Encontrados 12 documentos, a visualizar página 1 de 2
Polymer-vesicle association
Antunes, Filipe E.; Marques, Eduardo F.; Miguel, Maria G.; Lindman, BjörnMixed polymer-surfactant systems have been intensively investigated in the last two decades, with the main focus on surfactant micelles as the surfactant aggregate in interaction. The main types of phase behavior, driving forces and structural/rheological effects at stake are now fairly well understood. Polymer-vesicle systems, on the other hand, have received comparatively less attention from a physico-chemica...
Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gem...
Burrows, Hugh D.; Tapia, María J.; Silva, Cláudia L.; Pais, Alberto A. C. C.; Fonseca, Sofia M.; Pina, João; Melo, J. Seixas de; Wang, YujieUnderstanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diylcopolymer (PBS−PFP) and cationic gemini surfactants α,ω-(CmH2m+1N+(CH3)2)2(CH2)s(Br-)2 (m-s-m; m = 12, s = 2, 3, 5, 6, ...
Mechanisms behind the Faceting of Catanionic Vesicles by Polycations: Chain Cry...
Antunes, Filipe E.; Brito, Rodrigo O.; Marques, Eduardo F.; Lindman, Björn; Miguel, MariaVesicles composed of an anionic and a cationic surfactant, with a net negative charge, associate strongly with a hydrophobically modified polycation (LM200) and with an unmodified polycation with higher charge density (JR400), forming viscoelastic gel-like structures. Calorimetric results show that in these gels, LM200 induces a rise of the chain melting temperature (Tm) of the vesicles, whereas JR400 has the o...
Network Formation of Catanionic Vesicles and Oppositely Charged Polyelectrolyte...
Antunes, Filipe E.; Marques, Eduardo F.; Gomes, Ricardo; Thuresson, Krister; Lindman, Björn; Miguel, Maria G.In nonequimolar solutions of a cationic and an anionic surfactant, vesicles bearing a net charge can be spontaneously formed and apparently exist as thermodynamically stable aggregates. These vesicles can associate strongly with polymers in solution by means of hydrophobic and/or electrostatic interactions. In the current work, we have investigated the rheological and microstructural properties of mixtures of c...
Liquid Crystals and Phase Equilibria Binary Bile Salt-Water Systems
Marques, Eduardo F.; Edlund, Håkan; Mesa, Camillo La; Khan, AliThe phase behavior of several binary sodium bile salt-water systems is investigated over the entire concentration range, with emphasis on concentrated regions beyond the isotropic solution phase. The studied bile acid salts comprise the free salt sodium deoxycholate (SDC), the taurine conjugates sodium taurocholate (STC), sodium taurodeoxycholate (STDC), and sodium taurochenodeoxycholate (STCDC) and the glycine...
Micelles, Dispersions, and Liquid Crystals in the Catanionic Mixture Bile Salt−...
Marques, Eduardo F.; Regev, Oren; Edlund, Håkan; Khan, AliThe phase behavior and phase structure for the catanionic pair sodium taurodeoxycholate−didodecyldimethylammonium bromide (DDAB) are investigated, at 25 °C. A combination of techniques is used including light and electron microscopy, small-angle X-ray scattering, and pulsed field gradient NMR self-diffusion. The bile salt micellar solution incorporates large amounts of the double-chained amphiphile, with the so...
Liquid Crystals and Phase Equilibria Binary Bile Salt-Water Systems
Marques, Eduardo F.; Edlund, Håkan; Mesa, Camillo La; Khan, AliThe phase behavior of several binary sodium bile salt-water systems is investigated over the entire concentration range, with emphasis on concentrated regions beyond the isotropic solution phase. The studied bile acid salts comprise the free salt sodium deoxycholate (SDC), the taurine conjugates sodium taurocholate (STC), sodium taurodeoxycholate (STDC), and sodium taurochenodeoxycholate (STCDC) and the glycine...
Synergism and polymorphism in mixed surfactant systems
Khan, Ali; Marques, Eduardo FMixed surfactant systems have been, for a long time, one of the favorite areas for experimental studies on interfacial and bulk properties of surfactants. Beyond the well-known synergistic properties, with relevance to technical applications, recent studies increasingly focus on the bulk aggregation behavior. As more systematic and detailed experimental data is collected (for example, by use of scattering and d...
DNA conformational dynamics in the presence of catanionic mixtures
Mel'nikov, Sergey M.; Dias, Rita; Mel'nikova, Yuliya S.; Marques, Eduardo F.; Miguel, Maria G.; Lindman, BjörnDNA conformational behavior in the presence of non-stoichiometric mixtures of two oppositely charged surfactants, cetyltrimethylammonium bromide and sodium octyl sulfate, was directly visualized in an aqueous solution with the use of a fluorescence microscopy technique. It was found that in the presence of cationic-rich catanionic mixtures, DNA molecules exhibit a conformational transition from elongated coil t...
Interactions between Catanionic Vesicles and Oppositely Charged Polyelectrolyte...
Marques, Eduardo F.; Regev, Oren; Khan, Ali; Miguel, Maria da Graça; Lindman, BjörnStructural and phase behavior effects resulting from the addition of a polyelectrolyte to a solution of oppositely charged vesicles are investigated in this work. Two cationic polyelectrolytes derived from hydroxyethylcellulose were used: JR400, a homopolymer, and Quatrisoft LM200, a polymer modified with alkyl side chains. The vesicles are composed of mixed anionic surfactant (sodium dodecyl sulfate) and cati...
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