompany with obvious color changes. Further kinetic studies demonstrated that the introduction of hydroxymethyl or ethylene oxide group significantly improved electrochromic properties of 3,4‐ethylenedioxythiophene (PEDOT) and resulted in high contrast ratios (57.3% at 585 nm) and coloration efficiencies (338.5 cm2 C−1), low switching voltages, and fast response time. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1989–1999

Absolute MR thermometry using nanocarriers

Accurate time-resolved temperature mapping is crucial for the safe use of hyperthermia-mediated drug delivery. We here propose a magnetic resonance imaging temperature mapping method in which drug delivery systems serve not only to improve tumor targeting, but also as an accurate and absolute nano-thermometer. This method is based on the temperature-dependent chemical shift difference between water protons and the protons in different groups of drug delivery systems. We show that the chemical shift of the protons in the ethylene oxide group in polyethylene glycol (PEG) is temperature-independent, whereas the proton resonance of water decreases with increasing temperature. The frequency difference between both resonances is linear and does not depend on pH and physiological salt conditions. In addition, we show that the proton resonance of the methyl group in N-(2-hydroxypropyl)-methacrylamide (HPMA) is temperature-independent. Therefore, PEGylated liposomes, polymeric mPEG-b-pHPMAm-Lac2 micelles and HPMA copolymers can provide a temperature-independent reference frequency for absolute magnetic resonance (MR) thermometry. Subsequently, we show that multigradient echo MR imaging with PEGylated liposomes in situ allows accurate, time-resolved temperature mapping. In conclusion, nanocarrier materials may serve as highly versatile tools for tumor-targeted drug delivery, acting not only as hyperthermia-responsive drug delivery systems, but also as accurate and precise nano-thermometers.

Porous nickel films plated in supercritical carbon dioxide emulsified electrolyte using a series of fluorinated nonionic surfactants

Thin porous Ni films were fabricated in supercritical CO2 (Sc-CO2) emulsion with a series of nonionic fluorinated surfactants, F(CF(CF3)CF2O)3CF(CF3)COO(CH2CH2O)nCH3 (denoted as PFP3-EOn where n=1, 2 and 5). The film morphology and size distribution of pores were studied as a function of number of ethylene oxide groups and different concentrations of surfactants. Surfactant PFPO3-EO1 from low to medium concentrations showed a narrow size distribution of shallow pores on the films, and at high concentration it showed shallow pores and some large size deep pores. Surfactant PFPO3-EO2 at low concentration showed a narrow size distribution of shallow and deep pores on the film, and from medium to high concentrations the size distribution of deep pores increased. Compared to other surfactants, for all concentrations, surfactant PFPO3-EO5 showed a broad size distribution of deep pores, and it showed shallow pores only up to medium range of concentration. The increase of ethylene oxide groups and concentration of surfactants increased the size distribution of pores and decreased the number of pores on the films. There was a significant decline in the number of pores by the surfactant PFPO3-EO5. Sc-CO2 emulsion assisted Ni deposition using a series of nonionic fluorinated surfactants and concentrations shows great promise as a method to control porous structure on the plated films.

Comparing the spectral properties of pyrene as free molecule, label and derivative in some colloidal systems

This paper investigates the behavior of pyrene as free molecule (probe), label and derivative in some colloidal systems. Aqueous octaethylene glycol mono n-dodecyl ether (C12E8) with or without poly(acrylic acid) (PAA), and a hydrophobically modified polyacrylate are considered. The effect of C12E8 on PAA labeled with pyrene is also studied. As a probe, pyrene has a typical behavior in the absence or presence of PAA. The labeled PAA has the peak corresponding to the sandwich excimer even in the absence of surfactant. The pyrene derivative is 4-(N′,N′-diphenyl-hydrazine)-3,5-dinitrobenzoic acid 2-oxo-2-pyren-2-yl-ethyl ester. Its fluorescence emission is low and bathochromically shifted by 9nm with respect to pyrene. The low fluorescence emission of derivative is due to its self-quenching. The data reveal that pyrene probe is located in the free or polymer-bound micelles. The labels on PAA create hydrophobic domains and shrink the polymer coil. By surfactant addition, labeled pyrene is solubilized in micelles palisade layer, closer to the ethylene oxide (EO) chains. The derivative is also located into the micellar palisade layer, in the proximity of the EO groups. The fluorophore behavior is discussed in relation to the critical points of surfactant and polymer–surfactant systems.

Prelimenary Study on the Photovoltaic and Impedance Characteristics of Dye Sensitized Solar Cell (DSSC) using Polymer Gel Electrolyte

Dye sensitized solar cells (DSSC) have been fabricated by using polymer gel electrolyte consisting of ionic liquids in a composite polymers of siloxane and ethylene oxide groups. The structure of those DSSCs are ITO/Ti:ZnO/TiO2/Ru-dye/gel electrolyte/Pt/ITO, with active area of about 0,5 cm2. At this preliminary work, the structure parameters and fabrication procedures had not been optimized for achieving the best performance, but it had been carefully controlled to be same for all fabricated DSSCs. Those DSSCs shows the solar cell performance similar to that observed in DSSCs fabricated in the same cell structure but using conventional electrolyte solution. They exhibit better open voltage and filling factor, which is suggested to the reduction of charge carrier recombination probably taking place at the double layer region formed at the electrode interfaces. This is consistent with their impedance spectrum which is dominated by a Warburg-like characteristics indicating a diffusion limited migration process. It seems then the cell performances is improved by the reduction of charge recombination loss but restricted by diffusion limited ion migration process.