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Author(s): Yujie J Wang
Eduardo F Marques
Title: Mesophase formation and thermal behavior of catanionic mixtures of gemini surfactants with sodium alkylsulfates
Issue Date: 2010
Abstract: The thermal behavior for three homologous series of cationic geminis surfactants of the type n-2-n, alkanediyl-alpha,omega-bis(alkyldimethylammonium bromide), with n = 12, 14, 16, and 18, and sodium alkyl sulfates, SC (m) S, with m = 12, 14, and 16, is reported here. The cationic/anionic molar ratio is kept at 1:2 (equicharged mixtures), and salt is also present. Polarizing light microscopy and differential scanning calorimetry show a stepwise fusion for the mixtures with appearance of several mesophases between the crystalline structures and the isotropic liquid. A main endothermic transition is observed, associated with partial chain melting and consequent loss of crystalline order, followed by a transition to a smectic liquid crystal. The phase transition thermodynamics is interpreted in terms of an interplay between van der Waals chain-chain interactions and ionic head group interactions.
Subject: Termodinâmica aplicada, Química das superfícies, Química
Applied thermodynamics, Surface chemistry, Chemical sciences
Scientific areas: Ciências exactas e naturais::Química
Natural sciences::Chemical sciences
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FCUP - Artigo em Revista Científica Internacional

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