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A Gemini surfactant, sodium N, N'-di(4-n-butyloxy cinnamoly)-L-cystine, containing a cinnamoyl moiety in the alkyl chains and disulfide bond in the spacer was designed and synthesized. The incorporation of a cinnamoyl moiety into the alkyl chains of Gemini surfactant makes it easy to probe the conformational information of the amphiphile molecule. The UV/vis absorption spectra and steady-state fluorescence were investigated at a concentration far below the critical micelle concentration (cmc). Both blue-shift of absorption and red-shift of fluorescence emission spectra indicate the existence of intramolecular interaction between the two alkyl chains in Gemini surfactant in the singly dispersed state. Results based on the breakdown of the disulfide bond by dithiotheritol (DTT) further confirmed the conclusion. Moreover, the characteristic of intramolecular chain interaction in Gemini surfactant improves the topochemical geometrical requirements of cinnamoyl moiety and increases the local concentration of reactant in dilute solution. Utilizing the incorporation of cinnamoyl moiety into the alkyl chains of Gemini surfactant, the cinnamoyl moiety upon irradiation undergoes dimerization in dilute aqueous solution with high yield of 78%.

The adsorption of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) onto preformed particle gels (PPGs) and the effect of SDBS on the swelling ratio and rheology of PPGs were investigated. SDBS molecules can adsorb onto PPGs because of the hydrophobic association with the chain of PPGs at low concentration and the association of the SDBS micelles with the chains of PPGs at high concentration. PPGs contract and the shear stress of PPGs decreases after adsorption of SDBS. In addition, the storage modulus decreases first and then increases with increasing SDBS concentration. [ABSTRACT FROM PUBLISHER]

Abstract: We report in this work on the scaling behavior of wormlike micelles formed in a series of mixed systems of oppositely charged surfactants, including sodium decanote (SD)/hexadecyltrimethylammonium bromide (CTAB), sodium laurate (SL)/hexadecyltrimethylammonium bromide, sodium didecaminocystine (SDDC)/hexadecyltrimethylammonium bromide, and sodium dilauraminocystine (SDLC)/hexadecyltrimethylammonium bromide. Steady and dynamic rheological measurements were performed to characterize these wormlike micelles. The scaling behavior for these systems at various mixing ratios was systematically investigated and was compared with that given by the Cates model. It was found that the Cates law can be applied in these systems simply by manipulating the mixing ratio or the surfactant structure. Energetic analysis demonstrates that the scaling behavior of wormlike micelles in nonequimolar mixed cationic and anionic surfactant systems can be close to that predicted by the Cates model, if the electrostatic contribution is below a threshold value. [Copyright &y& Elsevier]

Abstract A novel CO 2 responsive anionic smart wormlike micelles (SWLMs) was constructed by simply mixing sodium oleate (NaOA) and the small organic counterion 2, 6, 10-trimethyl-2, 6, 10-triazaundecane (TMTAD) in a 3:1 M ratio without complex organic synthesis. After bubbling CO 2 , TMTAD and NaOA molecules in aqueous solution, a pseudo Gemini surfactant is formed in situ due to electrostatic interactions. This system shows two obvious performance transitions when CO 2 is continuously introduced, from a water-like solution to a viscoelastic fluid and then a milky solution. Such transitions reflect the continuous transformation of the self-assembled structure from spherical micelles to wormlike micelles and then vesicle or spherical micelles. Additionally, this system can exhibit two similar sequential transformations when the pH changes in the reverse process. Highlights • A novel CO 2 -controllable smart nanostructured fluids in a pseudo Gemini surfactant system is constructed. • Characteristics of SWLMs are systematically analyzed. • Reversible transition mechanisms of SWLMs induced by CO 2 are proposed. [ABSTRACT FROM AUTHOR]

Although extensive work has been reported that micelles can induce depletion attraction between two solid spheres or a sphere and a plate, the effect of different micelles on the depletion between two soft surfaces has been rarely reported. Optical tweezers were used to measure the forces between two oil-in-water emulsions in solutions of sodium dodecylbenzenesulfonate (SDBS), cetyltrimethylammonium bromide (CTAB), and octylphenol polyoxyethylene ether with ten oxyethylene glycol ether (OP-10) at varying concentrations. When the concentration of surfactant below their critical micelle concentration (cmc), force profiles between two emulsion droplets were purely repulsive. As the concentration of SDBS or CTAB above its cmc, the attraction between like-charged O/W emulsion droplets was dominant. The coalescence of the like-charged O/W emulsion droplets is observed. For nonionic surfactants OP-10, even if the cmc had been reached, the attractive force between O/W emulsion droplets couldn't be measured. Results shows that attractive forces between two like-charged emulsion droplets of several microns in solution can also be induced by ionic micelles and the depletion was enhanced by counterion osmotic pressure. Our work suggests that the effect of micelle-induced depletion on the force between two solid surfaces can be used to predict forces between several micrometers of emulsion droplets. [Display omitted] [ABSTRACT FROM AUTHOR]