Phase Behavior Controlled by the Addition of Long-Chain n-Alcohols in Systems of Cationic Surfactant/Anionic Polyion Complex Salts and Water

Autor(es)

Percebom, Ana M. ^{[1, 2]} ; Ferreira, Guilherme A. ^[1] ; Catini, Daniel Rege ^[1] ; Bernardes, Juliana S. ^{[3, 1]} ; Loh, Watson ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, UNICAMP, Inst Chem, POB 6154, BR-13084970 Campinas, SP - Brazil

^[2] Pontifical Catholic Univ Rio de Janeiro, Dept Chem, BR-22451900 Rio De Janeiro, RJ - Brazil

^[3] Brazilian Ctr Res Energy & Mat CNPEM, Brazilian Nanotechnol Natl Lab LNNano, BR-13083970 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry B; v. 122, n. 18, p. 4861-4869, MAY 10 2018.
• Citações Web of Science: 2

Resumo

Phase behavior of surfactants in water may be affected by the addition of a third component, and the present study discusses how long-chain n-alcohols affect phase transitions of systems formed by the surfactant hexadecyltrimethylammonium bromide, C16TAB, or its complex salts formed with polyacrylate, C16TAPA30, as well as other previously reported complex salts/water/alcohol systems. Structural characterization by X-ray diffraction patterns at small and wide angles and different temperatures was performed for samples containing n-decanol, n-dodecanol, or n-tetradecanol. Differential scanning calorimetry (DSC) was also used to study the phase transition. The results allowed us to observe and understand the coexistence of lamellar gel (L-beta) and lamellar liquid-crystal (L-alpha) phases, elucidating the structure of a previously reported mesophase, proposing an alternative assignment. Whereas the chain-melting transition is well-known to be sharp for lipids, we have found that it is broader for C(16)TAB and C(16)TAPA in the presence of these n-alcohols. We have investigated the effects of their composition and chain length on the temperature and enthalpy of transition. This elucidates why the addition of n-alcohols with chains slightly shorter than that of the surfactants leads to the formation of an ordered gel-like lamellar phase (L-beta). n-Alcohols act as neutral cosurfactants, leading to more packing, and all of the factors converge to a limit situation, associated with a common critical area occupied by each alkyl chain. We compared our results with other mesophase systems from the literature, demonstrating that the same trends of phase behavior occur for complex salts of other polyelectrolytes with alkyltrimethylammonium surfactants. (AU)

• Processo FAPESP: 05/54421-0 - Equilíbrio de fases e caracterização estrutural de misturas contendo poliânions e sulfatantes catiônicos
• Beneficiário: Juliana da Silva Bernardes
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 15/25406-5 - Organizando a matéria: colóides formados por associação de surfactantes, polímeros e nanopartículas
• Beneficiário: Watson Loh
• Modalidade de apoio: Auxílio à Pesquisa - Temático