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1.
Interactions between the diblock copolymer S15E63 and the surfactant sodium dodecyl sulfate (SDS) have been investigated by isothermal titration calorimetry (ITC) in the temperature range 10–40°C. At 20°C, the block copolymer is associated into micelles with a hydrodynamic radius of 11.6?nm, which is composed of a hydrophobic styrene oxide (S) core and a water-swollen oxypolyethylene (PEO) corona. The copolymer/surfactant system has been studied at a constant copolymer concentration of 0.25?wt% and over a wide range of surfactant concentration, from 7.5?×?10?6 up to 0.3?M. The titration calorimetric data for SDS in the temperature range 10–20°C presents a first endothermic increase indicating the formation of mixed copolymer rich-surfactant micelles. From that point, important differences in the ITC plots for surfactant titrations in the presence and in the absence of the copolymer are present. A shallow second endothermic peak is assigned to the interaction between SDS molecules and copolymer molecules resulting from the beginning of micelle disruption. An exothermic peak indicates the end of this disruption where only SDS micelles attached to single copolymer monomers are present, as shown by DLS in a previous paper. At higher temperatures in the range 25–40°C, the first endothermic maximum is not totally shown because interactions between surfactant and block copolymer start at very low SDS concentrations. Moreover, the second endothermic peak is absent and the exothermic minimum is less pronounced as a consequence of the increased micellization of the block copolymer.  相似文献   

2.
The premicellar and micelle formation behaviors of four cationic triphenylmethane dyes, viz, Pararosaniline (RN), Crystal violet (CV), Ethyl violet (EV), and Malachite green (MG), in aqueous anionic surfactant solutions of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium dodecyl sulfonate (SDSN) have been studied by spectral and surface tension measurements. The study was carried out within a pH range where the dyes are stable in their quinoid forms. The dyes have been found to form dye–surfactant ion pairs (DSIPs) with the surfactants, at the surfactant concentrations well below their critical micelle concentration, CMC*. The DSIPs behave like nonionic surfactants and form an air–water interfacial monolayer. The DSIPs have a lower critical micelle concentration (CMCIP), greater efficiency, and lower effectiveness than the corresponding pure surfactants. As the surfactant concentration is increased below the CMC*, the DSIPs start forming micelles of their own where the dye gets protonated and exists as a protonated dye–surfactant ion pair (PDSIP) in the ion pair micelles. As the concentration of the surfactant exceeds the CMC* of the pure surfactant, the protonation reverses gradually with the dye remaining in the micelles in solubilized form and the DSIPs in the air–water interfacial monolayer are replaced by pure surfactants. The distorted helical isomeric form (isomer B) of the dyes is favored in the PDSIPs. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

3.
A series of single‐chained N‐acyl tyrosine surfactants with varying chain lengths (C10‐C18) and degree of unsaturation, as well as an N‐acyl Gemini tyrosine surfactant with chain length C12, were synthesized, and the structures were confirmed using spectral analysis. The effect of chain length and level of unsaturation on the physicochemical and antibacterial properties of the N‐acyl tyrosine surfactants was evaluated. The C12 derivative displayed the optimum antibacterial activity among the single chain surfactants, and the presence of double bond in the oleoyl derivative enhanced the antibacterial activity over its saturated analogue. The N‐acyl Gemini surfactant displayed the highest antibacterial activity among the series and also showed greater micelle forming ability than its single chain analogue. Mixed micellar behavior of the N‐acyl Gemini surfactant with conventional cationic (CTAB) and anionic (SDS) surfactants in aqueous solution was studied. The negative value of the interaction parameter β12 observed for the N‐acyl Gemini in binary mixture with CTAB surfactant indicated a synergistic interaction within the mixed micellar system. However, the binary mixture with SDS displayed antagonistic behavior. The binary mixture of N‐acyl Gemini surfactant with CTAB displayed better antibacterial activity and foaming properties than with SDS mixtures. Optimum antibacterial activity was observed for N‐acyl Gemini surfactant with mole ratio 0.4 to 0.6 in the CTAB binary mixture, at which the lowest ocular irritation index was observed. Overall, the study showed that the Gemini surfactant in combination with the conventional surfactant CTAB can be used as potential ingredients in detergent and pharmaceutical formulations.  相似文献   

4.
Summary The adiabatic compressibility of ethanol-water mixtures was measured as a function of temperature and cosolvent concentration; the measurements were carried out at 5°C intervals over the range (10⋎40) °C, paying particular attention to the water-rich region (mole fraction of cosolventx 2<0.25). The observed concentration dependencies of the adiabatic compressibility in the low-concentration range were well explained if we consider the existence in the mixture of local structures with a composition that is close to ethanol-17 H2O like that of solid clathrate hydrate of type II. A simple model, involving the solutesolvent interactions and the molecular aggregation of the solute, is used to explain the observed behaviour. To speed up publication, the author of this paper has agreed to not receive the proofs for correction.  相似文献   

5.
Self-assembling behaviour of block copolymers and their ability to evade the immune system through polyethylene oxide stealth makes it an attractive candidate for drug encapsulation. Micelles formed by polyethylene oxide-polypropylene oxide- polyethylene oxide triblock copolymers (PEO-PPO-PEO), pluronic P123, have been employed for encapsulating the anti-cancer drug doxorubicin hydrochloride. The binding affinity of doxorubicin within the micelle carrier is enhanced through complex formation of drug and anionic surfactant, aerosol OT (AOT). Electrostatic binding of doxorubicin with negatively charged surfactants leads to the formation of hydrophobic drug-surfactant complexes. Surfactant-induced partitioning of the anti-cancer drug into nonpolar solvents such as chloroform is investigated. SANS measurements were performed on pluronic P123 micelles in the presence of drug-surfactant complex. No significant changes in the structure of the micelles are observed upon drug encapsulation. This demonstrates that surfactant- drug complexes can be encapsulated in block copolymer micelles without disrupting the structure of aggregates.   相似文献   

6.
The mixed micelles of nonionic decanoyl-N-methylglucamide (MEGA-10) with the anionic sodium dodecyl sulphate (SDS), the cationic dodecyltrimetylammonium bromide (DTAB), and the nonionic octaoxyethylene monododecyl ether (C12E8) have been studied using the fluorescence probe technique. The critical micelle concentration of the three mixed systems in the whole composition range were determined by the pyrene 1:3 ratio method, and the experimental results were analysed in the context of the pseudophase separation model, by using the regular solution theory. It was found that the mixed micelles containing the anionic surfactant are more stable than the pure micelles. This fact was attributed to the occurrence of ion–dipole interactions between the head groups of the component surfactants in the mixed micelle. The static quenching method was used to determine the mean aggregation number of pure and mixed micelles. It was found that whereas mixed micelles containing SDS show a positive deviation from the ideal behaviour, those constituted by DTAB deviate negatively. This different tendency was interpreted on the basis of both steric and electrostatic interactions. The evolution of the microstructure of the mixed micelles upon the participation of the co-surfactant was followed through the micropolarity and microviscosity of the mixed systems. Although the micropolarity studies do not allow definite conclusions, the microviscosity assays indicate that the participation of the co-surfactant induces the formation of less ordered micelles, this effect being more pronounced in the case of mixtures with the anionic surfactant.  相似文献   

7.
Sonolysis of aqueous solutions of n-alkyl anionic surfactants results in the formation of secondary carbon-centered radicals (-*CH-). The yield of -*CH- depends on the bulk surfactant concentration up to a maximum attainable radical yield (the 'plateau yield') where an increasing surfactant concentration (below the critical micelle concentration) no longer affects the -*CH- yield. In an earlier study it was found that the ratio of -*CH- detected following sonolysis of aqueous solutions of sodium pentane sulfonate (SPSo) to that of sodium dodecyl sulfate (SDS) (i.e. CH(SPSo)/CH(SDS)) depended on the frequency of sonolysis, but was independent of the ultrasound intensity, at the plateau concentrations [J.Z. Sostaric, P. Riesz, Adsorption of surfactants at the gas/solution interface of cavitation bubbles: an ultrasound intensity-independent frequency effect in sonochemistry, J. Phys. Chem. B 106 (2002) 12537-12548]. In the current study, it was found that the CH(SPSo)/CH(SDS) ratio depended only on the ultrasound frequency and did not depend on the geometry of the ultrasound exposure apparatus considered.  相似文献   

8.
Surfactant‐assisted specific‐acid catalysis (SASAC) for Diels–Alder reactions of dienophiles 1 and 4 with cyclopentadiene 2 in aqueous media at 32 °C was studied. This study showed that acidified anionic surfactants (pH 2) such as sodium dodecyl sulfate (SDS) and linear alkylbenzene sulfonic acid (LAS) accelerate Diels—Alder reactions. Conversely, under similar reaction conditions (pH 2) these reactions are inhibited by (acidified) cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), dodecyldimethylammonium bromide (DDAB), and dodecylmethylammonium bromide (DMAB). A modest rate acceleration resulting from the surfactant hydrogen‐bonding capacity is also recorded for the Diels–Alder reaction of naphthoquinones ( 6 ) with cyclopentadiene ( 2 ) in aqueous media at 32 °C. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

9.
Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H2O2. The effect of surfactants on the optical and structure of ZnO2 was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H2O2, and H2O2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO2 nanoparticles prepared with and without surfactants show a characteristic ZnO2 absorption at 435-445 cm−1. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV-vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830-840 and 420-440 cm−1.  相似文献   

10.
Mixtures of cationic and anionic surfactants (catanionic mixtures) are often highly non-ideal, exhibiting strong synergism in their interfacial properties, manifested for instance in significant reduction of the mixture critical micelle concentration (cmc) and enhanced adsorption onto surfaces. The magnitude of such effects is of fundamental interest and has important application-related uses (e.g. in detergent formulation). In this work, the micellization process of mixtures of cationic gemini surfactants of the alkanediyl-α,ω-bis(alkyl dimethylammonium bromide) type, denoted by 12–n–12 (where n is the spacer length), with several common anionic surfactants has been investigated by electric conductivity. For the purpose of comparison, cationic–cationic mixtures, where dodecyltrimethylammonium bromide is the second cationic surfactant, have also been investigated. The cationic/anionic mixtures show relatively significant deviations from ideal behavior, depending on the structure of the gemini surfactant and the anionic surfactant. The interaction parameter β12, within Rubingh's non-ideal model for mixed micelles, has been calculated for each mixture, as well as the mixed micelle composition as a function of mixture composition. The observed synergism in the different mixtures is interpreted in terms of the molecular structure of the surfactants and corresponding head–head and chain–chain interactions.  相似文献   

11.
The critical micelle concentration (CMC) of sodium dodecyl sulphate (SDS) in pure water and in the presence of amino acids (0.01, 0.02 and 0.03 mol kg?1), L-valine (Val) and L-leucine (Leu) was determined from conductometric and fluorometric methods using pyrene as luminescence probe. Depression in the CMC at low concentration of amino acids is attributed to the increased hydrophobic–hydrophobic interaction between the non-polar groups of the surfactant, while, at high concentration, amino acids bind strongly with the anion, DS?, head groups of SDS, thereby, delaying the micelle formation, resulting in increased CMC. A pronounced decrease in the CMC, while a marked increase in λ0+, with decrease in the solvated radius (rather than crystal radius) of the counterions is observed. Negative values of ΔG0m and ΔH0m indicate that micellisation of SDS in the presence of amino acids is thermodynamically spontaneous and exothermic. Highest negative value of ΔH0m in 0.01 m Val, with lowest CMC value, shows that 0.01 m aqueous Val is the most suitable medium favouring the micellisation of SDS. Decrease in I1/I3 from Val to Leu confirms the relative hydrophobicity of two amino acids. The observed values of the packing parameter, P, of SDS in water and in aqueous amino acids suggest that micelles formed are spherical in nature.  相似文献   

12.
Molecular dynamics of pyronin B (PyB) and pyronin Y (PyY) in aqueous solution containing different surfactants were investigated by using absorption and fluorescence spectroscopy techniques. First, the interactions of PyB and PyY with the negatively charged surfactant sodium dodecyl sulphate (SDS) were investigated in the below and above critical micelle concentration (cmc). The H-aggregate formation of the dye compounds was observed for below the cmc of SDS surfactant. The absorbance of H-aggregate absorption band of PyB and PyY decreased according to the aggregate-monomer equilibrium by increasing SDS surfactant concentration towards the cmc. Therefore, equilibrium constants of the aggregate formation and oscillator strengths of monomer and aggregate of the dye compounds were calculated from spectral studies. Moreover, aggregate formation dynamics was discussed in terms of thermodynamic functions by using temperature studies. The interactions of PyB and PyY with the positively charged hexadecyltrimethylammonium bromide (CTAB) and neutral Triton X-100 (TX-100) were also studied and it was observed that there was no aggregate formation on the absorption and fluorescence spectra for below and above the cmc.  相似文献   

13.
Spectral and surface tension behavior of aqueous neutral red in the presence of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfonate (SDSN) have been studied to understand the nature of the interactions in their submicellar concentration ranges. The variations in spectra and surface tension with variation in the concentrations of the surfactants suggest the formation of a 1:1 close-packed dye-surfactant ion pair, HNR+S between the acid form, HNR+ of the dye and the surfactant anion at very low concentrations of the surfactant below critical micelle concentration (cmc) of the pure surfactant. The dye-surfactant ion pair behaves like a nonionic surfactant having higher efficiency and lower cmc than that of the corresponding pure anionic surfactant. The ion pairs are adsorbed on the air/water interface at very low concentrations of the surfactant. As the concentration of the surfactant increases and the ion pairs form micelles of their own, the dye in the ion pair is protonated to form H2NR2+S. As the cmc of the pure surfactant is approached, the protonation equilibrium gradually reverses and pure surfactant ions gradually replace the ion pairs at the interface. Finally, a homogeneous monolayer of pure surfactant anions exists at the air/water interface and the dye remain solubilized in pure micelles above the cmc of the pure surfactant. The equilibrium constants, Kc for the close-packed protonated dye-surfactant ion pair (PDSIP) formation have been determined at varying pH. The submicellar interaction has been found to be stronger with SDS than SDBS. The plots of logarithm of Kc vs. pH have been found to be quite linear which consolidates the assumption of formation of the species, H2NR2+S. The interaction is driven by enthalpy as well as entropy.  相似文献   

14.
Nanoparticles of TiO2 and SnO2 were obtained by laser ablation of Ti and Sn targets in both deionized water and sodium dodecyl sulfate (SDS) solutions. The crystallinity of the nanoparticles strongly depended on the SDS concentration in the solution. Well-crystallized oxide nanoparticles were most abundantly fabricated in SDS solution with around the critical micelle concentration. An inorganic/organic layered nanocomposite consisting of a zinc hydroxide layer and a SDS lamellar interlayer was obtained by the ablation of Zn in SDS solutions. The oxide and/or hydroxide can be formed by the rapid reactive quenching with water in the liquid–plasma interface, where ablated species can be oxidized by aqueous oxidation. The surfactant in the liquid medium could affect the aggregation and growth of nuclei after the oxidation. The preparation of Pt/TiO2 nanocomposite particles by PLA of the bi-combinant target of Pt and TiO2 is also reported. PACS 81.16.Mk; 81.10.Dn; 81.07.Bc  相似文献   

15.
含苯氧基的非离子型和阴离子型表面活性剂在一定激发波长下可发出特定波长的荧光,在稀溶液中荧光发射强度与其浓度成正比,不受溶液里存在的其他物质的影响,在适当条件下相互之间也无影响。本文报道了用荧光检测复合驱油体系中的OP10、石油磺酸盐和OP10+石油磺酸盐的结果。此法选择性高,灵敏度高,操作简便,可望用于复合驱油体系中表面活性剂的分析、研究。  相似文献   

16.
Structural and electrochemical properties of polythiophene   总被引:1,自引:0,他引:1  
Polythiophenes (PTs) were prepared by chemical oxidative polymerization method in presence and absence of three different (cationic - CTAB, anionic - SDS and non-ionic - Triton X-100) surfactants using FeCl3 as oxidant. The prepared PTs were characterized by FT-IR, UV-Vis, XRD, SEM and cyclic voltammetry studies. The FT-IR spectra inferred the polymerization of thiophene and elucidate the corresponding functional groups of PTs. Our results on the UV-Vis spectra demonstrate the nπ* electronic transition of the conjugated molecules. Further the red shift in the absorption peak confirms the longer conjugation length of PTs. The amorphous nature of the PTs was inferred from the XRD pattern. The PTs prepared with surfactant exhibited different morphology compared to PT prepared without surfactant. The specific capacitances (SC) of the prepared PTs were calculated using cyclic voltammetry technique, the PT prepared with TRITRON X-100 exhibited higher SC of 117 F/g compared to SC of surfactant free PT (78 F/g). Hence, the PTs prepared with surfactants were found to be suitable electrode materials for redox supercapacitors.  相似文献   

17.
《Applied Surface Science》2005,239(3-4):285-291
Nanostructured titania film was synthesized using nonionic triblock copolymer P123 as surfactant template removed by ethanol extraction followed by calcination at different temperatures. The results of SAXRD indicate that the mesostructures of the films are not damaged until the calcination temperature as high to 450 °C. The results of TG/DSC, UV–visible and Raman spectra analyses provide the evidences for anatase phase to occur at 400 °C and above. The results of TEM and N2 adsorption and desorption measures indicate that, with temperature increasing from 350 to 500 °C, anatase nanocrystal sizes and pore diameter increase, while the calculated BET surface area decreases. The photocatalytic activity of the films was characterized by the degradation test of methylene blue, and the results show that it depends on both the specific surface area and the crystallinity of nanostructured titania film.  相似文献   

18.
The ultrasonic velocity in N-(p-n-pentyloxybenzylidene) p-n-butylaniline is measured as a function of temperature from the isotropic liquid phase to the smectic G phase. A mixed smectic phase (SAG) for a temperature interval of 2°C is reported. The derived parameters such as adiabatic compressibility (βad). Rao number (Rn) and molar compressibility (B) are also reported.  相似文献   

19.
通过紫外-可见光谱法研究了阴离子偶氮染料甲基橙(MO)与3种季铵盐表面活性剂之间的相互作用.当表面活性剂浓度远低于临界胶束浓度(CMC)时,表面活性剂与染料形成聚集体,反映为吸收带蓝移并伴随着吸收强度下降.继续加入表面活性剂,引起染料在阳离子胶束中的特征吸收.当表面活性剂浓度达到CMC及以上时,混合溶液的λ<,max>...  相似文献   

20.
Micellar solution of nonionic surfactantn-dodecyloligo ethyleneoxide surfactant, decaoxyethylene monododecyl ether [CH3(CH2)11(OCH2CH2)10OH], C12E10 in D2O solution have been analysed by small-angle neutron scattering (SANS) at different temperatures (30, 45 and 60° C) both in the presence and absence of sugars. The structural parameters like micelle shape and size, aggregation number and micellar density have been determined. It is found that the micellar structure significantly depends on the temperature and concentration of sugars. The micelles are found to be prolate ellipsoids at 30° C and the axial ratio of the micelle increases with the increase in temperature. The presence of lower concentration of sugar reduces the size of micelles and it grows at higher concentration of sugar. The structure of micelles is almost independent of the different types of sugars used.  相似文献   

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