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Author(s): Eduardo F Marques
Rodrigo O Brito
Sandra G Silva
Enrique E Rodriguez Borges
Maria Luisa do Vale
Paula Gomes
Maria J Araujo
Olle Soderman
Title: Spontaneous vesicle formation in catanionic mixtures of amino acid-based surfactants: Chain length symmetry effects
Issue Date: 2008
Abstract: The use of amino acids for the synthesis of novel surfactants with vesicle-forming properties potentially enhances the biocompatibility levels needed for a viable alternative to conventional lipid vesicles. In this work, the formation and characterization of catanionic vesicles by newly synthesized lysine- and serine-derived surfactants have been investigated by means of phase behavior mapping and PFG-NMR diffusometry and cryo-TEM methods. The lysine-derived surfactants are double-chained anionic molecules bearing a pseudogemini configuration, whereas the serine-derived amphiphile is cationic and single-chained. Vesicles form in the cationic-rich side for narrow mixing ratios of the two amphiphiles. Two pairs of systems were studied: one symmetric with equal chain lengths, 2C(12)/C(12), and the other highly asymmetric with 2C(8)/C(16) chains, where the serine-based surfactant has the longest chain. Different mechanisms of the vesicle-to-micelle transition were found, depending on symmetry: the 2C12/C12 system entails limited micellar growth and intermediate phase separation, whereas the 2C(8)/C(16) system shows a continuous transition involving large wormlike micelles. The results are interpreted on the basis of currently available models for the micelle-vesicle transitions and the stabilization of catanionic vesicles (energy of curvature vs mixing entropy).
Subject: Engenharia dos materiais
Materials engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia dos materiais
Engineering and technology::Materials engineering
Document Type: Artigo em Revista Científica Internacional
Rights: openAccess
Appears in Collections:FCUP - Artigo em Revista Científica Internacional

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